Fluvial and Eolian Sediment Mixing During Changing Climate Conditions Recorded in Holocene Andean Foreland Deposits From Argentina (31–33°S)

Abstract

Continental drainage systems archive complex records of rock uplift, source area relief, precipitation, glaciation, and carbon cyclicity driven largely by tectonics and climate. Significant progress has been made in linking such external environmental forcings to the geomorphic expression of landscapes and the stratigraphic record of depositional basins in coastal and offshore areas. However, there are large uncertainties in the degree to which sediment dispersal processes can modify signals between the erosional sources and the depositional sinks. We investigate a Holocene sediment transfer zone with contrasting fluvial and eolian sediment transport mechanisms to understand how river and wind processes impact the propagation of environmental signals in continentalscale drainage systems. To quantify these processes, we employ sediment fingerprinting methods for unconsolidated sand samples (detrital zircon U-Pb geochronology), incorporate sediment mixing models, and correlate the findings with the regional geologic and geomorphic framework. Three contrasting source regions deliver sediment to the Andean foreland: volcanic rocks of the Frontal Cordillera, sedimentary rocks of the Precordillera, and metamorphic basement of the Sierras Pampeanas. Although all samples of Holocene eolian dunes accurately record sediment input from three fluvial source regions, spatial variations in U-Pb results are consistent with north-directed paleowinds, whereby river sediments from Frontal Cordillera sources are transported northward and progressively mixed with river sediments from Precordillera and Sierras Pampeanas sources. In contrast, samples of modern rivers show progressive southward (downstream) mixing along a large axial fluvial system. Sediment mixing induced by eolian transport and reworking of various sources is likely a critical, climate-modulated process in the propagation of environmental signals, potentially involving the aliasing of tectonic signals, local storage and recycling of synorogenic river sediment, and cyclical patterns of sediment starvation and delivery to distal zones of accumulation.

Flow‐process controls on grain type distribution in an experimental turbidity current deposit: Implications for detrital signal preservation and microplastic distribution in submarine fans

“…Autogenic modulation of signal preservation is comparatively well‐studied in terrestrial and shallow‐marine environments compared to submarine fans (Capaldi et al, 2019; Covault et al, 2007; Garzanti et al, 2015; Jackson et al, 2019). Here, a known composition of mixed grain types was diluted at the scale of a single turbidity current (Figure 11).…”

Geochemistry of the Palaeocene‐Eocene Upper Kelalan Formation, NW Borneo: Implications on palaeoweathering, tectonic setting, and provenance

“…, climate, relief, as well as depositional and transport mechanisms (Basu, 1985;Capaldi, George, Hirtz, Horton, & Stockli, 2019;Dickinson, 1985;Dickinson et al, 1983) in addition to diagenetic processes (Ramkumar, Alberti, & Fürsich, 2015). Owing to their lower mobility in a variety of environments and lesser residence times in seawater (Cox, Lowe, & Cullers, 1995;Taylor & McLennan, 1985), the trace elements and rare earth elements (REEs) are useful in determining the provenance and tectonic settings.…”

Inversion of provenance data and sediment load into spatially varying erosion rates

“…An alternative explanation is that aeolian transport has delivered sediments from the Triassic fluvial unit to the west-south-west. This is supported by zircon ages of Holocene sediments of the Andean foreland that show the influence of north-north-eastward palaeowinds that were active during dry, glacial periods in this area (Capaldi et al, 2019). These sorts of complexities could be incorporated into future inverse methods if the dataset requires it.…”

“…Baumann et al (2011) mapped the debris flow hazard along the N7 road, which traverses the catchment from east to west, with high hazards on the northern shores upstream of Uspallata and the east-facing slopes between Uspallata and Potrerillos (Figure 15c). Detrital zircon analysis of Holocene aeolian sand dunes and modern sand samples in the region show that fluvial sediment mixing occurs along a southward (downstream) gradient during wet interglacial periods, while aeolian sediment mixing occurs along a northward gradient during glacial periods (Capaldi et al, 2019). In the Mendoza catchment, analyses using ionic and stable isotopic signatures for the different water sources of the catchment upstream of Potrerillos indicate a larger contribution of the Principal Cordillera than the Frontal Cordillera (Crespo et al, 2017).…”