Publications and Technical Reports
Portner, R.A., D.A. Clague, C. Helo, B.M. Dreyer, J.B. Paduan (2015) Contrasting styles of deep-marine pyroclastic eruptions revealed from Axial Seamount push core records. Earth Planet. Sci. Lett., 423: 219-231. doi: 10.1016/j.epsl.2015.03.043.
Clague, D.A., B.M. Dreyer, J.B. Paduan, J.F. Martin, D.W. Caress, J.B. Gill, D.S. Kelley, H. Thomas, R.A. Portner, J.R. Delaney, T.P. Guilderson, M.L. McGann (2014) Eruptive and tectonic history of the Endeavour segment, Juan de Fuca Ridge, based on AUV mapping data and lava flow ages. Geochem., Geophys., Geosyst., 15(8): 3364-3391. doi: 10.1002/2014GC005415. [Supplemental material]
Portner, R.A., D.A. Clague, J.B. Paduan (2014) Caldera formation and varied eruption styles on North Pacific seamounts: the clastic lithofacies record. Bull. Volcanol. 76: 845. doi: 10.1007/s00445-014-0845-3.
Chadwick, W.W., D.A. Clague, R.W. Embley, M.R. Perfit, D.A. Butterfield, D.W. Caress, J.B. Paduan, J.F. Martin, P. Sasnett, S.G. Merle, A.M. Bobbitt (2013) The 1998 eruption of Axial Seamount: New insights on submarine lava flow emplacement from high-resolution mapping. Geochem., Geophys., Geosyst. 14(10): 3939-3968, doi: 10.1002/ggge.20202 [Article] (Abstract: Submarine Volcanism web )
Clague, D.A., B.M. Dreyer, J.B. Paduan, J.F. Martin, W.W. Chadwick, D.W. Caress, R.A. Portner, T.P. Guilderson, M.L. McGann, H. Thomas, D.A. Butterfield, R.W. Embley (2013) Geologic history of the summit of Axial Seamount, Juan de Fuca Ridge. Geochem., Geophys., Geosyst., 14(10): 4403-4443. doi: 10.1002/ggge.20240 [Article] (Abstract: Submarine Volcanism web)
Yeo, I.A., D.A. Clague, J.F. Martin, J.B. Paduan, D.W. Caress (2013) Pre-eruptive flow focussing in dikes feeding historical pillow ridges on the Juan de Fuca and Gorda Ridges. Geochem. Geophys. Geosyst., 14(9): 3586-3599. doi: 10.1002/ggge.20210 [Article] (Abstract: Submarine Volcanism web)
Caress, D.W., D.A. Clague, J.B. Paduan, J.F. Martin, B.M. Dreyer, W.W. Chadwick Jr, A. Denny, D.S. Kelley (2012) Repeat bathymetric surveys at 1-metre resolution of lava flows erupted at Axial Seamount in April 2011. Nature Geoscience, 5(7): 483-488. doi: 10.1038/NGEO1496. (Abstract: Submarine Volcanism web)
Clague, G.E., W.J. Jones, J.B. Paduan, D.A. Clague, R.C. Vrijenhoek (2012) Phylogeography of Acesta clams from submarine seamounts and escarpments along the western margin of North America. Marine Ecology, 33: 75-87, doi: 10.1111/j.1439-0485.2011.00458.x.
Clague, D. A., J. B. Paduan, D. W. Caress, H. Thomas, W. W. Chadwick, Jr., and S. G. Merle (2011), Volcanic morphology of West Mata Volcano, NE Lau Basin, based on high-resolution bathymetry and depth changes, Geochem. Geophys. Geosyst., 12(11): 21 pp, QOAF03, doi:10.1029/2011GC003791. (Abstract: Submarine Volcanism web)
Davis, A. S., D. A. Clague, J. B. Paduan, B. L. Cousens, and J. Huard (2010), Origin of volcanic seamounts at the continental margin of California related to changes in plate margins, Geochem. Geophys. Geosyst., 11(7): 20 pp., Q05006, doi:10.1029/2010GC003064, 28 pages.
Faichney, I.D.E., J.M. Webster, D.A. Clague, J.B. Paduan, P.D. Fullagar (2010) Unraveling the tilting history of the submerged reefs surrounding Oahu and the Maui-Nui Complex, Hawaii. Geochemistry, Geophysics, Geosystems, 11(7): 20 pages. doi:10.1029/2010GC003044.
Clague, D., Lundsten, L., Hein, J., Paduan, J., Davis, A. (2010) Spotlight 6: Davidson Seamount. Oceanography 23(1): 126-127. [Article]
Clague, D.A. and J.B. Paduan (2009) Submarine basaltic volcanism, In: Submarine Volcanism and Mineralization: Modern through Ancient, B. Cousens and S.J. Piercey (eds.), Geological Association of Canada, Short Course 39-30 May 2008, Quebec City, Canada, p. 41-60.
Clague, D.A., J.B. Paduan, A.S. Davis (2009) Widespread strombolian eruptions of mid-ocean ridge basalt, Journal of Volcanology and Geophysical Research, 180: 171-188, doi:10.1016/j.jvolgeores.2008.08.007. [Article] [Abstract: Submarine Volcanism web]
Clague, D. A., J. B. Paduan, R. A. Duncan, J. J. Huard, A. S. Davis, P. R. Castillo, P. Lonsdale, and A. DeVogelaere (2009), Five million years of compositionally diverse, episodic volcanism: Construction of Davidson Seamount atop an abandoned spreading center, Geochem. Geophys. Geosyst., 10, Q12009, doi:10.1029/2009GC002665.
Paduan, J.B., D.W. Caress, D.A. Clague, C.K. Paull, H. Thomas (2009) High-resolution mapping of mass wasting, tectonic, and volcanic hazards using the MBARI Mapping AUV, Rendiconti Online Società Geologica Italiana, 7: 181-186. [Article (3MB)]
Paduan, J.B., D.A. Clague, A.S. Davis (2009) Evidence that three seamounts off southern California were ancient islands, Marine Geology, 265: 146-156, doi:10.1016/j.margeo.2009.07.003.
Caress, D.W., H. Thomas, W. J. Kirkwood, R. McEwen, R. Henthorn, D.A. Clague, C. K. Paull, J. Paduan, and K. L. Maier (2008) "High-Resolution Multibeam, Sidescan, and Subbottom Surveys Using the MBARI AUV D. Allan B.", Marine Habitat Mapping Technology for Alaska, J.R. Reynolds and H.G. Greene (eds.) Alaska Sea Grant College Program, University of Alaska Fairbanks. doi:10.4027/mhmta.2008.04. [Article (18 MB)]
Davis, A. S., D. A. Clague, B. L. Cousens, R. Keaten, J. B. Paduan (2008) Geochemistry of basalt from the North Gorda segment of the Gorda Ridge: Evolution toward ultraslow spreading ridge lavas due to decreasing magma supply, Geochemistry Geophysics Geosystems, 9: Q04004, doi:10.1029/2007GC001775. [Abstract: Submarine Volcanism web]
Paduan, J.B., D.A. Clague, A.S. Davis (2007) Erratic continental rocks on volcanic seamounts off the US west coast, Marine Geology, doi:10.1016/j.margeo.2007.07.007 [Abstract: Submarine Volcanism web]
Davis, A.S., D.A. Clague, J.B. Paduan (2007) Diverse origins of xenoliths from seamounts at the continental margin, offshore central California, Journal of Petrology, 48(5): 829-852, doi:10.1093/petrology/egm003.
Clague, D.A., J.B. Paduan, W.C. McIntosh, B.L. Cousens, A.S. Davis, J.R. Reynolds (2006) A submarine perspective of the Honolulu Volcanics, Oahu, Journal of Volcanology and Geothermal Research, 151: 279-307 doi: 10.1016/j.jvolgeores.2005.07.036
Paull C.K., B. Schlining, W. Ussler III, J.B. Paduan, D. Caress, and H.G. Greene (2005) Distribution of chemosynthetic biological communities in Monterey Bay, California, Geology 33(2): 85-88. doi:10.1130/G20927.1
MBARI Mapping Team. 2001. Northern California and Oregon Margin Multibeam Survey, MBARI Digital Data Series No. 5. Web site
MBARI Mapping Team. 2001. West Coast Seamounts and Ridges Multibeam Survey, MBARI Digital Data Series No. 7. Web site
Stakes, D.S., D. Orange, J.B. Paduan, K.A. Salamy, and N. Maher. 1999. Cold seeps and authigenic carbonate formation in Monterey Bay, California, Marine Geology, 159, 93-109. doi:10.1016/S0025-3227(98)00200-X Abstract (below)
Pilskaln, C.H., C. Lehmann, J.B. Paduan, and M.W. Silver. 1998. Spatial and temporal dynamics in marine aggregate abundance, sinking rate and flux: Monterey Bay, central California, Deep-Sea Research II, 45, 1803-1837, doi:10.1016/S0967-0645(98)80018-0. Abstract (below)
Pilskaln, C.H., F.P. Chavez, J.B. Paduan, R.Y. Anderson and W.M. Berelson. 1996. Carbon cycling in the coastal upwelling system of Monterey Bay, Central California, Journal of Marine Research, 54(6), 1-31, doi:10.1357/0022240963213772. Abstract (below)
Batiza R., N. Becker, D. Bercovici, T. Coleman, T. Gorman, J.W. Head III, L. Holloway, J. Karsten, A. Kelly, L.P. Keszthelyi, D. Maicher, W. Mueller, J. Muller, L. Norby, J. Paduan, G. Parker, L. Prockter, D. Stakes, J.D.L. White (1996) New evidence from Alvin for the origin of deep-sea eruptive hyaloclasite on Seamount 6: Cocos plate, 12°43′N. EOS 77:319.
