26Al/10Be Age of Peking Man

The chronological position of Peking Man, or Homo erectus pekinensis, has long been pursued, but has remained problematic due to lack of a suitable dating method^1-7^. Here we report cosmogenic ^26^Al/ ^10^Be burial dating of quartz sediments and artifacts from the lower strata of Zhoukoudian Locality 1 where the remains of early members of the Peking Man family were discovered. This study marks the first radioisotopic dating of any early hominin site in China beyond the range of mass spectrometric U-series dating. The weighted mean of six meaningful measurements, 0.75 +/-; 0.09 (0.11) Ma (million years), provides the best age estimate for lower cultural Layers ^7-10^. Together with previously reported U-series^3^ and paleomagnetic^4^ data, as well as sedimentological considerations^8, 9^ these layers may be further correlated to S6-S7 in Chinese loess stratigraphy or marine isotope stages 17-18, in the range of ~0.68-0.75 Ma. These ages are substantially older than previously supposed and may imply hominin presence in northern China throughout early Middle Pleistocene climate cycles

Dating of Caves by Cosmogenic Nuclides: Method, Possibilities, and the Siebenhengste Example

Kozmični žarki povzročajo nastanek kozmogenih nuklidov na površini zemlje in tik pod njo. Za datiranje jamskih sedimentov sta posebej pomembna 10Be in 26Al, ki nastajata v kremenu. Ko je kamen na površini in izpostavljen kozmičnemu sevanju, nastajata v stalnem razmerju. Ko ga zanese v podzemlje, se tvorba kozmogenih nuklidov ustavi, nadaljuje pa se njihov radioaktivni razpad. Ker 26 Al razpada hitreje, lahko iz razmerja med njima izračunamo čas, ki je potekel odkar je kremen pod zemljo. Metodo lahko uporabimo na sedimentih, ki so pokopani oziroma v jami med 0.1 in 5 milijoni let. Na ta način lahko v idealnih primerih izračunamo hitrost vrezovanja dolin. Z opisano metodo smo določili starost najstarejših delov sistema Siebenhengste v Švici. Najstarejši sediment je star 4.4 ± 0.6 Ma in nakazuje, da je na tem območju potekalo zakrasevanje že v pliocenu.  Cosmic rays produce nuclides at and near the Earthʼs surface. 10Be and 26Al in quartz are of particular interest for dating cave sediments. These two nuclides are produced at the surface at a fixed ratio. If the quartz is carried from the surface into a cave, the sediment is shielded from additional cosmogenic nuclide production, and the inherited 10Be and 26Al decay radioactively. Because 26Al decays more rapidly than 10Be, the ratio of these two nuclides indicates the time since the sediment was washed underground. The burial dating method can be applied to sediments in the age range of approximately 0.1 to 5 Ma. In ideal cases, we get information about valley lowering rates. If the provenance of the sediment is known, averaged erosion rates of the source area can be estimated. The oldest cave phases of the Siebenhengste system, Switzerland, were dated using cosmogenic nuclides. The oldest sediment is 4.4 ± 0.6 Ma and thus indicates Pliocene karstification of the Siebenhengste.   

REKONSTRUKCE PALEOHYDROGRAFIE NA ZÁKLADĚ DATOVÁNÍ SEDIMENTŮ HOLŠTEJNSKÉ JESKYNĚ (MORAVSKÝ KRAS)

Large sections in cave deposits are exposed in the Holštejnská Cave in the Moravian Karst. The periods of fluvial activity alternated with periods of speleothem deposition. The study of the genesis and age of these cave deposits poses a clue to the reconstruction of development of the Holštejnská Cave and of local paleohydrographic history. The time of deposition was determined by U-series dating of speleothems, 10Be and 26Al dating of quartz pebbles, radiocarbon dating of charcoal and measurement of paleomagnetic record in both clastic sediments and speleothems. The fluvial sediments were deposited during the Early, Middle and Late Pleistocene in the cave. The age of oldest cave sediment sequence deposited by a subsurface stream indicates that the local hydrographic situation has changed later than 0.8 Ma

Frost for the trees: Did climate increase erosion in unglaciated landscapes during the late Pleistocene?

Understanding climatic influences on the rates and mechanisms of landscape erosion is an unresolved problem in Earth science that is important for quantifying soil formation rates, sediment and solute fluxes to oceans, and atmospheric CO2 regulation by silicate weathering. Glaciated landscapes record the erosional legacy of glacial intervals through moraine deposits and U-shaped valleys, whereas more widespread unglaciated hillslopes and rivers lack obvious climate signatures, hampering mechanistic theory for how climate sets fluxes and form. Today, periglacial processes in high-elevation settings promote vigorous bedrock-to-regolith conversion and regolith transport, but the extent to which frost processes shaped vast swaths of low- to moderate-elevation terrain during past climate regimes is not well established. By combining a mechanistic frost weathering model with a regional Last Glacial Maximum (LGM) climate reconstruction derived from a paleo-Earth System Model, paleovegetation data, and a paleoerosion archive, we propose that frost-driven sediment production was pervasive during the LGM in our unglaciated Pacific Northwest study site, coincident with a 2.5 times increase in erosion relative to modern rates. Our findings provide a novel framework to quantify how climate modulates sediment production over glacial-interglacial cycles in mid-latitude unglaciated terrain

Abandonment of Unaweep Canyon (1.4–0.8 Ma), western Colorado: Effects of stream capture and anomalously rapid Pleistocene river incision

