Browsing by Autor "Frank Preusser"

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Quaternary Faulting and Fault-Related Geomorphology along the Orogenic Retro Arc Wedge-Front Structure of the Central Andes: The Mandeyapecua Thrust System, Southeastern Bolivia
(2026) Magda Patyniak; Ahmad Arnous; Victoria Alvarellos; Lucía Jagoe; Alana M. Williams; Jose M. Guerra Colque; Osvaldo A. Rosales Sadud; Frank Preusser; J Ramon Arrowsmith; Bodo Bookhagen
Actively deforming orogens are significant seismic hazard zones, especially in areas with steadily growing populations and infrastructure. An essential and yet oftentimes poorly understood attribute for a coherent hazard and risk assessment is whether the responsible tectonic fault systems are subject to permanent, creeping deformation or episodic, seismogenic rupture processes. In the southern Bolivian Subandes recent regional geodetic surface velocities measurements indicate that the décollement beneath the eastern orogen is the primary contributor to its lateral and vertical growth. Its surface manifestation is the Mandeyapecua Thrust Fault System (MTFS), which marks the active front of the Subandean fold-and-thrust belt in the Chaco foreland basin of Bolivia. Despite significant surface offsets within Quaternary landforms its geomorphic features and tectonic activity remain poorly understood. This study focuses on its longest fault segment – the ~300 km-long Mandeyapecua Fault (MF) located between 19° and 21°S. To evaluate its role in accommodating Quaternary deformation we used high-resolution DEMs, field-based mapping, and morphometric analyses, to document uplifted terraces, drainage anomalies, and fault-related landforms indicative of Quaternary tectonic activity. Electrical Resistivity Tomography surveys at two key sites reveal near-surface structures consistent with blind thrusting and folding. Where faults have reached the surface, the expressions of scarps suggest that the Mandeyapecua Fault (MF) may be segmented. Geochronological data along the front indicate fault activity during the past 12,000 years, with ruptures possibly spanning ~100 km, but the complex, distributed surface deformation indicates that the MF might not fit a standard thrust-fault model.
Reconstruction of a complex late Quaternary glacial landscape in the Cordillera de Cochabamba (Bolivia) based on a morphostratigraphic and multiple dating approach
(Cambridge University Press, 2011) Jan‐Hendrik May; Jana Zech; Roland Zech; Frank Preusser; Jaime Argollo; Peter W. Kubik; Heinz Veit
Abstract Although glacial landscapes have previously been used for the reconstruction of late Quaternary glaciations in the Central Andes, only few data exist for the Eastern Cordillera in Bolivia. Here, we present results from detailed morphostratigraphic mapping and new data of surface exposure dating (SED), optically stimulated luminescence (OSL), and radiocarbon dating ( 14 C) from the Huara Loma Valley, Cordillera de Cochabamba (Bolivia). Discrepancies between individual dating methods could be addressed within the context of a solid geomorphic framework. We identified two major glaciations. The older is not well constrained by the available data, whereas the younger glaciation is subdivided into at least four major glacial stages. Regarding the latter, a first advance dated to ~ 29–25 ka occurred roughly contemporaneous with the onset of the global last glacial maximum (LGM) and was followed by a less extensive (re-)advance around 20–18 ka. The local last glacial maximum (LLGM) in the Huara Loma Valley took place during the humid lateglacial ~17–16 ka, followed by several smaller readvances until ~10–11 ka, and complete deglaciation at the end of the Early Holocene.