SEQUENCE STRATIGRAPHY OF DINOSAUR LAKE: SMALL SCALE FLUVIO-DELTAIC STRATAL RELATIONSHIPS OF A DINOSAUR ACCUMULATION AT THE AARON SCOTT QUARRY, MORRISON FORMATION, SAN RAFAEL SWELL, UTAH

摘要: Stratal geometries, cyclical stacking patterns, and taphonomic analysis of the Aaron Scott Quarry in Jurassic Morrison Formation indicate that sediments accumulated within a prograding fluvio-deltaic lacustrine system. Sediments were deposited during progressive fill large lake. geometries patterns display relationships similar to larger-scale deltaic sequences caused by fluctuations base level. Stratigraphic, paleontologic, sedimentologic indicates water-volume-driven, base-level changes responsible for accumulation preservation assemblage. The assemblage lowering level late stages an overall fall drought was buried rapid rise at end drought. Fluvio-deltaic lake consists numerous off-lapping beds sparsely bioturbated, coarsening-upward mudstone capped thin, bioturbated silty mudstones. Erosional surfaces dip west cut older parasequences. Retrogradation, aggradation, progradation strata typify stratigraphic trends above erosion surface. Coarse braided stream sands cap off successive as accommodation is filled prior next lowstand sequence boundary incisement. quarry large, taxonomically diverse deposit formed concentration animals margins Animals congregated near banks smaller watering holes dried. Bone locations orientations reworking fluvial wave currents. Vertical preservational over period years. Trace fossil, invertebrate distributions, sedimentological evidence periodic establishment oxygen stratification waters may have contributed conditions favorable bone preservation.