Optically Stimulated Luminescence (OSL) studies to determine age of turbidite deposits
Description
Monterey Bay Aquarium Research Institute,United States Geological Survey, Menlo Park, California. Chief Scientist: Charlie Paull (). Geological data of field activity W-3-09-MB in Monterey Bay, California from 06/15/2009 to 06/20/2009
Location
California
Summary
(see excel file)
Info derived
Age of sediment by means of OSL and 14C techniques
Comments
1). We will conduct a novel sampling effort for Optically Stimulated Luminescence (OSL) studies. Our goal is to learn how long it takes for sand to move through the canyon system out onto Monterey Fan. We have shown that the last major sand-carrying event to move quartz sand within the channel of Monterey Fan occurred about 100 years ago and that this sand is compositionally indistinguishable from beach sand at the canyon head. However, these observations do not distinguish whether the sand moves from near the shoreline out onto the fan in a single event or whether the sand moves incrementally down-canyon. We are going to apply luminescence-dating techniques to resolve this question. OSL is an established technique for determining how long quartz sands have been buried (e.g., removed from sunlight). The principle is that natural gamma radiation damages quartz crystals (http://www.ndsu.nodak.edu/ndsu/klepper/BreifOSL.html) and these imperfections anneal only when the samples are exposed to sunlight. In the process of annealing a small, but measurable amount of photons are given off. If the amount of gamma radiation produced in the surrounding sediments is measured, the age (or time since last exposure to sunlight) can be calculated with some accuracy. This has never been done for deep-marine sand, but OSL has promise for determining when quartz sands left the nearshore environment. The critical step is to sub-sample cores in the dark without any exposure to stray ambient light. We have tested our techniques in a darkroom with a red safelight using beach sand and sand from Ventana-collected vibracores from the upper canyon and feel comfortable with the sub-sampling procedure. We propose to collect cores from the Monterey Fan Channel in areas where we already know appropriate stratigraphies exist. OSL measurements will be made by Dr. Thomas Stevens now at the University of London. 2). We will be recovering the battery powered instrument node from Shepard Meander. This was deployed on September 6, 2007 on Tiburon dive 1127. It is marked with Homer #80 and caries ADCP3 (sn5997), Seacat 16+ (sn 4190) Wetlabs (sn 0310010) OBS (sn 10025), HS-2 (sn H2oo31007) and ACM 10. 3). We will continue sample for organic carbon, DDTr, and infauna as well as collecting video transects. Operations plan: We are going to work primarily in areas where we have dove before. As many of the sites are well off-shore our schedule will be adjusted as by the weather. Getting the existing instruments back from Shepard Meander and getting the cores for ~3600 m are the highest priorities. June 15, 1600 - As this is a late start we will dive within the upper canyon to test the new vibracoring system on Doc Ricketts.
Staff information imported from InfoBank
Charlie Paull (MBARI, )
Lonny Lundsten (MBARI, )
Patrick Whaling (MBARI, )
Kurt Buck (MBARI, )
Thomas Stevens (Royal Holloway, University of London, )
Mary McGann (USGS, )
Non USGS data manager = Kim Fulton (Bennett)
