Crustal Structure Beneath the Atlantic Coastal Plain of South Carolina

1994 ◽  
Vol 65 (2) ◽  
pp. 180-191 ◽  
Author(s):  
James H. Luetgert ◽  
Harley M. Benz ◽  
Sriram Madabhushi
Keyword(s):  
South Carolina ◽  
Coastal Plain ◽  
Seismic Refraction ◽  
Crystalline Basement ◽  
Atlantic Coastal Plain ◽  
Passive Margin ◽  
P Wave ◽  
Eastern United States ◽  
Lateral Velocity ◽  
Atlantic Coastal

Abstract In April, 1991, a northwest-southeast trending 120-km-long seismic refraction/wide-angle reflection profile was recorded across the Atlantic Coastal Plain of South Carolina, the passive margin of the eastern United States formed by Mesozoic extension during the opening of the Atlantic and Gulf of Mexico. Two-dimensional ray tracing of first arrivals and reflections indicates large lateral velocity variations in the upper 5 km of the crust. From northwest to southeast along the profile, Coastal Plain sediments thicken from a few tens of meters to more than 1 km. P-wave velocities within the sediments range from 1.85 to 3.5 km s−1, while intercalated basalts have velocities of 5.2–5.5 km s−1. The top of the crystalline basement dips eastward and is characterized by velocities of 6.0–6.2 km s−1. High velocities of 6.2 km s−1 within the crystalline basement are locally restricted to a shallow 25-km-wide zone adjacent and east of the Dunbarton basin. Seismic, gravity and magnetic observations suggest that this anomaly represents a pre-Cretaceous mafic intrusion formed during Mesozoic rifting. Mesozoic rifting is also evident from observed eastward thinning of the crust from 37 to 32 km along the profile.

Theoretical Correlations and Lateral Discontinuities in the Quaternary Aminostratigraphic Record of the U.S. Atlantic Coastal Plain

1992 ◽  
Vol 38 (3) ◽  
pp. 275-291 ◽  
Author(s):  
J. F. Wehmiller ◽  
L. L. York ◽  
D. F. Belknap ◽  
S. W. Snyder
Keyword(s):  
South Carolina ◽  
Sea Level ◽  
Coastal Plain ◽  
Late Quaternary ◽  
Atlantic Coastal Plain ◽  
Passive Margin ◽  
Temperature History ◽  
Cape Fear ◽  
Atlantic Coastal ◽  
The U.S

AbstractAminostratigraphic correlations of emergent Quaternary deposits along the U.S. Atlantic Coastal Plain have employed independent radiometric data, regional temperature history models, and assumptions regarding the nature of the preserved late Quaternary sea-level record on this passive margin. A substantial “aminostratigraphic offset” is required if regional aminozones are rigorously constrained by all available Th/U data. New insights regarding the relation of this offset to subsurface stratigraphy in the Cape Fear region of southeastern North Carolina can explain these conflicts as consequences of the highly incomplete post-Cretaceous depositional record of the region. Southward projection of theoretical aminostratigraphic correlation trends suggests that stage 5 correlative marine units are rarely preserved on the emergent portion of the Coastal Plain between Cape Lookout and central South Carolina and that samples of this age would be most frequently found in this region only as fragmentary (and/or reworked) deposits on the inner shelf or in the subsurface of modern barrier islands. If this hypothesis is correct, then the accuracy of several Th/U coral dates from the South Carolina Coastal Plain must be questioned, along with sea-level, tectonic, and paleoclimatic conclusions derived from these dates.

Three forgotten earthquakes

1963 ◽  
Vol 53 (3) ◽  
pp. 687-692
Author(s):  
Gerald R. MacCarthy
Keyword(s):  
United States ◽  
New York ◽  
North Carolina ◽  
South Carolina ◽  
Coastal Plain ◽  
Maximum Intensity ◽  
Atlantic Coastal Plain ◽  
Eastern United States ◽  
Atlantic Coastal

Abstract For a given maximum intensity, most earthquakes of the Eastern United States are felt over much wider area than their western counterparts. Several of these eastern shocks, have, because of their relatively low maximum intensities, received little or no attention in seismological literature. Three such earthquakes will be described in terms of contemporary accounts: those of March 9, 1828, April 29, 1852, and of August 31, 1861. In no case did the maximum intensity exceed about VI on the Mercalli Scale, yet each was felt over many thousands of square miles. The 1828 shock affected at least 190,000 square miles, and was reported from Pennsylvania to South Carolina. That of 1852 affected about 187,000 square miles, and was reported from New York to North Carolina. That of 1861 affected at least 280,000 square miles, and was reported from Maryland to the Georgia-Alabama border. All three were felt from the Atlantic Coastal Plain westward into Ohio.

