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  • 1
    Publication Date: 2012-10-01
    Description: New cosmogenic burial and published dates of Colorado and Green river terraces are used to infer variable incision rates along the rivers in the past 10 Ma. A knickpoint at Lees Ferry separates the lower and upper Colorado River basins. We obtained an isochron cosmogenic burial date of 1.5 ± 0.13 Ma on a 190-m-high strath terrace near Bullfrog Basin, Utah (upstream of Lees Ferry). This age yields an average incision rate of 126 +12/–10 m/Ma above the knickpoint and is three times older than a cosmogenic surface age on the same terrace, suggesting that surface dates inferred by exposure dating may be minimum ages. Incision rates below Lees Ferry are faster, ~170 m/Ma–230 m/Ma, suggesting upstream knickpoint migration over the past several million years. A terrace at Hite (above Lees Ferry) yields an isochron burial age of 0.29 ± 0.17 Ma, and a rate of ~300–900 m/Ma, corroborating incision acceleration in Glen Canyon. Within the upper basin, isochron cosmogenic burial dates of 1.48 ± 0.12 Ma on a 60 m terrace near the Green River in Desolation Canyon, Utah, and 1.2 ± 0.3 Ma on a 120 m terrace upstream of Flaming Gorge, Wyoming, give incision rates of 41± 3 m/Ma and 100 +33/–20 m/Ma, respectively. In contrast, incision rates along the upper Colorado River are 150 m/Ma over 0.64 and 10 Ma time frames. Higher incision rates, gradient, and discharge along the upper Colorado River relative to the Green River are consistent with differential rock uplift of the Colorado Rockies relative to the Colorado Plateau.
    Electronic ISSN: 1553-040X
    Topics: Geosciences
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  • 2
    Publication Date: 2008-03-28
    Description: 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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Carbonell, Eudald -- Bermudez de Castro, Jose M -- Pares, Josep M -- Perez-Gonzalez, Alfredo -- Cuenca-Bescos, Gloria -- Olle, Andreu -- Mosquera, Marina -- Huguet, Rosa -- van der Made, Jan -- Rosas, Antonio -- Sala, Robert -- Vallverdu, Josep -- Garcia, Nuria -- Granger, Darryl E -- Martinon-Torres, Maria -- Rodriguez, Xose P -- Stock, Greg M -- Verges, Josep M -- Allue, Ethel -- Burjachs, Francesc -- Caceres, Isabel -- Canals, Antoni -- Benito, Alfonso -- Diez, Carlos -- Lozano, Marina -- Mateos, Ana -- Navazo, Marta -- Rodriguez, Jesus -- Rosell, Jordi -- Arsuaga, Juan L -- England -- Nature. 2008 Mar 27;452(7186):465-9. doi: 10.1038/nature06815.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Institut Catala de Paleoecologia Humana i Evolucio Social, Area de Prehistoria, Universitat Rovira i Virgili, Placa Imperial Tarraco 1, 43005 Tarragona, Spain. eudald.carbonell@urv.cat〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18368116" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Fossils ; Genetic Speciation ; Geologic Sediments ; History, Ancient ; Hominidae/anatomy & histology/*classification ; Mammals/anatomy & histology ; *Mandible/anatomy & histology ; Spain ; Technology
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2009-03-13
    Description: The age of Zhoukoudian Homo erectus, commonly known as 'Peking Man', has long been pursued, but has remained problematic owing to the lack of suitable dating methods. Here we report cosmogenic (26)Al/(10)Be burial dating of quartz sediments and artefacts from the lower strata of Locality 1 in the southwestern suburb of Beijing, China, where early representatives of Zhoukoudian Homo erectus 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 age measurements, 0.77 +/- 0.08 million years (Myr, mean +/- s.e.m.), provides the best age estimate for lower cultural layers 7-10. Together with previously reported U-series dating of speleothem calcite and palaeomagnetic stratigraphy, as well as sedimentological considerations, these layers may be further correlated to S6-S7 in Chinese loess stratigraphy or marine isotope stages (MIS) 17-19, in the range of approximately 0.68 to 0.78 Myr ago. These ages are substantially older than previously supposed and may imply early hominin's presence at the site in northern China through a relatively mild glacial period corresponding to MIS 18.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shen, Guanjun -- Gao, Xing -- Gao, Bin -- Granger, Darryl E -- England -- Nature. 2009 Mar 12;458(7235):198-200. doi: 10.1038/nature07741.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉College of Geographical Sciences, Nanjing Normal University, Nanjing, Jiangsu 210046, China. gjshen@njnu.edu.cn〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/19279636" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Fossils ; *Hominidae ; Radioisotopes/*analysis ; Radiometric Dating/*methods
