ALBERT

Description: The continental shelf off the northeastern coast of the United States was the first of our offshore coastal areas to be charted in detail by the Coast and Geodetic Survey, starting on Georges Bank in 1930. The techniques responsible for this increased accuracy in offshore waters were first described by Rudé (1938) and have been constantly improved. From these soundings Veatch and Smith (1939) compiled their set of contour charts aided by a grant from the Penrose Bequest of the Geological Society of America. These soundings reopened the submarine canyon problem first commented upon by Dana (1863), which had gradually lapsed into obscurity from insuffcient data. The reader is, of course, well aware of the major controversy, with all its far reaching implications, which has been precipitated since the 1930 surveys of Georges Bank were brought to the attention of geologists by Shepard (1933). As more of the new surveys were completed, data from the field sheets were kindly furnished by the U. S. Coast and Geodetic Survey to the Woods Hole Oceanographic Institution for use in dredging and coring operations. This field work, first reported in 1936, was continued from time to time until 1941 as new soundings became available. Rock dredging and coring has been carried out in every major canyon on the slope from Corsair Canyon at the tip of Georges Bank to Norfolk Canyon off the entrance to the Chesapeake (Fig. I). Numerous cores have also been taken from the areas in between; and while the whole slope from Georges to the Chesapeake has not been covered, it is believed that no significant areas have been missed. In fact, cores from the slope taken during the summers of 1940 and 1941 have yielded results that are corroborative rather than new. In 1938 on a cruise from Hudson Gorge to Norfolk Canyon, cores were taken on the slope in areas which Veatch had considered to be the most important (personal communication). In the following report the tows and cores will be described by areas from Georges Bank southwards, as the same region was revisited in successive years. The various samples, however, will be referred to by number followed by the year in which they were taken. The material is in storage in the Woods Hole Oceanographic Institution and in the Museum of Comparative Zoology at Harvard University. The late Joseph A. Cushman was kind enough to identify the Foraminifera which have been obtained in tows from the canyon walls and in cores, except for those described in Appendix A which is contributed by Fred B Phleger, Jr. Most of the type material is in storage in the Museum of Comparative Zoology, although at the present writing some is in the Cushman Laboratory in Sharon, Massachusetts. I am indebted to Lloyd W. Stephenson for identifying a molluscan fauna from one of the canyons, and to W. C. Mansfield who has reported on another formation. Numerous discussions with Percy E. Raymond have, as usual, proved most helpful, and thanks are also due to Eugenia C. Lambert for performing the mechanical analyses and to Constance French for other laboratory assistance. Phleger (1939, 1942, 1946) has previously published on the Foraminifera from the slope and deep water cores. This material is, at present, at Scripps Institution of Oceanography.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February, 2006

Description: In this thesis, I present high-resolution stable-isotope and planktonic-fauna records from Bering Sea sediment cores, spanning the time period from 50,000 years ago to the present. During Marine Isotope Stage 3 (MIS3) at 30-20 ky BP (kiloyears before present) in a core from 1467m water depth near Umnak Plateau, there were episodic occurrences of diagenetic carbonate minerals with very low δ13C (-22:4h), high δ18O (6.5h), and high [Mg]/[Ca], which seem associated with sulfate reduction of organic matter and possibly anaerobic oxidation of methane. The episodes lasted less than 1000 years and were spaced about 1000 years apart. During MIS3 at 55-20 ky BP in a core from 2209m water depth on Bowers Ridge, N. pachyderma (s.) and Uvigerina δ18O and δ13C show no coherent variability on millennial time scales. Bering Sea sediments are dysoxic or laminated during the deglaciation. A high sedimentation rate core (200 cm/ky) from 1132m on the Bering Slope is laminated during the Bolling warm phase, Allerod warm phase, and early Holocene, where the ages of lithological transitions agree with the ages of those climate events in Greenland (GISP2) to well within the uncertainty of the age models. The subsurface distribution of radiocarbon was estimated from a compilation of published and unpublished North Pacific benthic-planktonic 14C measurements (475-2700 m water depth). There was no consistent change in 14C profiles between the present and the Last Glacial Maximum, Bolling-Allerod, or the Younger Dryas cold phase. N. pachyderma (s.) δ18O in the Bering Slope core decreases rapidly (in less than 220 y) by 0.7-0.8% at the onset of the Bolling and the end of the Younger Dryas. These isotopic shifts are accompanied by transient decreases in the relative abundance of N. pachyderma (s.), suggesting that the isotopic events are transient warmings and sustained freshenings.

