Dr. A writes:
Just a quick question for the geologists here --- has anyone ever actually directly observed a turbidite sediment being deposed by a turbidity current, or does the proposed origin of these sediments rest on inference alone?
If the latter, what do you see as the best evidence that turbidite sediments are, in fact, turbidite sediments?
I doubt someone was actually underwater when a slope failure event occured. However there are lots of sidescan sonar pictures and siesmic of this deposition along with core data.
After the delta front work was completed, Jim served as co-chief scientist with Dr. Arnold Bouma on the 1988 Deep Sea Drilling Project, Leg 96 in the Gulf of Mexico. This project focused on drilling of the latest lobe of the Mississippi Fan. Results from this project provided the first ground truth of the sedimentology and stratigraphy of the Gulf’s fan deposits below the thin blanketing hemipelagic sediments that cover the entire fan. Coarse facies found in the channels and distal fan lobes changed our model of fan deposition and supported the thrust by petroleum companies to explore for oil and gas in deep water fan deposits.
from :
Doris Malkin Curtis Medal
In the early 80's I had the opportunity to fly around the Mississippi delta in a chopper with Jim Coleman looking at and landing at various different depositional areas in the delta. Phillips Petroleum spared no expense to keep their exploration geologists current. I made a lot of money for PPCo. and later myself off of what I learned from Jim. He had recently done the first sidescan sonar imagery of the delta slope and I got to see that as well. No problem seeing the turbidite channels and deposition but it wouldn't be for several years before the stuff was cored and it was seen just how coarse grained it was and the actual sedimentary sequence.
Lots of interest in this because if you put an oil platform in the wrong place it can end up dissapearing on you.
Here are a few free links.
http://kai.er.usgs.gov/...mex/centgulf/lcs/aapg97/index.html
Abteilung Oberflchengewsser - Eawag
http://jsedres.sepmonline.org/cgi/reprint/70/3/504.pdf
Abstract: Bryant Canyon/Fan and Rio Grande Fan Turbidite Systems: Shelf to Basin Modern Analogues for Productive Tertiary Mini-Basin Systems,
by John E. Damuth, C. Hans Nelson, and Hilary Clement Olson; #90078 (2008)
http://www.springerlink.com/content/k17r387t7310tqj6/
Martin
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