Dwight F. Coleman

Structure of the Dead Sea pull‐apart basin from gravity analyses

Analyses and modeling of gravity data in the Dead Sea pull-apart basin reveal the geometry of the basin and constrain models for its evolution. The basin is located within a valley which defines the Dead Sea transform plate boundary between Africa and Arabia. Three hundred kilometers of continuous marine gravity data, collected in a lake occupying the northern part of the basin, were integrated with land gravity data from Israel and Jordan to provide coverage to 30 km either side of the basin. Free-air and variable-density Bouguer anomaly maps, a horizontal first derivative map of the Bouguer anomaly, and gravity models of profiles across and along the basin were used with existing geological and geophysical information to infer the structure of the basin. The basin is a long (132 km), narrow (7–10 km), and deep (≤10 km) full graben which is bounded by subvertical faults along its long sides. The Bouguer anomaly along the axis of the basin decreases gradually from both the northern and southern ends, suggesting that the basin sags toward the center and is not bounded by faults at its narrow ends. The surface expression of the basin is wider at its center (<16 km) and covers the entire width of the transform valley due to the presence of shallower blocks that dip toward the basin. These blocks are interpreted to represent the widening of the basin by a passive collapse of the valley floor as the full graben deepened. The collapse was probably facilitated by movement along the normal faults that bound the transform valley. We present a model in which the geometry of the Dead Sea basin (i.e., full graben with relative along-axis symmetry) may be controlled by stretching of the entire (brittle and ductile) crust along its long axis. There is no evidence for the participation of the upper mantle in the deformation of the basin, and the Moho is not significantly elevated. The basin is probably close to being isostatically uncompensated, and thermal effects related to stretching are expected to be minimal. The amount of crustal stretching calculated from this model is 21 km and the stretching factor is 1.19. If the rate of crustal stretching is similar to the rate of relative plate motion (6 mm/yr), the basin should be ∼3.5 m.y. old, in accord with geological evidence.

Deepwater Archaeology of the Black Sea : The 2000 Season at Sinop, Turkey

In 2000, a major expedition for deepwater archaeology was conducted by the Institute for Exploration in the Black Sea along the northwestern coast of Turkey from the Bosporus to the Turkish seaport of Sinop. A complementary land-based expedition will be reported upon elsewhere. The 2000 underwater expedition had three research objectives: to search for evidence of human habitation prior to major flooding of the Black Sea that researchers predicted occurred some 7,500 years ago; to investigate a deepwater shipping route; and to search for ancient wooden ships in the seas anoxic bottom waters. Research methods included the use of a phased-array side-scan sonar, a towed imaging sled, and a small remotely operated vehicle (ROV) to collect deepsea survey data. Three shipwrecks and a probable site reflecting human habitation prior to the proposed flooding event were located at depths around 100m. One additional shipwreck was found within the anoxic layer at a depth of 324m. The ship found within the anoxic layer was intact, in a high state of preservation, and dated to the Byzantine period of 450 A.D. (Less)

Groundwater Plume Mapping in a Submerged Sinkhole in Lake Huron

A multidisciplinary exploratory project team from the Institute for Exploration, the Great Lakes Environmental Research Laboratory, Grand Valley State University, and the University of Michigan located and explored a submerged sinkhole in Lake Huron during September 2003. A CTD system and an ultra-short baseline (USBL) acoustic navigational tracking system integrated with an open frame remotely operated vehicle (ROV) provided high-resolution depth, temperature, and conductivity maps of the sinkhole and plume. Samples were also peristaltically pumped to the surface from a depth of 92 meters within and outside of the sinkhole plume. A 1-2 m thick cloudy layer with a strong hydrogen sulfide odor characterized the water mass close to the plume. Relative to ambient lake water, water samples collected within this layer were characterized by slightly higher (4-7.5 oC) temperatures, very high levels of chloride and conductivity (10-fold) as well as extremely high concentrations of organic matter (up to 400 mg C/L), sulfate, and phosphorus. Our observations demonstrated the occurrence of unique biogeochemical conditions at this submerged sinkhole environment. I N T R O D U C T I O N he Laurentian Great Lakes were formed about 10,000-12,000 years before present (ybp), and presently contain approximately 19% of the Earth’s surface liquid freshwater (Beeton, 1984). The Lake Huron Basin is mostly covered with a layer of glacial till, sand, silt and clay. Underlying these sediments are aquifers formed within Paleozoic (Silurian-Devonian) bedrock. These bedrock aquifers were laid down when the shallow seas still spread widely over the continental areas approximately 350430 million ybp. The Silurian-Devonian aquifer consists of carbonate, shale, and sandstone matrix with some evaporite beds, and has fresh and saline water, which can contain varying amounts of sulfates, chlorides and iron. Dissolution of the Silurian-Devonian evaporites has produced the major karst features (Olcott, 1992) such as the sinkholes discovered during the 2001 acoustic survey expedition (Coleman, 2002) conducted by the Thunder Bay National Marine Sanctuary and the Institute for Exploration. The sinkhole vents, producing a visible cloudy layer above the lake bottom (Figure 1), were a serendipitous discovery made during a 2002 remotely operated vehicle (ROV) survey of the sinkholes. Recharge areas of freshwater replenishment for the Silurian-Devonian aquifers have been documented on land in the Lake Huron basin; these areas are typically sinkholes (Figure 2). In this report, we discuss the mapping of the Isolated Sinkhole located approximately 10 miles from shore at a depth of 93 m in the north central region of the Thunder Bay National Marine Sanctuary during September 2003.

