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Comparison of Benthic Foraminiferal AMS 14C and Optically Stimulated Luminescence Dating Techniques Used to Determine the Timing of Holocene Sediment Transport Down the Monterey Submarine Canyon

McGann, M.; Stevens, T.; Paull, C. K.; Ussler, W., III; and Buylaert, J-P.
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Radiocarbon dating of foraminifera has commonly been used to date marine sediment. Optically Stimulated Luminescence (OSL) dating of fine silt-sized quartz in deep-marine settings has also been successful, but rarely has the technique been applied to coarse-grained sediment. We compare AMS 14C dates from benthic foraminifera with single grain and single-aliquot regenerative-dose (SAR) OSL dating of quartz in ROV-collected vibracores from the axial channel within the Monterey Canyon and Fan (offshore California). These are the first sediments obtained from Monterey Canyon dated by the OSL method that yield ages of grain entry into the canyon system. When coupled with benthic foraminiferal AMS 14C dates, the OSL technique provides a rare opportunity to test the applicability of an independent dating method to constrain the time-scale of coarse-grained sediment storage in a submarine canyon system.

We found AMS 14C and OSL dates to be comparable in samples taken from cores in upper Monterey Canyon (DR40 VC-12; 1,093 mbsl), the middle of the axial channel (DR38 VC-1; 3,456 mbsl), and the upper fan (DR39 VC-3; 3,612 mbsl). In contrast, the OSL ages for two sands in another upper fan core 57 m shallower (DR39 VC-9; 3,555 mbsl) are older than the 14C ages. These results suggest that sand is transported over time-scales of tens of years in the upper canyon, of 150-250 years in the lower canyon, and of centuries to millenia to the fan. The time lag between sand entering the canyon and being deposited on the submarine fan suggests the upper and middle canyon likely stores coarse-grained sediment over a range of timescales from tens to thousands of years. These results indicate that benthic foraminferal 14C and OSL dating of canyon sand can be a powerful tool for placing time-scales on storage and transport of coarse-grained material in submarine canyon systems.


AAPG Search and Discovery Article #90162©2013 Pacific Section AAPG, SPE and SEPM Joint Technical Conference, Monterey, California, April 19-25, 2013