| Abstract: | Deep water sands from the Colombia and Sigsbee basins were examined in order to ascertain whether a relationship exists between quartz grain surface microtextures and the type of subaqueous density flow which transported the grains. In the course of the investigation, information was obtained on the sedimentologic histories of the areas as well as on the mechanics of abrasion in subaqueous density flows. Scanning electron microscopy of the grains from the Colombia Basin revealed recurring microtextural patterns which varied with the abrasion characteristics in the transporting flows. Distinct associations were found on debris flow deposits, grain flow deposits, washover deposits from the Magdalena fan, and the "A" (massive and graded) division of turbidites. Particular examination of the "A" intervals showed that the density of impact features on the grains increases with distance of travel. Based upon the distribution of impact features and the internal patterns of flow in turbidity currents, the mechanism which produces the distinct impact patterns was hypothesized. ... |
|---|