Southeastern Section - 66th Annual Meeting - 2017

Paper No. 5-15
Presentation Time: 8:00 AM-12:00 PM


MELANDER, Scott1, STONE, Michael2, SPIVEY, Whittney E.2, RICE, Brooks2, ALBRIGHT, Brandon2 and ST. JOHN, Kristen2, (1)Biological Sciences, James Madison University, Harrisonburg, VA 22807, (2)Geology and Environmental Science, James Madison University, Harrisonburg, VA 22807,

Core MD02-2555 was collected from the Bush Hill Basin area, located in the Texas-Louisiana Slope of the Gulf of Mexico. Sediments from this region have been used to determine the timing and sources of meltwater spikes during the deglaciation of the Last Glacial Maximum. This course-based undergraduate research study attempted to describe MDO2-2555 by multiproxy approaches with XRD analysis, O and C isotope analysis, XRF analysis, color reflectance interpretation, and from the relative abundance of planktic forams.

Previous studies on core MD02-2555 lacked a detailed age model and attributed a band of darker clays, 650-500cmbsf, as the Last Glacial Maximum. This region was found to be poor for the preservation of planktic forams suggesting a cooling event. G. menardii abundance suggested that the Pleistocene-Holocene (Y-Z biozone) boundary in the core occurs deeper than earlier estimated. Combined with 14C age data, this stratigraphic interval is now tentatively defined as the Younger Dryas between ≈13.5-11.5ka. XRD analysis of smectite, illite, kaolinite, and chlorite shows a spiked change in clay minerals that occurred after the dark clay. Hypothesized to be Meltwater Pulse 1b, which occurred at ≈11ka, we see a dramatic increase in kaolinite and chlorite in the core. This may indicate increased meltwater from the Laurentide ice sheets passed through the southwest Mississippi drainage basin. XRF analysis was conducted with element ratios compared to relatively stable Al to account for the large amount of sediment runoff. Ca/Al was expected to be localized to the younger portions of the core with the majority source being inorganic CaCO3 from microfossils. However, being present though the entire core indicates that most Ca came from terrigenous sources, potentially in smectite, which was the dominant clay mineral group identified. A key element studied was K, a proxy for the relative proportions of kaolinite vs illite. Around 11ka we observe a general increase in K/Al further indicative of this being Meltwater Pulse 1b as described with the XRD analysis. The increase of the K/Al ratio also supports meltwater transport through the southwest region in the Mississippi drainage basin. Additional research and sampling would help with incomplete data like the δ18O and δ13C isotope analyses when foram preservation was poor.