Design and implementation of advanced underwater imaging systems for deep sea marine archaeological surveys

During the summer of 2000, the Institute for Exploration (IFE) will conduct a major oceanographic expedition in the Black Sea. The main objectives are: (1) To search the shallow shelf along the north coast of Turkey for submerged evidence of ancient humans from more than 7000 years ago when the Black Sea was an inland lake 150 meters below present-day sea level; (2) To search the deep waters for ancient shipwrecks that may have well-preserved wooden structural components due to the anaerobic environment; and (3) to document with video and still images any archaeologically significant discoveries. Woods Hole Marine Systems Inc. (WHMSI) is developing a new suite of deep submergence vehicles and systems that will be devoted to IFEs marine archaeology expeditions in the Black Sea and elsewhere. Two underwater imaging vehicles have already been completed. The first, ARGUS, is an optical tow sled equipped with tilting underwater video and film cameras, HMI lights, an electronic still camera, thrusters to control heading, and a scanning sonar. In addition to its own imaging capabilities, ARGUS is also the depressor for LITTLE HERCULES, a mid-sized fully maneuverable imaging ROV designed to support a High Definition underwater video camera. Each vehicle will transmit real-time images of archaeological sites via a fiber optic umbilical cable to a control room on board the surface ship, where the imagery and data will be viewed, processed, analyzed, and archived. To supplement the lighting during the survey of an archeological site, WHMSI has also built a new offload lighting package.

First Evidence for the Presence of Iron Oxidizing Zetaproteobacteria at the Levantine Continental Margins

During the 2010–2011 E/V Nautilus exploration of the Levantine basin’s sediments at the depth of 300–1300 m, densely patched orange-yellow flocculent mats were observed at various locations along the continental margin of Israel. Cores from the mat and the control locations were collected by remotely operated vehicle system (ROV) operated by the E/V Nautilus team. Microscopic observation and phylogenetic analysis of microbial 16S and 23S rRNA gene sequences indicated the presence of zetaproteobacterial stalk forming Mariprofundus spp. – like prokaryotes in the mats. Bacterial tag-encoded FLX amplicon pyrosequencing determined that zetaproteobacterial populations were a dominant fraction of microbial community in the biofilm. We show for the first time that zetaproteobacterial may thrive at the continental margins, regardless of crustal iron supply, indicating significant fluxes of ferrous iron to the sediment-water interface. In light of this discovery, we discuss the potential bioavailability of sediment-water interface iron for organisms in the overlying water column.

Underwater archaeology in Thunder bay national Marine sanctuary, Lake Huron: Preliminary results from a shipwreck mapping survey

Off northeastern Lower Michigan, the bottom waters of Lake Huron in the Thunder Bay National Marine Sanctuary and Underwater Preserve (TBNMS/UP) contain a vast array of historic shipwrecks representing more than a century of early Great Lakes shipping. During June 2001, in collaboration with the National Oceanic and Atmospheric Administration (NOAA) and the State of Michigan, the Institute for Exploration (IFE) mapped a large portion of Shipwreck Alley, which extends throughout the deep-water portion of the Sanctuary and continues farther north. Seventeen shipwrecks, two of which are new discoveries, and many other interesting lakebed features were acoustically imaged and carefully surveyed using a high-frequency side-scan sonar towfish. In addition, a number of submerged sinkholes and lakebed pockmarks were discovered and mapped. These karst features in the limestone bedrock were exposed subaerially from about 10000 to 8000 years ago, when the lake level was substantially lower following the last glacial maximum. The archaeological significance of these sinkholes, the newly discovered shipwrecks, and several other promising sonar targets will be evaluated when IFE returns to TBNMS/UP in 2002. Using a remotely operated vehicle (ROV) and an advanced underwater imaging platform, we will visually survey the most important sites, collect high-definition underwater video, and ground-truth sonar targets. The work will be performed by marine geologists in collaboration with underwater archaeologists and maritime historians. This effort is part of a long-term scientific, educational, and public outreach project in the TBNMS/UP supported by NOAAs National Marine Sanctuary Program and Office of Ocean Exploration.

