Publications

Sediments deposited on the western slope of the Guaymas Basin in the central Gulf of California are composed predominantly of detrital clastic material and biogenic silica (biopal), with minor organic material (average of 2.8% organic carbon) and calcium carbonate. The CaCO3 is derived from calcareous plankton and is highly variable ranging from 0% to 16%. In general, the CaCO3 content of the sedi

Many of the parks within the National Park System owe their uniqueness to their geologic framework. Their scenery is the result of diverse natural processes acting upon a variety of rocks that were deposited in varied environments in the geologic past. The Delaware Water Gap National Recreation Area (DEWA) contains a rich geologic and cultural history within its 68,714 acre boundary. Following the

The Culpeper basin is part of a much larger system of ancient depressions or troughs, that lie inboard of the Atlantic Coastal Plain, and largely within the Applachian Piedmont Geologic Province of eastern North America, and the transition region with the neighboring Blue Ridge Geologic Province. This basin system formed during an abortive attempt to make a great ocean basin during the Late Triass

The surficial geologic map shows the distribution of nonlithified earth materials at land surface in an area of 16 7.5-minute quadrangles (total 658 mi2) in northeast Massachusetts. The geologic map differentiates surficial materials of Quaternary age on the basis of their lithologic characteristics (grain size, sedimentary structures, mineral and rock-particle composition), constructional geomorp

New mapping and 60 new radiocarbon ages define the age and distribution of latest Pleistocene and Holocene (past 13,000 years) lava flows at Haleakalā volcano, Island of Maui. Paleomagnetic directions were determined for 118 sites, of which 89 are in lava flows younger than 13,000 years. The paleomagnetic data, in conjunction with a reference paleosecular variation (PSV) curve for the Hawaiian Isl

Combined analyses of cores, borehole geophysical logs, and cyclostratigraphy produced a new conceptual hydrogeologic framework for the triple-porosity (matrix, touching-vug, and conduit porosity) karst limestone of the Biscayne aquifer in a 0.65 km2 study area, SE Florida. Vertical lithofacies successions, which have recurrent stacking patterns, fit within high-frequency cycles. We define three id

The latest Oligocene and early Miocene diatom biostratigraphy (24.4 to 16.9 Ma) of equatorial Pacific ODP Site 199-1219 is documented and tied to paleomagnetic stratigraphy in 69 samples, allowing an average age resolution of about 100 kyrs. An updated taxonomy is provided and most of the 71 taxa are illustrated in 9 photographic plates. The equatorial Pacific diatom zonation for the latest Oligoc

No abstract available.

The USGS-NASA Langley corehole at Hampton, Va., was drilled in 2000 and was the first corehole to reach coastal plain basement in the late Eocene Chesapeake Bay impact structure. The Langley core provided samples of granite that had been concealed by 626.3 meters (2,054.7 feet) of preimpact, synimpact, and postimpact sediments. The granite, here named the Langley Granite, is pale red, medium grain

The late Eocene Chesapeake Bay impact structure on the Atlantic margin of Virginia is the largest known impact crater in the United States, and it may be the Earth's best preserved example of a large impact crater that formed on a predominantly siliciclastic continental shelf. The 85-kilometer-wide (53-milewide) crater also coincides with a region of saline ground water. It has a profound influenc

The USGS-NASA Langley corehole at Hampton, Va., was drilled 2000 as the first in a series of new coreholes drilled in the late Eocene Chesapeake Bay impact structure to gain a comprehensive understanding of its three-dimensional character. This understanding is important for assessing ground-water resources in the region, as well as for learning about marine impacts on Earth. We studied crystallin

A 1-kilometer-long (0.62-mile-long) seismic reflection and refraction profile collected at the National Aeronautics and Space Administration (NASA) Langley Research Center, Hampton, Va., provides a detailed image of part of the annular trough of the buried, 35-million-year-old Chesapeake Bay impact structure. This profile passes within 5 meters (m; 16.4 feet (ft)) of a 635.1-m-deep (2,083.8-ft-dee