28 Sep 2020

28 Sep 2020

Review status: this preprint is currently under review for the journal ESSD.

Last interglacial sea levels within the Gulf of Mexico and northwestern Caribbean Sea

Alexander R. Simms Alexander R. Simms
  • Department of Earth Science, University of California Santa Barbara, Santa 5 Barbara, CA 93106, USA

Abstract. During the Last Interglacial (LIG) the volume of additional water in the world's oceans was large enough to raise global sea levels about 6–9 m higher than present levels. However, LIG sea levels vary regionally and those regional differences hold clues about the past distribution of ice sheets and local rates of subsidence and tectonic uplift. In this study, I used a standardized database template to review and summarize the existing constraints on LIG sea levels across the northern Gulf of Mexico and Caribbean shoreline of the Yucatan Peninsula. In total, I extracted 32 sea-level indicators including the insertion of 16 U-series ages on corals, 1 electron spin resonance age, 2 amino acid racemization ages and 26 luminescence ages. Most dated sea-level indicators for the northern Gulf of Mexico are based on optically stimulated luminescence (OSL) ages of beach deposits of a mappable LIG shoreline. This shoreline extends from the Florida Panhandle through south Texas but is buried or removed by the Mississippi River across most of Louisiana. A similar feature is observed in satellite images south of the Rio Grande within the Mexican portions of the Gulf of Mexico but has yet to be dated. Elevations measured on portions of this feature close to the modern coast point to sea levels less than 1 m to ~ 5 m higher than present for much of the northern Gulf of Mexico. However, a few, albeit undated, portions of the same shoreline located at more inland locations point to sea levels up to +7.2 m attesting to up to 7 m of differential subsidence between the inland and coastal sites.

Across the Yucatan Peninsula, U-series dating of corals has provided the main index points for LIG sea levels. Other carbonate coastal features such as beach ridges and eolianites have also been described, but rely on corals for their dating. The maximum elevation of the LIG coral-based relative sea-level (RSL) estimates decrease from around +6 m across the Caribbean shoreline of the Yucatan Peninsula near Cancun, Mexico to as low as −6 m to the south beneath the southern atolls of Belize, although discussion continues as to the validity of the ages for these southern corals. If these lower elevations corals are LIG in age, their below-present elevations may be a result of vertical motion along faults dipping into the Cayman Trough. South of Belize only one purported LIG coral has been dated on the Isla de Roatán off the coast of Honduras at a likely tectonically uplifted elevation of 37.2 m. Thus the elevation of LIG sea levels within the inland siliciclastic shorelines of Guatemala and Honduras as well as the southwestern Gulf of Mexico remain poorly constrained and potential venues for future research.

The database described in this paper is available open-access in spreadsheet format as Simms (2020), at this link:

Alexander R. Simms

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Alexander R. Simms

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Last Interglacial Sea Levels within the Gulf of Mexico and northwestern Caribbean Sea A. R. Simms

Alexander R. Simms


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Short summary
This study is part of a larger community effort to catalogue the elevation of sea levels approximately 120,000 years ago; a time period when global temperatures were generally warmer than they are today. For this specific study I summarized the work of other scientists who had determined the age and elevations of ancient shorelines and coral reefs from across the Gulf of Mexico and Yucatan Peninsula.