Regional Sea-Level History of the Southern Cordilleran Passive Margin during Middle to Early Late Cambrian Time: Combined Sequence Stratigraphy and Subsidence Analysis

David A. Osleger, Javier Martin-Chivelet, and Isabel P. Montanez

Newly-acquired data from Middle to lower Upper Cambrian strata of the central Great Basin appear to corroborate a high-resolution sea-level signal derived from coeval rocks of the southern Great Basin. We have applied three distinct techniques that collectively delineate the accommodation history recorded by shallow-marine carbonates of the study interval. 1) Standard paleobathymetric analysis of 10 stratigraphic sections ranging from eastern California to west-central Utah permits a first-order approximation of the sedimentary response to changes in accommodation. 2) Cycle stacking patterns, integrated into a sequence stratigraphic framework, delineate four distinct sequence s separated by conformable sequence boundary zones. 3) Subsidence analysis of each of the sections refines the regional accommodation history into four separate episodes of 1 to 3 m.y. duration. The latter two methods attack the problem from different scales: analysis of stacking patterns uses the ubiquitous meter-scale cyclicity to determine a larger scale pattern whereas subsidence analysis proceeds by successively reducing the total accumulation into its smaller scale components.

The sea-level signal determined from these shallow-marine carbonates of the southern Cordilleran margin may act as a baseline curve for equivalent strata around the North American continent that are complicated by fine siliciclastics and apparent source terrane dynamics (i.e., Grand Cycles). Ultimately, continental and global correlations may help to determine the origin of Middle to lower Upper Cambrian depositional sequences and perhaps greatly increase the chronostratigraphic resolution beyond that afforded currently by the limited biostratigraphic control.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California