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1.
Middle Park, a high‐altitude basin in the Southern Rocky Mountains of north‐central Colorado, contains at least 59 known Paleoindian localities. At Barger Gulch Locality B, an extensive Folsom assemblage (˜10,500 14C yr B.P.) occurs within a buried soil. Radiocarbon ages of charcoal and soil organic matter, as well as stratigraphic positions of artifacts, indicate the soil is a composite of a truncated, latest‐Pleistocene soil and a younger mollic epipedon formed between ˜6000 and 5200 14C yr B.P. and partially welded onto the older soil following erosion and truncation. Radiocarbon ages from an alluvial terrace adjacent to the excavation area indicate that erosion followed by aggradation occurred between ˜10,200 and 9700 14C yr B.P., and that the erosion is likely related to truncation of the latest‐Pleistocene soil. Erosion along the main axis of Barger Gulch occurring between ˜10,000 and 9700 14C yr B.P. was followed by rapid aggradation between ˜9700 and 9550 14C yr B.P., which, along with the erosion at Locality B, coincides with the abrupt onset of monsoonal precipitation following cooling in the region ˜11,000–10,000 14C yr B.P. during the Younger Dryas oscillation. Buried soils dated between ˜9500 and 8000 14C yr B.P. indicate relative landscape stability and soil formation throughout Middle Park. Morphological characteristics displayed by early Holocene soils suggest pedogenesis under parkland vegetation in areas currently characterized by sagebrush steppe. The expansion of forest cover into lower elevations during the early Holocene may have resulted in lower productivity in regards to mammalian fauna, and may partly explain the abundance of early Paleoindian sites (˜11,000–10,000 14C yr B.P., 76%) relative to late Paleoindian sites (˜10,000–8000 14C yr B.P., 24%) documented in Middle Park. © 2005 Wiley Periodicals, Inc.  相似文献   

2.
The authors present a reconstruction of precipitation, seasonality, and vegetation cover over the period from 200 cal yr B.C. to 1600 cal yr A.D. for the archaeological site of Anse à la Gourde, Guadeloupe, based on the oxygen and carbon isotope composition of accelerator mass spectrometry (AMS) 14C‐dated aragonitic shells of the landsnail Bulimulus guadaloupensis. The results show that the Late Cedrosan Saladoid population (˜400–800 cal yr A.D.) disappeared at the beginning of a dry and stormy period lasting from 800 to 1000 cal yr A.D. The Mamoran Troumassoid started to populate the site around 1000 cal yr A.D. when the climate became wetter, and remained until ˜1300 cal yr A.D. The snail‐shell carbon isotope values changed significantly around the period that the Late Cedrosan Saladoid occupation started. This indicates a vegetational response either to the wetter conditions, or because of the replacement of existing C4 plant vegetation by introduced C3 crops. © 2006 Wiley Periodicals, Inc.  相似文献   

3.
Shallowly buried archaeological sites are particularly susceptible to surface and subsurface disturbance processes. Yet, because cultural deposition often operates on short time scales relative to geologic deposition, vertical artifact distributions can be used to clarify questions of site formation. In particular, patterns in artifact distributions that cannot be explained by occupation histories must be explained by natural processes that have affected sites. Buried only 10–50 cm beneath the ground surface for 10,450 14C yr, the Folsom component at Barger Gulch Locality B (Middle Park, Colorado) exhibits many signs of post‐depositional disturbance. Through examination of variation in the vertical distribution of the artifact assemblage, we are able to establish that only a Folsom component is present. Using vertical artifact distributions, stratigraphy, and radiocarbon dating, we are able to reconstruct the series of events that have impacted the site. The Folsom occupation (˜10,450 14C yr B.P.) was likely initially buried in a late‐Pleistocene eolian silt loam. Erosion brought the artifacts to rest on a deflation surface at some time prior to 9400 14C yr B.P. A mollic epipedon formed in sediments that accumulated between 9400 and 7000 14C yr B.P. Some time after 5200 14C yr B.P., this soil was partially truncated, and artifacts that had previously dispersed upward created a secondary lag at its upper contact. This surface was buried again and artifact dispersal continued. © 2005 Wiley Periodicals, Inc.  相似文献   

