TY - JOUR
T1 - Did a catastrophic lake spillover integrate the late miocene early pliocene Colorado river and the Gulf of California?
T2 - Microfaunal and stable isotope evidence from Blythe basin, California-Arizona, USA
AU - Bright, Jordon
AU - Cohen, Andrew S.
AU - Dettman, David L.
AU - Pearthree, Philip A.
AU - Dorsey, Rebecca J.
AU - Homan, Mindy B.
N1 - Funding Information:
This research was partly funded by the U.S. Geological Survey, by the Geological Society of America's Kerry Kelts Research Award (JB), and by the University of Arizona's Maxwell Short Scholarship (JB). A portion of this research was supported by funds from NSF EAR-1545998. We thank Jacob Favela for assistance with the SEM imaging. The University of Arizona's LaserChron SEM Facility is supported by funds from NSF EAR-0929777. We appreciate conversations with Jon Spencer, Kristin McDougall, and Kyle House, and their willingness to share their ideas about the Bouse Formation. We appreciate the comments of two anonymous reviewers that helped improve the clarity of the manuscript.
Publisher Copyright:
Copyright © 2016, SEPM (Society for Sedimentary Geology).
PY - 2016/3
Y1 - 2016/3
N2 - The southern Bouse Formation (late Miocene-early Pliocene) in Blythe basin, CA-AZ, contains a controversial record of the events that preceded the integration of the developing Colorado River with the Gulf of California. High resolution microfaunal and stable isotope (δ18O, δ13C; VPDB) data from a key outcrop of marl and claystone record an abrupt change in water chemistry that we interpret to be the result of a catastrophic sill breach. Basal marl contains a mix of brackish-water ostracodes and marine foraminifers. Ostracode δ18O values are slightly negative and 6% higher than the host sediment carbonate precipitated in the upper water column, indicating isotopically stratified hydrologic conditions during deposition. Freshwater ostracodes abruptly appear in the overlying sediments in association with marine foraminifers, in conjunction with an abrupt change in the isotopic composition of ostracode and host sediment carbonate. The δ18O values from brackish and freshwater ostracodes and the host sediment carbonate are similar (, -10%), indicating an isotopically well-mixed water body during deposition. Sediment δ13C values decrease by 4.5% across this transition but ostracode δ13C values remain unchanged. We infer that the transition from stratified to well-mixed conditions likely took less than 300 years. The abruptness of this transition is best explained by catastrophic failure of a paleodam that rapidly altered the isotopic composition and salinity of a lake in Blythe basin. A marine or estuarine environment is unlikely. Our interpretation is consistent with other evidence for catastrophic breaching of another lacustrine Bouse Formation-bearing basin to the north.
AB - The southern Bouse Formation (late Miocene-early Pliocene) in Blythe basin, CA-AZ, contains a controversial record of the events that preceded the integration of the developing Colorado River with the Gulf of California. High resolution microfaunal and stable isotope (δ18O, δ13C; VPDB) data from a key outcrop of marl and claystone record an abrupt change in water chemistry that we interpret to be the result of a catastrophic sill breach. Basal marl contains a mix of brackish-water ostracodes and marine foraminifers. Ostracode δ18O values are slightly negative and 6% higher than the host sediment carbonate precipitated in the upper water column, indicating isotopically stratified hydrologic conditions during deposition. Freshwater ostracodes abruptly appear in the overlying sediments in association with marine foraminifers, in conjunction with an abrupt change in the isotopic composition of ostracode and host sediment carbonate. The δ18O values from brackish and freshwater ostracodes and the host sediment carbonate are similar (, -10%), indicating an isotopically well-mixed water body during deposition. Sediment δ13C values decrease by 4.5% across this transition but ostracode δ13C values remain unchanged. We infer that the transition from stratified to well-mixed conditions likely took less than 300 years. The abruptness of this transition is best explained by catastrophic failure of a paleodam that rapidly altered the isotopic composition and salinity of a lake in Blythe basin. A marine or estuarine environment is unlikely. Our interpretation is consistent with other evidence for catastrophic breaching of another lacustrine Bouse Formation-bearing basin to the north.
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U2 - 10.2110/palo.2015.035
DO - 10.2110/palo.2015.035
M3 - Article
AN - SCOPUS:84962449133
SN - 0883-1351
VL - 31
SP - 81
EP - 91
JO - Palaios
JF - Palaios
IS - 3
ER -