Rosenfeld, L.K., R.E. Schramm, J.B. Paduan, G.A. Hatcher, Jr., T. Anderson. 1994. Hydrographic data collected in Monterey Bay during 1 September 1988 to 16 December 1992, MBARI Technical Report #94-15, 549 pp, supplement 292 pp.
Steinberg, D.K., M.W. Silver, C.H. Pilskaln, S.L. Coale, and J.B. Paduan. 1994. Mid-water zooplankton communities on pelagic detritus (giant larvacean houses) in Monterey Bay, California, Limnology and Oceanography, 39(7), 1606-1620. Abstract (below) [Abstract] [PDF]
Pilskaln, C.H. and J.B. Paduan. 1992. Laboratory techniques for the handling and geochemical analysis of water column particulate and surface sediment samples, MBARI Technical Report #92-9, 22 pp.
Brophy, J.E. and D.J. Carlson. 1989. Production of biologically-refractory dissolved organic carbon by natural seawater microbial populations, Deep-Sea Research, 36, 497-507, doi:10.1016/0198-0149(89)90002-2 Abstract (below)
Carlson, D.J., L.E. Morrill, and J.E. Brophy. 1987. Techniques of fluorescence depolarization for measuring seawater viscosities, Limnology and Oceanography, 32, 1377-1381. Abstract (below) [Abstract] [PDF]
Brophy, J.E. 1987. Production of biologically-refractory dissolved organic carbon by natural seawater microbial populations, M.S. Thesis, Oregon State University, 64 pp.
Posters and Presentations
Caress, D.W., Clague, D.A., Paduan, J.B., Thomas, H. (2015) Vertical deformation of the Axial Seamount summit from repeated 1-m scale bathymetry surveys with the MBARI Mapping AUV. Geological Society of America Abstracts with Programs, Vol. 47, No. 7, p.381.
Clague, D.A., Portner, R.A., Paduan, J.B., Dreyer, B. (2015) Summit overflow periods, caldera formation, explosive eruption periods, and varying magma flux at basaltic volcanoes. Geological Society of America Abstracts with Programs, Vol. 47, No. 7, p.228.
Paduan, J.B., Clague, D.A., Caress, D.W., Dreyer, B., Portner, R.A., Martin, J.F. and Chadwick, W.W. (2015) High-resolution mapping and sampling of historic flows on Juan de Fuca and Gorda Ridges. Geological Society of America Abstracts with Programs, Vol. 47, No. 7, p.381. Abstract
Portner, R.A., Dreyer, B., Clague, D.A., Spelz, R., Lowenstern, J., Paduan, J.B., Carey, S. (2015) Rhyolite eruption on a mid-ocean ridge: Alarcon Rise, Gulf of California. Geological Society of America Abstracts with Programs, Vol. 47, No. 7, p.380.
Zierenberg, R., Clague, D.A., Paduan, J.B., Caress, D.W. (2015) New maps focus 30-odd years of investigation of the Escanaba Trough spreading center. Geological Society of America Abstracts with Programs, Vol. 47, No. 7, p.381.
Paduan, J.B., D.A Clague, D.W. Caress (2014) Constructional talus: formed during eruption, not by later tectonism. Abstract V31B-4742 presented at 2014 Fall Meeting, AGU, San Francisco, Calif., 15-19 Dec. Abstract
Clague, D.A., J.B. Paduan, D.W. Caress (2014) Lava cones and shields on intermediate-rate mid-ocean ridges. Abstract V31B-4743 presented at 2014 Fall Meeting, AGU, San Francisco, Calif., 15-19 Dec.
Paduan, J.B., D.A Clague, D.W. Caress, H.J. Thomas (2013) Perched Lava Pond Complex on South Rift of Axial Volcano Revealed in AUV Mapping. Abstract OS33A-1753 presented at 2013 Fall Meeting, AGU, San Francisco, Calif., 9-13 Dec.Abstract
Clague, D.A., R.A .Portner, J.B. Paduan, B.M. Dreyer (2013) Fluidal deep-sea volcanic ash as an indicator of explosive volcanism (Invited) Abstract V33H-08 presented at 2013 Fall Meeting, AGU, San Francisco, Calif., 9-13 Dec.
Clague, D.A., D.W. Caress, L. Lundsten, J.F. Martin, J.B. Paduan, R.A. Portner, J.A. Bowles, P.R. Castillo, B.M. Dreyer, R. Guardado-France, C. Nieves-Cardoso, H. Rivera-Huerta, M. Santa Rosa-del Rio, R. Spelz-Madero (2012) Geology of the Alarcón Rise Based on 1-m Resolution Bathymetry and ROV Observations and Sampling. Abstract T44A-04 presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec.
Clague, D.A., J.B. Paduan, J.C. Braga, C. Humphrey, G. Hinestrosa, P.D. Fullagar (2012) Exploring Drowned Reefs on Gardner Pinnacles (Invited). Abstract OS51A-1843 presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec.
Caress, D.W., D.A. Clague, J.B. Paduan, J.F. Martin, H. Thomas, D. Thompson, C. Nieves-Cardoso, M. Santa Rosa-del Rio (2012) Morphology of the Alarcón Rise spreading axis from 1-m resolution AUV bathymetry surveys. Abstract T51B-2566 presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec.
Dreyer, B.M., R.A. Portner, D.A. Clague, P.R. Castillo, J.B. Paduan, J.F. Martin (2012) Rhyolite, dacite, andesite, basaltic andesite, and basalt volcanism on the Alarcon Rise spreading-center, Gulf of California. Abstract T51B-2570 presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec.
Martin, J.F., P. Lieberg-Clark, D.A. Clague, D.W. Caress, R.A. Portner, J.B. Paduan, B.M. Dreyer (2012) Effect of melt composition and crystal content on flow morphology along the Alarcón Rise, Mexico. Abstract T51B-2571 presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec.
Paduan, J.B., D.A. Clague, D.W. Caress, L. Lundsten, J.F. Martin, C. Nieves-Cardoso (2012) Newly discovered hydrothermal system on the Alarcón Rise, Mexico. Abstract T51B-2572 presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec. Abstract
Portner, R.A., D.A. Clague, B.M. Dreyer, J.F. Martin, J.B. Paduan (2012) Volcanology of the Alarcon Rise, Gulf of California. Abstract T51B-2569 presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec.
Portner, R.A., D.A. Clague, J.B. Paduan, J.F. Martin (2012) Competing styles of deep-marine explosive eruptions revealed from Axial seamount and Juan De Fuca ridge push core records (Invited). Abstract V21A-2751 presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec.
Spelz, R.M., J.M. Fletcher, C. Nieves-Cardoso, M. Santa Rosa-del Rio, D.W. Caress, D.A. Clague, J.B. Paduan, J.F. Martin, R. Guardado-France (2012) The Alarcón Rise: detail mapping and preliminary results on the geometry, distribution and kinematics of faults and fissures on a ridge-transform system. Abstract T51B-2567 presented at 2012 Fall Meeting, AGU, San Francisco, Calif., 3-7 Dec.
Paduan, J.B., D.A. Clague, D.W. Caress (2012) Lava ponds on south rift of Axial Volcano: AUV mapping reveals elaborate, extensive complex. Poster B0783 presented at the 2012 Ocean Sciences Meeting, Salt Lake City, UT, 20-24 Feb. Abstract
Caress, D.W., D.A. Clague, H. Thomas, D. Thompson, J.B. Paduan, J. Martin, W.J. Chadwick (2011) Extent of the 2011 Axial Seamount eruption from repeated 1 meter scale bathymetry surveys with the MBARI Mapping AUV. Abstract V11E-2557 presented at 2011 Fall Meeting, AGU, San Francisco, Calif., 5-9 Dec.
Caress, D.W., H. Thomas, C.K. Paull, D.A. Clague, D. Conlin, D. Thompson, E. Lundsten, K. Anderson, J.B. Paduan, J. Martin (2011) Recent MBARI Mapping AUV Surveys of Slumps, Scours, Gas Seeps, and Spreading Centers. Abstract OS24A-03 (invited) presented at 2011 Fall Meeting, AGU, San Francisco, Calif., 5-9 Dec.
Chadwick, W.W., D.A. Clague, R.W. Embley, D.W. Caress, J.B. Paduan, P. Sasnett (2011) High-resolution mapping of the 1998 lava flows at Axial Seamount . Abstract OS11C-01 (invited) presented at 2011 Fall Meeting, AGU, San Francisco, Calif., 5-9 Dec.
Clague, D.A., J.B. Paduan, B.M. Dreyer, D.W. Caress, J. Martin (2011) High-resolution AUV mapping and lava flow ages at Axial Seamount . Abstract V14C-05 (invited) presented at 2011 Fall Meeting, AGU, San Francisco, Calif., 5-9 Dec.
Paduan, J.B., D.A. Clague, B.M. Dreyer, D.W. Caress (2011) AUV Mapping and ROV Sampling of Ridges and Seamounts: No Longer Wandering Around in the Dark. Abstract OS11C-02 (invited) presented at 2011 Fall Meeting, AGU, San Francisco, Calif., 5-9 Dec. Abstract
Clague, D.A., D. W. Caress, K. H. Rubin, J. B. Paduan (2010), The 2008 Puipui eruption and morphology of the Northeast Lau Spreading Center between Maka and Tafu, Abstract T11E-03 presented at 2010 Fall Meeting, AGU, San Francisco, Calif., 13-17 Dec.
Clague, D.A., J. B. Paduan, B. M. Dreyer, D. W. Caress (2010), Lava Flow Ages and Geologic Mapping on Mid-ocean Ridges, Abstract V11A-2236 presented at 2010 Fall Meeting, AGU, San Francisco, Calif., 13-17 Dec.
