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D. S. Foster

Publications and source records attributed to D. S. Foster.

46 records · Page 3Linked to original sources
USGS1993

Seismic survey of Lake Baikal, Siberia cruise report: RV Balkhash 25 August to 25 September 1992

Introduction A comprehensive multichannel seismic-reflection (MCS) and ocean bottom seismometer (OBS) seismic-refraction survey of Lake Baikal, Siberia was undertaken during August-September 1992 as a collaborative research project by U.S. and Russian scientists. This project was supported by funding from the U.S. Geological Survey, the U.S. National Science Foundation and the Russian Academy of Sciences. Over 2200 km of multichannel seismic-reflection data on 42 profiles and over 500 km of seismic-refraction data on 4 OBS profiles were acquired during this study. On board seismic processing facilities were utilized for quality control and demultiplexing of seismic data during the cruise. Lost survey time due to weather was about 7 days, but most planned seismic profiling was completed, including the reshooting of profiles where necessary. This seismic study was carried out on two vessels, the RV BALKHASH for MCS work and the TITOV for OBS deployments. This report summarizes the general seismic program and the operations on the BALKHASH. Operations on the TITOV are summarized in a companion report by tenBrink and others. A detailed description of the logistical and technical aspects of the seismic program, including all seismic systems, is given in the companion report by Nichols and others.

Siberia↗
USGS1992

Depressions and other lake-floor morphologic features in deep water, southern Lake Michigan

The most common features are subcircular depressions, commonly compound, that are irregularly distributed across the lake floor. The depressions are most common in the southern basin of the lake where lacustrine sediments are more than a few meters thick, corresponding to water depths greater than about 90 m. We have divided the depressions into three types on the basis of their internal structure seen in seismic-reflection profiles. The depressions show varying degrees of muting, ranging from fresh to completely buried, suggesting a range in the time of their formation. The origin of the depressions is problematic, but their structure suggests collapse and(or) subsidence. -from Authors

Lake Michigan↗
USGS1990

Holocene paleoclimatic evidence and sedimentation rates from a core in southwestern Lake Michigan

Preliminary results of a multidisciplinary study of cores in southwestern Lake Michigan suggest that the materials in these cores can be interpreted in terms of both isostatically and climatically induced changes in lake level. Ostracodes and mollusks are well preserved in the Holocene sediments, and they provide paleolimnologic and paleoclimatic data, as well as biogenic carbonate for stable-isotope studies and radiocarbon dating. Pollen and diatom preservation in the cores is poor, which prevents comparison with regional vegetation records. New accelerator-mass spectrometer 14C ages, from both carbon and carbonate fractions, provide basin-wide correlations and appear to resolve the longstanding problem of anomalously old ages that result from detrital organic matter in Great Lakes sediments. Several cores contain a distinct unconformity associated with the abrupt fall in lake level that occurred about 10.3 ka when the isostatically depressed North Bay outlet was uncovered by the retreating Laurentide Ice Sheet. Below the unconformity, ostracode assemblages imply deep, cold water with very low total dissolved solids (TDS), and bivalves have ?? 18O (PDB) values as light as - 10 per mil. Samples from just above the unconformity contain littoral to sublittoral ostracode species that imply warmer, higher-TDS (though still dilute) water than that inferred below the unconformity. Above this zone, another interval with ?? 18O values more negative than - 10 occurs. The isotopic data suggest that two influxes of cold, isotopically light meltwater from Laurentide ice entered the lake, one shortly before 10.3 ka and the other about 9 ka. These influxes were separated by a period during which the lake was warmer, shallower, but still very low in dissolved solids. One or both of the meltwater influxes may be related to discharge from Lake Agassiz into the Great Lakes. Sedimentation rates appear to have been constant from about 10 ka to 5 ka. Bivalve shells formed between about 8 and 5 ka have ?? 18O values that range from-2.3 to-3.3 per mil and appear to decrease toward the end of the interval. The ostracode assemblages and the stable isotopes suggest changes that are climatically controlled, including fluctuating water levels and increasing dissolved solids, although the water remained relatively dilute (TDS < 300 mg/l). A dramatic decrease in sedimentation rates occurred at about 5 ka, about the time of the peak of the Nippissing high lake stage. This decrease in sedimentation rate may be associated with a large increase in effective wave base as the lake approached its present size and fetch. A dramatic reduction in ostracode and mollusk abundances during the late Holocene is probably due to this decrease in sedimentation rates, which would result in increased carbonate dissolution. Ostracode productivity may also have declined due to a reduction in bottom-water oxygen caused by increased epilimnion algal productivity.

Lake Michigan↗
USGS1990

Ancient channels of the Susquehanna River beneath Chesapeake Bay and the Delmarva Peninsula

The trunk channels of each system are 2 to 4 km wide and are incised 30 to 50 m into underlying strata; they have irregular longitudinal profiles and very low gradients within the Chesapeake Bay area. The youngest paleochannel is clearly of late Wisconsinan age, about 18 ka, and the intermediate one appears to be late Illinoian in age, or about 150 ka. The age of the oldest is in the range of about 200 to 400 ka. The three paleochannel systems imply a dynamic coastal-plain environment and at least two previous generations of the Chesapeake Bay. -from Authors

Chesapeake Bay, Delmarva Peninsula, Susquehanna Ri↗