Faults, Vents, and Seeps Logbook
Leg 5, Day 3: Pet rocks
March 28, 2012
Today we made two dives on either side of one of the faults that intersects the Gulf of California. We again collected vibracores and push cores.
We picked up rocks that were on both sides of the fault, confirming they had similar lithologies which suggested there was well over a kilometer offset of this feature. Each side of the fault had a very distinct lithology, separated by the trough. We collected a green volcanic rock covered in sponges and nereid and serpulid worms that probably came off the flank of the margin farther to the west. We also collected two beautiful deep-water limestones. Limestones are made up of skeletal remains of animals that have lived and died in the oceans and are partly crystallized pelagic sediments.
The only reason we were able to sample these rocks is because the faulting exposed them. Because of their biological origin, we will be able to date these rocks and they will help us to infer the geological history of this region. One of most the interesting things is that no one knows what types of rocks are in the flanks of the fault zone; this area is largely unexplored. Geologists have used drop cores to collect a few previous samples, but sampling with the remotely operated vehicle (ROV) gives us a much more precise way to sample the topology of the seafloor.
The sediment at these sites was also strange in that we were unable to take any complete vibracores. Most cores only penetrated about a meter before the stiff mud stopped the core from going any deeper. During the core processing, we found muddy aggregates in the smaller push cores. Once sieved, these aggregates appeared similar to the rock we collected and didn’t disintegrate even when we used the sonicator—a tool that uses sound energy to disrupt or agitate particles—to break it up. This is very different from the softer sediments we collected at the other sites.
One of the rocks we collected had beautiful lamini (layers of sediments). Tomorrow we will return to the site to find where the deeper sedimentary layers outcrop onto the seafloor and try to get a core into one of these outcropped layers.
On the descent of our second dive we happened upon Vampyroteuthis infernalis, or the vampire squid. This animal is not only cool looking, but also interesting because it is a living ancestor to both squid and octopus. These animals are known for living in the oxygen minimum zone (OMZ) and are typically found in the Monterey Bay around 500 meters (1,620 feet) depth—the OMZ in the Monterey Bay is around 500-700 meters depth. Today, the “vamp” we encountered was at nearly 1,100 meters (3,600 feet). This is probably due to the much wider OMZ found in the Gulf of California, which extends from about 400-1,100 meters depth.
It was fun transiting along the fault; it was covered by deep-sea corals, anemones, brittle stars, and seapens. Bonus: it was geologically interesting!
See below for a Spanish translation of today's log, courtesy of Juan Carlos Herguera
3er Día: Rocas preferidas
Hoy realizamos dos inmersiones a ambos lados de las grandes fracturas que disectan el Golfo de California y colectamos una vez más vibra-núcleos y núcleos por empuje. La diferencia entre ambos es que los primeros son cilindros de aluminio de dos metros de altura que penetran en el sedimento por vibración de un motor que se abraza a la parte superior del cilindro. Mientras que los de empuje se obtienen con la ayuda de uno de los brazos mecánicos, sujeto al costado del vehículo de operación remota submarino (VOR o ROV en ingles, remotely operated vehícle). Esta es una operación delicada que realizan los conductores del VOR a veces hasta de mas de dos kilometros de distancia del VOR mediante un brazo articulado desde la sala de control que simula todos los movimientos que puede tener éste, otro día trataremos explicar la sala de control ya que merece un capítulo aparte. Imagina este brazo como una grúa de unos dos metros de extensión con varias articulaciones que permiten mover las pinzas que tiene al final en varias direcciones. En este caso toma los cilindros de acrílico, de 30 cm de longitud, por uno de sus extremos de una caja en la parte inferior del VOR, los levanta y mueve hasta el lugar elegido visualmente para el núcleo y los empuja verticalmente en los sedimentos, para después extraerlos y volverlos a la caja especialmente diseñada como contenedor y en la que volverán a superficie.
