Publications and Technical Reports
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
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; doi: 10.1093/petrology/egm003. Abstract Article
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. Abstract Article
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. Abstract Article
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. Abstract Article
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. Abstract Article
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. Abstract Article
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 Article
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. Abstract
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
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., 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.
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. MBARI’s 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
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: 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.
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: 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)
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: 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
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)
Evidence that three seamounts off Southern California were ancient islands.
Paduan, J.B., Clague, D.A., and Davis, A.S. 2004.
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)
Pyroclastic fragmentation of alkalic lava in
abyssal depths at the North Arch Volcanic Field, Hawaii.
Davis, A.S, Clague, D.A., and Paduan, J.B. 2003.
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)
Distribution of seafloor seepage indicators under Monterey Bay,
California.
Paull, C.K., Schlining, B., Ussler, W., Paduan, J., Caress, D., Greene, H.G.
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)
MBARI’s 2001 Hawaii Expedition using the R/V Western Flyer and ROV Tiburon.
D.A. Clague, C.K. Paull, H.G. Greene, K. Jordahl, A.S.
Davis, and the shipboard Scientific Party. 2001.
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 Kilauea’s 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)
Stepwise reef growth, emergence and drowning
recorded on a rapidly subsiding margin, offshore Hawaii: the last 600,000
years.
Abstract: Clague, D.A, E.L. Winterer, C.K. Paull, J. Paduan, and D.C. Potts. 2001.
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)
Interactive 3D data visualization in Monterey Bay.
McCann, M., J.B. Paduan, and D. Brutzman. 1999.
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)
Progress in establishing a new natural history
collection.
J.B. Paduan, 1998.
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)
Cold-seeps and authigenic carbonate formation in
Monterey Bay, California.
Stakes, D.S., D. Orange, J.B. Paduan, K. Salamy, and N. Maher. 1999.
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)
Spatial and temporal dynamics in marine aggregate
abundance, sinking rate and flux: Monterey Bay, central California.
Pilskaln, C.H., C. Lehmann, J.B. Paduan, M.W. Silver, 1998.
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 Niño 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.
Carbon cycling in the coastal upwelling
system of Monterey Bay, Central California.
Pilskaln, C.H., F.P. Chavez, J.B. Paduan, R.Y. Anderson and W.M. Berelson, 1996.
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)
Mid-water zooplankton communities on
pelagic detritus (giant larvacean houses) in Monterey Bay, California.
Steinberg, D.K., M.W. Silver, C.H. Pilskaln, S.L. Coale, and J.B. Paduan, 1994.
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)
Production of biologically-refractory
dissolved organic carbon by natural seawater microbial populations.
J.E. Brophy and D.J. Carlson, 1989.
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)
Techniques of fluorescence
depolarization for measuring seawater viscosities.
Carlson, D.J., L.E. Morrill, and J.E. Brophy, 1987.
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)