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 4
    Publication Date: 2015-04-02
    Description: The cave infills at Sterkfontein contain one of the richest assemblages of Australopithecus fossils in the world, including the nearly complete skeleton StW 573 ('Little Foot') in its lower section, as well as early stone tools in higher sections. However, the chronology of the site remains controversial owing to the complex history of cave infilling. Much of the existing chronology based on uranium-lead dating and palaeomagnetic stratigraphy has recently been called into question by the recognition that dated flowstones fill cavities formed within previously cemented breccias and therefore do not form a stratigraphic sequence. Earlier dating with cosmogenic nuclides suffered a high degree of uncertainty and has been questioned on grounds of sediment reworking. Here we use isochron burial dating with cosmogenic aluminium-26 and beryllium-10 to show that the breccia containing StW 573 did not undergo significant reworking, and that it was deposited 3.67 +/- 0.16 million years ago, far earlier than the 2.2 million year flowstones found within it. The skeleton is thus coeval with early Australopithecus afarensis in eastern Africa. We also date the earliest stone tools at Sterkfontein to 2.18 +/- 0.21 million years ago, placing them in the Oldowan at a time similar to that found elsewhere in South Africa at Swartkans and Wonderwerk.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Granger, Darryl E -- Gibbon, Ryan J -- Kuman, Kathleen -- Clarke, Ronald J -- Bruxelles, Laurent -- Caffee, Marc W -- England -- Nature. 2015 Jun 4;522(7554):85-8. doi: 10.1038/nature14268. Epub 2015 Apr 1.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, USA. ; Department of Anthropology, University of New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada. ; 1] Evolutionary Studies Institute, University of the Witwatersrand, WITS 2050, Johannesburg, South Africa [2] School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, WITS 2050, Johannesburg, South Africa. ; Evolutionary Studies Institute, University of the Witwatersrand, WITS 2050, Johannesburg, South Africa. ; 1] School of Geography, Archaeology and Environmental Studies, University of the Witwatersrand, WITS 2050, Johannesburg, South Africa [2] French National Institute for Preventive Archaeological Research (Inrap), 561 rue Etienne Lenoir, km delta, 30900 Nimes, France [3] University of Toulouse Jean Jaures, UMR 5608 du CNRS (TRACES), Maison de la Recherche, 5 Allees Antonio Matchado, F-31058 Toulouse, France. ; 1] Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, USA [2] Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25830884" target="_blank"〉PubMed〈/a〉
    Keywords: Africa, Eastern ; Aluminum ; Animals ; Beryllium ; Burial ; *Fossils ; Geologic Sediments/analysis/chemistry ; *Hominidae/anatomy & histology/classification ; Paleontology/*methods ; Radioisotopes ; Radiometric Dating/*methods ; *Skeleton ; Skull/anatomy & histology ; South Africa ; Time Factors ; Tool Use Behavior
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 5
    Publication Date: 2003-04-26
    Description: Cosmogenic aluminum-26 and beryllium-10 burial dates of low-lying fossiliferous breccia in the caves at Sterkfontein, South Africa, show that associated hominid fossils accumulated in the Lower Pliocene. These dates indicate that the skeleton StW 573 and newly discovered specimens from Jacovec Cavern have much the same age: approximately 4 million years. These specimens are thus of an age similar to Australopithecus anamensis from East Africa.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Partridge, T C -- Granger, D E -- Caffee, M W -- Clarke, R J -- New York, N.Y. -- Science. 2003 Apr 25;300(5619):607-12.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Sterkfontein Research Unit and Climatology Research Group, University of the Witwatersrand, Private Bag 3, WITS 2050, Johannesburg, South Africa. tcp@iafrica.com〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12714736" target="_blank"〉PubMed〈/a〉
    Keywords: Aluminum/analysis ; Animals ; Beryllium/analysis ; Bone and Bones/anatomy & histology ; Burial ; Clavicle/anatomy & histology ; Femur/anatomy & histology ; *Fossils ; Geologic Sediments/chemistry ; History, Ancient ; *Hominidae/anatomy & histology ; Humans ; Humerus/anatomy & histology ; Isotopes/analysis ; Lumbar Vertebrae/anatomy & histology ; Paleodontology ; Skull/anatomy & histology ; South Africa ; Time ; Tooth/anatomy & histology
