Hilary Clement Olson

Paleoenvironmental evidence for latest Pleistocene sea-level fluctuations on the New Jersey outer continental shelf: combining high-resolution sequence stratigraphy and foraminiferal analysis

Foraminiferal assemblages in vibracored sediments within ∼5 m of the seafloor document high-resolution sea-level fluctuations and confirm the complex Quaternary depositional history of the New Jersey margin. Biostratigraphic data have been integrated with ongoing 2-D/3-D high-resolution seismic analyses to interpret paleoenvironments of surficial stratigraphy beneath the modern middle-to-outer shelf. Cluster analysis of foraminiferal assemblages sampled every 20 cm (average) define four sample groups (A–D) dominated by benthic species. Group A, characterized by Cibicides lobatulus, is a middle-to-outer-shelf assemblage (∼60–100 m water depths). Group B is composed of middle-shelf species (∼30–60 m water depths) and is characterized by low abundances and a fairly uniform distribution of foraminifera, which suggests reworking and/or a high rate of sediment accumulation. Group C, dominated by Elphidium excavatum, is an inner-to-middle-shelf assemblage (∼10–40 m water depths). Group D, present in only one core and dominated by Ammonia beccarii, represents marginal marine environments (∼0–10 m water depths, with fluctuations in salinity). In general, the modern sedimentary veneer (i.e., the upper ∼20 cm) is characterized by the deeper-water fauna of group A. Sediments below these modern deposits are characterized by groups B and C, reflecting shallower water depths and variable sediment-accumulation rates on the inner and middle shelf. Taken together, the group succession in the cores suggests an overall SE-to-NW (landward) transgression in these latest Pleistocene–Holocene deposits. Seismic analysis indicates that one core (27) penetrates the flank of a buried channel, including its fill and the pre-channel section. Within the channel, three alternations of groups C and D suggest fluctuations between marginal-marine and middle-shelf paleoenvironments; high-frequency, perhaps very small (<10 m?) changes in base level are indicated. Using previously published AMS 14C dates, these fluctuations can be constrained as having occurred between 45,000 yr B.P. (channel incision) and 12,500 yr B.P. (channel filling), suggesting the non-uniform nature of the last Wisconsinan deglaciation.

Foraminiferal constraints on very high-resolution seismic stratigraphy and late Quaternary glacial history, New Jersey continental shelf

Internal stratigraphy of a Late Quaternary sediment wedge on the New Jersey outer continental shelf has been investigated using regional and 3-D seismic surveys, sediment cores and foraminiferal biofacies analysis. Results from the study help constrain Late Wisconsinan glacialldeglacial history in this area. Three major reflectors (channels, S and R) define 5 stratigraphic units: Si -modern sediments; S2-sands overlying a channelized surface (Channels reflector); S3-muds, clays and sandy muds below the channelized surface and above reflector S; S4-an unsampled unit between reflectors S and R; and S5-sands underlying reflector R, the latter surface defining the base of the sediment wedge. Multivariate quantitative analysis delineates four major faunal groups characterizing these stratigraphic units. Faunal patterns are interpreted in terms of modern foraminiferal distributions, planktoniclbenthic ratios and faunal abundance patterns. Group A dominates units S2 and S5 and is characterized by Cibicides lobatulus and Cassidulina islandica. The fauna indicates middle neritic water depths, moderate to high current energy, and moderate accumulation rates. Group B dominates unit S3 (muddy unit) and is characterized by Elphidium excavatum s.l., Buccella frigida, Fursenkoina fusiformis and miliolid spp. This fauna represents an environment with no modern analogue on the New Jersey continental shelf, reflecting middle neritic, low-energy conditions and the accumulation of predominantly muddy sediments. Group C dominates the modern sediment veneer (unit Si), and its diverse fauna is consistent with modern faunal distributions and environmental conditions. Group D consists of a low-diversity fauna dominated by Fursenkoina fusiformis and Nonionella sp., which characterizes a few samples in unit S3. Environmental conditions are probably similar to those described for faunal group B. The distribution and interpretation of these faunas, combined with preliminary C-14 AMS dates, indicate that the Quaternary history of the outer-shelf sedi-

Neogene-Quaternary contourite and related deposition on the West Shetland Slope and Faeroe-Shetland Channel revealed by high-resolution seismic studies

