SUMMARYThe approximately 100‐foot thick Warrensburg sandstone (Nowata formation, Marmaton group, Pennsylvanian Desmoinesian Series, western Missouri) fills a valley‐shaped erosional channel. The rapidly lensing fluvial sediments are sandstones (45%) and siltstones and shales (50%), with subordinate basal conglomerate and coal. Sediment transport was southward, parallel to the north‐south channel. These fluvial sediments formed in a stream channel previously cut across a low coastal plain during a temporary retreat of the sea.The Warrensburg sandstone samples are a homogeneous group of fine‐grained to medium‐grained quartzose graywackes and micaceous quartzites. The grains, omitting 10% clayey matrix and 10% iron‐oxide and silica cements, average 47% common quartz, 34% metamorphic detritus (slate, phyllite, schist, highly undulose unit quartz, schistose and pressure metaquartzites, and mica), 14% plutonic detritus (feldspar and vein quartz), and 5% sedimentary grains (“second‐cycle” rounded quartz and chert). The accessory heavy mineral assemblage also reflects a mixture of metamorphic and plutonic detritus with subordinate “second‐cycle” grains (21% rounded zircon and tourmaline among the detrital, transparent, non‐micaceous grains). The distant sources of detritus in the Warrensburg and other Desmoinesian channel sandstones of Missouri are typified by metamorphic and subordinate feldspathic crystalline rocks.The average 10% feldspar (largely K‐feldspar) among the grains and 8% garnet among the detrital, transparent, non‐micaceous heavy minerals in the Warrensburg sandstone, in contrast to the near absence of these minerals in Desmoinesian channel sandstones of western Pennsylvanian, suggests that the principal sources were the Transcontinental Arch and Canadian Shield to the north and northeast. The Appalachian metamorphic belt is not as important a source area for the Western Interior Basin as