Paleohydrologic and Stratigraphic Significance of Crayfish Burrows in Continental Deposits: Examples from Several Paleocene Laramide Basins in the Rocky Mountains

摘要: ABSTRACT Paleocene crayfish burrows are present locally in great abundance the Greater Green River, Hanna, Wind and Piceance basins of Wyoming Colorado. In Washakie sub-basin River Basin, found (1) lenticular, cross-bedded sandstones fluvial-channel origin, (2) massive mudrocks floodplain origin that surround interfinger with sandstones, (3) thin, sandy ironstone beds overbank crevasse-splay origin. The burrows, which represent activity proximal to distal settings, assigned Camborygma symplokonomos, C. eumekenomos, litonomos on basis their architectural morphologies. araioklados is not present. Crayfish part pedogenically modified channel deposits. all studied, abundant only non-coal-bearing rocks. presence elongate indicates landscape was imperfectly drained (on a seasonal basis), burrow depths suggest paleo-water table 1-4+ m below paleosurface. Swampy conditions prevailed areas where carbonaceous shales coals formed, thus did construct deep burrows. associated lithologies warm, humid, wet-seasonal climate. eastern vertical lateral distribution reflect changes paleohydrologic regime over space time. Burrow depth overall decreases towards local basin lowlands, they rare. coupled progressively less climate through time allowed formation Cherokee coal zone late Paleocene. an otherwise lithologically homogeneous, non-variegated deposits, stratigraphically significant surfaces may be indicated by tops burrowed intervals other types paleosols. paleosurfaces varying environmental stability there different frequency magnitude sedimentation events. Immature cumulative paleosols characterized intensely or bedsets record higher rates. More many generations crayfish; hence, these layers longer durations exposure pedogenic modification infrequent no sedimentation. Paleosols represented intervals, conjunction sandstone mudrock stacking patterns, can used identify stratigraphic surfaces, such as parasequences sequence boundaries, fully continental environments.