The Neogene and Quaternary sediments of the Faeroe-Shetland Channel and West Shetland shelf and slope rest upon a major regional unconformity, the Latest Oligocene Unconformity (LOU), and have been deposited through the interaction of downslope and parallel-to-slope depositional processes. The upper to middle continental slope is dominated by mass-transport deposits (debris flows), which progressively diminish downslope, and were largely generated and deposited during glacial cycles when ice sheets supplied large quantities of terrigeneous sediment to the upper slope and icebergs scoured sea-floor sediments on the outer shelf and uppermost slope. Large-scale sediment failures have also occurred on the upper slope and resulted in deposition of thick, regionally extensive mass-transport deposits on portions of the lower slope and channel floor. In contrast, large fields of migrating sediment waves and drift deposits dominate most of the middle to lower slope below 700 m water depth and represent deposition by strong contour currents of the various water masses moving northeastward and southwestward through the channel. These migrating sediment waves indicate strong northeastward current flow at water depths shallower than ∼700 m and strong southwestward current flow at water depths from ∼700 to >1,400 m. These flow directions are consistent with present-day water-mass flow through the Faeroe-Shetland Channel. The Faeroe-Shetland Channel floor is underlain by thin conformable sediments that appear to be predominantly glacial marine and hemipelagic with less common turbidites and debris flows. No evidence is observed in seismic or core data that indicates strong contour-current erosion or redistribution of sediments along the channel floor.

Evaluating the influence of aseismic ridge subduction and accretion(?) on detrital modes of forearc sandstone: an example from the Kronotsky Peninsula in the Kamchatka Forearc

Abstract The Kronotsky Peninsula, in the forearc region of the Kamchatka magmatic arc, lies on trend with the Emperor Seamount chain situated on the currently subducting Pacific tectonic plate. Detrital modes of volcaniclastic sandstone interbedded with mafic Eocene(?) basement rocks and within the overlying sedimentary sequence provide insight into the late Cenozoic geologic history of this area. Eocene(?) and basal Miocene sandstones are primarily composed of variably altered mafic volcanic debris. Their detrital modes are similar to those of Emperor Seamount sandstones and Hawaiian beach sands. Although aspects of the stratigraphy and volcaniclastic sand composition are consistent with a seamount setting, there is no physical evidence for an accretion event, and the suggested Eocene age for this unit makes an Emperor Seamount origin unlikely. A seamount origin cannot be ruled out for older Kronotsky basement complexes, however. A Miocene lull in Kronotsky volcanism was followed by rapid basin subsidence and influx of arc-derived turbidites from the west. Detrital modes of these sandstones are typical of a moderately evolved continental or micro-continental arc. An anomalously high proportion of sedimentary lithic fragments is the only possible compositional fingerprint attributable to seamount or ridge subduction.

Latest Quaternary sedimentation in the northern Gulf of Mexico Intraslope Basin Province: I. Sediment facies and depositional processes

Very high-resolution seismic facies, classified, mapped, and interpreted from 3.5 kHz echograms, reveal that turbidity-current, mass-transport, and bottom-current depositional processes have all contributed to the regional sediment distribution in the intraslope basin province of the northwest Gulf of Mexico. Piston cores from these deposits confirm the interpretations of the processes. Turbidity currents transport sands into the intraslope mini-basins via channels and canyons. A few turbidity-current pathways, such as Bryant Canyon, allow extensive volumes of terrigenous sediment to bypass through many mini-basins and be deposited beyond the Sigsbee Escarpment to form large submarine fans, such as Bryant Fan. Bryant Fan is a large mud-rich fan that extends hundreds of kilometers from the mouth of Bryant Canyon but has only one meandering channel on the modern seafloor that extends down the length of the fan. In contrast, the much smaller Rio Grande Submarine Fan is deposited on a plateau area of the continental slope. Prolonged 3.5 echo character and numerous small, unleveed channels suggest this is a sand-rich fan with a braided channel system. These two submarine fans appear to present unique architectural and growth patterns not previously described in the numerous fan descriptions of W.R. Normark or other workers. Thus, these two fans appear to represent two new types of fans, which may be related to the complex structures of the intraslope basin province. Mass-transport deposits (MTDs) are ubiquitous throughout the mini-basins. Extensive areas affected by MTDs also occur along the upper continental slope and at the base of the eastern portion of the Sigsbee Escarpment. Piston cores confirm that the majority of MTDs are debris flows, which are characterized by mud clasts of variable size, shape, and color. Most have a muddy matrix, but sandy debris flows also occur in a few mini-basins. Some cores show deformation, folds, and faults that indicate slump or slide deposits. The East Breaks Slide Complex is the largest MTD complex and extends downslope from the shelf edge for >100 km off central Texas. The western portion of the complex is slump and/or slide blocks and debris flows. In contrast, the proximal part of the eastern portion of the complex is characterized by a modern leveed turbidite channel system. However, extensive MTDs underlie the channel-levee deposits and occur at the seafloor on the distal part of the eastern portion of the complex. Three large regions of migrating sediment waves occur on the Sigsbee Abyssal Plain and eastern Bryant Fan and appear to have been formed by circulation of the Loop Current. Sediment waves also occur locally at the base of the Sigsbee Escarpment in conjunction with previously reported erosional furrows.

