ABSTRACT This work refines previous interpretations of the structure and morphology of the Chesap... more ABSTRACT This work refines previous interpretations of the structure and morphology of the Chesapeake Bay impact crater on the basis of more than 1,200 km of multichannel and single-channel seismic reflection profiles collected in the bay and on the adjacent ...
Special Paper 339: Large meteorite impacts and planetary evolution; II, 1999
ABSTRACT This work refines previous interpretations of the structure and morphology of the Chesap... more ABSTRACT This work refines previous interpretations of the structure and morphology of the Chesapeake Bay impact crater on the basis of more than 1,200 km of multichannel and single-channel seismic reflection profiles collected in the bay and on the adjacent ...
Five coreholes (Exmore, Kiptopeke, NASA Langley, North, Bayside) have sampled crater-fill deposit... more Five coreholes (Exmore, Kiptopeke, NASA Langley, North, Bayside) have sampled crater-fill deposits of the Chesapeake Bay crater, and two others (Windmill Point, Newport News) have sampled partly equivalent deposits outside the outer rim (Fig. 6.1Fig. 6.2Fig. 6.3AFig. 6.3B, CD-ROM.7; Table 1.2). The crater-fill deposits can be subdivided into several distinctive units, which we will discuss in chronostratigraphic order from oldest
Analyses of the stable isotopes of the organic carbon and microscopic examination of the sediment... more Analyses of the stable isotopes of the organic carbon and microscopic examination of the sediment particles suggest that up to 90 percent of the organic matter in Ross Sea sediments is derived from the igneous and ancient metamorphic and sedimentary rocks that are being glacially eroded on the Antarctic continent and transported seaward.
The Chesapeake Bay impact structure is the focus of an ongoing federal-state-local research progr... more The Chesapeake Bay impact structure is the focus of an ongoing federal-state-local research program. Recent core drilling and geophysical surveys address the formative processes and hydrogeologic properties of this major 'wet-target' impact.
Postimpact deposits over and near the Chesapeake Bay impact crater consist of a thick (200-&g... more Postimpact deposits over and near the Chesapeake Bay impact crater consist of a thick (200->500 m) succession of fossiliferous siliciclastic formations, which range stratigraphically from regionally distributed barren silt and richly fossiliferous late Eocene clay deposits, to a variety of locally distributed Quaternary and Holocene sand units (see Chapter 2; Figs. 2.4, 2.5, 6.2, 7.1, 7.2). Because the impact took
Our extensive network of seismic reflection profiles clearly documents that the structural-morpho... more Our extensive network of seismic reflection profiles clearly documents that the structural-morphological features of the outer rim, annular trough, and displaced megablocks are expressed principally by preimpact sedimentary rocks, and to a much lesser degree, by crystalline basement rocks (Figs. 1.5, 4.1, 4.2A4.2B; CD-ROM.3-6). In contrast, the peak ring, inner basin, and central peak of the Chesapeake Bay crater are
third the age of Earth. Nevertheless, the mass fraction of diamond observed in carburanium is sev... more third the age of Earth. Nevertheless, the mass fraction of diamond observed in carburanium is several orders of magnitude smaller than that of carbonado. This presents a serious difficulty if a radiation process is to account for carbonado formation. Mass transport problems must b e . addressed; because <20% of the volume of carbonado is not diamond, some transport mechanism would have to concentrate diamond grains into large aggregates while removing the displaced uranium oxides and decay products. Because carburanium contains 500-nm polycrystalline aggregates, a sintering mechanism would then be required to coalesce these radiationformed aggregates into the micrometersized single crystal grains typical of carbonado. These factors indicate that a radiation mechanism alone cannot satisfactorily explain the formation of carbonado.
Analyses of the stable isotopes of the organic carbon and microscopic examination of the sediment... more Analyses of the stable isotopes of the organic carbon and microscopic examination of the sediment particles suggest that up to 90 percent of the organic matter in Ross Sea sediments is derived from the igneous and ancient metamorphic and sedimentary rocks that are being glacially eroded on the Antarctic continent and transported seaward.
