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SignificanceThe multiproxy approach represents a novel methodology and a unique opportunity to obtain a more detailed view of ancient resource use. Our multiproxy study, carried out on gomphotheres from Chile, widens potential occupied habitats to closed-canopy forests. This habitat variability supports the hypothesis that the diet of gomphotheres appears to be more constrained by resource availability than by the potential dietary range. We strongly recommend the use of a multiproxy approach, where morphology analyses are complemented by other sources of information. This approach prevents misleading conclusions about the origin of the proxy’s signal from arising, such as a leaf-browsing diet inferred from the dental calculus and microwear not necessarily being indicative of humidity.

The effect of mean precipitation rate on erosion is debated. Three hypotheses may explain why the current erosion rate and runoff may be spatially uncorrelated: (1) the topography has reached a steady state for which the erosion rate pattern is determined by the uplift rate pattern;(2) the erosion rate only depends weakly on runoff; or (3) the studied catchments are experiencing different transient adjustments to uplift or to climate variations. In the Chilean Andes, between 278S and 398S, the mean annual runoff rates increase southwards from 0.01 to 2.6 m a 21 but the catchment averaged rates of decadal erosion (suspended sediment) and millennial erosion ( 10 Be in river sand) peak at c. 0.25 mm a 21 for runoff c. 0.5 m a 21 and then decrease while runoff keeps increasing. Erosion rates increase non-linearly with the slope and weakly with the square root of the runoff. However, sediments trapped in the subduction trench suggest a correlation between the current runoff pattern and erosion over millions of years. The third hypothesis above may explain these different erosion rate patterns; the patterns seem consistent with, although not limited to, a model where the relief and erosion rate have first increased and then decreased in response to a period of uplift, at rates controlled by the mean precipitation rate.

Supply and transport of sediment in catchments involve processes with fundamental consequences for river management, land use, and the prediction of climate‐driven sediment fluxes. In the present study we addressed spatial variability in the water routes through the surface and subsurface of a catchment and the suspended sediment discharge (Qs) over a mountain‐piedmont system. We analyzed daily suspended sediment concentration (Cs) and water discharge (Q) measurements at stations located in different topographic settings (mountain and piedmont) in the Biobío River basin (southern central Andes, 37–39°S). In steep catchments, the Q versus Qs relationship has a marked seasonal hysteresis. In the piedmont, Qs is proportional to Q, with no seasonal hysteresis. The contrast in the hysteresis pattern between catchments with different topographies is explained by differences in the routing of rainfall‐derived water. In the piedmont, most of the rainfall is converted into surface runoff because the water table is near the surface. In the mountains, groundwater storage results in large seasonal variations in the proportion of Q that flows at the surface and transports sediment from the hillslopes, producing hysteresis. By separating the total Q into two components (direct discharge, Qd and base flow, Qb), we observed the response of Qs to the fraction of water that quickly leaves the catchment after a rainfall event (Qd). Similar results between the mountain and piedmont and the absence of hysteresis simplify the behavior of Qs into a linear relationship with Qd over the entire catchment and lead us to propose that sediment mobilization to the river along the Biobío catchment is primarily controlled by overland flow. Our findings highlight the importance of an adequate hydrological model for understanding the erosion and transport processes of a catchment, and which can be applied to other natural and modeled mountain‐piedmont systems.

We address the question of whether all large‐magnitude earthquakes produce an erosion peak in the subaerial components of fluvial catchments. We evaluate the sediment flux response to the Maule earthquake in the Chilean Andes (Mw 8.8) using daily suspended sediment records from 31 river gauges. The catchments cover drainage areas of 350 to around 10,000 km2, including a wide range of topographic slopes and vegetation cover of the Andean western flank. We compare the 3‐ to 8‐year postseismic record of sediment flux to each of the following preseismic periods: (1) all preseismic data, (2) a 3‐year period prior to the seismic event, and (3) the driest preseismic periods, as drought conditions prevailed in the postseismic period. Following the earthquake, no increases in suspended sediment flux were observed for moderate to high percentiles of the streamflow distribution (mean, median, and ≥75th percentile). However, more than half of the examined stations showed increased sediment flux during baseflow. By using a Random Forest approach, we evaluate the contributions of seismic intensities, peak ground accelerations, co‐seismic landslides, hydroclimatic conditions, topography, lithology, and land cover to explain the observed changes in suspended sediment concentration and fluxes. We find that the best predictors are hillslope gradient, low‐vegetation cover, and changes in streamflow discharge. This finding suggests a combined first‐order control of topography, land cover, and hydrology on the catchment‐wide erosion response. We infer a reduced sediment connectivity due to the postseismic drought, which increased the residence time of sediment detached and remobilized following the Maule earthquake.