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2007 GSA Denver Annual Meeting (28–31 October 2007)

Paper No. 27
Presentation Time: 1:30 PM-5:30 PM

STRATIGRAPHIC BOUNDARY DELINEATION USING SAND COMPOSITION, HEAVY MINERALS, AND SRTM DEM DATA: ULAHTAUNG STRUCTURE, SOUTHEASTERN BENGAL BASIN


RAHMAN, Mohammad Wahidur1, UDDIN, Ashraf1, MARZEN, Luke J.1 and AKHTER, Syed H.2, (1)Department of Geology and Geography, Auburn University, 210 Petrie Hall, Auburn, AL 36849, (2)Geology, University of Dhaka, Dhaka, 1000, Bangladesh, rahmamo@auburn.edu

The Ulahtaung anticline, located at southeastern Bengal basin, outcrops four stratigraphic units: Bhuban (Lower Miocene), Boka Bil (Upper Miocene), Tipam (Mio-Pliocene), and Dupi Tila (Plio-Pleistocene) formations. This study is aimed at confirming these formation boundaries based on (1) detailed geologic map of the structure, (2) sand(stone) modal analysis, (3) detrital heavy-mineral contents, and (4) various digital datasets including Landsat TM 5 satellite image, SRTM digital elevation model, existing regional-scale geological map, and field GPS data.

Modal analysis data distinctly document most boundaries between stratigraphic units. Sand(stone) composition from the lower Miocene unit (Qt49F39L11) is arkosic than those of the upper Miocene (Qt48F25L27) and Mio-Pliocene (Qt48F16L36) units. Lithic fragments increase in younger units. Most lithic types are sedimentary. Lower grade metamorphic fragments are more abundant in Miocene units than the Pliocene Tipam Sandstone. Plagioclase feldspars decrease at the younger units. In QtFL ternary diagram these Neogene sandstones plot in “recycled orogenic” provenance field of Dickinson (1985).

Miocene sandstones contain relatively more opaque and ZTR minerals than Pliocene sandstones. Older sandstones include abundant garnet, muscovite, biotite, spinel, chromite, chlorite and moderate to minor amounts of amphibole, epidote, sillimanite, kyanite, andalusite, monazite, and pyroxene, indicating a predominant metamorphic provenance. The Pliocene Tipam Sandstone contains abundant opaque minerals, amphibole, zircon, epidote, orthopyroxene and minor garnet, rutile, tourmaline, sillimanite, kayanite, andalusite.

Topographic slope and digital elevation model data also distinctly identify the stratigraphic boundaries. The Bhuban Formation is characterized by trellis drainage patterns, whereas the Boka Bil Formation shows trellis and dendritic drainage patterns because of its unique lithology of alternating sandstone and mudstone. The Tipam Sandstone and Dupi Tila formations show mostly dendritic drainage patterns.

This study recommends revision of the existing regional geological map of the Ulahtaung structure.

Session No. 55--Booth# 105

Stratigraphy (Posters)
Sunday, 28 October 2007: 1:30 PM-5:30 PM
Geological Society of America Abstracts with Programs. Vol. 39, No. 6, p.152
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