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MOUTOUX, JOHANNA J., and RONALD J. STEEL, Department of Geology and Geophysics, University of Wyoming, Laramie

ABSTRACT: Sequence Stratigraphic Analysis and Paleoshoreline Trend Interpretation of the Coniacian to Santonian Merged Hosta-Dalton Sandstone, Hagan Basin, New Mexico

Detailed sequence stratigraphic analysis of the Hosta-Dalton turnaround sandstone within the Hagan basin of north central New Mexico reveals a complex record of high-order relative sea level oscillations. At this location the Dalton and Hosta Sandstones converge as the basinward pinchout of a northerly-prograding clastic wedge deposited within the Upper Cretaceous Western Interior seaway. Approximately fifteen stratigraphic sections were measured and described along the -10 km long, north-northwest trending Hosta-Dalton outcrop. We observed multiple cycles of transgressive-to-regressive deposition, as well as related erosion surfaces and fossil shell layers. The transgressive facies are largely interpreted as back-barrier and shoreface sands, whereas the regressive facies are storm wave-dominated strandplain deposits. The paleoshoreline trend is determined from the interpreted depositional facies combined with collected paleocurrent data.

We are using our paleoshoreline trend interpretation as a proxy for the Hosta-Dalton pinchout trend within the Hagan basin and, as such, add another interpretation to the current pinchout trend debate. Most previous work on the Hosta-Dalton Sandstone presents a pinchout trend of ~N60-70 degrees W correlated as a relatively straight line across the Albuquerque Basin and into the Hagan basin. However, a recent study suggests a markedly different trend of ~N80-85 degrees E within the Hagan basin and nearby Placitas areas, thus suggesting significant Laramide dextral offset across the Albuquerque Basin.

AAPG Search and Discovery Article #90915©2000 AAPG Rocky Mountain Section, Albuquerque, New Mexico