4.
The Great Plains contain many of the best‐known Paleoindian sites in North America, and a number of these localities were key to determining the chronology of Paleoindian occupations in the years before, during, and since the development of radiocarbon and other chronometric dating methods. Initial attempts at dating were based on correlation with extinct fauna, the “geologic‐climatic” dating method, and stratigraphic relationships of artifacts within sites. By the time radiocarbon dating was developed (1950), the basic Paleoindian sequence (oldest to youngest) was: Clovis‐Folsom‐unfluted lanceolates (such as Plainview, Eden, and Scottsbluff). Initial applications of radiocarbon dating in the 1950s did little to further resolve age relationships. In the 1960s, however, largely through the efforts of C. V. Haynes, a numerical geochronology of Paleoindian occupations on the Great Plains began to emerge On the Southern Great Plains the radiocarbon‐dated artifact chronology is: Clovis (11,600–11,000 yr B.P.); Folsom and Midland (10,900–10,100 yr B.P.); Plainview, Milnesand, and Lubbock (10,200–9800 yr B.P.); Firstview (9400–8200 yr B.P.); St. Mary's Hall, Golondrina, and Texas Angostura (9200–8000 yr B.P.). The chronology for the Northern Great Plains is: Clovis (11,200–10,900 yr B.P.); Goshen (ca. 11,000 yr B.P.); Folsom (10,900–10,200 yr B.P.); Agate Basin (10,500–10,000 yr B.P.); Hell Gap (10,500–9500 yr B.P.); Alberta, Alberta‐Cody (10,200–9400 yr B.P.); Cody (Eden‐Scottsbluff) (9400–8800 yr B.P.); Angostura, Jimmy Allen, Frederick, and other parallel‐oblique types (9400–7800 yr B.P.). Fifty years after the development of radiocarbon dating, the basic typological sequence has not changed significantly except for the realization that there probably was significant temporal overlap of some point types, and that the old unilinear sequence does not account for all the known typological variation. The chronology has been continually refined with the determination of hundreds of radiocarbon ages in recent decades. © 2000 John Wiley & Sons, Inc.  相似文献   

5.
Geoarchaeological investigations in western Middle Park provide important information for understanding the soil‐stratigraphic context of Paleoindian components, as well as the latest Quaternary environmental change and landscape evolution in a Southern Rocky Mountain intermontane basin. Paleoindian components are associated with the oldest two of four latest Quaternary stratigraphic units (1–4) recognized in co‐alluvial mantles (combined slopewash and colluvium) in uplands and in alluvial valley fills. Limited data suggest accumulation of unit 1 as early as ∼12,500 14C yr B.P. in alluvial valleys and by at least ∼11,000 14C yr B.P. in uplands was followed by brief stability and soil formation. A relatively widespread disconformity marks earliest Holocene erosion and substantial removal of latest Pleistocene deposits in upland and alluvial settings followed by unit 2 deposition ∼10,000–9000 14C yr B.P., perhaps signaling the abrupt onset of an intensified summer monsoon. In situ Paleoindian components in uplands are found in a moderately developed buried soil (the Kremmling soil) formed in units 1 and 2 in thin (≤1m) hillslope co‐alluvial mantles. The Kremmling soil reflects geomorphic stability in upland and alluvial settings ∼9000–4500 14C yr BP, and represents a buried landscape with the potential to contain additional Paleoindian components, although elsewhere in western Middle Park Early Archaic components are documented in morphologically similar soils. Kremmling soil morphology, the relative abundance of charcoal in unit 2 relative to younger units, and charcoal morphology indicate the expansion of forest cover, including Pinus, and grass cover during the early and middle Holocene, suggesting conditions moister than present. © 2010 Wiley Periodicals, Inc.  相似文献   

