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Assessing rivers' and hillslopes' sensitivity to external forcing is paramount to understand landscape evolution, in particular as a response to Quaternary climate changes. River networks are usually considered to be the main conveyors of environmental signals, such as changes in precipitation, temperature, or baselevel. Yet because hillslopes provide the source of sediment for river networks, their response to environmental change also modulates landscape dynamics. In order to characterize such behavior, we analyze the response times of a transport‐limited hillslope. We use simple numerical models of denudation to study hillslope responses to oscillatory forcing and understand their filtering effects on environmental signals. Modifications in the frequency of climate oscillation, such as the change that occurred at the Mid‐Pleistocene Transition, can significantly modulate hillslope sediment‐flux response. We infer a wide range of hillslope responses, ranging from negligible change over the full range of climate‐forcing frequencies, to a significant filtering of long‐period signals.

The ~150‐km‐wide dextral Marlborough Fault System and adjacent Kaikōura Mountains accommodate oblique convergence between the Pacific and Australian plates at the NE end of the South Island, New Zealand. Low‐temperature thermochronology from this region places new limits on the timing and style of Marlborough faulting and mountain building. We sampled rocks for apatite and zircon (U‐Th/He) and apatite fission track dating from a range of elevations spanning ~2 km within the Kaikōura Ranges, which stand high above the active Marlborough dextral faults. The data reveal Miocene cooling localized to hanging wall rocks, first along the Clarence Fault in the Inland Kaikōura Range, then along the Jordan Thrust in the Seaward Kaikōura Range, followed by widespread, rapid cooling reflected in all samples across the study area starting at ~5 Ma. Our results suggest that topographic relief in this region predates the onset of dextral faulting and that portions of the Marlborough Faults were once thrust faults that coincided with the early development of the transpressive plate boundary. We relate Pliocene to present rapid exhumation across the field site, including at low‐elevation sample sites in Marlborough Fault foot walls, to seaward translation and overthrusting of crust atop the downgoing slab by dextral Marlborough Fault motion. Our results show that spatial and temporal patterns in exhumation reflect a complex and evolving deformation field in the Marlborough Fault System over the past ~25 million years of Kaikōura orogeny.

This study explores the frequency of bedrock exposure in a soil‐mantled low‐relief (i.e. non‐mountainous) landscape. In the High Plains of eastern Colorado, gully headcuts are among the few erosional features that will incise through the soil mantle to expose bedrock. We measured the last time of bedrock exposure using optically stimulated luminescence dating of alluvial sediment overlying bedrock in gully headcuts. Our dating suggests that headcuts in adjacent gullies expose bedrock asynchronously, and therefore, the headcuts are unlikely to have been triggered by a base‐level drop in the trunk stream. This finding supports the hypothesis that headcuts can develop locally in gullies as a result of focused scour in locations where hydraulic stress during a flash flood is sufficiently high, and/or ground cover is sufficiently weak, to generate a scour hole that undermines vegetation. Alluvium dating also reveals that gullies have been a persistent part of this landscape since the early Holocene. Copyright © 2016 John Wiley & Sons, Ltd.