The earliest hominin occupation of Europe is one of the most debated topics in palaeoanthropology. However, the purportedly oldest of the Early Pleistocene sites in Eurasia lack precise age control and contain stone tools rather than human fossil remains. Here we report the discovery of a human mandible associated with an assemblage of Mode 1 lithic tools and faunal remains bearing traces of hominin processing, in stratigraphic level TE9 at the site of the Sima del Elefante, Atapuerca, Spain. Level TE9 has been dated to the Early Pleistocene (approximately 1.2-1.1 Myr), based on a combination of palaeomagnetism, cosmogenic nuclides and biostratigraphy. The Sima del Elefante site thus emerges as the oldest, most accurately dated record of human occupation in Europe, to our knowledge. The study of the human mandible suggests that the first settlement of Western Europe could be related to an early demographic expansion out of Africa. The new evidence, with previous findings in other Atapuerca sites (level TD6 from Gran Dolina), also suggests that a speciation event occurred in this extreme area of the Eurasian continent during the Early Pleistocene, initiating the hominin lineage represented by the TE9 and TD6 hominins.

Exfoliation of rock deteriorates cli s through the formation and subsequent opening of fractures, which in turn can lead to potentially hazardous rockfalls. Although a number of mechanisms are known to trigger rockfalls, many rockfalls occur during periods when likely triggers such as precipitation, seismic activity and freezing conditions are absent. It has been suggested that these enigmatic rockfalls may occur due to solar heating of rock surfaces, which can cause outward expansion. Here we use data from 3.5 years of field monitoring of an exfoliating granite cli in Yosemite National Park in California, USA, to assess the magnitude and temporal pattern of thermally induced rock deformation. From a thermodynamic analysis, we find that daily, seasonal and annual temperature variations are su cient to drive cyclic and cumulative opening of fractures. Application of fracture theory suggests that these changes can lead to further fracture propagation and the consequent detachment of rock. Our data indicate that the warmest times of the day and year are particularly conducive to triggering rockfalls, and that cyclic thermal forcing may enhance the e cacy of other, more typical rockfall triggers. R ockfalls are common and hazardous in steep terrains around the world 1-4 , and are primary agents of landscape erosion in many environments 4-8 . In exfoliating landscapes (Fig. 1a), rockfalls frequently occur as detachments of the outer rock layers (exfoliation sheets) along surface-parallel fractures (joints). These detachments are typically thinner (measured normal to rock faces) than they are wide or long. The origin and formation of exfoliation sheets, particularly those formed in granitic landscapes, has been a subject of interest for more than a century 9-15 . The consensus that erosion-induced or palaeo-stresses are responsible for their formation has been challenged by recent work 16,17 proposing that a combination of regional compressive stresses and topographic curvature can generate exfoliation fractures. Regardless of their origin, understanding modern-day failure of rock masses along exfoliation fractures is important for studies of landscape erosion and rockfall hazards. Rockfalls can be triggered by a number of mechanisms, including precipitation, seismic shaking, and freeze-thaw conditions 6,18 . Yet many rockfalls lack recognized triggers and are seemingly spontaneous events, suggesting other factors at play. The role of thermal effects (temperature and insolation) on initiating rock deformation, where rock surfaces expand, contract, and eventually fail in response to cyclical temperature variations, was critically examined regarding exfoliation sheet formation, and subsequently dismissed 11,19,20 . However, these studies did not investigate what role thermal effects might have on the deformation of existing exfoliation sheets. Further, some studies 13 acknowledged that thermal effects could be important at depths of less than one metre-areas of obvious interest for rockfalls. Recent studies on building f...

We report 26 Al/ 10 Be based ages of Sierra Nevada caves that constrain detailed late Pliocene and Quaternary river incision histories for five river canyons. Rapid incision of ϳ0.2 mm/yr from 2.7 to ca. 1.5 Ma slowed markedly to ϳ0.03 mm/yr thereafter, likely reflecting the combined effects of a transient erosional response to Pliocene rock uplift and periodic mantling of riverbeds with glacially derived sediment in the late Quaternary. While ϳ400 m of incision has occurred in the past 2.7 m.y., outpacing interfluve erosion and thereby increasing the local relief, canyons as deep as 1.6 km existed prior to that time. These new erosion rates strengthen the case for tectonically driven late Cenozoic uplift.

The importance of rock type and tectonic history on rates of glacial erosion, and the relative roles of glacial quarrying and abrasion, are poorly understood. We use concentrations of cosmogenic 10 Be in glacial polish and measurements of bedrock fracture spacing to explore the relationship between erosion rates and rock fracturing at 23 sites along Tuolumne River valley and fi ve sites in Tenaya Canyon in Yosemite National Park, California, USA. Most sites yield 10 Be concentrations that can be best explained as refl ecting solely postglacial nuclide accumulation. Six sites, however, display anomalously high concentrations, implying incomplete removal of the pre-glacial nuclide inventory during the last glaciation; these require that erosion in the last glacial cycle was <2-3 m. These low-erosion sites occur preferentially in massive units of the Cathedral Peak Granodiorite and the El Capitan Granite. Fractures in high-erosion sites are more closely spaced than in low-erosion sites, with spacings that average 1.1 ± 0.03 m and 3.3 ± 0.1 m, respectively. Our data suggest that the distance between fractures in the rock, dictated in part by the original spacing in a particular pluton, and in part by the specifi c tectonic history of the Sierra Nevada, governs the pace of glacial erosion in Yosemite.

We present a new method for tracing sediment using detrital apatite (U-Th)/He (AHe) thermochronometry, and use this to quantify the spatial distribution of catchment erosion in the eastern Sierra Nevada, California. Well-developed age-elevation relationships permit detrital AHe ages to track the elevations where sediment grains were shed from bedrock. We analyzed sediment exiting nonglaciated Inyo Creek and adjacent (formerly) glaciated Lone Pine Creek. Statistical comparison of measured AHe age probability density functions (PDFs) with predicted PDFs based on catchment hypsometries suggests that Inyo Creek is eroding uniformly, consistent with field observations of weathered hillslopes tightly coupled to the fluvial system. In contrast, significant mismatch between measured and predicted PDFs from Lone Pine Creek reveals that sediment derives primarily from the lower half of the catchment. The dearth of older ages is likely due to sediment storage in cirques and moraines and/or focused erosion at intermediate elevations, both potential consequences of glacial modification. Measured PDFs can also improve cosmogenic nuclide-based erosion rates by more accurately scaling nuclide production rates. Our results demonstrate the utility of detrital AHe thermochronometry for quantifying erosion in fluvially and glacially sculpted catchments.