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Item type:Publication, The Tutupaca volcanic complex (Southern Peru): eruptive chronology and successive destabilization of a dacitic dome complex(Elsevier, 2021-08-01)Several processes have been proposed as triggering mechanisms for the large sector collapses that affect most volcanoes, and which may occur several times in the volcano's lifetime. Here we present and discuss the case of Tutupaca volcano, located in southern Peru and part of the Central Volcanic Zone of the Andes. Tutupaca is composed of an old, hydrothermally altered and highly eroded Basal edifice, as well as younger twin peaks located in the northern part of the complex (the Western and Eastern Tutupaca). The youngest Eastern edifice of Tutupaca is composed of at least seven coalescing lava domes and associated deposits, including block-and-ash flow and debris avalanche deposits. We identified two debris avalanche deposits. An older unit (Azufre debris avalanche deposit) was channeled in the valleys located to the E and SE of the basal volcano, reaching up to 3.5 km from its source region. Four cosmogenic nuclide exposure dates (10Be/feldspar) were obtained from boulders of this debris avalanche deposit and ranged between 6.0 ± 0.7 and 7.8 ± 1.5 ka. The younger unit (Paipatja deposit) was associated with the sector collapse of the edifice reconstructed just after the first debris avalanche (domes IV to VIII). The sector collapse produced a debris avalanche deposit that outcrops immediately to the NE of the amphitheater and was associated with a large pyroclastic density current deposit that was previously dated by radiocarbon at 218 ± 14 a BP (Samaniego et al., 2015). Both debris avalanche deposits have two contrasting sub-units: (1) the main subunit, hereafter called hydrothermal-altered debris avalanche deposit, is a whitish-yellow volcanic breccia with heterolithic and heterometric blocks, which originated from the Basal edifice, and (2) a dome-rich debris avalanche deposit, composed by non-altered dome blocks from Eastern Tutupaca. In proximal areas, the dome-rich unit overlaps the hydrothermally-altered unit while in distal areas, these two units are mixed forming a hummocky and/or ridged topography. In addition to the similarity of both debris avalanches, we propose that the triggering mechanism for these debris avalanches was similar. The dacitic dome growth, coupled with a substrate of older, hydrothermally-altered rock, induced the destabilization of the edifice, producing the debris avalanches and the related pyroclastic density currents. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Inventory of large landslides along the Central Western Andes (ca. 15°–20° S): Landslide distribution patterns and insights on controlling factors(Elsevier Ltd, 2022-06-01)The western flank of the Central Andes hosts some of the largest terrestrial landslides (v > km3), which morphologies are particularly well-preserved due to low erosion rates related to the hyper-arid climate prevailing in this region since the Miocene. First-order questions are pending about the factors controlling the development and the triggering of those large-scale slope failures. Previous studies provided some geomorphological analysis and dating on individual study cases, but a regional-scale vision of landslide processes long the Central Western Andes is missing. Here we report an original inventory of large landslides (areas from 0.1 to 180 km2) established along the western flank of the Central Andes between latitudes ca. 15 and 20° S, and from the Pacific coast to the Altiplano. Based on manual mapping (using satellite images analysis, Google Earth and DEMs analysis) and a compilation of previous works, we inventoried more than a thousand large landslides in this region. We then statistically explored the database according to the landslides typology, size, abundance and relation to geologic, tectonic and climatic settings of the Central Western Andes in order to provide a first insight on their controlling factors. Landslide size-frequency distribution follows a power-law with an exponent of 2.31 ± 0.16 and a cut-off of 4.0 ± 1.9 km2 showing a strong contribution of the largest landslides to the cumulated landslide area. We revealed a dominance of rockslide typology (86%) characterized by in-mass slides, the rest being rock-avalanche type (14%) marked by typical granular-flow morphologies. Combination of specific lithology and great local relief emerge as favorable conditioning factor for large landslide initiation, in particular in the case of river incisions though ignimbrites of the Paleogene-Neogene (Huaylillas Formation), concentrating >30% of the landslides. Moreover, landslide clusters tend to follow crustal faults networks suggesting a long-term control of tectonic activity. Most of the identified landslides are paleo events. We tentatively argue that their triggering could not have been possible in the current hyper-arid conditions of the Atacama Desert and its periphery. Future research providing dating on some of the landslide clusters identified in this study is needed to explore possible temporal correlations between periods of landslide activity and external seismic and/or climatic cycles. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Cosmogenic 3He and 10Be denudation rates in the Central Andes: Comparison with a natural sediment trap over the last 18 ka(Elsevier B.V., 2022-12-01)It is of major importance for Earth surface sciences to reconstruct denudation rates in the most precise and accurate way. For this, it can be useful to test on the same setting methods based on different assumptions, such as those relying on geomorphological and geochemical observations. Here, we use an exceptionally suited setting in the Locumba catchment (southwestern Peruvian Andes) that offers the unique opportunity to compare denudation rates derived from in situ cosmogenic 3He and 10Be with a geomorphological sediment budget integrated over the last 18 ka. The sediment budget is estimated by determining the volume of sediment trapped in the Aricota lake that formed 18 ka ago after the occurrence of a giant rockslide dam. We reconstructed the topography of the Locumba valley before the dam emplacement and established that the captured sediment volume is 0.8 ± 0.1 km3. Considering that the lake-water output is restricted to seepage through the dam and that overflow above the dam never occurred, this volume correctly represents the sediment flux integrated over the last 18 ka. Integrating this volume over the upstream catchment area (∼1500 km2), we derived a corresponding mean erosion rate of 30 ± 9 mm.ka−1. Fluvial sediments feeding the Aricota lake were sampled to derive denudation rates from in-situ cosmogenic 10Be in the silicates and from in-situ cosmogenic 3He in the ferromagnesian minerals. Cosmogenic nuclide denudation rates from the main stream are 30 ± 2, 33 ± 2, 21 ± 1 and 82 ± 5 mm.ka−1 for the 10Be-quartz, the 10Be-feldspar, the 3He-amphibole and 3He-pyroxene, respectively. The consistency between the cosmogenic nuclide denudation rates derived from 10Be in the silicates and the erosion rate derived from our sediment budget shows that the 10Be accurately estimates of the sediment flux. Additionally, this work provides the first successful application of 10Be-feldspar nuclide-mineral pair to derive catchment-mean denudation rate and demonstrate that 10Be-feldspar can thus be a good alternative in catchments dominated by volcanic rocks with no quartz. The discrepancies observed between the denudation rates derived from the 3He-amphibole and 3He-pyroxene couples require further studies.