Fjord sediments are increasingly used as high-resolution archives of climate and environmental change, including variations in glacier mass balance and terrestrial hydrology. To accurately interpret such sediment records, it is crucial to comprehend sediment transport processes and determine sediment provenance. With this in mind, our main objective is to identify cost-effective parameters that can be used to reconstruct relative variations in the origin of sediments deposited in the Baker-Martínez fjord system, which is located between the Northern (NPI) and Southern (SPI) Patagonian Icefields. We focus on estimating the proportions of sediment derived from each icefield, taking advantage of the clearly distinct lithologies that underlie NPI (Patagonian Batholith) and SPI (Eastern Andean Metamorphic Complex) glaciers. The magnetic susceptibility and inorganic geochemistry of 21 surface sediment samples collected along the fjord system and that of suspended sediment samples from the four main rivers that discharge at its heads were investigated. Results indicate that sediments derived from the NPI are characterized by higher magnetic susceptibility and log(Ti/Al) values than those from the SPI, reflecting the mafic nature of the batholith. In fjords that receive contributions from both the NPI and SPI, magnetic susceptibility and log(Ti/Al) primarily reflect sediment provenance. In fjords receiving sediment from only one icefield, however, these parameters are positively correlated with grain size and reflect the progressive settling of particles from the surficial plume. Our results suggest that magnetic susceptibility and log(Ti/Al) can be used to reconstruct sediment provenance within the Baker-Martínez fjord system, but that only log(Ti/Al) can provide quantitative estimates of the proportions of sediment derived from each icefield. Ultimately, applying these provenance indicators to long sediment cores from the Baker-Martínez fjord system could allow reconstructing relative variations in sediment input from each icefield, which may in turn be interpreted as changes in river discharge and/or glacier mass balance.
<p>Our understanding of glacial isostatic rebound across Patagonia is highly limited, despite its importance to constrain past ice volume estimates and better comprehend relative sea-level variations. With this in mind, our research objective is to reconstruct the magnitude and rate of Late Glacial to Holocene glacial isostatic adjustment near the center of the former Patagonian Ice Sheet. We focus on Larenas Bay (48&#176;S; 1.26 km<sup>2</sup>), which is connected to Baker Channel through a shallow (<em>ca.</em> 7.4 m) and narrow (<em>ca.</em> 150 m across) inlet, and hence has the potential to record periods of basin isolation and marine ingression. The paleoenvironmental evolution of the bay was investigated through a sedimentological analysis of a 9.2 m long, radiocarbon-dated, sediment core covering the last 16.8 cal. kyr BP. Salinity indicators, including diatom paleoecology, alkenone concentrations and CaCO<sub>3</sub> content, were used to reconstruct the bay&#8217;s connectivity to the fjord. Results indicate that Larenas Bay was a marine environment before 16.5 cal. kyr BP and after 9.1 cal. kyr BP, but that it was disconnected from Baker Channel in-between. We infer that glacial isostatic adjustment outpaced global sea-level rise between 16.5 &#8211; 9.1 cal. kyr BP. During the Late Glacial - Holocene transition, the center of the former Patagonian Ice Sheet rose <em>ca.</em> 96 m, at an average rate of 1.30 cm/year. During the remainder of the Holocene, glacial isostatic adjustment continued (<em>ca.</em> 19.5 m), but at a slower average pace of 0.21 cm/year. Comparisons between multi-centennial variations in the salinity indicators and existing records of global sea-level rise suggest that the glacial isostatic adjustment rate fluctuated during these time intervals, in agreement with local glacier dynamics. More specifically, most of the glacial isostatic adjustment registered between 16.5 &#8211; 9.1 cal. kyr BP seems to have occurred before meltwater pulse 1A (14.5 &#8211; 14.0 kyr BP). Likewise, it appears that the highest Holocene glacial isostatic rebound rates occurred during the last 1.4 kyr, most likely in response to glacier recession from Neoglacial maxima. This implies a relatively rapid response of the local solid earth to ice unloading, which agrees with independent modelling studies investigating contemporary uplift. We conclude that the center of the former Patagonian Ice Sheet experienced a glacial isostatic adjustment of <em>ca.</em> 115 m over the last 16.5 kyr, and that >80% occurred during the Late Glacial and early Holocene.</p>
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