Hydrocarbon-related microbial processes in the deep sediments of the Eastern Mediterranean Levantine Basin

During the 2011 exploration season of the EV Nautilus in the Mediterranean Sea, we conducted a multidisciplinary study, aimed at exploring the microbial populations below the sediment-water interface (SWI) in the hydrocarbon-rich environments of the Levantine basin. Two c. 1000-m-deep locations were sampled: sediments fueled by methane seepage at the toe of the Palmachim disturbance and a patch of euxinic sediment with high sulfide and methane content offshore Acre, enriched by hydrocarbon from an unknown source. We describe the composition of the microbial population in the top 5 cm of the sediment with 1 cm resolution, accompanied by measurements of methane and sulfate concentrations, and the isotopic composition of this methane and sulfate (δ¹³C(CH₄), δ¹⁸O(SO₄), and δ³⁴S(SO₄)). Our geochemical and microbiological results indicate the presence of the anaerobic methane oxidation (AOM) coupled to bacterial sulfate reduction (BSR). We show that complex methane and sulfur metabolizing microbial populations are present in both locations, although their community structure and metabolic preferences differ due to potential variation in the hydrocarbon source.

SUBMERGED PALEOSHORELINES IN THE SOUTHERN AND WESTERN BLACK SEA — IMPLICATIONS FOR INUNDATED PREHISTORIC ARCHAEOLOGICAL SITES

During the course of six field seasons, from 1998 to 2003, groups from the Institute for Exploration (IFE) and, recently, the Institute for Archaeological Oceanography (IAO) at the University of Rhode Island Graduate School of Oceanography (URI-GSO) have conducted expeditions to the Black Sea for marine geological and archaeological research. These expeditions were conducted in partnership with groups from other institutions, including the University of Pennsylvania, Florida State University, Massachusetts Institute of Technology, the Institute for Nautical Archaeology at Texas A&M University, and Woods Hole Oceanographic Institution. Oceanographically, the Black Sea is a distinctive body of water with highly preservative anoxic bottom water and a submerged coastal plain that was exposed and possibly habitable for periods of time in the recent geologic past. Archaeologically, the Black Sea basin has a rich maritime-oriented history with a number of coastal and near-coastal sites around the present-day perimeter that contain important information about human history from Pale o ithic times to the present. Using a suite of deep submergence technologies, a deep-towed side-scan sonar and subbottom profiling system, an optical imaging towsled, and remotely operated vehicle (ROV) systems, we have discovered, surveyed, imaged, and sampled several interesting geological and archaeological sites that shed more light on the ancient natural and human history of the region. These include several well-preserved prehistoric shorelines presently submerged about 150 m below present-day sea level, a very well preserved wooden ship dating to Byzantine times about 1500 years ago, an amphora-laden trading vessel dating to the Hellenistic period about 2400 years ago, and a possible site of human habitation along one of the ancient shorelines that was inundated during the Neolithic period more than 8000 years ago.

Mapping and exploration within and surrounding the Channel Islands National Marine Sanctuary

During July 2016, E/V Nautilus and the Corps of Exploration conducted a major research and exploration program within and surrounding the Channel Islands National Marine Sanctuary (CINMS) offshore southern California. The sanctuary was designated in 1980 to protect the natural and cultural resources around the five northern Channel Islands: Anacapa, Santa Cruz, Santa Rosa, San Miguel, and Santa Barbara. To carry out its mandate to manage these nationally significant regions, NOAA collects new data to help inform decision-making. This cruise included a large-scale multibeam sonar mapping effort to collect detailed bathymetric, acoustic backscatter, and video data, as well as samples both within CINMS and in regions outside of the sanctuary boundaries that are being considered by the public for designation as a new sanctuary and/or are of particular oceanographic interest.

Exploration of the Windward Passage and Jamaica Channel: Tectonic Gateways to the Caribbean Sea

The seafloor in the southern Lesser Antilles island arc is an area of active volcanism, cold seeps, and mud volcanoes (Figure 1). The Caribbean’s most active submarine volcano, Kick’em Jenny (KEJ), lying only 190 m below the surface, last erupted in 2001. The seafloor near Trinidad and Tobago hosts an extensive province of mud volcanoes and colds seeps that are generated by compression of fluid-rich marine sediments as the Atlantic plate subducts beneath the Caribbean plate in the forearc of the Lesser Antilles (Westbrook et al., 1983; Olu et al., 1996). During exploration with Nautilus in 2013, cold seeps were also discovered to the west of KEJ on a large debris avalanche deposit that extends to depths of more than 2,000 m (Carey et al., 2014). Their origin in this unusual geologic setting was attributed to overpressuring of subsurface fluids caused by the catastrophic collapse of the volcano and subsequent fluid movement downslope.