Lone Man and All My Relations

Lone Man is the central creation figure of the Mandan, an indigenous people of present-day North Dakota. The story of Lone Man begins with the creation figure becoming self-aware on the open ocean. He creates the Earth and sets off to discover his people. Doug Meigs is writing the oral history of Robert O’Brien, a modern Mandan man living in Omaha, Nebraska, who grew up without any knowledge of tribal identity. Late in life, he would set off to learn that he was Mandan. O’Brien is still coming to terms with the meaning of that identity

Late Cenozoic Foreland-to-Hinterland Low-Temperature Exhumation History of the Kashmir Himalaya

New apatite and zircon (U-Th)/He cooling ages quantify late Cenozoic exhumation patterns associated with fault activity across the Kashmir Himalaya. Apatite (U-Th)/He (AHe) cooling ages of detrital grains from the Sub-Himalayan foreland sediments indicate significant resetting. AHe data and thermal modeling reveal cooling and exhumation initiated by 4Ma at the deformation front and by 2-4Ma throughout other Sub-Himalayan structures. Exhumation rates for Sub-Himalayan structures are 1mm/year. In the hinterland, thrust sheet samples from the Main Boundary thrust and Main Central thrust yield AHe cooling ages between 5.1 and 21.1Ma. Published apatite fission track cooling ages (<3Ma) and high exhumation rates (3.6-3.2mm/year) across the Kishtwar window further to the north are consistent with AHe data from the Sub-Himalayan structures. The pattern of cooling ages and rates indicates that exhumation occurs in association with changes in the Himalayan basal decollement ramp geometry. Hinterland zircon (U-Th)/He (ZHe) data show a pronounced abundance and probability spike in cooling ages between 14 and 21Ma, a period when Main Central thrust motion is well documented throughout the Himalaya. ZHe single-grain ages from Sub-Himalayan samples contain a nearly identical cluster from 16 to 23Ma. Cooling patterns across the Kashmir Himalayas do not correlate spatially with modern monsoon precipitation, suggesting that climate-related precipitation and exhumation are decoupled. Coeval translation over the basal decollement and distributed imbricate thrust deformation of the foreland in the upper plate characterizes fault-related exhumation of the Sub-Himalayan orogenic belt after 4Ma. Our new data document the timing of cooling of rocks brought to the surface during mountain building of the Kashmir Himalaya. Mineral grains eroded from the Himalaya and deposited in the plain are now exposed in the Sub-Himalayan belt. The ages of these rocks that we have measured constrain the timing of burial and subsequent return to the Earth's surface (exhumation) during thrust fault-related deformation. Analysis of apatite grains reveals that cooling and exhumation initiated by 4Ma on the southernmost structure of the Kashmir Himalaya and by 2-4Ma on other distributed faults in the Sub-Himalayan belt. In the core of the mountain range rocks have young cooling ages (<3Ma) related to high uplift rates within the Kishtwar window, a zone of localized deformation in the High Himalaya. Thus, outward growth of the Sub-Himalayan belt occurred in concert with uplift in the hinterland over the past 4Myr. Precipitation rates vary systematically from south to north across the Himalaya, but these variations are not synchronous with the pattern of cooling and exhumation in Kashmir Himalaya. This result suggests that climate does not drive crustal deformation. Instead exhumation patterns primarily reflect the location, geometry, and partitioning of faulting within the Himalaya

Reconstructing the exhumation history of the Lesser Himalaya, NW India, from a multitechnique provenance study of the foreland basin Siwalik Group

This research presents the first multitechnique provenance study of the Siwalik Group in the Himalayan foreland basin in India, using the Jawalamukhi section, magnetostratigraphically dated at 13–5 Ma. Combined with provenance data from a Dharamsala Formation sedimentary section (21–13 Ma) located close by, it forms the longest temporally continuous record of Himalayan erosion in the Indian foreland basin. Sandstone petrography and heavy mineral analysis, conglomerate clast composition, Ar-Ar dating of detrital white micas, and Sm-Nd analyses on siltstones, conglomerate matrix and conglomerate clasts was undertaken to determine (1) shifts in source region through time and (2) changes in detrital lag times related to exhumation rates in the hinterland, together interpreted in the light of thrusting events. We interpret the data to show a slow down in exhumation rate of the Higher Himalaya by 16–17 Ma, after which time the locus of thrusting propagated south of the Main Central Thrust, and erosion of the low grade Haimanta Formation to the south became significant. The nonmetamorphosed Inner Lesser Himalaya breached its Haimanta cover by 9 Ma with the metamorphosed Inner Lesser Himalaya (Lesser Himalayan Crystalline Series) exhuming to surface by 6 Ma. This event caused sufficient disruption to established drainage patterns that all Higher Himalayan material was diverted from this location at this time