Description: The work in this thesis was supported by the National Science Foundation award OPP-9912122 to Lloyd Keigwin, the Oak Foundation of Boston, Massachusetts, the Stanley Watson Fellowship, the Paul Fye Fellowship, and the Academic Programs Office at WHOI.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution October, 1977.

Description: Sediment traps designed to yield quantitative data of particulate fluxes have been deployed and successfully recovered on four moorings in the deep sea. The traps were designed after extensive calibration of different shapes of containers. Further intercalibration of trap design was made in field experiments over a range of current velocities. Experiments with Niskin bottles showed that concentrations of suspended particulate matter obtained with standard filtration methods were low and had to be increased by an average factor of 1.5 to correct for particles settling below the sampling spigot. The trap arrays were designed to sample the particulate fluxes both immediately above and within the nepheloid layer. The data derived from the traps have been used to estimate vertical fluxes of particles including, for the first time, an attempt to distinguish between the flux of material settling from the upper water column (the "primary flux") and material which has been resuspended from some region of the sea floor (resuspension flux). From these data and measurements of the net nepheloid standing crop of particles one can also estimate a residence time for particles resuspended in the nepheloid layer. This residence time appears to be on the order of days to weeks in the bottom 15 m of the water column and weeks to months in the bottom 100 m. Between 80% and 90% of the particles collected in the six traps where particle size was measured were less than 63 μm. The mean size of particles collected in the nepheloid layer was about 20 μm, and above the nepheloid layer the mean was 11 μm. Less than 3% of the organic carbon produced in the photic zone at the trap sites was collected as primary flux 500 m above the sea floor. The primary flux measured at two sites was enough to supply 75% on the upper Rise and 160% on the mid Rise of the organic carbon needed for respiration and for burial in the accumulating sediments. From an intercomparison of the composition of particles falling rapidly (collected in traps), falling slowly or not at all (collected in water bottles), and resting on the sea floor (from a core top), it was determined that elements associated with biogenic matter, such as Ca, Sr, Cu, and I, were carried preferentially by the particles falling rapidly. Once the particles reached the bottom, the concentration of those elements was decreased through decomposition, respiration, or dissolution. Dissolution appears rapid in the vicinity of the sea floor, because despite an abundance of radiolarians, diatoms, and juvenile foraminifera collected in all traps, these forms were rare in core samples. The dynamic nature of thenepheloid layer makes it possible for particles to be resuspended many times before they are finally buried. This enables sediment to be carried long distances from its origin. The recycling of particles near the sea floor may increase dissolution of silicious and carbonate matter.

Description: Financial aid was provided in the form of a research assistantship from the Office of Naval Research through MIT and WHOI.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September, 1975

Description: Erosion processes involving fine-grained marine sediments were studied by using an in situ flume to erode undisturbed bottom sediments on the sea floor in Buzzards Bay, a shallow marine embayment off the Massachusetts coast. Tte muddy sea floor in that area is characterized by a deposit-feeding infauna that reworks the sediments. Observations made with the in situ flume suggest that erosion resistance of compacted bottom sediments is up to twice as great as the erosion resistance of biogenically reworked sediments. Estimates of erosional bed shear stress from the in situ flume experiments are similar to estimates made during this study of bed shear stress developed in near-bottom tidal currents. It is inferred that erosion by the in situ flume produces reasonable estimates of bed shear stress necessary to erode undisturbed bottom sediments on the sea floor. Buzzards Bay muds were redeposited in a laboratory flume and eroded after various periods of reworking by the deposit-feeding organisms contained in them. Other Buzzards Bay mud samples were treated to remove organic matter, and the erosion resistance of flat beds of these sediments was also investigated in a laboratory flume. The surface of a biogenically reworked bed after two months was covered with mounds, burrows, trails, and aggregates composed of sediments and organic material. This bed was similar in appearance to many of the beds eroded by the in situ flume. The two month bed eroded at an erosional shear stress similar to the erosional shear stress necessary to erode the in situ Buzzards Bay muds (0.8 dynes/cm2 ) . Beds biogenically reworked for shorter periods had high values of erosional shear stress, up to twice that of the two month bed. The bed shear stress necessary to erode flat beds of Buzzards Bay sediments increased as the concentration of organic matter in the sediments increased. Deposit-feeders were absent in these beds, and the mode of deposition was kept uniform, so the increase of erosion resistance with increase in organic content is considered a reliable indication of sediment behavior, and not an artifact of experimental conditions. During the in situ experiments, lee drifts were created behind resistant roughness elements on the sea floor. A brief study of lee drift formation in the laboratory suggests that the formation of lee drifts from fine-grained sediments can be predicted to take place when the body Reynolds number of the resistant roughness elements is below a critical value.

