Paleoenvironments & Sequence Stratigraphy
Chris Fedo's longest standing interest in clastic sedimentology has been facies analysis and sequence stratigraphy. Most of his perspective has been honed by a twenty-year project that began as his senior thesis investigating the sedimentology and sequence stratigraphy of Neoproterozoic and Cambrian rocks in southeastern California. This research has centered around interpreting the depositional environments of different units and placing the stratigraphy in a sequence stratigraphic framework. Depositional systems in this rift-through-passive-margin stratigraphy include alluvial fan, fluvial, tidal, and shallow marine. Reconstruction of the sequence stratigraphy has been difficult because of Mesozoic contractional, then Cenozoic extensional and strike-slip deformations that have compromised initial geographic positions. Despite these limitations, he is continuing to reconcile the stratigraphic relationships that span the Precambrian-Cambrian boundary, and which define the base of the Sauk Supersequence in an off-craton setting. Further, the research has been addressing the influential role of the Neoproterozoic craton-margin hinge-zone on paleoenvironments and sequence architecture. The main goals are to generate a detailed sequence stratigraphic correlation and to reconstruct the early paleogeographic history of the Cordilleran margin in this region.
Images showing sedimentary features of the Neoproterozoic Stirling Quartzite, Death Valley area, SE California. Top left: Measured section of the Johnnie Formation, Stirling Quartzite, and Wood Canyon Formation, Salt Spring Hills. Top right: Coset of unimodal, trough crost-stratified sandstone, the upper member Stirling Quartzite. Bottom left: Quartz pebble conglomerate, lower member Stirling Quartzite. Lower right: Interference ripple marks, middle member Stirling Quartzite.
Sequence stratigraphy and interpreted relative sea-level curve for the Neoproterozoic-Cambrian transition, southeastern California across the craton-margin hinge zone. From Hogan et al. (2011).
- Hogan, E.G., Fedo, C.M., and Cooper, J.D., 2011, Reassessment of the basal Sauk Supersequence boundary across the Laurentian craton-margin hinge-zone, southeastern California: Journal of Geology, v. 119, p. 661-685.
- Fedo, C.M., and Cooper, J.D., 2001, Sedimentology and sequence stratigraphy of Neoproterozoic and Cambrian units across a craton margin hinge zone, southeastern California, and implications for the early evolution of the Cordilleran margin: Sedimentary Geology, v. 141-142, p. 501-522.
- Hagadorn, J.W., Fedo, C.M., and Waggoner, B.M., 2000, Early Cambrian Ediacaran-type fossils from California: Journal of Paleontology, v. 74, p. 731-740.
- Cooper, J.D., and Fedo, C.M., 1993, Extending the western North American Proterozoic and Paleozoic continental crust through the Mojave Desert--Comment: Geology, v. 21, p.669-670.
- Fedo, C.M., and Cooper, J.D., 1990, Braided fluvial to marine transition: the basal Lower Cambrian Wood Canyon Formation, southern Marble Mountains, Mojave Desert, California: Journal of Sedimentary Petrology, v. 60, p. 220-234.
Chemostratigraphy of Proterozoic Sedimentary Successions
Carbon isotope chemostratigraphy has become a principal tool for stratal correlation and the primary mechanism by which Proterozoic strata are placed in a chronostratigraphic framework. Chemostratigraphic correlation is particularly well established for the latter Neoproterozoic (<800 Ma), during which marine carbon isotopes record both elevated average values and high amplitude variation. Unfortunately, the resolution of our global chemostratigraphic record remains limited for much of the earlier Proterozoic. Linda Kah's research on Mesoproterozoic (1600-1000 Ma) successions has permitted definition of broad intervals of isotopic similarity, and has resulted in modeling efforts to link carbon isotopic variability to the PCO2 evolution of the Early Earth.