Paper No. 294-7
Presentation Time: 3:35 PM
RECONSTRUCTING LATE PALEOZOIC LAURENTIAN SEDIMENT DISPERSAL VIA MIXTURE MODELLING OF DETRITAL ZIRCON U-PB AGES (Invited Presentation)
SAYLOR, Joel1, SMITH, Tyson Michael2, LEARY, Ryan J.3, LAPEN, Thomas J.2, UMHOEFER, Paul J.4, SMITH, M. Elliot5, BURR, Gregory L.E.5, LODES, Emma5 and FOLEY, Daniel J.5, (1)Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, 2020 – 2207 Main Mall, Vancouver, BC V6T1Z4, Canada, (2)Department of Earth and Atmospheric Sciences, University of Houston, 312 Science and Research 1, Houston, TX 77204, (3)Earth and Environmental Science, New Mexico Institute of Mining and Technology, Socorro, NM 87801, (4)School of Earth and Sustainability, Northern Arizona University, Flagstaff, AZ 86011, (5)School of Earth and Sustainability, Northern Arizona University, 625 Knoles Drive, Box 4099, Flagstaff, AZ 86011
Late Paleozoic orogenesis in along both the margins and SW interior of Laurentia resulted in regional sediment provenance changes marked by integration, disruption, and reintegration of west or southwest directed transcontinental sediment dispersal systems. We characterize changes in sediment provenance using a combination of forward and inverse mixture modelling of detrital zircon U-Pb age spectra. Late Paleozoic samples are best characterized as mixtures of eight unique sources based on inverse mixture modelling of 108 samples or groups of samples from across Laurentia. Samples are divided into five time intervals spanning the Mississippian–middle Permian.
Mixing proportions reveal a provenance gradient in the Mississippian, with samples from the eastern USA having a significant Appalachian contribution and samples in the southwest Laurentia having a strong western Laurentian affinity. This changes in the Early Pennsylvanian accompanying the onset of ARM and Alleghanian orogenesis. During the Early Pennsylvanian inverse mixture modelling shows consistently high Appalachian proportions across the USA, except for the Central Colorado Trough and proximal Denver Basin where a significant component is ascribed to local basement sources. However, in the Middle Pennsylvanian–early Permian, the proportion of Appalachian detritus west of the ARM decreases while the region of the ARM dominated by local basement-sourced detritus expands. By the middle Permian Appalachian-sourced detritus again dominates in all basins. These observations suggest that the ARM province was an effective barrier to westward sediment dispersal to ARM basins or southwestern Laurentia during ARM orogenesis.
Forward mixture modelling of the Paradox Basin confirms the tectonic isolation of the ARM basins during ARM orogenesis, and points to a method to integrate lithofacies, sediment thickness, and sediment provenance data into spatially referenced maps.
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