Deciphering Holocene sea-level history on the U.S. Gulf Coast: A high-resolution record from the Mississippi Delta

Research Article| July 01, 2004 Deciphering Holocene sea-level history on the U.S. Gulf Coast: A high-resolution record from the Mississippi Delta Torbjörn E. Törnqvist; Torbjörn E. Törnqvist 1Department of Earth and Environmental Sciences, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7059, USA Search for other works by this author on: GSW Google Scholar Juan L. González; Juan L. González 1Department of Earth and Environmental Sciences, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7059, USA Search for other works by this author on: GSW Google Scholar Lee A. Newsom; Lee A. Newsom 2Department of Anthropology, Pennsylvania State University, University Park, Pennsylvania 16802-3404, USA Search for other works by this author on: GSW Google Scholar Klaas van der Borg; Klaas van der Borg 3Robert J. Van de Graaff Laboratory, Utrecht University, PO Box 80000, NL-3508 TA Utrecht, The Netherlands Search for other works by this author on: GSW Google Scholar Arie F.M. de Jong; Arie F.M. de Jong 3Robert J. Van de Graaff Laboratory, Utrecht University, PO Box 80000, NL-3508 TA Utrecht, The Netherlands Search for other works by this author on: GSW Google Scholar Charles W. Kurnik Charles W. Kurnik 4University NAVSTAR Consortium (UNAVCO), PO Box 3000, Boulder, Colorado 80307-3000, USA Search for other works by this author on: GSW Google Scholar GSA Bulletin (2004) 116 (7-8): 1026–1039. https://doi.org/10.1130/B2525478.1 Article history received: 31 Aug 2003 rev-recd: 01 Feb 2004 accepted: 09 Feb 2004 first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Torbjörn E. Törnqvist, Juan L. González, Lee A. Newsom, Klaas van der Borg, Arie F.M. de Jong, Charles W. Kurnik; Deciphering Holocene sea-level history on the U.S. Gulf Coast: A high-resolution record from the Mississippi Delta. GSA Bulletin 2004;; 116 (7-8): 1026–1039. doi: https://doi.org/10.1130/B2525478.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Published Holocene relative sea-level (RSL) curves for the U.S. Gulf Coast are in mutual conflict, with some characterized by a smooth RSL rise akin to widely accepted eustatic sea-level curves versus others, including several recent ones, that are characterized by a conspicuous "stair-step" pattern with prolonged (millennium-scale) RSL stillstands alternating with rapid (meter-scale) rises. In addition, recent work in Texas and Alabama has revitalized the notion of a middle Holocene RSL highstand, estimated at 2 m above present mean sea level.An extensive sampling program in the Mississippi Delta (Louisiana) focused on the collection of basal peats that accumulated during the initial transgression of the pre-existing, consolidated Pleistocene basement. We used stable carbon isotope ratios to demonstrate that many of these samples accumulated in environments affected by frequent saltwater intrusion in the <30 cm zone between mean spring high water and mean sea level, and we selected plant macrofossils that were subjected to AMS 14C dating. Nearly 30 sea-level index points from a ∼20 km2 study area on the eastern margin of the delta suggest that RSL rise followed a relatively smooth trend for the time interval 8000–3000 cal yr B.P., thus questioning the occurrence of major RSL stillstands alternating with abrupt rises. Given the narrow error envelope defined by our data set, any sea-level fluctuations, if present, would have amplitudes of <1 m.Although a true middle Holocene highstand never occurred in the Mississippi Delta, the high level of detail of our time series enables a rigorous test of this hypothesis. Correction of our data set for a hypothetical tectonic subsidence rate of 1.1 mm yr−1 (assuming a constant subsidence rate compared to the tectonically relatively stable adjacent coast of Texas) leads to sea levels near 2 m above present during the time interval 6000–4000 cal yr B.P. However, this model also implies a RSL position near −2 m around 8000 cal yr B.P., which is inconsistent both with data of this age from Texas, as well as with widely accepted sea-level data from elsewhere. We therefore conclude that a middle Holocene highstand for the U.S. Gulf Coast is highly unlikely, and that the entire area is still responding glacio-isostatically, by means of forebulge collapse, to the melting of the Laurentide Ice Sheet. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.