Cold water polar argonitic bivalve elemental composition, East Antarctica

Aragonitic bivalves and abiotic aragonite are common in cold water Antarctic environments. Aragonitic bivalves have lower Mg, Sr, Fe and Mn and higher Na concentrations than those in abiotic polar aragonite. MgCO3 values in polar aragonitic bivalves and abiotic aragonite are related to pCO2. Sr values vary with aragonite types, seawater temperature and seawater content in the fluid precipitating aragonite. Abiotic polar aragonite contains much larger concentrations of Fe and Mn than those in aragonitic polar bivalves because abiotic aragonite formed subglacially below the zone of O2 minimum at very shallow water depths. Na values in aragonitic bivalves are indicative of both salinity and rates of crystal growth, whereas Na values in abiotic aragonite decrease with decreasing salinity. The concentrations of Mn, Na and Sr indicate that aragonitic bivalves formed faster than abiotic aragonite. The abiotic aragonite forms rapidly and precipitates significant amount in less than a year. This comparative study enables an understanding of cold water polar biotic and abiotic aragonites related to environment, water temperature, ice cover, pCO2 levels, redox potential, meltwater dilution, salinity and rate of carbonate formation. These aspects are essential in understanding modern and ancient glacial sedimentation and diagenesis.