Paduan, J.B., D. A. Clague, D. W. Caress, H. Thomas, D. Conlin,; D. Thompson (2010), Interpretation of 1.5-m resolution AUV bathymetry using ROV observations and samples at Davidson and Rodriguez Seamounts, Abstract V11C-2302 presented at 2010 Fall Meeting, AGU, San Francisco, Calif., 13-17 Dec. Abstract
Yeo, I.A., D. A. Clague, J. B. Paduan, D. W. Caress (2010), New Insights into Diking Processes from High Resolution Bathymetry of Pillow Ridges on the Juan de Fuca and Gorda Ridges, Abstract V11A-2236 presented at 2010 Fall Meeting, AGU, San Francisco, Calif., 13-17 Dec.
Paduan, J.B., Clague, D.A., Caress, D.W., Thomas, H., Thompson, D., Conlin D. (2009) High-Resolution AUV Mapping Reveals Structural Details of Submarine Inflated Lava Flows, Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract V51D-1732. Abstract
Caress, D.W., Clague, D.A., Thomas, H., Thompson, D., Calarco, M., Holden, J., Butterfield, D., Paduan, J.B., Meiner, M. (2008) Tectonic and volcanic character of the Endeavour Ridge axis from 1-m resolution AUV multibeam mapping surveys, Eos Trans. AGU, 89(53), Fall Meet. Suppl., Abstract V41B-2078.
Clague, D.A., Caress, D.W., Thomas, H., Thompson, D., Calarco, M., Holden, J., Butterfield, D., Paduan, J.B., Meiner, M. (2008) Abundance and distribution of hydrothermal chimneys and mounds on the Endeavour Ridge determined by 1-m resolution AUV multibeam mapping surveys, Eos Trans. AGU, 89(53), Fall Meet. Suppl., Abstract V41B-2079.
Caress, D., D.A. Clague, J.B. Paduan, W.W. Chadwick, D.A. Butterfield, H. Thomas, D. Conlin, and D.R. Thompson (2007) AUV Mapping of Axial Seamount, Juan de Fuca Ridge: The northern caldera floor and northeast rim, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract T33B-1355.
Clague, D.A., D. Caress, J.B. Paduan, W.W. Chadwick, D.A. Butterfield, H. Thomas, D. Conlin, and D.R. Thompson (2007) AUV Mapping of Axial Seamount, Juan de Fuca Ridge: The southern caldera floor and upper south rift, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract T33B-1354.
Davis, A.S., D.A. Clague, J.B. Paduan (2007) Origin of volcanic seamounts offshore California related to interaction of abandoned spreading centers with the continental margin, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract V21B-0606.
Paduan, J.B., D.A. Clague, A.S. Davis, P. Castillo, R. Duncan, P. Lonsdale, A. DeVogelaere (2007) Davidson Seamount: a volcano slowly built on an abandoned spreading center, Eos Trans. AGU, 88(52), Fall Meet. Suppl., Abstract V21B-0608. Abstract
Clague, D., Paduan, J., Cousens, B., Cornejo, E., Perfit, M., Wendt, R., Stix, J., Helo, C. (2006) Caldera Formation on the Vance Seamounts, Eos, Transactions, American Geophysical Union, 87(52), Fall Meeting Supplement, V13A-0644. Abstract
Davis, A.S., Clague, D.A., Paduan, J.B. (2006) Similarities in Chemistry of North Gorda Ridge basalts with Ultra-slow Spreading Ridge Lavas Due to Decreasing Magma Supply, Eos, Transactions, American Geophysical Union, 87(52), Fall Meeting Supplement, V23E-0687.
Paduan, J.B., Clague, D.A., Davis, A.S. (2006) Erratic Continental Rocks on Volcanic Seamounts off California and Oregon, Eos, Transactions, American Geophysical Union, 87(52), Fall Meeting Supplement, V13A-0640. Abstract
Thomas, H., Caress, D., Conlin, D., Clague, D., Paduan, J,. Butterfield, D., Chadwick, W., Tucker, P. (2006) Mapping AUV Survey of Axial Seamount, Eos, Transactions, American Geophysical Union, 87(52), Fall Meeting Supplement, V23B-0615.
Clague, D.A., Chadwick, W.W., Davis, A.S., Head, J.W., Mastin, L.G., Paduan, J.B., Ross, S.L., Wilson, L., Zierenberg, R.A. (2005) A New Look at the 1996 Gorda Ridge Eruption, Eos, Transactions, American Geophysical Union, 86(52), Fall Meeting Supplement, T41E-1360. Abstract
Davis, A.S., Clague, D.A., Paduan, J.B. (2005) Geochemistry of Basalt Lava and Hyaloclastite From Young (President Jackson) and Old (Taney) Near-ridge Seamount Chains, Eos, Transactions, American Geophysical Union, 86(52), Fall Meeting Supplement, V51C-1512.
Paduan, J.B., Clague, D.A., Davis, A.S., Chadwick, W., Cousens, B.L., Embley, R.W. (2005) Large Lava Pond Complex on the Juan de Fuca Ridge: an Effusive, Energetic Eruption that Drained Away, Eos, Transactions, American Geophysical Union, 86(52), Fall Meeting Supplement, V51C-1511. Abstract
Clague, D.A., Davis, A.S., and Paduan, J.B. 2004. Pyroclastic eruptions on the East Pacific Rise, Eos, Transactions, American Geophysical Union, 85(47), Fall Meeting Supplement, V31C-1455.
Davis, A.S., Clague, D.A., and Paduan, J.B. 2004. Volcanic rocks collected With ROV Tiburon From Rodriguez Seamount, located at the continental slope of the California Borderland, Eos, Transactions, American Geophysical Union, 85(47), Fall Meeting Supplement, V43E-1461.
Paduan, J.B., Clague, D.A., and Davis, A.S. 2004. Evidence that three seamounts off Southern California were ancient islands, Eos, Transactions, American Geophysical Union, 85(47), Fall Meeting Supplement, V43E-1463. Abstract [Press release]
Davis, A.S, Clague, D.A., and Paduan, J.B. 2003. Pyroclastic fragmentation of alkalic lava in abyssal depths at the North Arch Volcanic Field, Hawaii, Eos, Transactions, American Geophysical Union, 84(46), Fall Meeting Supplement, V22C-0592. Abstract
Paull, C.K., Schlining, B., Ussler, W., Paduan, J., Caress, D., Greene, H.G. 2003. Distribution of seafloor seepage indicators under Monterey Bay, California, EGS-AGU-EUG Joint Assembly, 183. Abstract
D.A. Clague, C.K. Paull, H.G. Greene, K. Jordahl, A.S. Davis, and the shipboard Scientific Party. 2001. MBARIs 2001 Hawaii Expedition using the R/V Western Flyer and ROV Tiburon, Eos, Transactions, American Geophysical Union, 82(47), Fall Meeting Supplement, V12B-0969. Abstract
Clague, D.A., E.L. Winterer, C.K. Paull, J. Paduan, and D.C. Potts. 2001. Stepwise reef growth, emergence and drowning recorded on a rapidly subsiding margin, offshore Hawaii: the last 600,000 years, GSA Annual Meeting. Abstract
Paduan, J.B., M. McCann, H. Baum, R. Schramm, and D. Wilkin. 2000. Collecting-event capture: a new specimen database, coordinated with a video annotation system and accessed over the web, Eos, Transactions, American Geophysical Union, 80 (1999), 151. Abstract
Paduan, J.B. 1999. Progress in establishing a new natural history collection. Oral presentation at the 14th Annual Meeting of the Society for the Preservation of Natural History Collections, Program and Abstracts, 38. Abstract
McCann, M., J.B. Paduan, and D. Brutzman. 1999. Interactive 3D data visualization in Monterey Bay. Poster at the Monterey Bay National Marine Sanctuary Research Symposium, Program and Abstracts, 14. Abstract
Paduan, J. B. 1998. Collecting event capture: A new specimen database, coordinated with a video information management system and accessed over the web. Oral presentation at the 13th Annual Meeting of the Society for the Preservation of Natural History Collections, Program and Abstracts, 23.
Orange, D.L., J. Barry, N. Maher, D. Stakes, J. Paduan, H.G. Greene, J.B. Martin, B. McAdoo, and J. Yun. 1996. ROV studies of fluid expulsion in Monterey Bay, California, American Association of Petroleum Geologists Program and Abstracts, 5, A109.
Pilskaln, C.H., J.B. Paduan, F.P. Chavez, J.T. Pennington, and R.Y. Anderson. 1993. Carbon cycling in the coastal upwelling region of Monterey Bay, Central CA. Poster at the Third Meeting of the Oceanography Society, Program of Abstracts, 206, AND Poster at the Gordon Research Conference in Chemical Oceanography.
Jackson, R.J., J. Brophy-Paduan and P.M. Shaffer. 1990. Cloning of genes for L-asparaginase in Aspergillus nidulans. Presentation by R.J. Jackson at Southern California American Chemical Society Undergraduate Research Conference, Los Angeles.
Brophy, J.E. and D.J. Carlson. 1986. Production of biologically-refractory dissolved organic carbon by natural seawater microbial populations. Poster at American Geophysical Union and American Society of Limnology and Oceanography Meeting, San Francisco.
Selected abstracts, linked from citations above
High-resolution mapping and sampling of historic flows on Juan de Fuca and Gorda Ridges.
Paduan, J.B., Clague, D.A., Caress, D.W., Dreyer, B., Portner, R.A., Martin, J.F. and Chadwick, W.W. (2015) GSA, Vol. 47, No. 7, p.381.
Abstract: Since the mid-1980s, 8 eruptions occurred along the Juan de Fuca and Gorda Ridges. MBARI surveyed at 1-m lateral resolution with our Mapping AUV and conducted ROV dives at 6 of them. Prior ROV dive observations were put into spatial context and subsequent dives targeted specific sites to ground-truth the maps, collect lava samples of these and nearby flows to assess chemical variability, and collect sediment cores to obtain absolute ages of underlying flows using 14C dating of foraminifera that first settled on them. Relative age relationships derived from sediment cover estimates, fault densities, and flow contact overlaps can be calibrated using the absolute ages. We have outlined flow extents, defined fissure systems, gained insights into flow emplacement processes, and constructed field maps and volcanic histories of the spreading ridges, much like volcanologists do on land; all unprecedented for submarine volcanoes.
