228TH AS AN ANNUAL-SCALE GEOCHRONOLOGICAL TOOL: APPLICATIONS TO THE 2010 BP BLOWOUT EVENT
210Pb and 234Th analyses have shown that surficial Gulf of Mexico sediments following the 2010 BP blowout event accumulated at extremely rapid rates, up to 100x greater than rates of underlying, “natural” sediments. Since over two years has passed since the BP event, the time frame is now ideal for investigating the utility of 228Th as a geochronological tool.
Using gamma spectroscopy, 212Pb and 208Tl are used as proxies for 228Th, and are detected to depths of 5-6 cm in cores collected almost 2 years following the event. Down-core 228Th profiles are consistent with decay profiles and support 210Pb and 234Th data indicating extremely rapid sediment accumulation following the 2010 BP blowout event.
While work is still in progress, 228Th appears to be a promising tool for bridging the gap between 210Pb (half-life ~22.3 years) and 234Th (half-life ~24 days) geochronometers, thereby allowing for the investigation of sedimentary processes over a range of time scales.