TY - JOUR
T1 - Late quaternary fluvial incision and aggradation in the Lesser Himalaya, India
AU - Dosseto, Anthony
AU - May, Jan-Hendrik
AU - Choi, Jeong-Heon
AU - Swander, Zachary J.
AU - Fink, David
AU - Korup, Oliver
AU - Hesse, Paul
AU - Singh, Tejpal
AU - Mifsud, Charles
AU - Srivastava, Pradeep
PY - 2018/10/1
Y1 - 2018/10/1
N2 - Reconstructing how rivers respond to changes in runoff or sediment supply by incising or aggrading has been pivotal in gauging the role of the Indian Summer Monsoon (ISM) as a geomorphic driver in the Himalayas. Here we present new chronological data for fluvial aggradation and incision from the Donga alluvial fan and the upper Alaknanda River, as well as a compilation of previous work. In addition to conventional OSL-SAR (Single-Aliquot Regenerative-Dose) dating method, we have tested and applied pulsed OSL (POSL) dating for quartz samples that include K-rich feldspar inclusions, which is expected to improve the applicability and validity of OSL ages in the Lesser Himalaya. For previously dated deposits, our OSL ages are shown to be systematically older than previously reported ages. These results suggest periods of aggradation in the Alaknanda and Dehradun Valleys mainly between ∼25 and 35 ka. This most likely reflects decreased stream power during periods of weakened monsoon. In addition, in-situ cosmogenic beryllium-10 was used to infer bedrock surface exposure ages, which are interpreted as episodes of active fluvial erosion. Resulting exposure ages span from 3 to 6 ka, suggesting that strath terraces were exposed relatively recently, and incision was dominant through most of the Holocene. In combination, our results support precipitation-driven fluvial dynamics, which regulates the balance between stream power and sediment supply. On a larger spatial scale, however, fluvial dynamics are probably not spatially homogeneous as aggradation could have been taking place in adjacent catchments while incision dominated in the study area.
AB - Reconstructing how rivers respond to changes in runoff or sediment supply by incising or aggrading has been pivotal in gauging the role of the Indian Summer Monsoon (ISM) as a geomorphic driver in the Himalayas. Here we present new chronological data for fluvial aggradation and incision from the Donga alluvial fan and the upper Alaknanda River, as well as a compilation of previous work. In addition to conventional OSL-SAR (Single-Aliquot Regenerative-Dose) dating method, we have tested and applied pulsed OSL (POSL) dating for quartz samples that include K-rich feldspar inclusions, which is expected to improve the applicability and validity of OSL ages in the Lesser Himalaya. For previously dated deposits, our OSL ages are shown to be systematically older than previously reported ages. These results suggest periods of aggradation in the Alaknanda and Dehradun Valleys mainly between ∼25 and 35 ka. This most likely reflects decreased stream power during periods of weakened monsoon. In addition, in-situ cosmogenic beryllium-10 was used to infer bedrock surface exposure ages, which are interpreted as episodes of active fluvial erosion. Resulting exposure ages span from 3 to 6 ka, suggesting that strath terraces were exposed relatively recently, and incision was dominant through most of the Holocene. In combination, our results support precipitation-driven fluvial dynamics, which regulates the balance between stream power and sediment supply. On a larger spatial scale, however, fluvial dynamics are probably not spatially homogeneous as aggradation could have been taking place in adjacent catchments while incision dominated in the study area.
UR - http://www.scopus.com/inward/record.url?scp=85051489786&partnerID=8YFLogxK
UR - http://purl.org/au-research/grants/arc/FT0990447
U2 - 10.1016/j.quascirev.2018.07.035
DO - 10.1016/j.quascirev.2018.07.035
M3 - Article
AN - SCOPUS:85051489786
SN - 0277-3791
VL - 197
SP - 112
EP - 128
JO - Quaternary Science Reviews
JF - Quaternary Science Reviews
ER -