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Dixon 2013 QI. Sobre Beringia Temprano Muy Bueno

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  This article appeared in a journal published by Elsevier. The attachedcopy is furnished to the author for internal non-commercial researchand education use, including for instruction at the authors institutionand sharing with colleagues.Other uses, including reproduction and distribution, or selling orlicensing copies, or posting to personal, institutional or third partywebsites are prohibited.In most cases authors are permitted to post their version of thearticle (e.g. in Word or Tex form) to their personal website orinstitutional repository. Authors requiring further informationregarding Elsevier’s archiving and manuscript policies areencouraged to visit:http://www.elsevier.com/copyright  Author's personal copy Late Pleistocene colonization of North America from Northeast Asia: New insightsfrom large-scale paleogeographic reconstructions E. James Dixon * Maxwell Museum of Anthropology, Department of Anthropology, University of New Mexico, MSC01 1050, Albuquerque, NM 87131-0001, United States a r t i c l e i n f o  Article history: Available online 10 March 2011 a b s t r a c t Advances in large-scale paleogeographic reconstruction de 󿬁 ne physical and environmental constraintsrelevant to understanding the timing and character of the  󿬁 rst colonization of the Americas duringthe late Pleistocene. Diachronic mapping shows continental glaciers coalesced in central Canada duringthe Last Glacial Maximum (LGM) 20,000 e 14,000 years ago while unglaciated refugia existed along theNorthwest Coast. The Bering Land Bridge connected Asia and North America until about 10,000 years agowhen the two continents were separated by rising sea level. This visual analysis from large-scalesynthesis of recent geological and environmental research establishes timelines for biotically viablecolonization corridors connecting eastern Beringia to southern North America and provides insights intoprobable Paleoindian srcins and subsistence strategies.   2011 Elsevier Ltd and INQUA. All rights reserved. 1. Introduction Geologic and biotic events constrained the routes and timing of colonization of the Americas fromnortheast Asia. Researchers havede 󿬁 ned two competing theories about the  󿬁 rst movement of peoplefromAsiatotheAmericas:aninteriormid-continentalroutethrough a Late Wisconsin deglaciation corridor in central westernCanadaversusamaritimeroutealongtheNorthwestCoastofNorthAmerica. Paleoenvironmental and geologic data are summarizedand used to evaluate the viability of each route at selected periodsof time during the late Pleistocene.Large-scalepaleogeographicreconstructionshavebeenproducedasaseriesofsixmapsofNorthAmericaandBeringia(Fig.2A e F).Themaps integrate current data about changing sea level and glaciationover vast areas for the very late Pleistocene (18,000 e 12,500 cal BP).These reconstructions are based on Geographic Information System(GIS) analyses and digital elevation modeling (DEM) compiled byEhlers and Gibbard (2004) and Manley (2002). The data are taken primarily from Ehlers and Gibbard ’ s CDs 1and 2 that were derived fromvarious scholarly, public domain, andcopyrighted sources. These include the public domain Digital Chartof theWorld (Rose,2004)and ESRI,Inc.(EhlersandGibbard,2004). ESRI used public domain sources and modi 󿬁 ed, cleaned, andtransformed these data (ESRI Data License Agreement.pdf fromEhlersandGibbard,2004,CDs1and2).Theintegratedanalysisalsoused Penn State URL DCW: http://www.maproom.psu.edu/dcw/dcw_about.shtml and Manley ’ s Postglacial Flooding of the BeringLand Bridge: A Geospatial Animation employed ETOPO2v2c GlobalGridded 2-min Database, NGDC Marine Geology and GeophysicsDivision, National Geophysical Data Center (NGDC), and NationalOceanic and Atmospheric Administration (NOAA), URL: http://www.ngdc.noaa.gov/mgg/global/etopo2.html (Manley, 2002). Radiocarbon dates were calibrated using IntCal 09 and OxCal 4.1http://c14.arch.ox.ac.uk.Integrationof thesedata provides apaleogeographicfoundationfor diachronically interpreting the biological and geologicalconstraints in 󿬂 uencing the  󿬁 rst human colonization of theAmericas. These maps represent the synthesis of extensive glacialmapping, compilations of large numbers of radiocarbon determi-nations, and regional sea level curves. This scienti 󿬁 cally accurateintercontinental scale interpretation more precisely de 󿬁 nes thepresence, absence, and character of paleogeographic corridorsbeginning about 18,000 cal BP (15,000  14 