Do circum-Bahamian carbonates record climate information about the ice ages?
Shallow carbonates represent one of the most abundant archives of Earth history. Specifically, carbonate geochemistry serves as a proxy for paleoclimate parameters such as the global carbon cycle and relative sea level. Understanding the mechanisms controlling the mineralogy and geochemistry of modern carbonates therefore is key to accurate reconstruction of past climates. The ancient record principally preserves carbonate formed in shallow waters, but in the more recent past extreme alteration during periods of low sea level makes it difficult to build a reliable long-term record from shallow environments directly. Shallow carbonate in the Bahamas accumulates not just on the Bahama Banks, but also in adjacent deeper waters as it is exported from the shelf edge during storms. These deep sediments are protected from alteration during periods of low sea level, and thus contain a continuous record of shallow carbonate geochemistry not preserved on the shelf. I study 20 sediment cores from environments adjacent to the Bahama Banks to understand what fraction of carbonate is produced in the open ocean, what fraction is from the shallow shelf, and how it is altered at the sea floor. By deconvolving these signals, I construct a record of shallow carbonate production and geochemistry over the past 200 kyr to understand how shallow environments respond to sea level change during glacial cycles, how this response is recorded in the geologic record, and how we can use this understanding to learn about the ancient past.