The North Gorda 1996, North Cleft 1986, and CoAxial 1982-91 and 1993, and the deep south rift portion of the Axial 2011 eruptions produced discontinuous ridges of coalesced pillow mounds atop dikes that intersected the sea floor along parts of their length (Yeo et al., 2013). Adjacent and underlying flows include pillow ridges and ponded sheet flows, whose eruptive fissures have stepped back and forth across the axial valley through time. The Axial 1998 (Chadwick et al, 2013) and 2011 flows (Caress et al, 2012) near the summit are inflated sheet flows that erupted through fissures and flowed down channels created during prior eruptions. Comparing AUV bathymetry before and after the 2011 eruption allowed precise calculation of volume and area of the flow. Axial's summit caldera has been paved with similar eruptions for the past 725 years (Clague et al, 2013), but explosive eruptions occurred at the summit (Portner et al, 2014) from about 1400 to 1000 years ago, at the same time that vast ponded flows on the deep rifts erupted, which may have triggered caldera collapses.
Prior to these technological advances, our understanding of mid-ocean ridges was based on magnetic anomalies, widely distributed lava samples, and generalized flow type. The synergistic high-resolution mapping and targeted ROV sampling of the ridges has permitted better understanding of how, how much, how often, and when spreading ridges erupt. (Up to list)
Abstract: Talus does not always indicate mass wasting due to destructive faulting, landslides, or caldera collapse. That talus slopes might be constructed during submarine volcanic eruptions was first recognized in 2005 from ROV observations and samples of lava that dripped over a cliff of a steep pillow mound of the 1996 eruption on the Gorda Ridge. Such talus was also found in 2013 along the steep pillow ridge that formed on the South Rift of Axial Volcano during the 2011 eruption. At each site, wedges and stubby cylinders of broken glass-rimmed pillow lava lie at the base of a vertical cliff of truncated pillows, as they do in other places where faults may have broken them. However, more telling evidence of this process is slender, elongate glassy rods of lava, which we call "lavacicles" from their resemblance to icicles, which were lying below the overhanging cliffs from which they had dripped and fallen. The drips can be phyric and aphyric lava, primitive to evolved in composition. Therefore they don't indicate a particular basaltic composition or viscosity; they probably result from very slow eruption rate that builds a steep stack of pillows.
In 1 meter resolution AUV bathymetric maps, these talus slopes appear much like talus found at the base of fault-block slices at other parts of those ridges and at the highly faulted Endeavour Segment, however these pillow ridges are too young to have been tectonically faulted. Their orientations are not necessarily aligned with the dominant strike of faults in the area, but instead with the outline of the pillow mounds. We now have identified numerous other constructional talus slopes at Gorda and Juan de Fuca Ridges, Alarcon Rise, and Davidson Seamount off California that meet this criterion so are likely to be constructional also. At intermediate rate ridges constructional talus and cliffs contribute a small amount of the area, but perhaps significant permeability pathways for hydrothermal circulation. (Up to list)
Abstract: An extraordinary lava pond complex is located on Axial Volcano's distal south rift. It was discovered in EM300 multibeam bathymetry collected in 1998, and explored and sampled with ROVs Tiburon in 2005 and Doc Ricketts in 2013. It was surveyed with the MBARI Mapping AUV D. Allan B. in 2011, in a complicated mission first flying above the levees at constant depth, then skimming ~5 m over the levees at a different constant depth to survey the floors, then twice switching to constant altitude mode to map outside the ponds. The AUV navigation was adjusted using the MB-System tool mbnavadjust so that bathymetric features match in overlapping and crossing swaths. The ~1-m resolution AUV bathymetry reveals extremely rough terrain, where low-resolution EM300 data had averaged acoustic returns and obscured details of walls, floors, a breach and surrounding flows, and gives context to the ROV observations and samples.
The 6 x 1.5 km pond complex has 4 large and several smaller drained ponds with rims 67 to 106 m above the floors. The combined volume before draining was 0.56 km3. The ponds overflowed to build lobate-flow levees with elongate pillows draping outer flanks, then drained, leaving lava veneer on vertical inner walls. Levee rim depths vary by only 10 m and are deeper around the southern ponds. Deep collapse-pits in the levees suggest porosity of pond walls. The eastern levee of the northeastern pond breached, draining the interconnected ponds, and fed thick, rapidly-emplaced, sheet-flows along the complex's east side. These flows travelled at least 5.5 km down-rift and have 19-33 m deep drained ponds. They extended up-rift as well, forming a 10 x 2.5 km ponded flow with level "bathtub rings" as high as 35 m above the floor marking that flow's high-stand. Despite the breach, at least 0.066 km3 of the molten interior of the large ponds also drained back down the eruptive fissures, as the pond floors are deeper than the sill and sea floor outside the complex. Tumulus-like structures and jumbled sheet flows on the floors suggest the eruption was on-going when the ponds emptied. 14C-dating of foraminifera from basal sediments on the pond floors gives a minimum age for the ponds of ~1500 years, which is older than any of the surface flows in Axial's summit caldera. Limu o Pele was abundant. Glass contents of the recovered lavas are 7.6 to 8.0 wt% MgO with few exceptions, and other than being plagioclase-phyric, the chemistry is similar to the majority of lavas at the summit. Lava samples from the floors of several ponds have a few tenths of a weight percent lower MgO than the nearby levees, suggesting the pond's molten interior or resupplied lavas had some time to cool.
The varying levee rim heights and abundance of ponds in the vicinity suggest this type of activity occurred many times in this area, but it is an unusual eruption style for mid-ocean ridges. Another lava pond complex with even higher levees occurs on the north rift of Axial Volcano. Formation of these ponds requires long-lived, steady, moderate-eruption-rate lava effusion on nearly horizontal seafloor and may occur only on deep distal rift zones of central volcanoes. (Up to list)
Abstract: The Alarcón Rise lies at the mouth of the Gulf of California, and is the last segment of the East Pacific Rise before the plate boundary redirects into the gulf. As part of MBARI’s expedition to the gulf in 2012, the neovolcanic zone of the entire ridge segment was mapped by MBARI’s mapping AUV. 110 potential hydrothermal chimneys were identified in the new high resolution maps, and 70 were visited with the ROV Doc Ricketts, after having been sought in vain without the maps on an expedition in 2003.
Two active vent fields were found, and have been named Meyibó and Ja sít from local native languages. They lie 2.5km apart at ~2300m depth, and are associated with a large, young sheet flow 1/3 of the way along the ridge from the south, on the most inflated part of the ridge. The southern field, Meyibó, contains 14 active chimneys (confirmed with ROV observations) nestled in grabens of several highly fractured cones surrounded by the sheet flow, and generally aligned with its discontinuous, 8km-long fissure system. The northern field, Ja sít, is a broad cluster of 8 active chimneys (also confirmed) rising above the sheet flow’s channel system, more than 150m from the fissure. The chimneys stand as tall as 18 m. The most vigorous vent “black smoke” (mineral-rich fluid) >300°C and others are bathed in “white smoke”. The active chimneys are populated with bacterial mat and dense clumps of Riftia pachyptila with tubes as long as 1.5m. Abundant limpets, Bythograea thermydron and galatheid crabs, and the pink vent fish Thermarces cerberus were on and near the giant tube worms. Alvinellid worms were observed at 2 chimneys. Some cracks in nearby lava flows vented clear fluid and were populated with tubeworms or Calyptogena magnifica clams. Several chimneys exhibited signs of waning activity: dead tubeworms were still attached and only a minor portion of the edifice supported bacterial mat and live tubeworms.
Inactive chimneys are more numerous (48 were confirmed with ROV observations; 40 more were not visited but are presumed inactive, as turbid bottom waters were only observed in the vicinity of the active vents). Most are almost 10km NE of the Ja sít active field in a ridge-parallel array stretching 2.3km. These were deeper (to 2392m) and associated with older flows. Some had only recently ceased venting, as clam shell fragments and relatively fragile vent orifices were still present. Inactive chimneys are also intermingled with the active chimneys. Some of the recovered samples have abundant chalcopyrite, but most are predominantly zinc and iron sulfide.
Inactive chimneys stand tall in the AUV maps but as they are no longer venting, would not be detected by traditional water-column surveys. Elsewhere, however, sulfide-bearing sediments were also recovered, evidence of prior hydrothermal activity that would not be detected in the AUV maps. Features that could be mistaken for sulfide chimneys also appear in the maps, but morphology distinguishes them as lava pillars along margins of collapsed flows, fault blocks, pressure ridges, or steep summits of pillow mounds. (Up to list)
Abstract: An extraordinary lava pond complex is located on Axial Volcano’s distal south rift. It was discovered in EM300 multibeam bathymetry (collected 1998), explored and sampled with ROV Tiburon (2005), and surveyed with the MBARI Mapping AUV (2011). The ~1-m resolution AUV bathymetry shows a 6x1.5 km complex of 4 large and several smaller ponds with rims 57-95m above the floors. The combined volume before draining was 0.56km3. The ponds overflowed to build lobate-flow levees with elongate pillows draping outer flanks, then drained, leaving lava veneer on vertical inner walls and sheet flows on the floors. 14C-dated foraminifera from basal sediments on pond floors are ~1500yr. Levee rim depths vary by only 10m. Deep collapse-pits in levees suggest porosity of pond walls. The eastern levee of one pond breached, draining the interconnected ponds, and fed thick, rapidly-emplaced, sheet-flows along the complex’s east side. These sheet-flows extend at least 5.5km down-rift and have 19-33m deep collapses. Formation of these ponds requires long-lived, steady, moderate-eruption-rate lava effusion on nearly horizontal seafloor and may occur only on deep distal rift zones of central volcanoes. (Up to list)
Abstract: Exploration by submersible has been described as akin to dangling from a helicopter, at night, in a snowstorm, with a flashlight. Until recently, the divers were further hampered by not knowing where they were: the best bathymetric maps had resolution the length of a football field, and detailed maps could be constructed only after considerable investment in ship time to deploy and calibrate long baseline networks on the sea floor. Since then, maps have greatly improved with the use of high-frequency multibeam sonars flown close to the bottom, reliable navigation systems on the vehicles and surface ships, and sophisticated software to process the data.