Con este brazo mecánico también recogimos rocas que encontramos a ambos de la gran fractura, confirmando que tenían litología similares lo que sugiere al menos 1km de desplazamiento. Ambos lados de la fractura separados por una depresión tienen una litología muy definida. Colectamos una roca volcánica verdosa cubierta por esponjas, gusanos Nereideos y Serpúlidos que probablemente proviene de uno de los flancos del margen hacia el occidente. También colectamos dos preciosas calizas del mar profundo. Estas calizas están formadas por restos de organismos con placas y caparazones calcíticos que vivieron en el mar y que durante su enterramiento recristalizaron parcialmente. La única razón por la que estas rocas están expuestas en el fondo y por la que pudimos colectarlas es porque la fractura las expuso. El origen biológico de estas rocas y los microfósiles que contienen nos pueden ayudar a su datación lo que nos va a permitir inferir la historia geológica de esta región. Una de las cosas más interesantes es que nadie sabe que tipos de rocas hay en los flancos de esta zona fracturada debido a que este área está prácticamente inexplorada. Anteriormente los geólogos han utilizado nucleadores de gravedad para colectar estas muestras. El muestreo que realizamos con el VOR nos proporciona una forma mucho más precisa para caracterizar la topografía del fondo oceánico al poder ver físicamente donde y lo que estamos muestreando.
Los sedimentos de estos lugares también eran extraños ya que no pudimos tomar ningún vibranúcleo completo. Todos los núcleos llegaban a penetrar menos de uno metro hasta que el lodo mas compacto y endurecido frenaba el avance del nucleador y teníamos que finalizar la operación. Durante el procesado de los cortos núcleos de empuje encontramos unos agregados lodosos que al lavarlos sobre un tamiz aparecían similares a las rocas endurecidas que habíamos colectado y que no conseguimos disgregar incluso sumergiéndolas en un sonicador, otra muestra de lo diferentes que eran estos con respecto a los que habíamos colectado anteriormente.
Una de las rocas que colectamos mostraba unas laminaciones muy finas, un tipo de estratificación que requiere de unas condiciones muy especiales durante su formación, y que al mismo tiempo mostraba los efectos de una recristalización importante lo que nos sugiere su transformación probablemente por procesos de flujo de fluidos y calentamiento durante el enterramiento. Mañana vamos a intentar volver al lugar en el que observamos el afloramiento de las rocas mas profundas en el piso oceánico y colectar núcleos de una de estas capas claramente visibles en las líneas sísmicas.
Durante el descenso de la segunda inmersión nos cruzamos con un Vampyroteuthis infernalis, una forma muy educada de denominar al calamar vampiro. Este animal no solo se ve bien chido, sino que además es el ancestro sobreviviente de los calamares y los pulpos. Otra lindeza de estos animales es que les gusta vivir en las zonas del mínimo de oxígeno (ZMO), profundidades intermedias del Pacífico Nororiental características por sus bajísimas concentraciones de oxígeno disuelto en el agua, y que en la bahía de Monterey se encuentra a unos 500 metros de profundidad. En esta inmersión encontramos al vampiro a unos 1,100 metros de profundidad debido a que en el Golfo de California esta ZMO abraca en general entre los 300 a los 1,000 metros de profundidad.
A lo largo de nuestro agradable paseo a lo largo de esta gran fractura pudimos admirar numerosos corales de mar profundo, Swiftia kofoidii, anémonas, y frágiles estrellas de mar y blancas esponjas de formas caprichosas creciendo sobre las rocas que aparecían dispersas sobre un fondo geológico fascinante.
R/V Western Flyer
The R/V Western Flyer is a small water-plane area twin hull (SWATH) oceanographic research vessel measuring 35.6 meters long and 16.2 meters wide. It was designed and constructed for MBARI to serve as the support vessel for ROV operations. Her missions include the Monterey Bay as well as extended cruises to Hawaii, Gulf of California and the Pacific Northwest.
ROV Doc Ricketts is MBARI's next generation ROV. The system breaks new ground in providing an integrated unmanned submersible research platform, with many powerful features providing efficient, reliable and precise sampling and data collection in a wide range of missions.
MBARI's heat-flow probe is mounted on the side of the ROV Doc Ricketts inside the vertical stainless steel box. This both protects the delicate probe and provide the track so that the probe can be inserted into the sediment along a totally straight path. The probe contains five high precision platinum sensors which are used to measure the vertical temperature gradient in the sediments. This gradient along with some knowledge of the heat capacity of the sediment allows scientists to calculate the rate of heat loss from the sediments into the ocean.In situ gas sampler
These are devices that are used to collect and sample gaseous gases bubbling out of seafloor vents. The way they work is by having small pressure vials (like tiny scuba tanks) from which the air is pumped out with a vacuum pump on the surface and sealed with the valve. On the bottom gases are captured underneath an overturned funnel so that a large gas headspace is developed. Then the value on the pressure vial is opened, gas is sucked into the vial, and the vial's value is re-closed. This way a sample of the gas at the high seafloor pressures is recovered.In situ ultraviolet spectrophotometer (ISUS)
The ISUS is a sensor used to measure concentrations of dissolved chemicals directly from their Ultraviolet Absorption Spectrum. A variety of chemicals absorb light in the UV and each of these chemicals has a unique absorption spectrum. We can determine the concentration of these chemicals directly, with no chemical manipulation, by measuring the absorption spectrum of seawater in the UV and then deconvolving the spectra to yield the concentration of each component. ISUS has been used to determine nitrate concentrations while deployed on CTD/Rosette profilers, undulating towed vehicles such as a SeaSoar or SeaSciences Acrobat, and on deep-sea moorings. It has also been used to measure sulfide flux from cold seeps in Monterey Bay while deployed on the ROV Ventana.