ABSTRACT This work refines previous interpretations of the structure and morphology of the Chesap... more ABSTRACT This work refines previous interpretations of the structure and morphology of the Chesapeake Bay impact crater on the basis of more than 1,200 km of multichannel and single-channel seismic reflection profiles collected in the bay and on the adjacent ...
Special Paper 339: Large meteorite impacts and planetary evolution; II, 1999
ABSTRACT This work refines previous interpretations of the structure and morphology of the Chesap... more ABSTRACT This work refines previous interpretations of the structure and morphology of the Chesapeake Bay impact crater on the basis of more than 1,200 km of multichannel and single-channel seismic reflection profiles collected in the bay and on the adjacent ...
Five coreholes (Exmore, Kiptopeke, NASA Langley, North, Bayside) have sampled crater-fill deposit... more Five coreholes (Exmore, Kiptopeke, NASA Langley, North, Bayside) have sampled crater-fill deposits of the Chesapeake Bay crater, and two others (Windmill Point, Newport News) have sampled partly equivalent deposits outside the outer rim (Fig. 6.1Fig. 6.2Fig. 6.3AFig. 6.3B, CD-ROM.7; Table 1.2). The crater-fill deposits can be subdivided into several distinctive units, which we will discuss in chronostratigraphic order from oldest
Analyses of the stable isotopes of the organic carbon and microscopic examination of the sediment... more Analyses of the stable isotopes of the organic carbon and microscopic examination of the sediment particles suggest that up to 90 percent of the organic matter in Ross Sea sediments is derived from the igneous and ancient metamorphic and sedimentary rocks that are being glacially eroded on the Antarctic continent and transported seaward.
The Chesapeake Bay impact structure is the focus of an ongoing federal-state-local research progr... more The Chesapeake Bay impact structure is the focus of an ongoing federal-state-local research program. Recent core drilling and geophysical surveys address the formative processes and hydrogeologic properties of this major 'wet-target' impact.
Postimpact deposits over and near the Chesapeake Bay impact crater consist of a thick (200-&g... more Postimpact deposits over and near the Chesapeake Bay impact crater consist of a thick (200-&gt;500 m) succession of fossiliferous siliciclastic formations, which range stratigraphically from regionally distributed barren silt and richly fossiliferous late Eocene clay deposits, to a variety of locally distributed Quaternary and Holocene sand units (see Chapter 2; Figs. 2.4, 2.5, 6.2, 7.1, 7.2). Because the impact took
Our extensive network of seismic reflection profiles clearly documents that the structural-morpho... more Our extensive network of seismic reflection profiles clearly documents that the structural-morphological features of the outer rim, annular trough, and displaced megablocks are expressed principally by preimpact sedimentary rocks, and to a much lesser degree, by crystalline basement rocks (Figs. 1.5, 4.1, 4.2A4.2B; CD-ROM.3-6). In contrast, the peak ring, inner basin, and central peak of the Chesapeake Bay crater are
third the age of Earth. Nevertheless, the mass fraction of diamond observed in carburanium is sev... more third the age of Earth. Nevertheless, the mass fraction of diamond observed in carburanium is several orders of magnitude smaller than that of carbonado. This presents a serious difficulty if a radiation process is to account for carbonado formation. Mass transport problems must b e . addressed; because <20% of the volume of carbonado is not diamond, some transport mechanism would have to concentrate diamond grains into large aggregates while removing the displaced uranium oxides and decay products. Because carburanium contains 500-nm polycrystalline aggregates, a sintering mechanism would then be required to coalesce these radiationformed aggregates into the micrometersized single crystal grains typical of carbonado. These factors indicate that a radiation mechanism alone cannot satisfactorily explain the formation of carbonado.
Analyses of the stable isotopes of the organic carbon and microscopic examination of the sediment... more Analyses of the stable isotopes of the organic carbon and microscopic examination of the sediment particles suggest that up to 90 percent of the organic matter in Ross Sea sediments is derived from the igneous and ancient metamorphic and sedimentary rocks that are being glacially eroded on the Antarctic continent and transported seaward.
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