Quaternary Science Reviews 26 (2007) 920–940 Sea-level history of the Gulf of Mexico since the Last Glacial Maximum with implications for the melting history of the Laurentide Ice Sheet Alexander R. Simms a,Ã , Kurt Lambeck b , Anthony Purcell b , John B. Anderson c , Antonio B. Rodriguez d a T. Boone Pickens School of Geology, Oklahoma State University, 105 NRC, Stillwater, OK 74078, USA b Research School of Earth Sciences, Building 61 Mills Road, The Australian National University, Canberra ACT 0200, Australia c Department of Earth Science, Rice University, 6100 S. Main, MS-126, Houston, TX 77005, USA d Institute of Marine Sciences, University of North Carolina, at Chapel Hill, 3431 Arendell Street, Morehead City, NC 28557, USA Received 26 January 2006; received in revised form 8 January 2007; accepted 9 January 2007 Abstract Sea-level records from the Gulf of Mexico at the Last Glacial Maximum, 20 ka, are up to 35 m higher than time-equivalent sea-level records from equatorial regions. The most popular hypothesis for explaining this disparity has been uplift due to the forebulge created by loading from Mississippi River sediments. Using over 50 new radiocarbon dates as well as existing published data obtained from shallow- marine deposits within the northern Gulf of Mexico and numerical models simulating the impact of loading due to the Mississippi Fan and glacio-hydro-isostasy, we test several possible explanations for this sea-level disparity. We find that neither a large radiocarbon reservoir, sedimentary loading due to the Mississippi Fan, nor large-scale regional uplift can explain this disparity. We do find that with an appropriate model for the Laurentide Ice Sheet, the observations from the Gulf of Mexico can be explained by the process of glacio- hydro-isostasy. Our analysis suggests that in order to explain this disparity one must consider a Laurentide Ice Sheet reconstruction with less ice from 15 ka to its disappearance 6 ka and more ice from the Last Glacial Maximum to 15 ka than some earlier models have suggested. This supports a Laurentide contribution to meltwater pulse 1-A, which could not have come entirely from its southern sector. r 2007 Elsevier Ltd. All rights reserved. 1. Introduction Arguing that the Gulf of Mexico was tectonically stable, Shepard (1960) produced one of the first ‘‘eustatic’’ sea- level curves for the last 30 ka from radiocarbon dates obtained from shallow marine mollusks and wood fragments. Redfield (1967) and Emery and Garrison (1967) both noted that the sea-level curves of Shepard (1960), and later works by McFarland (1961), obtained from the Gulf of Mexico were up to 35 m shallower at the Last Glacial Maximum (LGM), and 15 m shallower 10 ka, than sea-level curves from other places across the globe. On the basis of submerged shoreline features and deltas, some authors have argued for a sea-level lowstand of 120 m within the Gulf of Mexico, bringing the ‘‘global’’ and Gulf of Mexico records into agreement at the LGM (Curray, 1960; Berryhill et al., 1986). However, none of these features have been dated nor corrected for the high subsidence rates usually present on the outer shelf. Continued work on refining the ‘‘global’’ sea-level record by Fairbanks (1989), Chappell and Polach (1991), Bard et al. (1996), Yokoyama et al. (2000), and Hanebuth et al. (2000) and the Gulf of Mexico sea-level record by Nelson and Bray (1970) and Bart and Ghoshal (2003) continues to indicate sea levels within the Gulf of Mexico 35 m shallower during the LGM, and 15 m shallower at 10 ka, than ‘‘global’’ sea-level records (Fig. 1a). A similar disparity has been noted by other studies of sea-level indicators from Florida and the Caribbean (e.g. Scholl et al., 1969; Toscano and Macintyre, 2003). Many authors have noted great variability in Late Quaternary/Holocene sea-level records globally. Pirazzoli ARTICLE IN PRESS 0277-3791/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.quascirev.2007.01.001 Ã Corresponding author. Tel.: +1 405 744 7725; fax: +1 405 744 7841. E-mail addresses: alex.simms@okstate.edu (A.R. Simms), kurt.lambeck@anu.edu.au (K. Lambeck), tony@rses.anu.edu.au (A. Purcell), johna@rice.edu (J.B. Anderson), abrodrig@email.unc.edu (A.B. Rodriguez).