Our submersible dives are now guided, and older dives reinterpreted, using 1-meter resolution maps made with the MBARI Mapping AUV. We have utilized this combo at 7 sites along NE Pacific mid-ocean ridges, 3 seamounts off California, and 2 back-arc volcanoes in the Lau Basin. Among these, on the northern Cleft Segment of the Juan de Fuca Ridge, four ROV dives were conducted over six years on a 30 km-long section of the ridge axis that was mapped with the AUV in two 18-hour surveys in 2009. Our experiences there will be used to illustrate advantages and challenges of studying the sea floor armed with better maps.
The AUV maps are at a resolution where individual sulfide chimneys, lava pillars, eruptive fissures, lava channels and flow margins can be distinguished. Inflated flows and tectonically faulted seamounts can be examined in detail. Characteristic progressions in flow morphology from eruptive fissures through collapsed channels to pillowed margins can be traced along lava flow units. Relative age relationships can be determined from truncations of flow channels and tectonic fractures. The ROV’s HD camera and array of samplers permit ground-truthing and refining of our interpretations of the maps. The mapped relationships of flows allow us to focus ROV sampling efforts and give wider context to the camera’s relatively small field of view. New features have been discovered due to the maps, for example, hydrothermal chimneys that had not been stumbled upon before.
While the great detail of the AUV maps is revolutionary, it is not enough to use just the one technique: distinguishing between lava channels and eruptive fissures sometimes requires visual observation; and map interpretation may indicate that there should be a contact between flows, but the contact can be too subtle for visual observation and must be confirmed with analysis of samples. A frustration has been that even well-calibrated ultra-short- and even long-baseline navigation has larger errors than the precision of the maps, so the maps must be relocated post-survey to GPS-navigated, albeit lower resolution, ship-based multibeam data. Also, an ROV’s ultra-short baseline location during a dive may appear to be offset from the map. A tremendous benefit is that by applying insights from the new maps to dives done prior to the maps, those older dive observations and samples become even more valuable though we were “wandering in the dark” at the time. (Up to list)
Interpretation of 1.5-m resolution AUV bathymetry using ROV observations and samples at Davidson and Rodriguez Seamounts,
Paduan, J.B., D. A. Clague, D. W. Caress, H. Thomas, D. Conlin, D. Thompson (2010) V11C-2302.
Abstract: The summits and upper flanks of Rodriguez and Davidson Seamounts off California were mapped at 1.5-m resolution by the MBARI Mapping AUV. The seamounts were built by episodic eruptions on abandoned spreading ridges 10-12 and 10-15 Ma, respectively. They consist of ridges and elongate cones that parallel the old spreading axes, yet have strikingly different summit morphologies. Video observations and samples from prior ROV Tiburon dives are used to interpret the textures revealed in the AUV data, and are extrapolated to make geologic maps of the seamounts. The summit of Davidson is rugged and studded with cones of three general classes: completely smooth cones with nearly circular bases, mounds elongated into subparallel ridges, and disorganized mounds of rounded shapes. The elongated mound ridge-lines are roughly rectangular in cross-section, and smooth apron-like slopes descend below. They and the smooth cones occupy the highest points on the seamount but also occur deeper, whereas the disorganized mounds occur only deeper. Smooth, flat pockets lie between the cones. The disorganized mounds were identified as pillow lavas during ROV dives. The mounds that form ridges are blocky ’a’a-like flows, probably oriented over eruptive fissures. Lava samples vary from basalt to trachyte, and there is no correlation between the presumed fluidity of the lavas and occurrence of pillows. The smooth aprons below the blocky flows, and presumably the smooth cones, are glass-rich, volcaniclastic debris produced by explosive activity above. The debris has bedding parallel to the steep slopes, and has lithified into pavement. Pelagic sediment has accumulated between the cones. An inflated flow drained at its distal end in a valley between two ridges; collapses in the flow have drainback veneers like bath-tub rings on the inner surfaces. The summit of Rodriguez has no cones, but they dot the flanks. They are smooth with nearly circular bases and mounds elongated into ridges with smooth aprons. Their shapes and sizes are similar to cones at Davidson. The summit is a broadly domed, smooth platform, with subtle contour-parallel steps on the margins. It is punctuated by small, irregular-shaped outcrops, one of which has a leveed channel emanating from it. Faults cross the platform and large and small landslide scars indent the rim. The smooth summit was identified during ROV dives to be horizontally bedded beach deposits of volcanic sand, and the summit outcrops to be degassed blocky lava flows eroded by wave action. Volcaniclastic debris is abundant on the cones and flanks downslope. Pillow flows do not occur in the AUV survey, but were observed with the ROV much deeper on the seamount. ROV samples and observations are consistent with Rodriguez having been subaerial while active, whereas Davidson may have erupted in shallow water but was not an island. The AUV maps clearly show the contrast between the morphologies of the summits, and the types of cones produced by different eruption styles. The summit shapes, eruption styles, and subsequent erosion were profoundly influenced by proximity to the sea surface millions of years ago. (Up to list)
Abstract: The MBARI mapping AUV D. Allan B. has now been used to map volcanic terrain at mid-ocean ridges, back-arc spreading centers, and seamounts. These include the summit caldera and upper south rift zone at Axial Volcano, the summit of Davidson Seamount, the Endeavour hydrothermal fields, the Northeast Lau Spreading Center and West Mata Volcano, and, most recently, the CoAxial, North Cleft and North Gorda historic eruption sites on the Juan de Fuca and Gorda Ridges. ROV and submersible dives at most of these sites have provided groundtruth for the textures and features revealed in the roughly 1-m resolution maps.
A prominent feature in the maps from four of the sites are inflated flows that did not deflate or drain. These resemble subaerial tumuli but differ in being located on level terrain, apparently atop or very near eruptive vents instead of being in the distal portions of flows.
The largest inflated flow at Axial Volcano is on the caldera floor. The main part is 500 by 300 m, and up to 30 m high, with a lobe that extends another 750 m in a sinuous path. It and two nearby, medium-sized inflated flows were first described from sidescan imagery and a submersible dive by Appelgate and Embley (Bull. Volcanol., 54, 447-458, 1992). The AUV maps show clearly the smooth, gently domed relief of the large inflated flow and its sinuous shape on the seafloor, the medium-sized nearby inflated flows, and several additional smaller ones. Particularly striking is a network of 4 to 10 m deep cracks along the crest of each inflation. The cracks occur 30 to 50 m from the margins on all sides of the wider parts of the inflated flows, and become medial cracks along the entire length of the narrow parts, which are nearly triangular in cross-section. An inflation pit 35 m in diameter has a depth equal to the surrounding lava fields. ROV Doc Ricketts dove on these flows in August 2009 and photographed the deeply cracked, uplifted, once flat-lying lineated and ropy sheet flows that form the inflated flows.
An even larger, 2.3 km long, up to 550 m wide, and up to 25 m high, inflated flow lies in the axial valley at North Cleft. Its cross-section is similar to the large one at Axial, but has been subsequently rifted by long tectonic fractures parallel to the axis of spreading. Five small inflated flows also occur within two large sheet flows at CoAxial.
An inflated flow at Davidson Seamount off California is 690 by 180 m, and stands 18m above the floor of a steep valley 430 m below the summit. It differs from all the others mapped in that downslope is a part of the same flow that has complex collapse features within pillowed margins. The lava composition here is viscous mugearite rather than MORB.
