This project,
whose ultimate goal is to develop a high-resolution temporal framework
for the Leonardian (Lower Permian) using a synthesis of conodont
and fusulinid biostratigraphy, strontium isotope chemostratigraphy,
and sequence stratigraphy, was completed in 2002. The sequence stratigraphy
of the Leonardian was worked out through integrated studies of outcrops
in the Sierra Diablo Mountains of West Texas and subsurface data
from the Permian Basin. Primary focus during the past year was the
collection of additional samples from outcrops and subsurface cores
within this sequence-stratigraphic framework for processing and
recovery of conodonts. Outcrop samples were collected from platform
margin sections where the likelihood of recovery of conodonts appears
greatest. Additional samples were collected from a subsurface core
that spans a large part of the Leonardian section. Conodonts recovered
from these samples and from whole rock samples likely to preserve
original seawater chemistry were analyzed for 87Sr/86Sr to provide
a secular record of seawater variations in 87Sr/86Sr during the
Leonardian. Diagenetic mineral phases (anhydrite and dolomite) were
also sampled from subsurface cores and analyzed for 87Sr/86Sr to
investigate the history and timing of carbonate diagenesis. The
87Sr/86Sr data provided from conodonts and nondiagenetic phases
will serve as a primary reference standard for comparison, correlation,
and dating of equivalent successions worldwide. Data from diagenetic
phases will provide important insights into the process of reflux
diagenesis. The project was funded by the Texas Higher Education
Coordinating Board as part of the Advanced Research Program.
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