Abstract: Optimal Settings for Isolating Eustatic from Relative Sea Level Behavior at Non-Glacial Times

James Pindell, Walter C. Pitman, III, A.M. Celal Sengor, John F. Dewey

Strata from optimal settings for isolating the correlatable eustatic component from multi-variant relative sea level histories (eustasy plus local/regional tectonism, climate, sedimentation) have received little public attention, especially for non-glacial times which lack a short-tern/high amplitude eustatic driver (Jurassic-Eocene). Most study areas thus far are poor for isolating true eustasy: Subsurface sections, whether deposited at passive margins (e.g., Cretaceous Atlantic margins) or syntectonically (Jurassic and Late Cretaceous-Tertiary Britain/Europe), offer less than ideal 3-dimensional appreciation of lateral/migrating facies changes due to well spacing and seismic resolution. Exposed sections do allow 3-D study at the bed level, but most were deposited syntectonically (e. ., Cretaceous West US Interior). Optimal settings for isolating eustatic behavior in the absence of glaciation are: little-deformed, relatively shallow-water but continuous, low- or high-latitude clastic/carbonate sections of non-glacial age deposited at long-lived (>50 m.y.) passive margins with shelf-slope break(s) that have since been uplifted to allow 3-D study at the bed level. Our global review identified few such settings: most ideal is the Valanginian-Eocene (80 m.y.) of Venezuela's Serrania del Interior Oriental. Paucity of regionally-correlatable short-term sequences in 3-D study there (Erikson, this session) reflects the passivity/low latitude, and implies amplitudes of short-term eustatic change far smaller than often inferred. Smaller amplitudes are achievable by slower r tes of change, such that known local/regional controls can dominate non-glacial short-term eustatic changes, preventing absolute genetic correlation, even at passive margins. Comparison of the longer-term regional sequence boundaries from the Serrania's Valanginian-Bocene (global reference section?) and those from overlapping sections of other optimal coeval settings may eventually establish which might be eustatic, to be used with care in traditional ways.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994