Inflated flows can generally be distinguished from old pillow mounds dissected by tectonic fractures by the smooth domed shape and cracks that are parallel to the outer perimeters or radiate toward the corners of lobes, but stop at the margins of the structure. Their topographically high and smooth but cracked morphology distinguishes them from inflated lobate flows that then drained to form lava pillars and collapsed roof terrain. (Up to list)
Abstract: Davidson Seamount is located 80 km off Big Sur, California, and rises from the 3500 m abyssal plain to 1254 m depth. The elongated volcanic edifice consists of a series of parallel ridges serrated with steep cones, built over millions of years above an abandoned spreading center. It has been explored and sampled with the ROV Tiburon, and the lithologic distribution, glass chemistry, and ages of the rocks are presented here. Large, bulbous pillow lavas are common deep on the seamount. The shallower cones are mainly composed of blocky flows that provide substrate for large corals and sponges. The cones are draped with volcaniclastic rocks ranging from sandstone to breccia as thick, layered pavements that are now eroded with pits and potholes. This fragmental material is evidence of explosive eruptions. A perched lava pond was discovered in high-resolution maps made by MBARI's Mapping AUV and explored with the ROV Tiburon. Nothing like it has been found elsewhere on Davidson or the other seamounts off the California continental margin. The pond lies between high ridges near the summit. It was a vigorous flow that overtopped its levees with elongate pillows, and then drained, leaving collapse pits a few meters deep veneered with "bathtub rings" and no lava pillars. Deeper than 2000 m, glass from pillow rinds and breccias are basalt and hawaiite. Shallower than 2000 m depth, the rocks include basalt and hawaiite, and also fractionated lavas of mugearite and trachyte. The lavas were all submarine erupted, even the fragmental material, as inferred from high sulfur content in the glasses. Ages of the lavas range from 9.8 to 14.8 Ma. The oldest rocks are along the central ridge, and the youngest rocks are on the flanks and southern end of the edifice. The volcano erupted onto much older crust, which is inferred to be 20 Ma from magnetic anomalies. The numerous small cones of disparate chemistry and long eruptive period suggest episodic growth of the volcano over 5 to 10 million years. (Up to list)
Abstract: The Vance Seamounts are a chain of near-ridge volcanoes located just west of the southern Juan de Fuca Ridge. The six volcanoes are built on ocean crust ranging from 0.78 Ma at the southeastern end to 2.55 Ma in the northwest. Morphologic analysis indicates that the volcanoes were constructed sequentially and get younger to the southeast towards the ridge axis. Like many near-ridge volcanoes, some of the Vance Seamounts have large offset calderas that presumably formed above evacuated shallow magma chambers within the upper ocean crust. In summer 2006, we completed 6 dives using MBARI's ROV Tiburon to study the formation of these calderas. The floor of each caldera consists of flat-lying volcaniclastite, under about 25 cm of pelagic sediment. Some caldera floors have mounds of post-caldera pillow flows. The caldera walls have a lower section covered by talus and an upper section of interbedded massive flows with columnar joints (to 11 m thick) and pillow basalts. The top of each caldera wall has a unit of volcanic mudstone to sandstone ranging from 20 cm to 2 m thick. The fine matrix of many of these samples is green hydrothermal clay. The finest siltstone to mudstone samples appear to be layers of massive tan hydrothermal clays. Talus fragments, lava and volcaniclastite outcrops are universally coated and cemented by 1 to 4 cm-thick deposits of hydrothermal Mn-oxide crusts, even on the youngest of the volcanoes. Volcanic particles in the sandstones are mostly dense angular glass, but bubble-wall fragments (limu o Pele) are present and indicate formation during low-energy pyroclastic eruptions. Without the few percent limu o Pele fragments, the glass fragments would resemble those inferred to form by quench granulation. We suggest that quench granulation is actually pyroclastic fragmentation that occurs as coalesced magmatic gas bubbles disrupt the molten lava surface at the vents. Our observations confirm that the more southeasterly offset calderas truncated thick flows that ponded inside older calderas to the northwest, as proposed based solely on morphology (Clague et al., 2000). The limu o Pele fragments in the volcaniclastic deposits on the rim and floor of the calderas demonstrate that the formation of each caldera was accompanied by pyroclastic eruptions. At the same time, the abundance of hydrothermal clays and thick Mn-crusts, and the wide dispersal of the glass particles show that discharge of voluminous warm hydrothermal fluids accompanied the pyroclastic eruptions and caldera collapse. Seawater apparently migrated down along the normal faults bounding the caldera and mixed with existing high- temperature hydrothermal aquifers within each volcano, leading to discharge of large volumes of mixed warm hydrothermal fluid. The hydrothermal clays and Mn-oxides precipitated directly from this plume of fluid. This focusing of hydrothermal fluid discharge along ring faults is similar to that observed in large silicic calderas. Each caldera collapsed during a brief time period since no volcaniclastic deposits were observed in any of the sequences in the caldera walls. Only a tiny percentage of the magma stored in the magma chamber prior to collapse erupted during the pyroclastic eruptions, so the vast majority must have been intruded into the ocean crust adjacent to the volcanoes, probably along still active ridge-parallel faults. (Up to list)
Abstract: The seamounts off the California continental margin, and those well offshore of California and Oregon that formed near mid-ocean ridges, are all constructed of basaltic lava flows and volcanic breccias and sandstones. However, explorations of these seamounts using dredges, and more recently, the remotely operated vehicle Tiburon, frequently recover rocks of a wide assortment of continental lithologies including gabbro, granodiorite, silicic volcanics, limestone, dolomite, and metamorphic rocks. These rocks are often rounded like river and beach cobbles, and the softer rocks are bored as by worms or bivalves. They are covered with manganese oxide crusts of thicknesses that range from a patina to several cm, approaching the thickness on the in-situ basaltic rocks. These rocks are often easier to collect than the basalts. We recognize these rocks to be erratics of continental origin. Erratics have been documented as being transported by icebergs at higher latitudes, but this mechanism is unlikely to be responsible for the erratics we have found as far south as 31.9 N. Three brief papers published by K.O. Emery from 1941 to 1954 proposed that such erratics found in many thick sections of fine-grained sedimentary sequences such as the Monterey Formation, were transported long distances by kelp holdfasts, tree roots, or in the guts of pinnipeds. We propose that these vectors also transport erratics to seamounts, where they have been accumulating since the seamounts formed millions of years ago. Those seamounts that were once islands would have intercepted even more erratics along their shorelines while they stood above sea level. We have recovered or observed such erratics on the Vance Seamounts; Gumdrop, Pioneer, Guide, Davidson, Rodriguez, San Juan, Little Joe, and San Marcos Seamounts; on the muddy bottom of Monterey Bay; and on Northeast Bank and along the Patton Escarpment at the western edge of the California Borderland. These locations are as far as 250 nautical miles from shore and extend along the entire west coast of the continental United States. Studies that fail to recognize the presence of erratics, even at temperate latitudes, may result in unrealistically complex interpretations of the regional geology. (Up to list)
Large Lava Pond Complex on the Juan de Fuca Ridge: an Effusive, Energetic Eruption that Drained Away
Paduan, J.B., Clague, D.A., Davis, A.S., Chadwick, W., Cousens, B.L., Embley, R.W. (2005) V51C-1511.
Abstract: We explored an unusually large, deep, drained lava lake complex on the south rift of Axial Seamount on the Juan de Fuca Ridge during three dives with the ROV Tiburon in August 2005. The complex of five large ponds, first identified from EM300 multibeam bathymetry, is 5 km long and more than 1 km wide. The ponds are separated from one another by narrow levees that rise about 90 meters above the pond floors. The levees are all about the same depth, which suggests that the ponds formed at the same time. The volume of the lake, prior to draining, was 0.2-0.4 km3, making it the largest lava lake known along the ridge system. The outer slopes of the pond levees are constructed of elongate pillows that flowed down the steep slopes. The rims are narrow, level plateaus of lobate flows with many collapses. The inner walls are vertical cliffs, overhanging in places, with horizontal shelves from the top of the levees down to the floors of the ponds. Left like bathtub rings, these shelves mark former surfaces of the lava pond as it drained away while the lava was still molten. In many places, this veneer has collapsed to reveal truncated lobate flows and pillows. The floor of one small pond was entirely talus blocks. However, the floors of the other, larger ponds had little talus and, instead, were vast expanses of thin broken crusts, lobate flows, and very fluid, chaotic, folded and jumbled sheet flows. The lavas from each pond have abundant large feldspar and rarer olivine crystals, suggesting that all were from the same eruption. This eruption apparently began with sheet flows whose advance was limited by topography. It then ponded and built up the levees that were left when the lava drained away. On the floor of one pond we found a deposit several meters tall that was delicate and difficult to sample, and turned out to be agglutinated spatter. Limu o Pele (lava bubble wall fragments) was abundant in all the sediment samples in and around the ponds. The spatter and limu demonstrate that the eruptions were magmatic-gas-rich and mildly explosive to the end, with strombolian-like bursts and even fire fountains, though such activity had been presumed to be impossible at 2300m depth. We did not find obvious signs where the lavas went that drained from the ponds. A delta-like fan of partially drained and collapsed lobate flows extended from breaches in two adjacent levees, but since the pond floors are considerably deeper than the breaches and delta surface, the lake must have drained elsewhere after it breached the levees. The ridge axis outside the pond complex is severely tectonized, with numerous faults, gaping fissures, and shattered lavas of similar, unusually feldspar-rich composition, so there is no evidence that the ponds drained down-rift. We propose that the drained lava was recycled back into a crustal magma chamber below the ponds. (Up to list)
Abstract: Lava flows of known age are rare on the mid-ocean ridge system. The only such flow on the Gorda Ridge erupted during an intense seismic swarm in Feb.-March 1996. We revisited the 1996 eruption site on the northern Gorda Ridge with the ROV Tiburon in August 2005. The lava flow, although less than 10 years old, has accumulated noticeable sediment, the glossy sheen on the pillow flow is now a dull finish, and sessile fauna have begun to colonize it. With more extensive surveys, we found that the flow is significantly smaller than originally proposed, consisting of a northern mound extending from 42.688 °N to 42.675 °N and a small southern mound centered at 42.67 °N, separated by about 1 km of older flows. A Tiburon dive in 2002 also shows that the hypothesized flow 5-7 km farther south is all older, so the 1996 eruption was limited to the two small pillow mounds. The northern mound is unusual in that it consists of a narrow 80-90m tall pillow ridge surrounded by talus at the base. In places the tall narrow pillow ridge has vertical to overhanging slopes consisting of elongate and truncated pillow flows. On the northern edge of the flow, the 1996 talus directly overlies older flows. The talus and surrounding older flows are peppered with angular glassy debris spalled from the pillow fragments as they tumbled down the steep slopes. The top of the pillow mound consists of lobate to rounded pillow forms. The eruption produced little pyroclastic debris, as limu o Pele (bubble-wall fragments) is rare in all sediment and suction samples from on and adjacent to the 1996 flow. Some of the talus at the base of the 1996 pillow ridge is elongate 'lavacicles' that formed when elongate pillows disgorged over vertical or overhanging slopes, forming cylindrical stalactite-like lava forms up to 2-3 m long, with glassy rinds that are wrinkled on a millimeter scale, in contrast to smooth glassy rinds on pillow toes. A tall narrow pillow mound with abundant talus at its base would usually be interpreted as tectonically modified by subsequent faulting, and would therefore be considered an older flow. In this case, however, the talus formed during the eruption and is therefore a constructional landform. Exploration of the flows adjacent to the 1996 flow found other similar structures that are also interpreted to be relatively young based on their thin sediment cover and poorly developed faunal communities. Such narrow, tall pillow mounds most likely form during very low-flux extrusion of lava and may be a common constructional landform on slow- to moderate-spreading ridges, such as the northern Gorda Ridge. (Up to list)
