Indicators of Methane-Derived Carbonates and Chemosynthetic Organic Carbon Deposits: Examples from the Florida Escarpment

Abstract

Abyssal chemosynthetic communities are supported by bacterial oxidation of reduced chemicals in brines which seep out through sediments at the base of the Florida Escarpment. They are surrounded by carbonate hardgrounds and sediments rich in fresh organic carbon that contain a record of the metabolic pathways and geochemical processes which are active at these sites. The isotopic composition of tissue samples (δ 13 C as low as #7576.40∓), carbonate crusts (δ 13 C as low #7545.19∓) and sedimentary organic matter (δ 13 C as low #7567.87∓) indicate that biogenic methane dissolved in the brines (δ 13 C #7583.3 ± 5.8∓) is a major carbon source for many of the locally synthesized compounds