6.
Playas are small, circular basins forming a ubiquitous component of the southern High Plains landscape. They are filled with carbonaceous mud deposited since the terminal Pleistocene. The stratigraphy and geochronology of 30 playas was investigated to better understand the paleoenvironmental record of basin filling. At the base of the fill in some playas is a well sorted eolian sand dated between ~ 13,000 and ~ 11,000 14C yr BP. The beginning of mud deposition, representing aggradation of eolian dust on a moist, vegetated playa floor was largely between ~ 12,000 and ~ 10,500 14C yr BP. Playa filling slowed ~ 9000 to ~ 4000 14C yr BP, probably due to dry conditions, increased ~ 4000 to ~ 2000 14C yr BP, then slowed again. Eolian sand and loam, likely representing regional aridity, accumulated in some basins episodically just prior to ~ 10,700 14C yr BP, between ~ 8600 and ~ 4700 14C yr BP, and at ~ 1300 14C yr BP. Stable C isotopes from one basin indicate that the playa was inundated only seasonally throughout the record beginning ~ 11,500 14C yr BP. The phytolith record in that basin indicates an abrupt shift toward cooling ~ 11,400 to ~ 11,200 14C yr BP and then increasing importance of xeric-adapted C4 grasses through the Holocene.  相似文献   

7.
The orthodox archaeological sequence at the Sigatoka Dunes site (VL 16/1) in Fiji proposes three phases of occupation spanning Fijian prehistory, each associated with a period of dune stability. It has been taken as the standard model of Fijian prehistory for more than 30 years. Recently, however, it has been argued that there is no stratigraphic support for three discrete levels and that the occupation history was fragmented, complex, and continuous within a volatile dune system. We present new data, from optical and radiocarbon dating, to argue that a three‐phase model, although somewhat more complex in detail, remains the most robust interpretation of site history. The longest stable phase (Level 2) began 2500–2300 cal yr B.P. and is possibly associated with relatively low ENSO frequency. Substantial sand dune accumulation began after ˜1300 cal yr B.P. © 2006 Wiley Periodicals, Inc.  相似文献   

8.
The locations of reliable surface water exposures during the Middle Paleoindian period (10,800–10,200 14C yr B.P.) in north‐central Florida are reconstructed and compared to the concentrations of Middle Paleoindian projectile points. Estimates of water table levels and surface water flow in Florida's karst geology confirm prior climate reconstructions for that time indicating the area was arid and supported a xeric ecology in most upland locales. Surface water flow data from recent extreme droughts and water table estimations are used to identify the areas of highest probability for surface water availability. The distribution of the highest concentrations of Middle Paleoindian points correlates with the areas of highest probability, indicating that scarce surface water sources were the strongest constraint on occupation location during that time. © 2009 Wiley Periodicals, Inc.  相似文献   

9.
Geoarchaeological investigations at the Clovis type site, Blackwater Locality No. 1, in 1983 and 1984 included core drilling, archaeological test excavations, stratigraphic profiling, sedimentary analyses, and radiocarbon dating. Six lines of core holes transverse to the outlet channel clearly defined the subsurface configuration and stratigraphy of the prehistoric spring run. Pieces of large animal bone from units B, C, D, and E that elsewhere in the site contain Paleoindian artifacts suggest occurrences of additional buried sites along the ancient spring run. Four Paleoindian projectile points recovered during archaeological testing confirm these prospects. The Clovis type site, located in an abandoned gravel pit, is in a natural depression initially occupied by a late Pleistocene lake. After breaching of the depression by overflow or sapping, it became a springhead and was enlarged by slumping and slopewash. Detailed stratigraphic profiling of the south wall of the abandoned gravel pit provided precise stratigraphic control for sediment sampling and radiocarbon dating, and revealed more complex microstratigraphy and facies relationships than heretofore known for the site. The interfingering of dune facies around the depression with lacustrine and spring-laid facies within it aid paleoclimatic interpretation. Deflational contacts within the depression appear to correlate with adjacent wedges of dune sand reflecting relatively arid intervals. Between these arid episodes occur intervals of increased ground water level attended initially by deposition of spring-laid sands of unit B during the late Pleistocene (13,000–11,500 yr B.P.). As the water table rose following a period of severe deflation, slumping and gravity flow deposited clayey sand, Unit C, on the floor of the blowout between 11,500 and 11,000 yr B.P. During this time Clovis people first appeared at the site. After another brief period of deflation, a lake rose causing sand of Unit D0 to be washed in from shore followed by deposition of diatomities, units D1 and D2. These were separated by a brief influx of eolian sand, unit D2z. Between 10,800 and 10,000 yr B.P. outflow from the lake was reduced by accumulation of eolian sand in the outlet while Folsom people and later Agate Basin people arrived to hunt bison during this time. Cody complex people appeared during and after a brief erosional episode that preceded deposition of eolian silt and sand of units E and F from 10,000 to 8000 yr B.P. Eolian deposition during post-Folsom time converted the pond to a wet meadow and eventually, during Cody time, to a grassy swale. Some of these deposits were blown out during the Altithermal arid period (ca. 8000-5000 yr B.P.), a time when prehistoric Archaic peoples excavated wells in the floor of the depression. Subsequent eolian activity has resulted in deflation and dune migration during the late Holocene. The best prospects for Paleoindian finds are along the buried outlet south of the south wall and in early Holocene dune sands on the uplands around the depression. © 1995 John Wiley & Sons, Inc.  相似文献   

