Depositional history and tectonic significance of alluvial sedimentation in the Permo-Pennsylvanian Sangre de Cristo Formation, Taos Trough, New Mexico
Kristian Soegaard and Kenneth R. Caldwell
The Pennsylvanian-Permian Sangre de Cristo Formation in northern New Mexico represents a southward-thinning, coarse-grained elastic wedge of braided alluvial sediments deposited in response to orogenesis in the ancestral Rocky Mountains. The Sangre de Cristo Formation is subdivided into two alluvial megasequences which signify a temporal variation in style of sedimentation. The lower alluvial megasequence is composed of vertically stacked, tabular conglomerate units deposited on a proximal braided alluvial plain. The lower alluvial megasequence is aggradational and was deposited in response to an uplifted source in the Cimarron highlands to the north.
The upper alluvial megasequence consists of interbedded sandstones/conglomerates and mudstones. Depositional paleoenvironments for the upper megasequence are subdivided into two domains: major, coarse grained, braided-channel-sandstone sequences and mudstone-dominated floodplain sequences. Deposition of coarsegrained, braided-channel-sandstone bodies was controlled by discharge from tectonic highlands in the Cimarron arch to the north and was dictated by allogenic mechanisms. A marginal muddy floodplain sourced subordinate sinuous channel sandstones on the distal fan to the south. In the north, lacustrine limestones are encased within floodplain mudstones implying an internal drainage system on the proximal fan. Overall retrogradation in the upper alluvial megasequence manifests source-area diminution due to cessation of uplift in the Cimarron arch.
The Sangre de Cristo Formation represents a foreland basin fill. Uplift associated with deposition of the succession was in response to convergent-margin faulting along the northern margin of the Taos trough. This late Desmoinesian-Wolfcampian, north-south compression in the trough is related to northward convergence in the Marathon foldbelt at that time.
- Soegaard, Kristian; Caldwell, Kenneth R., 1990, Depositional history and tectonic significance of alluvial sedimentation in the Permo-Pennsylvanian Sangre de Cristo Formation, Taos Trough, New Mexico, in: Tectonic development of the southern Sangre de Cristo Mountains, New Mexico, Bauer, Paul W.; Lucas, Spencer G.; Mawer, Christopher K.; McIntosh, William C., New Mexico Geological Society, Guidebook, 41st Field Conference, pp. 277-289.