TRANSIENT INFLUENCES UPON LATE PALEOZOIC SEDIMENT PROVENANCE AND DISPERSAL IN LAURENTIAN PANGEA

Sediment movement and storage on late Paleozoic Laurentia took place in depositional systems that had peculiarly ephemeral sedimentologic and provenance characteristics related to a combination of transient factors. These included sediment balance in evolving foredeeps, climatic change due to northward continental drift from the tropics to the horse latitudes, and glacio-eustatic sea level fluctuations that imposed geographic shifts on system termini. Linked sediment-transport systems included alluvial and fluvial networks, ergs, littoral zones, and submarine fans. Three major orogenic sources produced sediment for Laurentian sediment-delivery networks: (1) The Alleghanian-Ouachita-Marathon collision orogen (AOMO), with a hinterland of exotic terranes and Gondwana itself; (2) intracratonic basement uplifts of the Ancestral Rocky Mountains (ARM), which intersected the AOMO at a high angle; and (3) the SW Laurentian Borderland (SLaB). In addition, the transcontinental arch (TA) strongly influenced long-distance sediment transfer. Near the AOMO, overfilled foredeep conditions created proximal transverse clastic wedges and long rivers, whereas underfilled conditions fostered various types of axial transport. The Late Mississippian part of the Mauch Chunk-Pottsville clastic wedge crossed an overfilled foredeep in Pennsylvania, routing sediment cross country via a river that was deflected southwest by the TA to a delta in NW Arkansas on the northern flank of the Arkoma foreland basin. Detritus eroded from the southern part of the Alleghanian belt passed via an underfilled Pennsylvanian Arkoma foredeep to the Fort Worth basin. Sediment delivered by transcontinental rivers from the AOMO tended to overwhelm local basement-derived sediment in Pennsylvanian-Permian ergs that flanked the ARM and shallow-marine deposits of the western seaway; however, local SLaB and ARM sources were locally important (Wood River basin) to dominant (Weber Ss). Archean zircon grain proportions vary widely in different samples of some ergs, such as the Glorieta-Coconino erg, likely due to deflation from ephemeral rivers with some tributaries in the Superior province. Eustatic lowstand periods permitted sediment from the collision orogen to ultimately reach sedimentary basins of the SLaB in southern California.