Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 112, Issue 49, Pages 15042-15047Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1512549112
Keywords
tectonic-climate interactions; orogenesis; Mid-Pleistocene transition; ass flux; ocean drilling
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Funding
- NERC [NE/L002426/1, NE/L002639/1] Funding Source: UKRI
- Natural Environment Research Council [NE/L002426/1] Funding Source: researchfish
- Division Of Ocean Sciences
- Directorate For Geosciences [1436903, 1360894] Funding Source: National Science Foundation
- Division Of Ocean Sciences
- Directorate For Geosciences [1435121, 1434945] Funding Source: National Science Foundation
- Grants-in-Aid for Scientific Research [26281006] Funding Source: KAKEN
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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 (similar to 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 (similar to 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.
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