Thinly interbedded, asymmetric ripple laminated sandstone (with abundant climb), siltstone and mudstone found adjacent to submarine channel cuts are typically interpreted as overbank deposits equivalent to the cut and fill stage of the channel complex. Stratal relations and paleocurrent data in the sand-rich Brushy Canyon Formation (Permian, Guadalupian) of the Delaware Mountains, West Texas, show that well-developed packages (>30cm beds) of climbing ripple sandstone are laterally equivalent to amalgamated to non-amalgamated lenticular and sheet-like sandstones that represent the unconfined spill phase of both individual channel stories and, ultimately, the channel belt complex. This relationship may be important when using rippled sandstone as an indicator of channel cutting and sediment bypass. Abundant climbing rippled sandstone in the Brushy still indicates proximity to a channel however the temporal correlation between the tipples and the channel cut and any potential sediment bypass is a half cycle apart. Furthermore, the ripples are not direct indicators of bypass but instead indicate updip filling of the channel complex. This model is supported by the fact that paleocurrents in the rippled sandstone are similar to the channel deposits rather than oblique that would indicate a component of transverse overbank flow.

The Brushy cut, fill and spill model is for a mud-poor system that has limited ability to build levees and generate true overbank sedimentation. Mud-rich submarine channels, however, must also have spill phases of sedimentation. There is potential for misinterpreting tipple packages deposited during the unconfined phase of the channel as overbank deposits.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah