Timing and nature of alluvial fan and strath terrace formation in the Eastern Precordillera of Argentina

QUATERNARY SCIENCE REVIEWS

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Article

Hedrick, Kathryn¹  Owen, Lewis A.¹  Rockwell, Thomas K.²  Meigs, Andrew³  Costa, Carlos⁴  Caffee, Marc W.⁵  Masana, Eulalia⁶  Ahumada, Emilio⁴ 

[1] Univ Cincinnati, Dept Geol, Cincinnati, OH 45221 USA

[2] San Diego State Univ, Dept Geol Sci, San Diego, CA 92182 USA

[3] Oregon State Univ, Coll Earth Ocean & Atmospher Sci, Corvallis, OR 97331 USA

[4] Univ Nacl San Luis, Dept Geol, RA-5700 San Luis, Argentina

[5] Purdue Univ, Dept Phys, W Lafayette, IN 47907 USA

[6] Univ Barcelona, Dept Geodinam & Geofis, E-08007 Barcelona, Spain

关键词: Terrestrial cosmogenic nuclide dating;    Optically stimulated luminescence dating;    Climate change;    Tectonics;    Erosion rates;   

DOI  :  10.1016/j.quascirev.2013.05.004

来源: Elsevier

【 摘 要 】

Sixty-eight Be-10 terrestrial cosmogenic nuclide (TCN) surface exposure ages are presented to define the timing of alluvial fan and strath terrace formation in the hyper-arid San Juan region of the Argentine Precordillera. This region is tectonically active, and numerous fault scarps traverse Quaternary landforms. The three study sites, Marquesado strath complex, Loma Negra alluvial fan and Carpinteria strath complex reveal a history of alluvial fan and strath terrace development over the past similar to 225 ka. The Marquesado complex Q3(m), surface dates to similar to 17 +/- 3 ka, whereas the Loma Negra Q1(ln), Q2(ln), Q3(ln), Q4(ln), and Q5(ln) surfaces date to similar to 24 +/- 3 ka, similar to 48 +/- 2 ka, similar to 65 +/- 13 ka, similar to 105 +/- 21 ka, and similar to 181 +/- 29 ka, respectively. The Carpinteria complex comprises eight surfaces that have been dated and include the Q1(c) (similar to 23 +/- 3 ka), Q2(c) (similar to 5 +/- 5 ka), Q3a(c) (similar to 25 +/- 12 ka), Q3b(c) (similar to 29 +/- 15 ka), Q4(c) (similar to 61 +/- 12 ka), Q5(c) (similar to 98 +/- 18 ka), Q6(c) (similar to 93 +/- 18 ka), and Q7(c) (similar to 212 +/- 37 ka). Be-10 TCN depth profile data for the Loma Negra alluvial fan complex and Carpinteria strath terrace complex, as well as OSL ages on some Carpinteria deposits, aid in refining surface ages for comparison with local and global climate proxies, and additionally offer insights into inheritance and erosion rate values for TCNs (similar to 10 x 10(4) Be-10 atoms/g of SiO2 and similar to 5 m Ma(-1), respectively). Comparison with other alluvial fan studies in the region show that less dynamic and older preserved surfaces occur in the Carpinteria and Loma Negra areas with only younger alluvial fan surfaces preserved both to the north and south. These data in combination with that of other studies illustrate broad regional agreement between alluvial fan and strath terrace ages, which suggests that climate is the dominant forcing agent in the timing of terrace formation in this region. (C) 2013 Elsevier Ltd. All rights reserved.

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