14 Subsurface Exploration Techniques in the South-Central U.S.

Tuesday, 14 March 2017
8:00 AM - 12:00 PM
Grand Ballroom F

USING GRAINSIZE ANALYSIS TO REFINE INTERNAL CHARACTERISTICS OF THE FALSE RIVER POINT BAR; LOWER MISSISSIPPI RIVER, LOUISIANA

Paper number: 14-11
Program: Theme Sessions
Time: 11:00 AM – 11:20 AM

Authors

Abstract

Understanding the stratigraphic progression of the False River Point Bar provides key information needed to interpret the internal structure of the complex. By conducting grainsize analysis on cores from sites around the point bar, models were created to observe the variability in grainsize with depth relative to the traverse across the floodplain. The associated sites progress inland from the floodplain and out towards the channel. We sampled the bar head, terminal bar apex, and bar tail. Histograms produced by the grainsize analysis for each site provided data for modeling site characteristics, including sorting, kurtosis, and skewness of the grainsizes. These models were compared with electrical conductivity (EC) and gamma ray (GR) log analyses in addition to standard point par models. Comparative results reveal that the best sorted sediments are found at the bar head and parts of the bar tail, while the tail and apex contained the worse sorted material. Specifically, the bar head sediments are well sorted, and stratigraphic progressions resembled a standard point bar morphology. Away from the bar head, however, lateral heterogeneity is significant. The bar apex sediments resemble standard morphology yet show a fining downward in grainsize. This trend is observed towards the base of the core, which is near the point where point bar accretion ceased. Bar tail sediments are the most heterogeneous and display various trends of coarser sediments with interbedded shales. Again, heterogeneity increases towards the end of bar accretion. The comparison of grainsize models and downhole log analysis provides a means of locating any given sediment in a point bar complex. These methods are beneficial in understanding internal point bar characteristics, which leads to a more thorough understanding of how point bars at the largest scale are constructed.

Geological Society of America Abstracts with Programs. Vol. 49, No. 1

doi: 10.1130/abs/2017SC-289185

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