Paleoclimate and Paleoaltimetry
Paleoaltimetry and paleoclimate of the North American Cordillera
How and when did the North American Cordillera rise? And what impacts did this have on the assembly of modern climate and seasonality in western North America?
In 2012, Page Chamberlain (then my PhD advisor) wrote a comprehensive paper based on my metaanalysis of Cenozoic and late-Mesozoic stable isotope records from western North America.
Chamberlain, C.P., Mix, H.T., Mulch, A., Hren, M.T., Kent-Corson, M.L., Davis, S.J., Horton, T.W., Graham, S.A. (2012) The Cenozoic Climatic and Topographic Evolution of the Western North American Cordillera. American Journal of Science, v. 312, p. 213-262. Download ▸
This was our “splash” paper, where I documented the north-to-south progressive uplift of the North American Cordillera.
Mix, H.T., Mulch, A., Kent-Corson, M.L., Chamberlain, C.P. (2011). Cenozoic migration of topography in the North American Cordillera. Geology, v. 39, p. 87-90. Download ▸
The ancient lake basins just east of the Cordillera recorded this transition as well.
Davis, S.J., Mix, H.T., Wiegand, B.A., Carroll, A.R. and Chamberlain, C.P. (2009) Synorogenic evolution of large-scale drainage patterns: Isotope paleohydrology of sequential Laramide basins. American Journal of Science, v. 309, p. 549-602. Download ▸
Along with Ran Feng and Chris Poulsen at the University of Michigan, we compared our results to those simulated by an isotope-tracking general circulation model.
Feng, R., Poulsen, C.J., Werner, M., Chamberlain, C.P., Mix, H.T., Mulch, A. (2013) Early Cenozoic evolution of topography, climate and stable isotopes in precipitation in the North American Cordillera. American Journal of Science, v. 313, p. 613-648. Download ▸
The Palisades, Eastern Sierra, CA.
Dan Ibarra and I reanalyzed the kaolinites of Mulch et al., 2006, showing a similar elevation gradient in oxygen isotopes as hydrogen. Further, we used the combined oxygen-hydrogen records to calculate Eocene paleotemperatures.
Mix, H.T., Ibarra, D.E., Mulch, A., Graham, S.A., Chamberlain, C.P. (2016) A hot and high Eocene Sierra Nevada. Geological Society of America Bulletin, v. 128, p. 531-542. Download ▸
Following the theoretical work of Joe Galewsky and Alex Lechler, we attempted to reconstruct the history of atmospheric flow over and around the Sierra Nevada. Our results show that circulation similar to modern has been in place at least 10 million years.
Mix, H.T., Rugenstein, J.K.C., Reilly, S.P., Ritch, A.J., Winnick, M.J., Kukla, T., Chamberlain, C.P. (2019) Atmospheric flow deflection in the late Cenozoic Sierra Nevada. Earth and Planetary Science Letters, v. 518, p. 76-85. Download ▸
By looking at stable isotope records spatially rather than temporally in individual sections, we documented the progressive rise of the North American Cordillera by late Eocene. Mix et al., 2011.
Davis et al., 2009
Jeremy Caves Rugenstein (Colorado State) and Matt Winnick (U Mass Amherst) above Taatsin Gol, Mongolia
Paleoclimate and paleoaltimetry of Central Asia
How and when did Central Asian ranges like the Hangay, Altai, Sayan, and Tian Shan rise? Our work showed that Central Asian aridity was driven by these uplifts and the role of westerlies rather than uplift of the Tibetan Plateau.
Caves, J.K., Sjostrom, D.J., Mix, H.T., Winnick, M.J., Chamberlain, C.P. (2014) Aridification of Central Asia and uplift of the Altai and Hangay Mountains, Mongolia: Stable isotope evidence. American Journal of Science, v. 314, p. 1171-1201. Download ▸
Caves, J.K., Bayashashov, B.U., Zhamangara, A., Ritch, A.J., Ibarra, D.E., Sjostrom, D.J., Mix, H.T., Winnick, M.J., Chamberlain, C.P. (2017) Late Miocene uplift of the Tian Shan and Altai and reorganization of Central Asia climate. GSA Today, v. 27, p. 20-26. Download ▸
Paleoaltimetry and paleoclimate of the Alaska Range
How and when did the Alaska Range rise? We produced a new late Cenozoic stable isotope record from tephras and compared these findings to thermochronologic and sedimentological studies.
Bill, N.S., Mix, H.T. (shared first author), Clark, P.U., Reilly, S.P., Jensen, B.J., Benowitz, J.A. (2018) A stable isotope record of late Cenozoic surface uplift of southern Alaska. Earth and Planetary Science Letters, v. 482, p. 300-311. Download ▸
The linked evolution of grasslands and climate
How did the dramatic rise of grasslands in the late Cenozoic affect the hydrologic cycle? Our new records from western North America, other grassland records worldwide, and modeling suggest that grasses greatly increased the amount and seasonality of vapor recycling. Could grasses engineer the conditions favorable for their own expansion?
The rise of C4 grasslands and grazers coincided with dramatic changes in vapor recycling along North American moisture trajectories. Mix et al., 2013.
Mix, H.T., Winnick, M.J., Mulch, A., Chamberlain, C.P. (2013) Grassland expansion as an instrument of hydrologic change in Neogene western North America. Earth and Planetary Science Letters, v. 377, p. 73-83. Download ▸
Chamberlain, C.P., Winnick, M.J., Mix, H.T., Chamberlain, S.D., Maher, K. (2014) The impact of Neogene grassland expansion and aridification on the isotopic composition of continental precipitation. Global Biogeochemical Cycles, v. 28, p. 992-1004. Download ▸
Clay mineral paleothermometry
Can clay minerals provide reliable records of past temperature? By combining oxygen and hydrogen isotope records from smectite, I reconstructed Cenozoic mineral formation temperatures from the Basin and Range, Rocky Mountains and Great Plains.
Mix, H.T. and Chamberlain, C.P. (2014) Stable isotope records of hydrologic change and paleotemperature from smectite in Cenozoic western North America. Geochimica et Cosmochimica Acta, v. 141, p. 532-546. Download ▸
The 8.2 Ka event
8200 years ago, Lake Agassiz catastrophically drained, flooding the North Atlantic with freshwater. How did this event affect California hydroclimate? We produced a cave record which suggested that the Pacific winter storm track intensified during this time.
Oster, J.L., Sharp, W.D., Covey, A.K., Gibson, J., Rogers, B., Mix, H.T. (2017) Climate response to the 8.2 ka event in coastal California. Scientific Reports, v. 7, p. 1-9. Download ▸
A Miocene ash, Middle Park, CO.