STRATIGRAPHIC ANALYSIS OF EOLIAN INTERACTIONS WITH MARINE AND FLUVIALDEPOSITS, MIDDLE JURASSIC PAGE SANDSTONE AND CARMEL FORMATION, COLORADO PLATEAU, USA

The eolian Page Sandstone (Middle Jurassic) in south-central Utah and adjacent Arizona consists of multiple mostly eolian sequences and sequ ence bounding unconformities (super surfaces). The super surfaces are a powerful correlation tool that provide the basis for a detailed regi onal stratigraphic analysis of the Page Sandstone and coeval parts of the marine and coastal plain Carmel Formation. Some Page Sandstone sup er surfaces correlate with sharp lithologic breaks in the Carmel Forma tion that are interpreted as marine flooding surfaces. Others correlat e with fluvial surfaces in the Carmel Formation. The lower part of the Page-Carmel interval encompasses seven on-lapping accumulation sequen ces bounded by marine flooding surfaces. The uppermost two represent t he Middle Jurassic marine high-water mark. These seven units comprise marine transgressive and marine highstand system tracts. Each interval is composed of progradational eolian deposits over marine deposits. M ajor tectonic and sedimentologic changes affected accumulation sequenc es 8 and 9. The two intervals are continental in origin, fluvial to th e west and eolian to the east. A major slightly angular regional uncon formity marks the top of accumulation sequence 9. The unconformity ref lects regional tilting, up to the northeast, and ensuing erosion of ol der units in the Page Sandstone. Accumulation sequence 10, the top of the study interval, displays complexly juxtaposed continental and mari ne facies that buried the unconformity as regional subsidence continue d. The broad patterns described above can be correlated with thick mar ine carbonate and minor siliciclastic deposits of the Twin Creek Limes tone 400 km north of the study area. The resulting depositional patter ns define three broad depositional events. The oldest of these ''seque nces'' defines a regional marine transgression and highstand. The seco nd ''sequence'' reflects strong siliciclastic influx and slight region al tilting that resulted in widespread continental deposition. Regiona l tilting and erosion closed out this event. The youngest ''sequence'' indicates a partial return to marine transgressive conditions but was complicated by regional uplift and tilting related to arc tectonism. This study demonstrates that a sequence stratigraphic framework can be applied to sparsely fossiliferous eolian, sabkha, and restricted mari ne deposits in a marine coastal setting. Using detailed sedimentologic and stratigraphic studies, tectonic, eustatic, and possibly climatic signals can be differentiated within the complex, cyclic facies patter ns displayed in the Page Sandstone and Carmel Formation.