Stable-isotope record of organic carbon from an evolving carbonate banktop, Bight of Abaco, Bahamas
Stable-isotope record of organic carbon from an evolving carbonate banktop, Bight of Abaco, Bahamas
Geology (Boulder) (August 1990) 18 (8): 790-794
- algae
- Atlantic Ocean
- Bahamas
- banks
- biofacies
- biogenic structures
- C-13/C-12
- carbon
- carbonate platforms
- carbonate sediments
- Caribbean region
- Cenozoic
- changes of level
- cyclic processes
- environmental analysis
- Foraminifera
- Gastropoda
- geochemistry
- Holocene
- Invertebrata
- isotopes
- lagoonal environment
- lagoonal sedimentation
- lithofacies
- Little Bahama Bank
- marine environment
- marine sediments
- Mollusca
- North Atlantic
- organic carbon
- organic compounds
- organic materials
- paleoecology
- Plantae
- Protista
- Quaternary
- sedimentary structures
- sedimentation
- sediments
- stable isotopes
- stratigraphy
- terrestrial environment
- West Indies
- Bight of Abaco
The stable-isotope composition (delta (super 13) C) of total organic carbon (TOC) was measured as a function of depth throughout a 217-cm-thick sequence of Holocene carbonate sediment within the Bight of Abaco lagoon, Little Bahama Bank. Biofacies and lithofacies analyses indicate progressive banktop submergence and paleoenvironmental response during Holocene sea-level rise. Stable-isotope values shift markedly from -27.7ppm within the 7900 B.P. paleosol at the base of the core to -11.1ppm at the present-day sediment-water interface. An abrupt excursion toward heavy-isotope values records the first establishment of Thalassia seagrass upon open-marine flooding. A multitracer approach, combining biofacies, lithofacies, and stable-isotope analysis of TOC confirms that the dramatic +17ppm shift observed in Delta (super 13) C was a direct result of sea-level rise and associated environmental changes over the banktop; there is little evidence of spurious diagenetic overprint. Stable-isotope analyses of organic carbon may enhance the reconstruction of carbonate sequences by revealing a distinctive geochemical signature of banktop flooding, including the onset of growth of otherwise unpreservable Thalassia seagrass.