A push-core looks like a clear plastic tube with a rubber handle on one end. Just as its name implies, the push core is pushed down into loose sediment using the ROV's manipulator arm. As the sediment fills up the core, water exits out the top through one-way valves. When the core is pulled up again, these valves close, which (most of the time) keeps the sediment from sliding out of the core tube. When we bring these cores back to the surface, we typically look for living animals and organic material in the sediments.
Vibracoring is a common technique used to obtain samples from water-saturated sediment. These corers work by attaching a motor that induces high frequency vibrations in the core liner that in turn liquefies the sediment directly around the core cutter, enabling it to pass through the sediment with little resistance.Gravity corer
Device lowered off the ship to the seafloor on a wire which consists of a long tube that extends below a moderately heavy weight. When the device encounters the bottom, the weight forces the tube into the sediments. When it is pulled out of the bottom the tube will contain a sediment sample (i.e., core) of the upper layers of the ocean floor.
R/V Western Flyer
ROV Doc Ricketts
Leg 5 Research Team
Charlie Paull has been a marine geologist and geochemical stratigrapher at MBARI since January 1999. The central theme of Charlie's work involves investigating the fluxes of fluids and gases through continental margins. Over the past decade his primary focus has been gas hydrate research on the Blake Ridge gas hydrate field on the continental rise off of southeastern North America. Assessing the global distribution of gas hydrate and interstitial gas is a continuing interest as well as the development of new techniques to detect the presence of gas hydrate in marine sediments. Charlie's other ongoing work is focused on the geology associated with seafloor seepage sites, including investigating the deposits associated with chemosynthetic communities, determining the processes that occur at the methane-sulfate boundary, and understanding the origin of pockmarks and other potential seafloor fluid venting sites.
Ken's research interests are focused on the development of new analytical methods for chemicals in seawater and application of these tools to studies of chemical cycling throughout the ocean. Over the past 15 years, Ken's Chemical Sensor Program at MBARI has developed a variety of sensors and analyzers that operate in situ to depths of 4,000 meters. These instruments have been used to study processes ranging from the distribution of sulfide in deep-sea hydrothermal vent systems, to nitrate in coastal ponds surrounded by intensive agricultural activities.
Krystle Anderson is a research technician working for Charlie Paull in the Continental Margins Lab. Krystle's background is primarily in the acquisition and processing of seafloor mapping data. She came from the California State University, Monterey Bay Seafloor Mapping Lab where she obtained her data processing and Geographic Information System (GIS) skills. Krystle spends a majority of her time processing and creating high-resolution maps of multibeam data collected from the mapping AUV. The high-resolution maps Krystle helps create will then be used to aid navigation for the ROV to explore particular areas of interest. On this expedition Krystle will assist with running the GIS system, and processing and cataloguing sediment samples and vibracores. This is Krystle's second research expedition with MBARI and she is very excited to be involved in this expedition.
Roberto is a geochemist by training. His interests lie at the intersection of marine geology and sediment and water chemistry. During cruises Roberto operates a custom-built, portable chemistry lab that includes a complete set of analytical platforms for measurements of fluids and gases. On this expedition, Roberto will be responsible for analytical measurements of pore water chemistry on samples taken from sediment cores. He will also be in charge of collecting gas samples emanating from fluid vents and performing hydrocarbon analyses on dissolved gases collected from pore waters, from gas vents and from seawater.
