Sequence Stratigraphy and Fluvial Facies Architecture, Farrer and Tuscher Formations (Campanian), Tusher Canyon, Utah

P. E. Patterson, A. R. Sprague, R. E. Hill, K. M. McDonald

A sequence-stratigraphic and facies-architectural framework was developed for fluvial strata of the Farrer and Tuscher Formations, Utah. This framework consists of a hierarchy of discrete stratal units (facies architectural elements) characterized according to their external geometry and dimensions, and their internal facies organization. Three hierarchical orders of facies architectural elements are recognized: basic elements (beds and bedsets), building-block elements (channel fills and non-channel deposits), and composite elements (channel-fill complexes, floodplain complexes, sequences, and composite sequences). Channel-fill complexes are multi-storey elements, dominated by vertically and laterally amalgamated single channel fills. Channel-fill complexes, possessing a rially extensive, erosional basal bounding surfaces (sequence boundaries), are interpreted to be allocyclic; their formation controlled by restricted flow, increased sediment discharge and minimal aggradation. Sequences are unconformity-bounded stratal units that consist of a basal allocyclic channel-fill complex overlain by one or more floodplain complex. Each sequence is interpreted as the product of a single eustatically driven cycle of baselevel fall and rise. Composite sequences are composed of multiple, vertically-stacked sequences, each of which has a single, regionally extensive, erosional basal bounding surface (composite sequence boundary) formed in response to significant baselevel fall. The composite sequence is interpreted to be controlled by a longer period eustatic fall an rise cycle, punctuated by higher frequency baselevel falls and rises (individual sequences). Relative rates and magnitudes of baselevel fluctuations, within the longer cycle, control the dimensions and stacking patterns of individual sequences within the composite sequences, thereby defining the sequence stratigraphic framework.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995