Multi-proxy evaluation of early Holocene Acropora cervicornis from the Enriquillo Valley, Dominican Republic: implications for local climate dynamics and coral biochemistry
Tropical climate may be a significant driver in global climate change. Therefore, it is important to understand tropical climate dynamics and scales of variability. When carefully examined through various field and laboratory methods, reef-building corals can provide tremendous insight into past climate change in the tropics. Several proxies preserved in ancient coral records have the potential to significantly aid paleoclimate reconstruction. Locales, such as the semi-arid southwestern part of the Dominican Republic, that exhibit seemingly pristine, subaerially exposed, coral reefs represent an ideal place to study early Holocene tropical climate dynamics because most reefs of such age are still submerged. Through multi-proxy analyses of the rarely studied branching coral Acropora cervicornis, this study has provided new insight into: 1) the coral biochemistry of this coral species; 2) regional Caribbean climate dynamics; and 3) the effects of laboratory drilling on biogenic aragonite materials. Oxygen and carbon stable isotope analyses show that the time frame of the corals studied (~9350-~8800 yrs BP) was not characterized by extraordinary seasonality induced by the presence of the InterTropical Convergence Zone, the position of which controls the distribution of moisture near the equator. Hence, this study corroborates the onset of an episode of tropical aridity (~9000-8000 yrs BP) inferred from elsewhere in the world. Correlations between stable isotopes and trace element compositions reveal that the two main skeletal fabrics, lateral and axial corallites, vary significantly in their geochemical patterns, leading to the conclusion that lateral corallites preserve more information about original ambient seawater conditions than axial corallites do. Petrographical analysis confirmed lack of freshwater diagenesis, which indicates that the climate since emergence has been relatively dry, and it is unlikely that there has been a freshwater lens significantly altering the integrity of coral chemistry and structure through meteoric diagenesis. Furthermore, radiocarbon dating in this study and others in the same field area shows that corals colonized the Enriquillo embayment earlier than had been previously assumed. Coral sampling methodologies have also been addressed in this study, confirming the induction of aragonite-calcite thermal inversion through laboratory drilling. Such analytical transformation has the potential to significantly skew geochemical data derived from corals.
Franklin and Marshall College Archives, Undergraduate Honors Thesis 2006
- F&M Theses Collection