Chemical oceanographic influences on sediment accumulations of a carbonate ramp: Holocene Yucatan Shelf, Mexico

Abstract

Global controls on the oceanographic influences on the nature of carbonate factories are broadly understood. The details of the influences of changes in temperature and nutrients across individual carbonate shelves are less well constrained, however. This study explores spatial and temporal variations in chemical oceanography along and across the Yucatan Shelf, a modern carbonate ramp, and how these factors relate to variable bottom character, sediment and sediment geochemistry. In-situ sensors and remote-sensing data indicate the sporadic presence of cool, upwelled water with low dissolved oxygen and elevated Chlorophyll-a. This current-driven, westward flow of upwelled water is most evident in a zone just offshore of the northern peninsular shoreline, but its influence wanes ca 75 km offshore and as the shore turns southward. The impacts of this water mass include a transitional photozoan-heterozoan assemblage with biosiliceous components, relict grains and common thin Holocene sediment accumulations nearshore; further offshore are coralgal reefs and expansive sand plains. Geochemical proxies of bulk sediment, including high d 18 O and elevated HREE/LREE (heavy rare-earth element/light rareearth element) ratios near, and downcurrent of, the upwelling source, are interpreted to represent the signal of nearshore, westward movement of the cool and nutrient-rich, upwelled water. Collectively, these data emphasize how local processes such as upwelling and longshore transport can variably influence carbonate sediment accumulations and their geochemical signatures, both along and across individual shelves. These data and insights provide an analogue for the influences of spatial variability of water masses in the geological record, and for accurate interpretation of stratigraphic changes of sedimentary and geochemical proxy data in carbonate archives.

Flooding of a carbonate platform: The Sian Kaʼan Wetlands, Yucatán, Mexico—A model for the formation and evolution of palustrine carbonate factories around the modern Caribbean Sea and in the depositional record

“…The modern environments of the Yucatán coast provide the setting for many classic analogues of ancient shallow marine and coastal carbonate deposition, including beaches and barrier islands (Lowery, 2016;Ward, 1975;Ward & Brady, 1979), eolianites (Ward, 1973), offshore sand bars (Harms et al, 1974) and carbonate ramps (Logan et al, 1969;Rankey et al, 2013), while F I G U R E 3 Map of the Yucatán Peninsula, showing location of the Sian Ka'an Wetlands and the MesoAmerican Reef (reef outline from Smith et al, 2012). Blue arrows show the directions of groundwater flow (see Gondwe et al, 2010aGondwe et al, , 2010bGondwe et al, , 2010cGondwe et al, , 2010dGondwe et al, , 2012…”

“…The modern environments of the Yucatán coast provide the setting for many classic analogues of ancient shallow marine and coastal carbonate deposition, including beaches and barrier islands (Lowery, 2016; Ward, 1975; Ward & Brady, 1979), eolianites (Ward, 1973), offshore sand bars (Harms et al, 1974) and carbonate ramps (Logan et al, 1969; Rankey et al, 2013), while the MesoAmerican Reef offshore forms the second longest coastal barrier reef in the world (Back et al, 1986; Ginsburg & James, 1974; Kramer & Kramer, 2000, 2002; McField et al, 2005).…”

Climate and sea‐level controlling internal architecture of a Quaternary carbonate ramp (Northwest Shelf of Australia)

“…Research on modern examples including the Yucatan Shelf (e.g. Ward & Brady, 1973; Rankey et al ., 2021) and the Northwest Shelf of Australia (e.g. James et al ., 2004), is largely based on present‐day seafloor sedimentation and therefore of limited use in predicting the temporal evolution of these systems.…”