Abstract: Eleven ROV Tiburon dives in 2003 and 2004 explored Rodriguez and San Juan Seamounts, and Northeast Bank off southern California. Now submerged, these seamounts appear to have been subaerially exposed while the volcanoes were active. The summit of Rodriguez seamount, now at 630 m depth, is a smooth, gently domed platform. The shallowest points are low, rough hills standing above the platform and consist of thick, dense, degassed `a`a flows erupted and oxidized subaerially. Coarse bedded and cross-bedded sandstones and rounded cobbles interpreted to be beach deposits occur near the top of a major break-in-slope at about 700 m. Rodriguez stood at least 70 m above sea level and formed a small island 6.8 km2 in area prior to subsiding at least 700 m. The summit of Northeast Bank, now at about 360 m depth, is another smooth, gently domed platform. Wave-sculpted lava flows, sandstone, and pebbly conglomerate beach deposits were observed between 510 and 554 m depth, below the sharp break-in slope at about 500 m depth. Although the bathymetry of the entire summit is poorly known, Northeast Bank was a large island perhaps 200 m above sea level and 90 km2 in area. The summit of San Juan Seamount, now at 560 m depth, is a northeast-southwest trending series of rough ridges rather than a dome. However, subaerially oxidized `a`a-like lava flows were found above 700 m. San Juan's summit ridge emerged as a line of eight small islands with a total area of about 2.8 km2, and the tallest island rose 140 m above sea level. The 550 to 700 m of subsidence recorded by Northeast Bank within the California borderland, Rodriguez Seamount on the continental slope, and San Juan Seamount on the adjacent ocean crust occurred since these seamounts formed, most likely since the late Miocene. (Up to list)
Abstract: Pyroclastic submarine eruptions are generally considered to become less likely with increasing depth due to the increasing hydrostatic pressure of the overlying water column. Volcaniclastic deposits from the North Arch Volcanic Field, north of Oahu, have textural characteristics of explosive fragmentation. The presence of glass spheres and bubble-wall, spindle- and ribbon-shapes, or Pele's hair-like fragments, indicate at least mildly explosive eruptions occurred in water depths greater than 4200 m. Given the tectonic setting and young age of these deposits, there is no doubt that sampling depths closely corresponds with eruption depth. The most abundant volcaniclastic samples from the North Arch are clast-supported breccia of highly vesicular, angular clasts that most likely are near vent, pyroclastic deposits formed from eruption columns of limited height. Interbedded with highly vesicular pillow lava, they form steep-sided cones of low height (50 to 200 m) around the vent sites. Less common stratified samples with graded bedding, include one sample with a layer of imbricated, bubble-wall fragments that probably formed from density currents associated with the collapse of an eruption column. Numerous glass spheres, delicate spindle, ribbon and Pele's hair-like fragments as well as curved bubble-wall glass fragments resembling limu o' Pele occur in the finer size fraction of some samples. Another sample consists of glass fragments dispersed in a marine clay matrix that apparently was reworked and deposited farther from the vents by bottom currents. Glass compositions include low (~0.4%) and medium (~0.7%) K2O alkalic basalt, basanite, and nephelinite. Sulfur and chlorine are high reaching a maximum of 1800 and 1300 ppm, respectively. The ubiquitous presence of bubble-wall fragments regardless of glass composition suggests bursts of strombolian-like activity accompanied most eruptions. The coalescing vesicles observed in larger pyroclasts and some pillow lava suggest accumulation of gas, dominated by CO2, was driving the eruptions. Initial explosive eruptions apparently were followed by effusive eruptions that formed thin, degassed sheet flows that traveled long distances over nearly flat terrain. If these volatile-rich magmas had erupted in shallow water depth or subaerially, tall fountains would likely have resulted. The great hydrostatic pressure (>400 Pa) limited fountain and eruption column heights. (Up to list)
Abstract: Numerous seafloor sites have been discovered along continental margins where a supply of reduced inorganic compounds, such as hydrogen sulfide or methane, support chemosynthetic biological communities (CBC), authigenic mineralization, and early diagenesis. While CBC sites and authigenic carbonate deposits were initially viewed as rare, isolated occurrences, they now have been encountered along all continental margin segments where much of the seafloor has been visually imaged. The question being increasingly asked is whether these are actually common features along continental margins. Here, we report the first quantitative evaluation of the distribution of seafloor fluid seepage indicators along the California continental margin off Monterey Bay. A systematic analysis of dive videos and navigation from the 1,192 benthic ROV dives conducted by MBARI provides data on the occurrence and distribution of CBC and authigenic carbonates. These seepage indicators are common, occurring within 2% of the 25 m square grid cells within which there have been bottom observations within 45 km of the head of Monterey Bay, and within 9% of the visited cells that are below 550 m water depth. A surprising result is that the frequency of seepage indicators does not increase in known fault zones crossing Monterey Bay. Instead, these seepage indicators are most commonly observed on steep and recently eroded seafloor. (Up to list)
Abstract: The MBARI research vessel Western Flyer with the Tiburon remotely operated vehicle (ROV) spent 36 days at sea doing mainly geologic investigations offshore the Hawaiian Islands during March to May 2001. During these operational days we conducted 57 dives at depths ranging from 150 m to 3820 m and collected 1198 volcanic and carbonate rock samples; 185 sediment samples using sediment scoops, push-cores and short vibracores; and assorted megafauna. We occupied 32 closely spaced heat flow stations, and collected 167 water filtration samples for radium analysis. We also recorded about 280 hours of digital beta format video of the bottom. Heat flow and in-situ thermal conductivity was measured on the northwest flank of Oahu. The radium samples were collected during all of the dives east of Oahu by filtering about 200 liters of seawater on the ROV using a new pump/filtration system. The dives addressed a range of research topics that can be roughly subdivided into four groups.Volcanologic observations and petrologic sampling of constructional volcanic features were done on eruptive fissures on the Kohala terrace west of Hawaii, cones on Kilaueas Puna Ridge and the west rift of Kahoolawe, rejuvenated stage cones and flat-topped cones offshore Oahu, Kauai, and Niihau, and postshield stage cones offshore Niihau. The analyzed lavas from the Puna Ridge are tholeiitic basalts with 4.8-6.4/% MgO. The samples from the west rift of Kahoolawe are submarine-erupted, high-SiO2, tholeiitic basalt and tuff. The analyzed rejuvenated and postshield stage lavas and tuffs are alkalic and submarine erupted.
The subsidence history of the islands and paleoclimatic history were addressed by sampling old shoreline feature such as drowned coral reefs and drowned beaches. Dives with this objective were done on six terraces on the Kohala terrace, one on East Kohala, four south and southwest of Lanai, one north of Molokai, one south of Oahu, one on the Kaena Ridge, and one northwest of Niihau. We recovered corals from most of these locations and reef limestone from all but the Kaena Ridge dive.
We explored the origin of submarine canyons northeast of Oahu, north and south of Molokai and east of Kohala. A related objective was to examine several deep plunge pools that occur at the base of the steep slope below the break-in-slope that marks old shorelines. These topics are covered in other abstracts at this meeting.
The structure of the flanks of the volcanoes, mainly associated with the headwalls of giant landslides, was investigated during dives on the south Kona slide, east of Kohala, north of Molokai, west of Oahu on a block in the Waianae landslide, and on the northwest flank of Niihau. The analyzed samples are mostly pillow breccia and hyaloclastite composed of subaerially-erupted tholeiitic basalts, although submarine-erupted lavas occur at the base of the Waianae slide block and the slope of Molokai.
Video highlights of the dives and preliminary results will be presented. (Up to list)
Abstract: Eight progressively deeper reefal terraces off the northwest coast of Hawaii have terrace tops at about 150, -400, -585, -690, -900, -1150, -1225, and 1300 m depth. The terraces formed over the past 600,000 years on a flank of Hawaii that is subsiding at about 2.4-2.6 mm/yr; the higher rate closer to the island, so the terraces are tipped slightly towards the southeast. The stratigraphy and morphology of the terraces should constitute a high-fidelity record of sea-level fluctuations over this time period. Terraces at about 150, -400, and 1150 m formed robust complexes with barrier reefs and lagoons whereas those at 585, -690, and -900 m are mainly lava flows and volcaniclastic rocks capped by thin coral reefs. The 1150 m reef has a narrow shelf at -1175 m and a broader terrace at about 1150 m. Corals collected with the ROV Tiburon include Porites lobata, P. compressa, P.evermanni, Lepastrea purpurea, and species of Pocillipora, Montipora, and Fungia suggesting shallow water environments. The corals occur on the reef surfaces in growth position and as outcrops of bafflestone and boundstone. Along the ROV traverses, most of the carbonate rocks are sandstone and fine-grained algal and bioclastic limestone. Outcrops are deeply pocked, probably by a combination of bio-erosion and dissolution.
Computer models of the formation of these reefal platforms on a subsiding slope using the OJ96 sea level curve broadly agree with multibeam bathymetric and ROV sample data but fail explain the terrace at 585 m and the lower step in the 1150 m terrace. The models suggest reef construction during periods when eustatic sea level was falling at, or a little more slowly than, island subsidence. Coral samples recovered from the tops of the shallowest 6 terraces have variable amounts of secondary cement that may have formed during brief episodes of emergence when eustatic sea level was falling more rapidly than subsidence.. Emergence is also suggested by the set of longitudinal and transverse dune- or beach-ridge forms topping the 400 m terrace and enclosing box-like (karstic) depressions about 30 to 50 m deep. The final drowning of each platform occurred as sea level rose rapidly at the onset of interglacial periods. (Up to list)
Abstract: Thorough documentation of specimens enhances their long-term scientific value. In practice, however, it can be difficult to ensure that accurate information is recorded at the time of collection, and specimens risk becoming worthless because too little is known about them. To address this problem, MBARI has developed a system to capture collecting event information and automatically populate a specimen database for our biological and geological samples. Specimen collecting events are observed with a video camera on our research submersible. The video is transmitted in real-time to the support ship, where it is recorded, time-stamped, and annotated. Following the dive, a script merges annotations of samples with navigation data, digital still images from the video, and ancillary sensor data. It also generates an HTML form that lists the samples with the corresponding data in a table and loads the data into the specimen database on shore. The specimen database manages not only this collecting event data, but also the associated hazardous material, storage, citation, and loan information, and can be queried over the web. The timely capture of collecting event information, ease of merging disparate data sets, and availability of data over the web ensure that valuable specimen information is widely accessible and not forgotten. (Up to list)
Abstract: At MBARI, we measure and observe oceanographic phenomena with a variety of instruments. The large, diverse data sets we collect will be more easily analyzed if they can be viewed in an integrated way.
