Widespread Marker Units in Delaware Basin Area Permit Regional Mapping of Guadalupian Composite and High Frequency Sequences

TYRRELL, WILLIS W., Consulting Geologist, 5718 Bentway Dr., Charlotte, NC, [email protected] and JOHN A. DIEMER, Department of Geography and Earth Sciences, University of North Carolina at Charlotte, Charlotte, NC 28223

    Subsurface marker units are used to regionally map Guadalupian outcrop-defined composite sequences (CS) and high frequency sequences (HFS) in southeast New Mexico and adjacent Texas. This paper concerns only two of these markers - the Bowers Sand in the lower Seven Rivers Formation and the Two Finger Limestone in the Bell Canyon Formation. The Bowers Sand is a rarely productive, shallow water, late Wordian, cyclic siliciclastic - carbonate (or evaporite) unit on the Northwest Shelf and Central Basin Platform. The Two Finger Limestone is a slightly older late Wordian, deep water deposit in the northern Delaware Basin.

    The Bowers Sand has typical wireline log character in the Artesia Group subsurface reference section located 36 miles northeast of Carlsbad. It can be traced to outcrops in the Guadalupe Mountains where it defines the base of HFS G-18 of Kerans and Tinker (1999) and equates to siltstone beds X, Y and Z of Hurley (1989) in North McKittrick Canyon.

    The Two Finger Limestone is a limestone-sandstone-limestone unit in the northern Delaware Basin. Except near its gradation into the lower Capitan Reef it is generally 10 to 30 feet thick. It was cored in the Gulf PDB-04 research well. We trace the Two Finger Limestone to the Guadalupe Mountains where it equates to typical outcrops of the Hegler Limestone Member of the Bell Canyon Formation. Using these relationships Tyrrell and Diemer (2003) have mapped both the highstand and lowstand facies of HFS G – 17 regionally.