Constraining Deformation in the North Pamir and the Westernmost Tarim Basin

Abstract HKT-ISTP 2013 A

Spatial and temporal uplift history of South America from calibrated drainage analysis

A multidisciplinary approach is used to analyze the Cenozoic uplift history of South America. Residual depth anomalies of oceanic crust abutting this continent help to determine the pattern of present-day dynamic topography. Admittance analysis and crustal thickness measurements indicate that the elastic thickness of the Borborema and Altiplano regions is ≤₁₀ km with evidence for sub-plate support at longer wavelengths. A drainage inventory of 1827 river profiles is assembled and used to investigate landscape development. Linear inverse modeling enables river profiles to be fitted as a function of the spatial and temporal history of regional uplift. Erosional parameters are calibrated using observations from the Borborema Plateau and tested against continent-wide stratigraphic and thermochronologic constraints. Our results predict that two phases of regional uplift of the Altiplano plateau occurred in Neogene times. Regional uplift of the southern Patagonian Andes also appears to have occurred in Early Miocene times. The consistency between observed and predicted histories for the Borborema, Altiplano, and Patagonian plateaux implies that drainage networks record coherent signals that are amenable to simple modeling strategies. Finally, the predicted pattern of incision across the Amazon catchment constrains solid sedimentary flux at the Foz do Amazonas. Observed and calculated flux estimates match, suggesting that erosion and deposition were triggered by regional Andean uplift during Miocene times

Non-monotonic cooling history in the southern Central Andes recorded by multisystem low-temperature thermochronology

Three low-temperature thermochronometers are used to study the temperature and exhumation history of the Sierra Laguna Blanca, a major basement range that rises over 6 km in the backarc region of the Central Andes. Five samples analyzed with zircon (U-Th-Sm)/He thermochronology yield early Carboniferous to early Triassic dates. Ten apatite fission-track samples provide ~50 to 70 Ma ages with shortened, ~11-12 µm track lengths. Ten apatite (UTh-Sm)/He samples yield highly dispersed dates ranging from ~30 Ma to 120 Ma, with eU values ranging from ~50 to 500 ppm. Time-temperature inverse and forward models reveal three major cooling events at the late Paleozoic, late Cretaceous and mid-late Miocene, and a heating event during late Eocene to early Oligocene. This study demonstrates that accumulated radiation damage, in this case caused by very high eU instead of a prolonged low-temperature history, may lead to significant apatite (U-Th-Sm)/He date dispersion

Cooling history for the Sierra Laguna Blanca (NW Argentina) on the Southern Puna Plateau, Central Andes

Various dynamic models have been proposed to explain deformation history and topographic evolution for the southern Altiplano-Puna Plateau, including inversion of the Cretaceous Salta rift structures, formation of an orogenic wedge, flat subduction, climate-tectonic coupling, and lithospheric foundering. Controversies persist in the southern Puna Plateau, where preexisting rift structures are unknown and Cenozoic shortening events are sparsely documented. The 6-km high Sierra Laguna Blanca (LB) (NW Argentina) is among the most outstanding topographic features in the interior of the southern Puna Plateau. We document cooling history for LB with apatite (U-Th)/He, apatite fission-track and zircon (U-Th)/He thermochronometers for a vertical profile from 3.6-5.6 km on its eastern flank. Preliminary results from apatite fission-track (AFT) analysis yield ages ranging from 45-65 Ma, with top samples being the oldest. Dpar values for all samples are low (1.54 to 1.74), suggesting a relatively low-temperature partial annealing zone. All samples have shortened mean track lengths ranging from 10.9 to 12.3 micrometers, suggesting partial resetting. Preliminary apatite U-Th/He (AHe) ages are compatible with AFT ages but are widely dispersed, perhaps due to U zoning and small U-rich inclusions which have been observed on AFT external detectors. Inverse modeling of AFT data and selected AHe data using the HeFTy program reveal two major cooling events for LB. All models start ~90-70 Ma and immediately decrease their temperatures to ~60°C before ~50 Ma. Samples may have stayed ~60°C without additional thermal events until ~15-10 Ma, when the most recent cooling event took place, bringing all samples to surface temperature. Our first finding is that the interior of the southern Puna Plateau may have been influenced by the Salta Rift during the Cretaceous, extending the known zone of influence further west. Second, the most recent cooling phase (mid-late Miocene) is consistent with out-of-sequence deformation in the southern Puna Plateau, which might be genetically linked to a proposed lithospheric dripping event

Tectonic geomorphology and Plio-Quaternary structural evolution of the Tuzgolu fault zone, Turkey: Implications for deformation in the interior of the Central Anatolian Plateau

Situated within the interior of the Central Anatolian Plateau (Turkey), the 200-km-long Tuzgolu extensional fault zone offers first-order constraints on the timing and pattern of regional deformation and uplift. In this study, we analyze the morphometrics of catchments along the Tuzgolti range-front fault and the parallel, basinward Hamzali fault using a variety of measured morphometric indicators coupled with regional geomorphic observations and longitudinal profile analysis. In addition, we use field and remote mapping to constrain the geometry of two key marker beds, the Pliocene Kizilkaya ignimbrite and Kisladag limestone, in order to investigate deformation in the footwall of the Tuzgolu fault zone. The marker beds form a broad arch along the footwall of the fault, with greatest cumulative displacement along the central part of the fault zone, suggesting early Pliocene extensional reactivation of the Tuzgolu fault with a typical fault-displacement profile. However, a change in deformation pattern is marked by transient knick-points along river channels; morphometric indicators sensitive to shorter (1-3 Ma) time scales, including river steepness, basin elongation, and mountain front sinuosity, indicate an overall southeastward increase in footwall uplift rate of the Tuzgolu fault zone, which could reflect block rotation or interaction with the Hasan Dag volcano. Basin asymmetry and basin-fault azimuth measurements indicate north-northwest tilting of footwall catchments, which may be linked to regional tilting across the Central Anatolian Plateau interior. Varying patterns of spatial and temporal deformation along the length of the Tuzgolu fault zone are likely due to the interference of crustal- and lithospheric-scale processes, such as rotation of crustal blocks, extrusion of the Anatolian microplate, crustal heating, gravitational collapse associated with plateau uplift, and mantle-driven vertical displacements

Fragmentation of a foreland basin in response to out-of-sequence basement uplifts and structural reactivation: El Cajon-Campo del Arenal basin, NW Argentina,

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