Upper Jurassic Tithonian-centered source mapping in the deepwater northern Gulf of Mexico

AbstractLong the subject of speculation, the origin, distribution, and quality of Mesozoic source beds in the deepwater Gulf of Mexico (GOM) are now open to analytical study and hypothesis. We have developed new maps and concepts for organic richness and lithofacies patterns of the primary Upper Jurassic oil-prone source rock interval spanning the Kimmeridgian to Lower Berriasian in the northern GOM. This interval, previously referred to as the Tithonian-centered source, includes the Haynesville and Bossier shales, which lie within supersequences representing second-order transgressive and high-stand systems tracts, respectively. A newly developed gulf-wide Cotton Valley-Bossier paleogeographic map based on a novel paleotectonic model for the Mesozoic provides the framework for this source mapping study. Organic richness averages up to 4.7% and 6.5% total organic carbon for the Kimmeridgian and Tithonian-Lower Berriasian supersequences, respectively, based on the log overlay Δ log R technique and increase...

Character, Distribution and Timing of Latest Quaternary Mass-Transport Deposits in Texas-Louisiana Intraslope Basins Based on High-Resolution (3.5 kHz) Seismic Facies and Piston Cores

Systematic mapping of 3.5 kHz seismic facies (echo character) reveals the geometry, scales and distribution of Late Quaternary mass-transport deposits (MTDs) within the northern Gulf of Mexico (GOM) intraslope basin province and adjacent Sigsbee Abyssal Plain. The 3.5 kHz seismic facies indicate that localized MTDs are common in the intraslope mini-basins. MTDs of larger scale occur on the upper continental slope (e.g. East Breaks Slide Complex) and seaward from the eastern base of the Sigsbee Escarpment. Approximately 120 piston cores from these deposits “ground truth” the seismic facies interpretations and reveal that the sedimentary facies of the MTDs in intraslope basins contain a spectrum of slumps, slides and debris flows. Most MTDs are muddy deposits, but sandy MTDs are also common. The presence of sandy debris flows suggests that similar, more deeply buried MTDs may constitute significant reservoir sands. Many piston cores containing MTDs were biostratigraphi-cally and chemically zoned using G. menardii complex and calcium carbonate fluctuations to determine the timing and sourcing of MTDs in relation to glacio-eustatic sea-level changes associated with the Last Glacial and Holocene. This stratigraphic analysis indicates that the majority of downslope transport (including sandy turbidites, sandy and muddy debris flows, and slumps) occurred during the Last Glacial cycle. Downslope transport of MTDs during the Holocene Interglacial was rare.

Enhancing Geoscience Education within a Minority-Serving Preservice Teacher Population.

ABSTRACT The University of Texas Institute for Geophysics and Huston-Tillotson University collaborated on a proof of concept project to offer a geoscience course to undergraduate students and preservice teachers in order to expand the scope of geoscience education within the local minority student and teacher population. Students were exposed to rigorous Earth science materials, geoscientists conducting cutting-edge research, headliner topics, and pedagogical approaches to teaching. An evaluation of the data reveal that the course received mixed, but overall positive reviews and that student performance was mixed. Pre- and posttest results indicate that students made only modest gains. Half of the students performed at levels that matched our expectations and will be able to apply the geoscience knowledge and skills that they learned in an elementary school setting. The course contributed to the preparation of minority teachers to teach Earth science in Texas, filling a critical need. The authors, in collaboration with a minority-serving institution and as part of the preparation for a preservice teacher program, benefited from the experience; they subsequently applied the lessons learned to a program of professional development for minority-serving science teachers, the TeXas Earth and Space Science (TXESS) Revolution.

Avoiding Trouble: Exploring Environmental Risk Information Avoidance Intentions.

This study explores predictors of risk information avoidance intentions in the context of a novel environmental threat—induced earthquakes in Texas. Given the paucity of research on risk information avoidance, this work was guided by a cognitive information behavior model. Survey data (N = 541) from a random sample of Texas adults allowed us to explore these variables. While previous research has shown risk information seeking intentions to be robustly guided by a number of constructs, our current data suggest that risk information avoidance intentions may be more narrowly predicated on risk information avoidance-related subjective norms, attitudes, and perceived knowledge insufficiency. We discuss these findings and suggest avenues for future environmental risk research.

Gulf of Mexico Intraslope Basins (GIB) Phase II 2002-2006 Project Atlas

The Gulf of Mexico Intraslope Basins (GIB) Project was an industry-sponsored project. It was a collaborative effort between the University of Texas at Austin Institute for Geophysics, the Department of Earth and Environmental Sciences at the University of Texas at Arlington, and the Instituto Andaluz de Ciencias de la Tierra at the University of Grenada, Spain. This atlas presents reports and maps from Phase II (2002-2006) of the project. For more information, contact gib@ig.utexas.edu.