An analysis and comparison of observed Pleistocene South Carolina (USA) shoreline elevations with predicted elevations derived from Marine Oxygen Isotope Stages

Abstract

Geological maps of South Carolina, covering >6800 km2, confirm the existence of eight preserved Pleistocene shorelines above current sea level: Marietta (+ 42.6 m), Wicomico (+ 27.4 m), Penholoway (+ 21.3 m), Ladson (+ 17.4 m), Ten Mile Hill (+ 10.7 m), Pamlico (+ 6.7 m), Princess Anne (+ 5.2 m), and Silver Bluff (+ 3 m). Current geochronologic data suggest that these eight shorelines correlate with Marine Oxygen Isotope Stages (MIS) as follows: Marietta—older than MIS 77; Wicomico—MIS 55–45; Penholoway—MIS 19 or 17; Ladson—MIS 11; Ten Mile Hill—MIS 7; Pamlico—MIS 5; Princess Anne—MIS 5; and Silver Bluff—MIS 5 or 3. Except for the MIS 5e Pamlico, and possibly the MIS 11 Ladson, the South Carolina elevations are higher than predicted by isotope proxy-based reconstructions. The <4 m of total relief from the Pamlico to the Silver Bluff shoreline in South Carolina, for which other reconstructions suggest an expected relief of ~ 80 m, illustrates the lack of match. Our results suggest that processes affecting either post-depositional changes in shoreline elevations or the creation of proxy sea-level estimates must be considered before using paleo sea-level position on continental margins.

Sea-level records from the U.S. mid-Atlantic constrain Laurentide Ice Sheet extent during Marine Isotope Stage 3

“…These observations have been considered enigmatic given that previously published GIA models predict RSL in this region to be more than 60 m below present level at MIS 3 (ref. 18 ). However, we have shown that GIA models can be reconciled with the observational record from the Albemarle Embayment under two conditions: (1) global mean sea level during MIS 3 reached approximately −40 m, consistent with a recent analysis of sediment core records from the Bohai Sea 10 and within the bounds of several earlier studies 37 38 39 40 41 42 43 ; and (2) the eastern sector of the LIS remained largely ice-free over an extended period from MIS 5a through mid-MIS 3, consistent with recent field-based evidence 34 .…”

“…1; Supplementary Table 1), but GIA calculations predict that these markers should presently be found as much as ∼70 m below sea level8. Tectonic uplift of the markers is insufficient to explain their present-day elevation1718 and sediment compaction has led to only minor subsidence in this region19.…”

Depositional Environments and Stratigraphy of Quaternary Paleochannel Systems Offshore of the Georgia Bight, Southeastern U.S.A.

“…freshwater swamps, estuaries, tidal inlets, and salt marshes (Weems, Lewis, and Lemon, 2014). Pleistocene barrier island and backbarrier deposits define a scarp-and-terrace morphology that documents the location of successive Quaternary sealevel highstands across the coastal plain (Cooke, 1936;Colquhoun and Johnson, 1968;Doar and Kendall, 2014). These ancient barrier systems decrease in elevation and age toward the modern coast, where they commonly form the cores of Holocene barrier islands (Cooke, 1936;Hayes, 1994;Hoyt, Weimer, and Henry, 1964;MacNeil, 1949;Weems, Lemon, and Nelson, 1994).…”

Evidence of an Marine Isotope Stage 3 transgression at the Baixada Santista, south-eastern Brazilian coast

“…Rodriguez et al (2000) identified a 15 mbsl deposit, associated with MIS3, on the Texas continental shelf. Also in the United States, Doar III and Kendall (2017) reported MIS3 ages for the 3 mabsl of the Silver Bluff formation, in South Carolina.…”