Sedimentology and Structure Working Group

Sedimentology and Structure Working Group of the Intermountain West Project

Research Topics

Cordilleran Basin Analysis Across the Intermountain West

• Description and correlation of stratigraphy and depositional environments: Measured sections, field samples, and drillhole data are paired with accessory geochronology, paleontology, geochemistry, geophysics, and/or provenance data, etc., to enhance regional stratigraphic frameworks.
• Sedimentary architecture and processes: Spatial and temporal variations within and between alluvial, fluvial, aeolian, lacustrine, and marine, as well as their bounding stratigraphic surfaces, are analyzed to understand the drivers of sedimentation in the geologic record.
• Paleodrainage evolution and source-to-sink studies: New and existing geochronology, isotope, and paleocurrent data are analyzed to determine sediment sources and paleodrainage pathways across the Cordillera.
• Paleogeography and landscape evolution: Paleo-landscape models are used to highlight the links and feedbacks between tectonic activity, structural deformation, uplift, basin accommodation, and drainage evolution.
• Areas of topical interest:
  • Late Paleozoic Ancestral Rocky Mountains basins and uplifts
  • Permian, Triassic, and Jurassic basins of the Cordilleran margin and their connections to continental, magmatic arc, and exotic terrane sources
  • Comparative studies in the Late Cretaceous to Eocene Laramide foreland basins
  • Sedimentary processes recorded in shoreline environments and their relations to heavy mineral placer deposits
  • Sedimentary ecological basin records from the early Cenozoic
  • Cenozoic transition from compression to extension across the southwestern USA
  • Neogene extensional basins in the Rio Grande Rift and Basin and Range Province

Structural Analysis Across the Intermountain West

• Structural analysis: Petrographic and outcrop assessment of deformation fabrics, mineralogical changes, and rheology of sheared and brecciated rocks are combined with meso- and macro-scale mapping of structures and shear-sense data to reconstruct deformational history.
• Data synthesis: Petrographic analyses, field measurements, and map geometries of structures are integrated at regional scale to derive holistic, kinematic interpretations of a wide variety of tectonic and magmatic systems that generate deformation.
• Fault kinematics: Dynamics of real-world fault partitioning, fault-tip propagation, reactivation, strain transfer, and complex, coseismic fault geometries are analyzed to better understand the effects of faults in orogenic systems. 
• Balanced cross-sections: Schematic representations of structural and stratigraphic geometries are built to characterize 3-D geologic frameworks and test structural models.
• Metamorphism and mylonitic shear zones: In coordination with the Igneous and Metamorphic Working Group, petrochronology, isotope analysis, and geothermobarometry are paired with mapping and microstructural analysis to test Proterozoic tectono-magmatic associations with localized, mid-crustal shear.
• Integration of geophysical data to improve structural understanding: Airborne data acquisitions by EarthMRI are paired with traditional mapping to interpret complex cross-cutting relationships that are important for understanding tectonic history and resource distributions.
• Big data analysis: Statistical trends in large datasets of contact, fault, fold, foliation, and lineation orientations across entire structural provinces are analyzed for patterns and variations to assess deformation models.
• Areas of topical interest:
  • Proterozoic accretion and deformation in the southern Rocky Mountains
  • Variations in strain accumulation across the lithosphere
  • Structural inheritance—influence of Proterozoic structure on younger deformation
  • Structural connections across the Laramide foreland province
  • Dynamics and drivers of structural collapse in areas of thickened crust
  • Role of strike-slip shear in transition from compression to extension
  • Influence of extensional structures on magmatic systems
  • Detachment faulting associated with strike-slip shear
  • Eocene to Oligocene structural development of the Rio Grande Rift
  • Identifying optimally oriented faults within modern and paleo-stress fields