Constraining Properties of Sedimentary Strata Using Receiver Functions: An Example from the Atlantic Coastal Plain of the Southeastern United States

2020 ◽  
Vol 110 (2) ◽  
pp. 519-533 ◽  
Author(s):  
Erin Cunningham ◽  
Vedran Lekic
Keyword(s):  
United States ◽  
Coastal Plain ◽  
Velocity Profiles ◽  
Receiver Functions ◽  
Atlantic Coastal Plain ◽  
P Wave ◽  
Seismic Velocities ◽  
Eastern United States ◽  
Converted Wave ◽  
Atlantic Coastal

ABSTRACT Thickness and seismic velocities of sedimentary sequences strongly affect their response during earthquakes, which can prolong and amplify ground motions. We characterize shallow structure of Atlantic Coastal Plain (ACP) sediments using a passive-seismic approach based on high-frequency P-to-S receiver functions. We map the site-specific fundamental frequency for 64 USArray Transportable Array stations and confirm that the method yields results similar to those from traditional spectral ratio techniques, with fundamental frequencies between 0.1 and 1 Hz. In addition, using sediment S-wave reverberations and P-to-S phase arrival times measured directly from the receiver functions, we invert for average S- and P-wave velocity profiles of the ACP sedimentary strata. We find that VS increases with depth following a power-law relationship (VS∝z) whereas the increase of VP with depth is more difficult to constrain using converted wave methods; therefore, we choose to use the Brocher (2005) relationship to obtain VP through a VP/VS relationship. Finally, we use the variation of measured S-reverberation amplitudes with depth to validate these velocity profiles. These results have implications for seismic shaking across the ACP, which covers large portions of the eastern United States.

P ‐Wave Reflectivity of the Crust and Upper Mantle Beneath the Southern Appalachians and Atlantic Coastal Plain Using Global Phases

2020 ◽  
Vol 47 (18) ◽  
Author(s):  
Devon N. Verellen ◽  
Erik C. Alberts ◽  
Gustavo A. Larramendi ◽  
E. Horry Parker ◽  
Robert B. Hawman
Keyword(s):  
Coastal Plain ◽  
Upper Mantle ◽  
Atlantic Coastal Plain ◽  
P Wave ◽  
Southern Appalachians ◽  
Crust And Upper Mantle ◽  
Atlantic Coastal

Comparison of Amino Acid Racemization Geochronometry with Lithostratigraphy, Biostratigraphy, Uranium-Series Coral Dating, and Magnetostratigraphy in the Atlantic Coastal Plain of the Southeastern United States

1982 ◽  
Vol 18 (3) ◽  
pp. 337-359 ◽  
Author(s):  
L. McCartan ◽  
J. P. Owens ◽  
B. W. Blackwelder ◽  
B. J. Szabo ◽  
D. F. Belknap ◽  
...  
Keyword(s):  
South Carolina ◽  
Amino Acid ◽  
Coastal Plain ◽  
Atlantic Coastal Plain ◽  
Amino Acid Racemization ◽  
Uranium Series ◽  
Myrtle Beach ◽  
Atlantic Coastal ◽  
North And South ◽  
Integrated Study

AbstractThe results of an integrated study comprising litho- and biostratigraphic investigations, uranium-series coral dating, amino acid racemization in molluscs, and paleomagnetic measurements are compared to ascertain relative and absolute ages of Pleistocene deposits of the Atlantic Coastal Plain in North and South Carolina. Four depositional events are inferred for South Carolina and two for North Carolina by all methods. The data suggest that there are four Pleistocene units containing corals that have been dated at about 100,000 yr, 200,000 yr, 450,000 yr, and over 1,000,000 yr. Some conflicts exist between the different methods regarding the correlation of the younger of these depositional events between Charleston and Myrtle Beach. Lack of good uranium-series dates for the younger material at Myrtle Beach makes the correlation with the deposits at Charleston more difficult.

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