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

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• 作者：Kathryn Hedrick ; Lewis A. Owen ; Thomas K. Rockwell ; Andrew Meigs ; Carlos Costa ; Marc W. Caffee ; Eulalia Masana ; Emilio Ahumada
• 关键词：Terrestrial cosmogenic nuclide dating ; Optically stimulated luminescence dating ; Climate change ; Tectonics ; Erosion rates
• 刊名：Quaternary Science Reviews
• 出版年：15 November, 2013
• 年：2013
• 卷：80
• 期：Complete
• 页码：143-168
• 全文大小：10370 K

文摘

Sixty-eight ¹⁰Be 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 Carpinter铆a strath complex reveal a history of alluvial fan and strath terrace development over the past 鈭?25聽ka. The Marquesado complex Q3_m surface dates to 鈭?7聽卤聽3聽ka, whereas the Loma Negra Q1_ln, Q2_ln, Q3_ln, Q4_ln, and Q5_ln surfaces date to 鈭?4聽卤聽3聽ka, 鈭?8聽卤聽2聽ka, 鈭?5聽卤聽13聽ka, 鈭?05聽卤聽21聽ka, and 鈭?81聽卤聽29聽ka, respectively. The Carpinter铆a complex comprises eight surfaces that have been dated and include the Q1_c (鈭?3聽卤聽3聽ka), Q2_c (鈭?聽卤聽5聽ka), Q3a_c (鈭?5聽卤聽12聽ka), Q3b_c (鈭?9聽卤聽15聽ka), Q4_c (鈭?1聽卤聽12聽ka), Q5_c (鈭?8聽卤聽18聽ka), Q6_c (鈭?3聽卤聽18聽ka), and Q7_c (鈭?12聽卤聽37聽ka). ¹⁰Be TCN depth profile data for the Loma Negra alluvial fan complex and Carpinter铆a strath terrace complex, as well as OSL ages on some Carpinter铆a 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 (鈭?0聽脳聽10^{4 10}Be atoms/g of SiO₂ and 鈭?聽m聽Ma^鈭?, respectively). Comparison with other alluvial fan studies in the region show that less dynamic and older preserved surfaces occur in the Carpinter铆a 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.