Orogen proximal sedimentation of a composite foreland basin : investigation of Permian foreland basin provenance

Soto-Kerans, Graham Mateau
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The sedimentary fill of peripheral foreland basins has the potential to preserve a record of the processes of ocean closure and continental collision (e.g., the later phases of the Wilson cycle), as well as the long-term (i.e., 10⁷-10⁸ yr) sediment-routing evolution associated with these processes. However, the detrital record of these deep-time tectonic processes and the sedimentary response have rarely been documented during an entire cycle of supercontinent assembly. The stratigraphy within the southern margin of the Delaware Basin and Marathon Fold and Thrust Belt captures the record of the Carboniferous-Permian Pangean continental assembly, culminating in the formation of the Permian foreland basins. To evaluate the provenance and sediment-routing evolution of the southern, orogen-proximal region of this foreland-basin system, 1720 new detrital zircon (DZ) U-Pb ages were measured from 13 stratigraphic and paleogeographic-representative samples within the Marathon Fold and Thrust Belt and the Glass Mountains of West Texas. Additionally, 85 separate age core-rim relationships from eight of the samples further constrain source terranes and sediment routing. Crystallization ages of zircon grains are linked to potential sediment source areas to illuminate provenance and reconstruct sediment-routing pathways. The DZ age spectra from the Marathon region exhibit marked shifts in provenance starting with the Mississippian to Pennsylvanian syn-orogenic record then transitioning to the Permian post-orogenic phase of basin fill. Changes in provenance record the evolution of the collisional margin and its linked proximal foreland. Results from this study demonstrate that the southern orogenic highlands and Gondwanan hinterland regions serve as the dominant sediment source within the proximal (southern) basin. Though extensive paleocurrent and subsurface mapping of the northern portions of the Delaware Basin have yielded sediment input from the north, these distal portions of the Delaware Basin also potentially show a strong southerly sediment source during both syn- and post-orogenic basin filling periods. In the studied area, the appearance of Neoproterozoic—Cambrian zircon grains in the Pennsylvanian Haymond Formation points towards basin inversion and the uplift and exhumation of volcanic units related to Rodinian rifting. Moreover, the upsection decrease in Grenvillian (~1300-920 Ma) and increase in Paleozoic zircons denotes a steady provenance shift from that of dominantly orogenic highland sources to that of sediment sources deeper in the Gondwanan hinterland during tectonic stabilization. The lack of drastic changes in provenance during the early to middle Permian supports the argument for tectonic quiescence within the collisional domain during this time period. Furthermore, the ability to pull multiple ages of zircon crystallization from individual grains demonstrates zircon histories correlative with igneous and metamorphic occurrences within the southern Gondwanan continent, aiding in constraint of a dominant southern source. We supplemented these new data with published DZ geochronologic datasets of regional provenance studies from older and contemporaneous basin filling episodes along the Appalachian-Ouachita suture zone as well as within the Laurentian cratonic interior. Our results suggest dominant sediment delivery to the Marathon region from the nearby southern orogenic highland; less sediment was delivered from the axial portion of the Ouachita or Appalachian regions suggesting that this area of the basin was not affected by the so-called transcontinental drainage. The provenance evolution of sediment provides insights into how continental collision directs the dispersal and deposition of sediment in the Permian Basin and analogous foreland basins.