Neogene fluvial landscape evolution in the hyperarid core of the Atacama Desert

Dating of extensive alluvial fan surfaces and fluvial features in the hyperarid core of the Atacama Desert, Chile, using cosmogenic nuclides provides unrivalled insights about the onset and variability of aridity. The predominantly hyperarid conditions help to preserve the traces of episodic climatic and/or slow tectonic change. Utilizing single clast exposure dating with cosmogenic 10Be and 21Ne, we determine the termination of episodes of enhanced fluvial erosion and deposition occurring at ~19, ~14, ~9.5 Ma; large scale fluvial modification of the landscape had ceased by ~2–3 Ma. The presence of clasts that record pre-Miocene exposure ages (~28 Ma and ~34 Ma) require stagnant landscape development during the Oligocene. Our data implies an early onset of (hyper-) aridity in the core region of the Atacama Desert, interrupted by wetter but probably still arid periods. The apparent conflict with interpretation that favour a later onset of (hyper-) aridity can be reconciled when the climatic gradients within the Atacama Desert are considered

Evidence for multiple Plio-Pleistocene lake episodes in the hyperarid Atacama Desert

Cosmogenic nuclide exposure dating of ancient shoreline terraces of the Quillagua-Llamara Soledad Lake in the central Atacama Desert of northern Chile provides new insights in the paleohydrology of the driest desert on Earth. The lake developed in a paleo-endorheic drainage system in the Central Depression prior to draining into the Pacific due to incision of the Río Loa canyon. The durations of lake stages were sufficiently long to form wave-erosion induced shoreline terraces on the wind-exposed slopes of former islands. Successively younger shoreline levels are preserved over an elevation range of 250 m due to progressive uplift of the islands coeval with the lake stages. Cosmogenic 10Be- and 21Ne-derived exposure ages of the shorelines reveals that the hyperarid conditions in the Río Loa catchment were interspersed by several pluvial stages during the Pliocene and Pleistocene, which generated a large and persistent lake in the Quillagua-Llamara basin. The exposure ages of the final lake stage provide the maximum age for the incision of the Río Loa canyon (274 ± 74 ka) and the subsequent breaching of the Coastal Cordillera

Periodic input of dust over the Eastern Carpathians during the Holocene linked with Saharan desertification and human impact

L

Holocene coastal stratigraphy, coastal changes and potential palaeoseismological implications inferred from geo-archives in Central Chile (29–32° S)

Coastal geomorphology and the stratigraphy of coastal geoarchives record past coastal and fluctuations of coastal environments. In addition, these archives potentially store traces of past extreme events such as earthquakes and tsunamis, severe storms, and major flfl oodings of the coastal hinterland, e.g. due to El Niño conditions. Studying their characteristics may thus improve the knowledge of past frequency and magnitude patterns of such extreme events. For instance, large scaled spatial information about past earthquakes is needed for the understanding and estimation of seismo-tectonic processes. Misinterpretations in the size of preceding earthquakes may lead to incorrect strain balance estimations along megathrusts. Thus, fundamental research on the occurrence of past earthquakes is needed, which can be reflected in sudden or long-term coastal changes. Using sedimentological, geomorphological and microfaunal evidence, coeval geomorphodynamic and palaeoenvironmental changes at four different locations between 29° 50′ and 32° 20′ S in Central Chile were identififi ed in estuary systems, coastal swamps and coastal plains. The results may represent possible indirect evidence for palaeoseismicity, affecting the coastal system by vertical tectonic movements. Changes of coastline elevation, morphodynamic activity and/or coastal environments, as well as the formation of a liquefaction layer took place during the last c. 400 years. Moreover, major flfl ooding events related to strong El Niño conditions are assumed to have influenced the coastal stratigraphy by depositing high energy fluvial deposits. Our results suggest that the coastal environment, geomorphology and stratigraphy are considerably inflfl uenced by tectonic processes in the study area; a relation of the presented fifi ndings to the 1730 Great Valparaíso Earthquake is assumed. In general, the findings may encourage the implementation of comparable detailed studies, which may ultimately contribute to a better understanding of the Holocene coastal evolution and its relation to palaeoseismicity in Central Chile

Petrophysical characterization of the lacustrine sediment succession drilled in Lake El‘gygytgyn, Far East Russian Arctic

Seismic profiles of Far East Russian Lake El’gygytgyn which was formed by a meteorite impact some 3.6 million years ago show a stratified sediment succession that can be separated into Subunits Ia and Ib at approximately 167 m below lake floor (= ∼3.17 Ma). The former is well-stratified, while the latter is acoustically more massive. The sediments are intercalated with frequent mass movement deposits mainly in the proximal parts, while the distal part is almost free of such deposits at least in the upper part. In spring 2009, a long core drilled in the lake center within the framework of the International Continental Scientific Drilling Program (ICDP) penetrated the entire lacustrine sediment succession down to ~320 m below lake floor and about 200 m further into the meteorite-impact related bedrock. Downhole logging data down to 390 m below lake floor show that the bedrock and the lacustrine part of the core differ largely in their petrophysical characteristics. The contact between the bedrock and the lacustrine sediments is not abrupt, but rather transitional with a mixture of impact-altered bedrock clasts in a lacustrine matrix with varying percentages. Physical and chemical proxies measured on the cores can be used to divide the lacustrine part into five different clusters. These can be plotted in a redox-condition vs. input type diagram with total organic carbon content and magnetic susceptibility values indicating anoxic or oxic conditions and with the Si/Ti ratio representing more clastic or more biogenic input. Plotting the clusters in this diagram allows identifying clusters that represent glacial phases (Cluster I), super interglacials (Cluster II), and interglacial phases (Clusters III and IV)