Description: The Office of Naval Research supported this research and provided salary support through grants to the Woods Hole Oceanographic Institution and the Massachusetts Institute of Technology.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution August 1982

Description: In an effort to understand the more general mechanisms and rates of pre-depositional reactions that transform organic matter, the types and relevant time scales of reactions that transform carotenoid pigments in the oceanic water column were studied. Suspended particulate matter collected from surface waters of Buzzards Bay, Massachusetts and the Peru upwelling system has a carotenoid distribution reflecting the phytoplanktonic source of the material. The carotenoid distribution of sediment trap samples collected in these same areas was dominated by transformation products. Fucoxanthin, the primary carotenoid of marine diatoms, typically constituted 77-100% of the total fucopigments in suspended particulate material. In sediment trap samples this pigment constituted only 4-85% of the total. The remaining 15-96% of the pigments consisted of the fucoxanthin transformations products: free alcohols (2-94%), dehydrates (0-6%), and opened epoxides (0-19%). Preliminary results suggest that carotenoid esters are hydrolyzed to free alcohols at a rate determined by the turnover of primary productivity. The dehydrated and epoxide opened intermediates of fucoxanthin represent products of transformation reactions that operate over much longer time scales (0.1-10 yrs). Dehydration and epoxide opening are not significant water column transformations, but are important in surface sediments.

Description: This research was supported by the Ocean Sciences Section, National Science Foundation grants OCE 79-25352 and OCE 81-18436, the Office of Naval Research Contract N00014-74-Co-262NR 083-004, the Woods Hole Coastal Research Center project 25 000067 04, and a Woods Hole Oceanographic Institution Student Fellowship.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution May 1980

Description: This study of particulate matter in the water column and the underlying surface sediments verifies the occurrence of local, present-day resuspension in the deep sea. The location of the major portion of this work was the South Iceland Rise, a region influenced by the flow of Norwegian Sea Overflow Water. Measured current velocities exceeded 20 cm/sec in the axis of the bottom current for the duration of the deployments, approximately two weeks. Particulate matter was sampled with Niskin bottles, to obtain the standing crop of suspended matter and with sediment traps, to obtain the material in flux through the water column. Box cores were taken to obtain surface sediment samples for comparison with the trap samples. Suspended particulate matter (SPM) and light-scattering studies demonstrate that in the Iceland Rise area the correlation of the L-DGO nephelometer to concentration of SPM differs between clear water and the nepheloid layer. Correlations of light scattering to SPM concentration also differ regionally, but for predicting concentration from light scattering, regression lines at two locations are indistinguishable. Particle size distributions have lower variance in the nepheloid layer than those in clear water which have roughly equal volumes of material in logarithmically increasing size grades from 1-20 μm. Apparent density differences between SPM in clear water and the nepheloid layer are not distinguishable in the Iceland Rise study; apparent densities increase in the nepheloid layer in the western North Atlantic. An apparent density of 1.1 g/cm3 adequately separates clear water from nepheloid layer samples in this region. Compositional variations seen between clear water and the nepheloid layer include a decrease in small coccoliths and an increase in clays and mineral matter. These compositional variations are more dramatic in the western North Atlantic region, due to dissolution of carbonate at the seafloor, later resuspended into the nepheloid layer. Sedimentological evidence of resuspension and redistribution of material are: 1) presence of sediment drifts throughout the Iceland Basin; 2) occurrence of coarse, glacial age sediments beneath the axis of the bottom current; and 3) differences in mineralogy, carbonate and organic carbon contents between surface sediments beneath the bottom current and those in a channel. A comparison of the vertical flux of material measured by sediment traps at 500 meters above bottom (mab) with the accumulation rate in cores, shows that the present-day surface input is an order of magnitude smaller than the accumulation rate. This observation suggests transport of material into some sections of the region by bottom currents or by turbidity currents. The horizontal flux of particulate matter into and out of the region by the bottom current is 100 kg/sec. This material may contribute to the formation of Gardar sediment drift downstream. The trends in % CaC03 and % organic carbon through the water column and in the surface sediments suggest that dissolution of carbonate and decomposition and consumption of organic carbon occurs primarily at the seafloor. These data also suggest preferential preservation at channel stations and/or preferential erosion beneath the bottom current. A comparison of sediment-trap samples with box-core surface samples further supports present-day resuspension. Benthic foraminifera, iron-oxidicoated planktonic foraminifera and the glacial, subpolar planktonic foraminifera (Neogloboquadrina pachyderma (sinistral)) in traps at 10,100 and a few specimens at 500 mab, provide conclusive evidence for local resuspension. The coarse fraction (〉125 μm) of the sediment trap material collected at 10 mab comprises 21-34% of the samples Calculations indicate that this material is locally derived (few kilometers) resuspended material.

