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The AAPG/Datapages Combined Publications Database

Utah Geological Association


Geology of East-Central Utah, 1991
Pages 95-110

Fluvial Sedimentology of the Upper Cretaceous Castlegate Sandstone, Book Cliffs, Utah

Marjorie A. Chan, Bruce J. Pfaff


The Upper Cretaceous Castlegate Sandstone in central Utah records an eastward prograding fluvial-deltaic complex, shed from the Sevier orogenic belt. Eight facies are recognized: trough crossbedded sandstone; inclined rippled sandstone; horizontal rippled sandstone; organic-rich sandstone, siltstone and shale; interbedded sandstone and siltstone; lenticular shale and siltstone; small-scale planar tabular sandstone; and conglomerate. Vertical and lateral facies relationships permit interpretation of basinal changes in the depositional system.

The Castlegate type section at Price Canyon contains three stratigraphic units. The lower unit is dominated by trough-crossbedded, multiple-scoured, fine- to medium-grained sandstone. The middle unit is characterized by: (1) rippled lateral accretion deposits; (2) rippled overbank sandstones; and (3) increased amounts of floodplain sandstones and siltstones. This middle unit also contains deep channel scours and well developed upward-fining sequences. An upper channelized unit (Bluecastle Tongue) is similar to the lower unit.

A high fluvial gradient and a relatively coarse sediment supply in the lower unit is associated with thrusting episodes of the Sevier Orogeny. These conditions favored the development of braided channels. Vertical changes from the lower to the middle unit represent a transition to higher sinuosity channels with greater overbank deposition. The middle unit also grades eastward into marine, shoreline, and coastal plain deposits, as the Cretaceous sea transgressed westward. Braided deposition of the upper unit suggests renewed orogenic activity, accompanied by a relative drop in sea level.

Lateral changes in the Castlegate Sandstone reflect the relative proximity to the orogenic belt. Areas close to the mountain belt produced braided fluvial channels. Over a 81 mi (130 km) distance, channels were larger and more sinuous in the distal part of the fluvial system. High sinuosity conditions persisted where gradients were lower and sediment was finer grained. Both vertical and lateral facies relationships in the Castlegate Sandstone indicate the interplay of tectonism and relative sea level change in fluvial sedimentation styles along the Western Interior seaway.

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