C BP) (Fig. 2A) until circa12,500 cal BP (10,500  14 C BP) (Fig. 2F). The analysis couples thetemporal and spatial deglaciation sequence of North Americafollowing the LGM with the progression of post-Pleistocene sealevel rise on the Bering and Chukchi continental shelves(Fig. 2A e F). By comparing synchronic events in the interior of northern North America with the Northwest Coast, the parameterslimiting and facilitating human colonization are more clearlyidenti 󿬁 ed and linked to archeological evidence necessary to de 󿬁 nethe character and timing of colonization. *  Fax:  þ 1 505 277 1547. E-mail address:  jdixon@unm.edu. Contents lists available at ScienceDirect Quaternary International journal homepage: www.elsevier.com/locate/quaint 1040-6182/$  e  see front matter    2011 Elsevier Ltd and INQUA. All rights reserved.doi:10.1016/j.quaint.2011.02.027 Quaternary International 285 (2013) 57 e 67  Author's personal copy 2. Mid-continental route Nearly 80 years ago, Johnston (1933) suggested the possibilitythat a relatively narrow strip of unglaciated land may have existedinCanadabetweentheLaurentideandCordilleranicesheetsduringthe late Wisconsin glaciation of North America. If this relativelynarrow  “ ice free corridor ”  had existed, it would have provideda terrestrial environment between Asia and areas south of thecontinental glaciers through the Last Glacial Maximum (LGM).Theoretically, such a corridor would have enabled the dispersal of plants, animals and humans between these two regions duringlate-glacial times. The idea of an  “ ice-free corridor ”  has playeda signi 󿬁 cant role in stimulating  󿬁 eld research and efforts to inter-pret North American biogeography, glacial history, and archeology.Multidisciplinary evidence resulting from a number of indepen-dent investigations led an increasing number of investigators toconclude that an ice-free corridor did not exist throughout the LateWisconsin(Wilson,1983,1990,1996;MacDonald,1987;Burns,1996,2009;JacksonandDuk-Rodkin,1996).Thereisnowbroadconsensusthat a corridordid not exist during the LGM (Fig. 2A). Because of theconfusiongeneratedbytheapplicationoftheterm “ icefreecorridor, ” several researchers have suggested alternative terminology de 󿬁 nedstrictly on geographic grounds including  “ Western Corridor ” (Beaudoin,1989) and “ westerninteriorroute ” (Burns,1996:111). Theopening of the ice-free corridor (or more accurately stated, deglaci-ation corridor) probablyoccurred between 15,000 and 14,000 cal BP(12,500 e 12,000 14 CBP)(Dyke,2004)(Fig.2CandD).Thisconstructof  the glacial geology is based primarily on glacial mapping and radio-carbondating.Itde 󿬁 nesconstraintsthatprovideausefulframeworkfor interpreting the colonization of the Americas.These data indicate that by at least 14,000 calendar years ago(12,000  14 C BP) (Fig. 2D) a narrow deglaciation corridor had openedbetween the Laurentide and Cordilleran glaciers in west centralCanada. The processes of deglaciation re-established a terrestrialconnection between eastern Beringia and regions south of thecontinentalglaciers.ItenabledthemigrationofterrestrialplantsandanimalssouthwardfromBeringiaandnorthwardfromareassouthof the continental glaciers from distinctly different environments thathad been isolated from each other for about 10,000 years (Younget al., 1994). The mid-continental deglaciation corridor was signi 󿬁 -cantly different than other newly deglaciated regions because it laysandwiched between two massive wasting continental glaciers.Most newly deglaciated terrain at the end of the Pleistocene wasadjacent to large biomes and this enabled biological colonization tooccurrapidlyalongabroadfront.However,thedeglaciationcorridorwas unique in that it had only two relatively narrow openings to Fig. 1.  Map of Northwest North America and adjacent maritime regions illustrating signi 󿬁 cant geographic locations and key archeological sites discussed in the text. E.J. Dixon / Quaternary International 285 (2013) 57  e 67  58  Author's personal copy Fig. 2.  Last Glacial Maximum (LGM) deglaciation sequence in relation to sea level rise on the Bering Land Bridge between 18,000 cal BP (15,000 14 C BP) and 12,500 cal BP (10,500 14 CBP). Extent of glaciation in relation to sea level: A) circa 18,000 cal BP (15,000 14 C BP); B) circa 16,000 cal BP (13,500 14 C BP); C) circa 15,000 cal BP (12,500 14 C BP); D) circa 14,000 calBP (12,000  14 C BP); E) circa 13,000 cal BP (11,000  14 C BP); F) circa 12,500 cal BP (10,500  14 C BP). E.J. Dixon / Quaternary International 285 (2013) 57  e 67   59
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