In this collaborative project between MBARI and the Naval Postgraduate School, we are developing visualization tools to create richly detailed, three-dimensional objects and imagery from our ROV (Remotely Operated Vehicle) dives. Following each dive, a post-dive VRML creator will combine the data collected on the dive into a three-dimensional (3D) virtual world.
This technology will enable scientists and submersible operators to view dive sites on a larger scale than possible through the camera's eye and merge this view with archived data and images. Our goal is to make these virtual worlds compelling, efficient, and user-friendly. They also can be used to transfer our results to a worldwide audience because they are viewed within a web browser. (Up to list)
Abstract: The MBARI Sample Archive was established in 1997 to manage at an institutional level the specimens collected for individual marine research projects. Since then, improvements to the ways specimens are stored and their data are managed have been implemented. A wet-collections storage and lab facility has been constructed, specially designed to comply with strict local codes for earthquake and hazardous material safety. A collections policy and curation procedures have been drafted and are on the web. Finally, a data management system has been developed to capture specimen collecting event information, manage the archive inventory, and make this information available over the web. These improvements provide the framework to operate the archive and the tools that enable research teams to participate in the curation and documentation of the specimens. (Up to list)
Abstract: Authigenic carbonate associated with modern "cold seep" biological communities and their extinct analogues exhibit a broad range in stable isotope and mineral composition within the limited geographic area of Monterey Bay. Although such variations in ancient samples have been used to infer differing tectonic settings, these carbonates all formed within a faulted continental margin environment and chemical variations reflect local differences in the sources and flux of carbon to sediment pore fluids. The slow seepage of fluid, and with it dissolved carbon, along the transform-faulted continental margin results in discrete areas of enhanced microbial sulfate reduction, oxidation of methane from both biogenic and thermogenic origins, as well as the active precipitation of both high-Mg calcite (HMC) and dolomite. The authigenic carbonates include semi-continuous pavements of shallow cemented sediments surrounding benthic communities; circular or pipe-like "chimneys" interpreted as cemented conduits formed as a result of methane gas expulsion; centimeter- to meter-scale rings, doughnuts or slabs winnowed from variable depths within sediments; and carbonate veins (ankerite or calcite) or cements in faulted basement rocks draped with bacterial mat. Abundant pyrite framboids, preferentially filling the tests of the benthic foraminifer Uverigerina peregrina and characteristic of the HMC-bearing samples, are products of a zone of shallow microbial sulfate reduction, a process fundamental to the nourishment of the chemosynthetic cold seep communities.
Sites on a sedimented ridge west of the San Gregorio Fault Zone have carbon isotopic values between -35 to -56 that are strongly influenced by carbon derived from methane. The higher values are found closer to the active fault zone. Carbonate from sites within the San Gregorio Fault Zone or from Monterey Canyon floor exposures of Miocene sediments have carbon isotope values between -7 and -26, that are mixtures of sedimentary organic carbon and microbially oxidized hydrocarbons from organic-rich, petroleum source rocks. Dolomite-bearing samples have higher values of both d18O and d13C. High values for d18O (d18O >3.5) result from the abundance of authigenic dolomite and low temperatures of formation. Local destabilization of clathrates might also create pore fluids with high values of both d13C and d18O. (Up to list)
Abstract: Seasonal profiles of marine aggregate abundance and in situ sinking rate experiments were carried out using a uniquely instrumented ROV platform in the midwater column of Monterey Bay California between 1991 and 1994. Variations of an order of magnitude in the midwater 100-500 m abundance of aggregates within the 0.5 to >5 mm size range were observed on an inter- and intra-annual basis at the study site. Maximum midwater aggregate abundances of 15-40 aggregates per liter were common during the 1991 spring/summer upwelling season, with values of less than 5 aggregates per liter being more typical of the non-upwelling winter months and the 1992 El Nio period. Midwater aggregate peaks represented the temporal signal of sinking aggregate material produced in the overlying waters, with no correlation observed between the vertical distribution of aggregates and the density structure, or the relative suspended particle abundance measured as cp. Additionally, significant injection of aggregate material to the midwater profiles via lateral advection was not evidenced by the combined aggregate, hydrographic, and physical flow data sets obtained simultaneously at the study site. In situ aggregate sinking rates were measured using an ROV-mounted settling chamber. Mean rates ranged from 16.3 to 25.5 m/day with a trend of increasing sinking rate with aggregate diameter observed. An analysis of aggregate shape showed a decrease in spherical shape with increasing aggregate diameter and sinking rate. Seasonal aggregate POC fluxes as 450 m for 1991-1992 were calculated from the in situ aggregate property data sets to compare with coincident, 450 m trap-measured POC fluxes. The calculated aggregate POC fluxes ranged from 26.3 to 481.2 mgC/m2d and were at least 1.5-2 times greater than the trap POC fluxes, with the exception of the non-upwelling winter months where values are similar. Trapping efficiency and interannual variations in aggregate sinking rates are believed to explain the differences between the aggregate and trap-based POC fluxes.
Abstract: In order to quantify the role of coastal upwelling regions as source or sink areas for carbon, the relationships between particulate organic carbon (POC) production, export, remineralization, and accumulation were examined in Monterey Bay from 1989 through 1992. During a normal upwelling year (1989-1990), a high positive correlation (r = 0.91) is observed between biweekly production and POC export at 450m. Primary production values range from 500 mgC/m2/d during the winter, to 2600 mgC/m2/d in the spring and summer upwelling months. Corresponding deep-water (450 m) POC fluxes vary from a minimum of 10 mgC/m2/d in December, to 120 mgC/m2/d in May. In contrast, the mid-1991 through 1992 data sets obtained during the '91-'92 El Nino period show a relatively poor correlation (r = 0.23) between productivity and carbon export. Calculated ratios of POC export to POC production (defined as e-ratios) display a trend for the three-year data sets in which the e-ratio values are greatest during periods of low productivity and decrease to minimal values when surface production is high. Upwelling-induced, offshore Ekman transport of organic matter and probable seasonal changes in planktonic community structure are mechanisms likely to be responsible for the e-ratio trends. Based on the data sets reported from this work, a simple box model of the annual export and regeneration of particulate organic carbon is presented for the Monterey Bay region. An appreciable advective and/or recycling "loss" from the euphotic zone of 362.8 gC/m2/y is estimated, representing primarily algal material transported offshore and/or recycled within the upper 100 m of the water column. Annual mid-water (~100-450 m) and deep-water (>450 m) POC remineralization rates of 71.8 gC/m2/y and 7.2 gC/m2/y, respectively, are reported for Monterey Bay. The average POC rain rate to the underlying slope sediments is sufficient to satisfy reported benthic utilization requirements without invoking an additional input source of POC via deep lateral advection and/or downslope movement of particulate material. (Up to list)
Abstract: The mucus feeding structures or "houses" of the giant larvacean Bathocordaeus provide abundant material for the study of deep-sea detrital communities, particularly their poorly known zooplankton associates. We sampled houses between 100 and 500 m in Monterey Bay with a submersible ROV (remotely operated vehicle) and surveyed houses for metazoans by database search of video footage taken from the ROV. Up to an order of magnitude more metazoans were found on houses than in the surrounding waters. On average, copepods constituted as much as 96% of the assemblage on houses, and many of the species possess benthiclike morphology and feeding strategies. Poecilostomatoid copepods (genus Oncaea) averaged as many as 64.6 house-1, and scarcely known calanoid copepods (genus Scopalatum) occurred in 56% of the samples. Higher numbers of metazoans occurred on shallower houses (100-300m), likely due to a difference in the species of larvacean present and (or) to reduced oxygen levels at greater depths. At least one copepod species, Scopalatum vorax, occurred on houses more frequently during the non-upwelling season, possibly due to the lack of other food. Our results suggest that midwater detritus contains a unique invertebrate community that has been largely undetected, mostly due to sampling difficulties. The houses also provide benthiclike habitats for midwater zooplankton and serve as feeding centers. These particle-associated zooplankton may therefore contribute to remineralization of particulate organic carbon at depth. (Up to list)
Abstract: Carbon from glucose and leucine added at natural concentrations to seawater was biologically transformed to higher molecular weight (mol. wt) dissolved materials which persisted through 6 months of incubation. At the end of incubation, the amount of carbon in high mol. wt dissolved fractions was approximately equal to the amount of carbon incorporated into particulate fractions. In tests of their resistance to biological utilization, only 1-17% of the higher mol. wt materials were respired when re-incubated with seawater microbial populations, whereas 40-75% of the monomers were respired over the same time span. In situ transformations of biologically available carbon may be an important source of refractory dissolved organic carbon in the oceans. (Up to list)
Abstract: Conventional techniques are unsuited for measuring the viscosity of seawater when organisms, particles, or surface-active organic materials are present. We have adapted a fluorescence depolarization technique to measure intrinsic solution viscosity and find that all of the factors listed can influence seawater viscosity. The technique, which determines viscosity by measuring the rotational freedom of fluorochromes added to seawater, is accurate in the presence of seawater particles and organics and requires only small volumes, making it useful for samples taken from locations or under conditions in which influences of viscosity on molecular-scale processes may be important.(Up to list)