HIGH-RESOLUTION CYCLOSTRATIGRAPHY OF A LATE GUADALUPIAN – OCHOAN TRANSITIONAL SEQUENCE: NEW CONSTRAINTS ON DEPOSITIONAL RATES IN A BASINAL CONDENSED MARINE SEQUENCE, DELAWARE BASIN, WEST TEXAS

Newly determined depositional rates for the upper Guadalupian series, Delaware Basin, West Texas, are used to refine rates previously established utilizing “varve” counting. This work indicates that laminations in a basinal condensed (marine) sequence may be most consistent with some form of decadal climate variability. By using a magnetic susceptibility (MS) dataset from a Guadalupian – Ochoan transitional section in the Apache Mountains, Texas, it was possible to recognize distinct eccentricity, obliquity and processional cyclicities. Multiple MS datasets from the Apache Mountains region are easily correlated locally and regionally where eccentricity cycles are consistent with records on the other side of the basin. Our analysis suggests that sedimentation rates averaged ~ 1.4 cm/kyr throughout the upper Guadalupian sequence. These depositional rates are an order of magnitude smaller than previous estimates but consistent with established basinal sedimentation rates and our other ongoing work from the Guadalupe and Apache Mountains regions. Published conodont biostratigraphy from the study section (e.g. EF in Lambert et al., 2002) is also consistent with these results. Refined depositional rates may also lead to a reevaluation of the Ochoan (Lopingian) sequence, where “varve” chronologies were previously utilized to constrain the duration of the Ochoan Series in West Texas.