Eve Lundsten works with Charlie Paull in the Continental Margins Lab. Eve's background is in hydrology but she uses her technical and mapping skills to help understand the processes that create the morphology we see on the seafloor. The Continental Margins Lab uses high-resolution, AUV-collected bathymetric maps to help direct research to the precise location of interest on the seafloor where samples can be collected for further analysis. Eve's responsibilities on this cruise include running the GIS mapping system, assisting with the processing of vibracores, and push cores collected on ROV dives, and documentation of the many samples collected during this leg of the cruise. Eve is very excited to participate in this cruise and is looking forward to many exciting discoveries.
Shannon is a molecular ecologist. This means she uses genetics to solve mysteries about how invertebrates like worms, snails, mussels and clams, who live at hydrothermal vents, cold seeps, wood, and whale falls move around in the deep sea. These environments act like islands in the ocean because most of the animals that inhabit these environments depend on chemosynthetic bacteria for food. The reducing environments provide mineral-rich water that feed the bacteria, creating an abundance of life. On the cruise, Shannon will be responsible for collecting, identifying, and dissecting invertebrates as well as filtering water to study their larvae.
Susan von Thun
Susan works in the video lab at MBARI, where she is a senior research technician. Her primary role at MBARI is to help manage and annotate the remotely operated vehicle (ROV) video archive. Observations about the biology, geology, and equipment in ROV videos are logged using software designed by MBARI engineers called the Video Annotation and Reference System (VARS). On this expedition, Susan will use VARS to annotate and document video coming back to the ship from ROV Doc Ricketts. As one of the few biologists on this leg of the expedition, Susan will be busy identifying and processing biological samples.
Teresa has worked as a Logistics Specialist in the Division of Marine Operations at MBARI for 12 years. She has spent much of the past year planning and preparing for this expedition, including obtaining scientific permits from the Mexican government, scheduling the science missions and port stops, arranging for services during port stops, and arranging visas for the scientists. During this expedition Teresa will help process samples collected with the ROV, assist in the ROV control room with video tapes and frame grabs, and other science tasks. Teresa is very excited to sail as a member of the science team and will no doubt learn a lot from both marine operations and science perspectives.
Brian specializes in sedimentary processes and stratigraphy, integrating insights gleaned from seafloor rock and sediment samples with information from remote-mapping products, such as close-up photographs of the seafloor, high-resolution bathymetric maps, and seismic-reflection profiles. His recent studies have focused on how sediment moves from the land to the deep sea, processes controlling submarine landslides, saltwater intrusion into coastal aquifer systems, marine pollution, seafloor habitats, and the Cenozoic history of the Arctic Ocean.
Juan Carlos Herguera
Juan Carlos is interested in the history of past oceans, how changes in climate and ocean circulation contribute to the ecology and biogeochemical cycling sustained by coastal environments in the California Current and the Gulf of California regions. During this cruise he will be involved in sampling benthic foraminifera to help characterize their genomic information, and, through their stable isotopic and metal compositions, to understand how these geochemical markers reflect their ambient conditions. He will further use planktonic foraminifera for dating the deep-sea cores with radiocarbon techniques, which hold important clues on the tectonic rupturing rhythm along the boundary between the North American and Pacific plates. He is fascinated by these new observation windows opened up by the ROV deployed from the Western Flyer, making possible the discovery of new vent environments along these fractured boundaries and the chemosynthetic oasis sustained by these leaky enclaves that connect the deep ocean with the lower crust and mantle dynamics.
Mary's interests focus on using microbiota (primarily foraminifera but also pollen) to investigate marine sediment transport, geohazards (faulting, landslides and paleotsunamis), climate change, and the pathways and impact of invasive species introductions using sediment records and molecular analysis techniques. She also uses foraminifera in biomonitoring marine pollution sites and carbon-14 chronostratigraphy—the study of the age of rock layers in relation to time.
Luis Arturo Terán Ortega
As a member of the Mexican Geological Survey (SGM), Luis has conducted extensive geological research and prospective surveying mining studies focused on detecting resources with potential economic value. In 2007, the Mexican government commissioned the Mexican Geological Survey to conduct prospective efforts over the entire Mexican territory and adjacent sea to identify potential energy resources such as gas, coal, uranium, and other strategic minerals. Luis is the Manager of Regional Exploration of SGM and his prospective studies encompass Sonora, the Gulf of California, the Baja California peninsula, and the territorial Sea in the Pacific Ocean. This is his first experience on a research cruise and he hopes to gain a better understanding of the richness of the Gulf of California environment from a geologic, biologic, and mineral resources perspective. Luis is very eager to learn from and collaborate with his peers from MBARI.