New Integrated Data Analyses Software Components

Data management in scientific drilling programs such as the Integrated Ocean Drilling Program (IODP), the International Continental Scientific Drilling Program (ICDP), and the Antarctic Drilling Program (ANDRILL) performs two functions: firstly, the capture of drilling and scientific data during an expedition, and secondly, the long-term storage and dissemination of these data. Here we describe the progress in linking data management with stand-alone data capture and visualization applications. This provides a two-way flow of data between the database and the applications, and a more integrated data environment for scientists. The new system has been tested, so far, with cores from the IODP Expedition 313 New Jersey Shallow Shelf and the ICDP Lake El’gygytgyn Drilling Project

Impact of CaSO4-rich soil on Miocene surface preservation and Quaternary sinuous to meandering channel forms in the hyperarid Atacama Desert

The Atacama Desert is the driest and oldest desert on Earth. Despite the abundance evidence for long-term landscape stability, there are subtle signs of localised fluvial erosion and deposition since the onset of hyperaridity in the rock record. In the dry core of the Atacama Desert, pluvial episodes allowed antecedent drainage to incise into uplifting fault scarps, which in turn generated sinuous to meandering channels. Incision of ancient alluvial fan surfaces occurred during intermittent fluvial periods, albeit without signs of surface erosion. Fluvial incision during predominantly hyperarid climate periods is evident from these channels in unconsolidated alluvium. The absence of dense vegetation to provide bank stability and strength led us to investigate the potential role of regionally ubiquitous CaSO4-rich surface cover. This has enabled the preservation of Miocene surfaces and we hypothesize that it provided the required bank stability by adding strength to the upper decimetre to meter of incised alluvium to allow high sinuosity of stream channels to form during pluvial episodes in the Quaternary

A 68 ka precipitation record from the hyperarid core of the Atacama Desert in northern Chile

[Abstract] The Atacama Desert in northern Chile is one of the driest deserts on Earth. Hyperaridity persists at least since the Miocene and was punctuated by pluvial phases. However, very little is known about the timing, regional spread and intensities of precipitation changes. Here, we present a new precipitation record from a sedimentary sequence recovered in a tectonically blocked endorheic basin that is located in the hyperarid core of the Atacama Desert. The chronostratigraphic framework of the record is given by a multi-disciplinary dating approach, suggesting an age of ca. 68 ka BP for the core base. The sequence consists of three sediment types, whose sedimentological and geochemical characteristics suggest different depositional processes that reflect different degrees in humidity. First, particularly fine-grained sediments with high clastic but low calcium sulfate and carbonate contents reflect a particularly dry climate with only sporadic precipitation events and fluvial supply via channel systems. Second, more coarse-grained sediments with lower clastic and higher calcium sulfate and carbonate contents reflect more moist conditions with stronger precipitation events that lead to fluvial activity not restricted to the channels but involving the slopes and plains in the catchment. Third, normally graded layers with an equally high proportion of calcium sulfate and carbonate reflect occasional high-precipitation events that caused sediment supply also from most distant parts of the catchment via severe flash floods. The sedimentary succession suggests that precipitation changes took place on orbital but also on millennial time scales. Rather moist periods occurred during most of MIS 2, several shorter periods within MIS 3 and parts of MIS 4. Comparison of the findings from the Huara record with selected climate records from continental and marine sites in South America suggests a strong precipitation heterogeneity across the Atacama. This heterogeneity is caused by pronounced differences in the dominating climate patterns and a shift from predominant summer rain in the north to winter rain in the south. Precipitation supply to the Huara clay plan is controlled by the atmospheric circulation rather than the surface temperature of the adjacent ocean

Northern Eurasian large lakes history: sediment records obtained in the frame of Russian-German research project PLOT

Russian-German project PLOT (Paleolimnological Transect) aims at investigating the regional responses of the quaternary climate and environment on external forcing and feedback mechanisms along a more than 6000 km long longitudinal transect crossing Northern Eurasia. The well-dated record from Lake El´gygytgyn used as reference site for comparison the local climatic and environmental histories. Seismic surveys and sediment coring up to 54 m below lake floor performed in the frame of the project on Ladoga Lake (North-West of Russia; 2013), Lake Bolshoye Shchuchye (Polar Ural; 2016), Lake Levinson-Lessing and Lake Taymyr (Taymyr Peninsula; 2016-2017), Lake Emanda (Verkhoyansk Range; 2017). Fieldwork at Polar Ural and Taymyr Peninsula was conducted in collaboration with the Russian-Norwegian CHASE (Climate History along the Arctic Seaboard of Eurasia) project. Here, we present the major results of the project obtained so far