Cretaceous and Cenozoic tectonism on the Atlantic coastal margin

Prowell, David C.

doi:10.1130/dnag-gna-i2.557

Cited by 25 publications

(26 citation statements)

References 26 publications

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“…Based on thk observation, he suggested that stream cutting progresses in the direction of the regional dip of the sedimentary units. Regional tilting of the land surface by flexing of the lithospheric crust in the seaward direction is widely observed in the Coastal Plain (Beaumont 1978(Beaumont , 1979Pazzaglia andGardner 1992 Pavich 1985;Sykes 1978;Prowell 1988) and is consistent with the observed asymmetry in most of the tributary streams. Neither of these possible mechanisms is consistent with the asymmetry of the Savannah River valley in the reach between Upper Three Runs and Steel Creek, where the asymmetry is towards the southwest rather than southeast.…”

Section: Asymmetry Of Stream Valleysupporting

confidence: 72%

SRS Geology/Hydrogeology Environmental Information Document

Denham¹

1999

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Section: Asymmetry Of Stream Valleysupporting

confidence: 72%

SRS Geology/Hydrogeology Environmental Information Document

Denham¹

1999

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“…The closest Triassic rift basin lies 250 km to the southeast, and the 200 Ma mafi c dike swarms that cut northwestward across rocks of the Carolina terrane and Inner Piedmont decrease abruptly near the Brevard fault zone (Hames et al, 2000;Schlische et al, 2003), with very few dikes extending into the Blue Ridge (King, 1961). Extension may have been followed by shortening as early as 200 Ma, at the onset of seafl oor spreading (Schlische et al, 2003); thrust faults mapped in the coastal plain suggest that the dominant horizontal stress has been compressional since at least the Cretaceous (Prowell, 1988;Manspeizer et al, 1989).…”

Section: Geologic Settingmentioning

confidence: 95%

Isostatic compensation for a portion of the Southern Appalachians: Evidence from a reconnaissance study using wide-angle, three-component seismic soundings

Hawman

Khalifa

Baker

2011

Geological Society of America Bulletin

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Wide-angle refl ections generated by fi ve controlled blasts and over 110 timed quarry blasts in the Southern Appalachians were used to test models for isostatic compensation of topog raphy. The profi les cross the Appa lachian gravity gradient and gravity low and sample the highest elevations within the orogen. Migration of P, SV, and SH refl ections suggests that crustal thickness varies from 35 to 39 km within the coastal plain and 37-39 km within the Carolina terrane. It increases northwestward from 40 to 45 km across the Inner Piedmont, and then thickens to 50-52 km along the southeastern fl ank of the Blue Ridge Mountains. Crustal thickness within the Blue Ridge Mountains ranges from 47 to 56 km. Receiver functions for broadband stations GOGA and MYNC show a similar pattern in crustal thickness. Assuming Airy compensation, the correlation between elevation and Moho depth suggests a range of 50-150 kg/m 3 for the density contrast between the crustal root and mantle. The greatest Moho depths are associated not with the tallest peaks, but rather with the broadest portions of the mountain chain. This observation is consistent with regional bending of the lithosphere. However, the planar basement surface suggests that the root either predates Alleghanian thrusting, and therefore is unrelated to the present topography, or formed in response to some other mechanism. Bounds on curvature of the basement surface suggest a lower bound of 30-40 km for the effective elastic thickness of the lithosphere. This is consistent with previous estimates for the southern Appalachians based on analysis of gravity data.

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“…Several significant reverse faults, fault systems, and anticlinal folds disrupt Cretaceous and Cenozoic sediments near the inner edge of the Virginia Coastal Plain Newell, 1977, 1978;Prowell, 1983Prowell, , 1988Mixon and Powars, 1984;Dischinger, 1987;Mixon et al, 1989;Mixon et al, 1992). Maximum displacement (above the basement) is seen in the Lower Cretaceous section (15-50 m), intermediate displacements occur in Paleocene and Eocene strata (10-15 m), and minor displacements have been noted in younger beds (l-3 m).…”

Section: Coastal Plain Reverse Faultingmentioning

confidence: 99%

“…30). and the preimpact sedimentary cover is exposed or only shallowly buried in the updip areas (Prowell, 1988). Faults that cut this crystalline-sedimentary contact are much easier to detect in the field than those displacing sedimentary rocks of similar lithology.…”

Section: Coastal Plain Reverse Faultingmentioning

confidence: 99%

The Chesapeake Bay bolide impact: a convulsive event in Atlantic Coastal Plain evolution

Poag

1997

Sedimentary Geology

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Until recently, Cenozoic evolution of the Atlantic Coastal Plain has been viewed as a subcyclical continuum of deposition and erosion. Marine transgressions alternated with regressions on a slowly subsiding passive continental margin, their orderly succession modified mainly by isostatic adjustments, occasional Appalachian tectonism, and paleoclimatic change. This passive scenario was dramatically transformed in the late Eocene, however, by a bolide impact on the inner continental shelf. The resultant crater is now buried 400-500 m beneath lower Chesapeake Bay, its surrounding peninsulas, and the continental shelf east of Delmarva Peninsula. This convulsive event, and the giant tsunami it engendered, fundamentally changed the regional geological framework and depositional regime of the Virginia Coastal Plain, and produced the following principal consequences. (1) The impact excavated a roughly circular crater, twice the size of Rhode Island (-6400 km2) and nearly as deep as the Grand Canyon (-1.3 km deep). (2) The excavation truncated all existing ground-water aquifers in the target area by gouging -4300 km3 of rock from the upper lithosphere, including Proterozoic and Paleozoic crystalline basement rocks and Middle Jurassic to upper Eocene sedimentary rocks. (3) Synimpact depositional processes, including ejecta fallback, massive crater-wall failure, water-column collapse, and tsunami backwash, filled the crater with a porous breccia lens, 600-1200 m thick, at a phenomenal rate of -1200 m/hr. The breccia lens replaced the truncated ground-water aquifers with a single 4300 km3 reservoir, characterized by ground water -1.5 times saltier than normal sea water (chlorinities as high as 25,700 mg/l). (4) A structural and topographic low, created by differential subsidence of the compacting breccia, persisted over the crater at least through the Pleistocene. In the depression are preserved postimpact marine lithofacies and biofacies (upper Eocene, lower Oligocene, lower Miocene) not known elsewhere in the Virginia Coastal Plain. (5) Long-term differential compaction and subsidence of the breccia lens spawned extensive fault systems in the postimpact strata. Many of these faults appear to reach the bay floor, and may be potential hazards for motion-sensitive structures in population centers around Chesapeake Bay. Near-surface fracturing and faulting generated by the impact shock may extend as far as 90 km from the crater rim. (6) Having never completely filled with postimpact sediments. the sea-floor depression over the crater appears to have predetermined the location of Chesapeake Bay. (7) As large impact craters are principal sources for some of the world's precious metals, it is reasonable to expect that metal-enriched sills, dikes, and melt sheets are present in the inner basin of the crater.In addition to these specific consequences, the crater and the convulsive event that produced it, have widespread implications for traditional interpretations of certain structural and depositional features of the Atla...

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Cretaceous and Cenozoic tectonism on the Atlantic coastal margin

Cited by 25 publications

References 26 publications

SRS Geology/Hydrogeology Environmental Information Document

SRS Geology/Hydrogeology Environmental Information Document

Isostatic compensation for a portion of the Southern Appalachians: Evidence from a reconnaissance study using wide-angle, three-component seismic soundings

The Chesapeake Bay bolide impact: a convulsive event in Atlantic Coastal Plain evolution

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