Description: This work was financially supported by the Woods Hole Oceanographic Institution, ONR through contracts N00014-79-C-00-7l NR 083-004, N00014-74-C0262 NR 083-004, and N00014-75-C-029l and ERDA through contracts 13-7923 and 13-2559.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2003

Description: The cosmogenic radionuclide 10Be is a unique tracer of shallow sediment subduction in volcanic arcs. The range in 10Be enrichment in the Central American Volcanic Arc between Guatemala and Costa Rica is not controlled by variations in 10Be concentrations in subducting sediment seaward of the Middle America Trench. Sedimentary 10Be is correlated negatively with 143Nd/144Nd, illustrating that 10Be concentrations varied both between and within cores due to mixing between terrigenous clay and volcanic ash endmember components. This mixing behavior was determined to be a function of grain size controls on 10Be concentrations. A negative correlation of bulk sedimentary 10Be concentrations with median grain size and a positive correlation with the proportion of the sediment grains that were 〈32 μm in diameter demonstrated that high concentrations of 10Be in fine-grained, terrigenous sediments were diluted by larger grained volcanogenic material. The sharp decrease in 10Be enrichment in the Central American Volcanic Arc between southeastern Nicaragua and northwestern Costa Rica correlates with changes in fault structure in the subducting Cocos plate. Offshore of Nicaragua, extensional faults associated with plate bending have throw equal to or greater than the overlying subducting sediment thickness. These faults enable efficient subduction of the entire sediment package by preventing relocation of the décollement within the downgoing sediments. Offshore of Costa Rica, the reduction of fault relief results in basement faults that do not penetrate the overlying sediment. A conceptual model is proposed in which the absence of significant basement roughness allows the décollement to descend into the subducting sediment column, leading to subsequent underplating and therefore removal of the bulk of the sediment layer that contains 10Be. Basement fault relief was linearly related to plate curvature and trench depth. The systematic shoaling of the plate from southeastern Nicaragua to northwestern Costa Rica is not explained by changes in plate age for this region. Instead, it is hypothesized that the flexural shape of the plate offshore of southeastern Nicaragua and northwestern Costa Rica represents a lateral response to a buoyant load caused by the thick crust and elevated thermal regime in the Cocos plate offshore of southeastern Costa Rica.

Description: Funding for this work was provided by the National Science Foundation Graduate Research Fellowship, the WHOI Ocean Ventures Fund, the WHOI Deep Ocean Institute Graduate Fellowship, and Geological Society of America Graduate Research Grant #7179-02.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution June 2003

Description: This thesis examines the evolution of a mud-dominated coastal sedimentary system on multiple time scales. Fine-grained systems exhibit different properties and behavior from sandy coasts, and have received relatively little research attention to date. Evidence is presented for shoreline accretion under energetic conditions associated with storms and winter cold fronts. The identification of energetic events as agents of coastal accretion stands in contrast to the traditional assumption that low-energy conditions are required for deposition of fine-grained sediment. Mudflat accretion is proposed to depend upon the presence of an unconsolidated mud sea floor immediately offshore, proximity to a fluvial sediment source, onshore winds, which generate waves that resuspend sediment and advect it shoreward, and a low tidal range. This study constrains the present influence of the Atchafalaya River on stratigraphic evolution of the inner continental shelf in western Louisiana. Sedimentary and acoustic data are used to identify the western limit of the distal Atchafalaya prodelta and to estimate the proportion of Atchafalaya River sediment that accumulates on the inner shelf seaward of Louisiana's chenier plain coast. The results demonstrate a link between sedimentary facies distribution on the inner shelf and patterns of accretion and shoreline retreat on the chenier plain coast.

