Mid-Pleistocene climate transition drives net mass loss from rapidly uplifting St. Elias Mountains, Alaska

Erosion, sediment production, and routing on a tectonically active continental margin reflect both tectonic and climatic processes; partitioning the relative importance of these processes remains controversial. Gulf of Alaska contains a preserved sedimentary record of the Yakutat Terrane collision w...

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Published in:	Proceedings of the National Academy of Sciences - PNAS Vol. 112; no. 49; pp. 15042 - 15047
Main Authors:	Gulick, Sean P. S., Jaeger, John M., Mix, Alan C., Asahi, Hirofumi, Bahlburg, Heinrich, Belanger, Christina L., Berbel, Glaucia B. B., Childress, Laurel, Cowan, Ellen, Drab, Laureen, Forwick, Matthias, Fukumura, Akemi, Ge, Shulan, Gupta, Shyam, Kioka, Arata, Konno, Susumu, LeVay, Leah J., März, Christian, Matsuzaki, Kenji M., McClymont, Erin L., Moy, Chris, Müller, Juliane, Nakamura, Atsunori, Ojima, Takanori, Ribeiro, Fabiana R., Ridgway, Kenneth D., Romero, Oscar E., Slagle, Angela L., Stoner, Joseph S., St-Onge, Guillaume, Suto, Itsuki, Walczak, Maureen D., Worthingtona, Lindsay L., Baileyb, Ian, Enkelmannc, Eva, Reeced, Robert, Swartz, John M.
Format:	Journal Article
Language:	English
Published:	United States National Academy of Sciences 08-12-2015 National Acad Sciences
Subjects:	Climate Oceans Physical Sciences Plate tectonics Sediments Soil erosion orogenesis tectonic−climate interactions ocean drilling Mid-Pleistocene transition mass flux
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Summary:	Erosion, sediment production, and routing on a tectonically active continental margin reflect both tectonic and climatic processes; partitioning the relative importance of these processes remains controversial. Gulf of Alaska contains a preserved sedimentary record of the Yakutat Terrane collision with North America. Because tectonic convergence in the coastal St. Elias orogen has been roughly constant for 6 My, variations in its eroded sediments preserved in the offshore Surveyor Fan constrain a budget of tectonic material influx, erosion, and sediment output. Seismically imaged sediment volumes calibrated with chronologies derived from Integrated Ocean Drilling Program boreholes show that erosion accelerated in response to Northern Hemisphere glacial intensification (∼2.7 Ma) and that the 900-km-long Surveyor Channel inception appears to correlate with this event. However, tectonic influx exceeded integrated sediment efflux over the interval 2.8–1.2 Ma. Volumetric erosion accelerated following the onset of quasi-periodic (∼100-ky) glacial cycles in the mid-Pleistocene climate transition (1.2–0.7 Ma). Since then, erosion and transport of material out of the orogen has outpaced tectonic influx by 50–80%. Such a rapid net mass loss explains apparent increases in exhumation rates inferred onshore from exposure dates and mapped out-of-sequence fault patterns. The 1.2-My mass budget imbalance must relax back toward equilibrium in balance with tectonic influx over the timescale of orogenic wedge response (millions of years). The St. Elias Range provides a key example of how active orogenic systems respond to transient mass fluxes, and of the possible influence of climate-driven erosive processes that diverge from equilibrium on the million-year scale.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 2Present address: Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, Tsukuba 305-8567, Japan. Author contributions: S.P.S.G., J.M.J., A.C.M., and L.J.L. designed research; S.P.S.G., J.M.J., A.C.M., H.A., H.B., C.L.B., G.B.B.B., L.C., E.C., L.D., M.F., A.F., S. Ge, S. Gupta, A.K., S.K., L.J.L., C. März, K.M.M., E.L.M., C. Moy, J.M., A.N., T.O., F.R.R., K.D.R., O.E.R., A.L.S., J.S.S., G.S.-O., I.S., M.D.W., and L.L.W. performed research; S.P.S.G., J.M.J., A.C.M., I.B., E.E., R.R., and J.M.S. analyzed data; and S.P.S.G., J.M.J., and A.C.M. wrote the paper. Edited by John P. Grotzinger, California Institute of Technology, Pasadena, CA, and approved October 27, 2015 (received for review June 26, 2015)
ISSN:	0027-8424 1091-6490
DOI:	10.1073/pnas.1512549112