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
    Publication Date: 2003-08-02
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Clarke, R J -- Partridge, T C -- Granger, D E -- Caffe, M W -- New York, N.Y. -- Science. 2003 Aug 1;301(5633):596-7; author reply 596-7.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/12893923" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Bone and Bones/anatomy & histology ; *Fossils ; Geologic Sediments/chemistry ; History, Ancient ; *Hominidae/anatomy & histology ; Humans ; Isotopes/analysis ; South Africa ; Time
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
    Publication Date: 2014-05-29
    Description: 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 (Colorado, USA) occurred between 1.4 and 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/m.y. The Gunnison River removed 400–500 km 3 of erodible Mancos Shale and incised as deep as 360 m in 0.17–0.76 m.y. (incision rates of ~470–2250 m/m.y.). Prior to canyon abandonment, long-term (ca. 11–1 Ma) Gunnison River incision averaged ~100 m/m.y. 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 (to ~500 m/m.y.) 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.
    Electronic ISSN: 1553-040X
    Topics: Geosciences
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  • 8
    Publication Date: 2015-11-29
    Description: 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 CO 2 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.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 9
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    Mineralogical Society of America
    In: Elements
    Publication Date: 2014-10-17
    Description: Landscapes are sculpted by a variety of processes that weather and erode bedrock, converting it into soils and sediments that are moved downslope. Quantifying erosion rates provides important insights into a wide range of questions in disciplines from tectonics and landscape evolution to the impacts of land use. Cosmogenic nuclides contained in quartz sediment provide a robust tool for determining spatially averaged erosion rates across scales ranging from single hillslopes to continental river basins and are providing fundamental clues to how landscapes evolve. Cosmogenic nuclides in buried sediments contain unique information about paleo–erosion rates up to millions of years in the past. This article explores some of the basic ideas behind various methods used to infer catchment-wide erosion rates and highlights recent examples related to problems in tectonics, climate, and land use.
    Print ISSN: 1811-5209
    Electronic ISSN: 1811-5217
    Topics: Geosciences
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  • 10
    Publication Date: 2017-04-29
    Description: Climate regulation of erosion in unglaciated landscapes remains difficult to decipher. While climate may disrupt process feedbacks that would otherwise steer landscapes toward steady erosion, sediment transport processes tend to erase past climate landforms and thus bias landscape evolution interpretations. Here, we couple a 50 k.y. paleoenvironmental record with 24 10 Be-derived paleo-erosion rates from a 63-m-thick sediment archive in the unglaciated soil-mantled Oregon Coast Range. Our results span the forested marine oxygen isotope stage (MIS) 3 (50–29 ka), the subalpine MIS 2 (29–14 ka), and the forested MIS 1 (14 ka to present). From 46 ka through 28.5 ka, erosion rates increased from 0.06 mm yr –1 to 0.23 mm yr –1 , coincident with declining temperatures. Mean MIS 2 erosion rates remained at 0.21 mm yr –1 and declined with increasing MIS 1 temperatures to the modern mean rate of 0.08 mm yr –1 . Paleoclimate reconstructions and a frost-weathering model suggest periglacial processes were vigorous between 35 and 17 ka. While steady erosion is often assumed, our results suggest that climate strongly modulates soil production and transport on glacial-interglacial time scales. By applying a cosmogenic paleo-erosion model to evaluate 10 Be concentrations in our sedimentary archive, we demonstrate that the depth of soil mixing (which is climate-dependent) controls the lag time required for cosmogenic erosion rates to track actual values. Our results challenge the widely held assumption that climate has minimal impact on erosion rates in unglaciated midlatitude terrain, which invites reconsideration of the extent to which past climate regimes manifest in modern landscapes.
    Print ISSN: 0016-7606
    Electronic ISSN: 1943-2674
    Topics: Geosciences
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