Description: Among my funding sources was a two-year fellowship from the Clare Booth Luce Foundation. I have received research grants from the Geological Society of America Foundation (Grant 6873-01) and the American Association of Petroleum Geologists (Kenneth H. Crandall Memorial grant).

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 2009

Description: Observations and inverse models suggest that small-scale turbulent mixing is enhanced in the Southern Ocean in regions above rough topography. The enhancement extends 1 km above the topography suggesting that mixing is supported by breaking of gravity waves radiated from the ocean bottom. In other regions, gravity wave radiation by bottom topography has been primarily associated with the barotropic tide. In this study, we explore the alternative hypothesis that the enhanced mixing in the Southern Ocean is sustained by internal waves generated by geostrophic motions flowing over bottom topography. Weakly-nonlinear theory is used to describe the internal wave generation and the feedback of the waves on the zonally averaged flow. A major finding is that the waves generated at the ocean bottom at finite inverse Froude numbers drive vigorous inertial oscillations. The wave radiation and dissipation at equilibrium is therefore the result of both geostrophic flow and inertial oscillations and differs substantially from the classical lee wave problem. The theoretical predictions are tested versus two-dimensional and three-dimensional high resolution numerical simulations with parameters representative of the Drake Passage region. Theory and fully nonlinear numerical simulations are used to estimate internal wave radiation from LADCP, CTD and topography data from two regions in the Southern Ocean: Drake Passage and the Southeast Pacific. The results show that radiation and dissipation of internal waves generated by geostrophic motions reproduce the magnitude and distribution of dissipation measured in the region.

Description: Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution December 1985

Description: Samples from time-series sediment traps deployed in three distinct oceanographic settings (North Pacific, Panama Basin, and Black Sea) provide strong evidence for rapid settling of marine particles by aggregates. Particle water column residence times were determined by measuring the time lag between the interception of a flux event in a shallow trap and the interception of the same event in a deeper trap at the same site. Effective sinking speeds were determined by dividing the vertical offset of the traps (meters) by the interception lag time (days). At station Papa in the North Pacific, all particles settle at 175 m day-1, regardless of their composition, indicating that all types of material may be settling in common packages. Evidence from the other two sites (Panama Basin and Black Sea) shows that particle transport may be vertical, lateral, or a combination of directions, with much of the Black Sea flux signal being dominated by lateral input. In order to ascertain whether marine snow aggregates represent viable transport packages, surveys were conducted of the abundance of these aggregates at several stations in the eastern North Atlantic and Panama Basin using a photographic technique. Marine snow aggregates were found in concentrations ranging from ~1 mm3 liter-1 to more than 500 mm3 liter-1. In open ocean environments, abundances are higher near the surface (production) and decline with depth (decomposition). However, in areas near sources of deep input of resuspended material, concentrations reach mid-water maxima, reflecting lateral transport. A model is proposed to relate the observed aggregate abundances, time series sediment flux and inferred circulation. In this model, depthwise variations in sediment flux and aggregate abundance result from suspension from the sea floor and lateral transport of suspended aggregates which were produced or modified on the sea floor. Temporal changes in sediment flux result from variations in the input of fast-sinking material which falls from the surface, intercepts the suspended aggregates, and transports them to the sea floor. A new combination sediment trap and camera system was built and deployed in the Panama Basin with the intent of measuring the flux of marine snow aggregates. This device consists of a cylindrical tube which is open at the top and sealed at the bottom by a clear plate. Material lying on the bottom plate is illuminated by strobe lights mounted in the wall of the cylinder and photographed by a camera which is positioned below the bottom plate. Flux is determined as the number of aggregates arriving during the time interval between photographic frames (# area-1 time-1). Results show that essentially all material arrives in the form of aggregates with minor contributions of fecal pellets and solitary particles. Sinking speeds (m day-1), calculated by dividing the flux of aggregates (# m-2 day-1) by their abundance (# m-3), indicate that the larger (4-5mm) aggregates are flocculent and sink slowly (~1m day-1) while the smaller aggregates (1-2.5mm) are more compact and sink more quickly (~36m day-1). These large, slow-sinking aggregates may have been re-suspended from the sediment water interface at nearby basin margins.

Description: This research was supported by ONR contract numbers N00014-82-C-0019 and N00014-85-C-0001, NSF grant numbers OCE-83-09024, OCE-84-17106, and DPP-85-01152 and the WHO1 education office.