Cosmogenic-burial and U-series dating, identification of fluvial terraces and lacustrine deposits, and river-profile reconstructions show that capture of the Gunnison River by the Colorado River and abandonment of Unaweep Canyon occurred between 1.4-0.8 Ma. This event led to a rapid pulse of incision unlike any documented in the Rocky Mountains. Following abandonment of Unaweep Canyon by the ancestral Gunnison River, a wave of incision propagated upvalley rapidly through Mancos Shale at rates of ~90-440 km/Ma. The Gunnison River removed 400-500 km3 of erodible Mancos Shale and incised up to 360 m deep in 0.17-0.76 My (incision rates of ~470-2250 m/Ma). Prior to canyon abandonment, long-term (~11-1 Ma) Gunnison River incision averaged ~100 m/Ma. The wave of incision also caused the subsequent capture of the Bostwick-Shinn Park River by the ancestral Uncompahgre River ca. 0.87-0.64 Ma, at a location ~70 km upvalley from Unaweep Canyon. This event led to similarly rapid (up to ~500 m/Ma) but localized river incision. As regional river incision progressed, the juxtaposition of resistant Precambrian bedrock and erodible Mancos Shale within watersheds favored the development of significant relief between adjacent stream segments, which led to stream piracy. The response of rivers to the abandonment of Unaweep Canyon illustrates how the mode and tempo of long-term fluvial incision are punctuated by short-term geomorphic events such as stream piracy. These short-term events can trigger significant landscape changes, but the effects are more localized relative to regional climatically- or tectonically-driven events. Powered byThis is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Geological Society of America and can be found at: http://geosphere.gsapubs.org/.Keywords: Stream piracy, Gunnison River, Knickpoint, Fluvial incision, Unaweep Canyo

The first hominin of Europe

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(1-5). 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(6-8). 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(9-13)), 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.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62855/1/nature06815.pd

A transient search using combined human and machine classifications

Large modern surveys require efficient review of data in order to find transient sources such as supernovae, and to distinguish such sources from artefacts and noise. Much effort has been put into the development of automatic algorithms, but surveys still rely on human review of targets. This paper presents an integrated system for the identification of supernovae in data from Pan-STARRS1, combining classifications from volunteers participating in a citizen science project with those from a convolutional neural network. The unique aspect of this work is the deployment, in combination, of both human and machine classifications for near real-time discovery in an astronomical project. We show that the combination of the two methods outperforms either one used individually. This result has important implications for the future development of transient searches, especially in the era of Large Synoptic Survey Telescope and other large-throughput surveys

Pliocene−Pleistocene incision of the Green River, Kentucky, determined from radioactive decay of cosmogenic 26Al and 10Be in Mammoth Cave sediments

Cosmogenic 26Al and 10Be in sediments washed into Mammoth Cave, Kentucky, record the history of 3.5 m.y. of water-table position, governed by incision and aggradation of the Green River, a tributary of the Ohio River. Upper levels of the cave formed during a period of slow river incision and were later filled with sediment due to river aggradation at 2.3–2.4 Ma. A brief surge of river incision ca. 2 Ma was followed by river stability and cave-passage formation at a lower level. Rapid incision through 15 m of bedrock ca. 1.5 Ma was prompted by repositioning of the Ohio River to its present course along an ice-sheet margin. Renewed incision ca. 1.2 Ma and aggradation at 0.7–0.8 Ma correlate with major ice advances in the Ohio River basin. Measurements of 26Al and 10Be also indicate that sandstone-capped uplands have maintained slow erosion rates of 2–7 m/m.y. for the past 3.5 m.y., despite accelerated Pleistocene river incision rates of ∼30 m/m.y

New ²⁶Al/¹⁰Be and (U-Th)/He constraints on the age of the Upland Complex, central Mississippi River Valley

The Upland Complex is a widespread terrace of the ancestral Mississippi River. It has played a central role in studies of the Pliocene Mississippi River drainage, as well as uplift and seismicity in the central Mississippi River Valley. Previous efforts to date the Upland Complex have yielded a range of age estimates spanning the Miocene through Pleistocene. We dated gravels and Fe-oxide cements from quarries of the Upland Complex in Arkansas, Kentucky, Mississippi, and Tennessee using ²⁶Al/¹⁰Be burial dating and (U-Th)/He geochronology. Our ²⁶Al/¹⁰Be burial dates revealed possible Pliocene-to-Pleistocene depositional ages, while (U-Th)/He dating showed that the onset of weathering dates to at least the Pliocene. Taken together, the ²⁶Al/¹⁰Be and (U-Th)/He age constraints demonstrate that the Upland Complex is at least Pliocene in age, and likely formed during a prolonged period of base level stability that preceded Pleistocene glaciations

New ²⁶Al/¹⁰Be and (U-Th)/He constraints on the age of the Upland Complex, central Mississippi River Valley

The Upland Complex is a widespread terrace of the ancestral Mississippi River. It has played a central role in studies of the Pliocene Mississippi River drainage, as well as uplift and seismicity in the central Mississippi River Valley. Previous efforts to date the Upland Complex have yielded a range of age estimates spanning the Miocene through Pleistocene. We dated gravels and Fe-oxide cements from quarries of the Upland Complex in Arkansas, Kentucky, Mississippi, and Tennessee using ²⁶Al/¹⁰Be burial dating and (U-Th)/He geochronology. Our ²⁶Al/¹⁰Be burial dates revealed possible Pliocene-to-Pleistocene depositional ages, while (U-Th)/He dating showed that the onset of weathering dates to at least the Pliocene. Taken together, the ²⁶Al/¹⁰Be and (U-Th)/He age constraints demonstrate that the Upland Complex is at least Pliocene in age, and likely formed during a prolonged period of base level stability that preceded Pleistocene glaciations