10.
The Big Eddy site (23CE426) in the Sac River valley of southwest Missouri is a rare recorded example of distinctly stratified Early through Late Paleoindian cultural deposits. Early point types recovered from the site include Gainey, Sedgwick, Dalton (fluted and unfluted), San Patrice, Wilson, and Packard. The Paleoindian record at Big Eddy represents only a fraction of the site's prehistoric cultural record; stratified cultural deposits in alluvium above the Paleoindian components span the entire known prehistoric sequence, and terminal Pleistocene alluvium may contain pre‐Early Paleoindian cultural deposits. This study focused on the paleogeomorphic setting, stratigraphy, depositional environments, pedology, geochronology, and history of landscape evolution of the late Pleistocene and early Holocene alluvium at the site. The Paleoindian sequence is associated with a complex buried soil 2.85 m below the modern surface (T1a) of the first terrace of the Sac River valley in the site vicinity. This soil formed at the top of the early submember of the Rodgers Shelter Member (underlying the T1c paleogeomorphic surface) and contains at least 70 cm of stratified Paleoindian cultural deposits, all in floodplain and upper point‐bar facies. A suite of 36 radiocarbon ages indicates that the alluvium hosting the Paleoindian sequence aggraded between ca. 13,250 and 11,870 cal yr B.P. (11,380 and 10,180 14C yr B.P.). Underlying deposits accumulated between ca. 15,300 and 13,250 cal yr B.P. (12,950 and 11,380 14C yr B.P.). By ca. 11,250 cal yr B.P. (9,840 14C yr B.P.) the T1c paleogeomorphic surface was buried by the earliest increment of a thick sequence of overbank sheetflood facies, ultimately resulting in deep burial and preservation of the Paleoindian record. The landform‐sediment assemblage that hosts the Paleoindian and possibly earlier cultural deposits at Big Eddy is both widespread and well preserved in the lower Sac River valley. Moreover, the terminal Pleistocene and early Holocene depositional environments were favorable for the preservation of the archaeological record. © 2007 Wiley Periodicals, Inc.  相似文献   

11.
Well-preserved aragonitic land snail shells (Vallonia) from late Pleistocene Eolian sediment in the Folsom archaeological site in New Mexico exhibit an overall decrease of δ18OPDB from maximum values of +2.7‰ (more positive than modern) to younger samples with lower average values of about −3.6‰ (within the modern range). The age of the samples (approximately 10,500 14C yr B.P.) suggests that the decrease in δ18O may manifest climatic changes associated with the Younger Dryas. Some combination of increased relative humidity and cooler temperatures with decreased δ18O of precipitation during the times of snail activity can explain the decrease in shell δ18O. A well-known Paleoindian bison kill occurred at the Folsom site during this inferred environmental transition.Average δ13C values of the aragonite shells of the fossil Vallonia range from −7.3 to −6.0‰ among different archaeological levels and are not as negative as modern values. This suggests that the proportion of C4 vegetation at the Folsom site approximately 10,500 14C yr B.P. was greater than at present; a result which is consistent with other evidence for higher proportions of C4 plants in the region at that time.  相似文献   

12.
Examination of a sample of 150 fluted-point localities from southern Ontario, Canada in relation to datable features of Late Wisconsinan ice retreat discloses maximum possible ages for early Palaeo-Indian occupation and reveals selection of specific physiographic situations. General relationship to maximum ice-advance positions suggests occupation during the Two Creeks Interstade after Port Huron ice retreat about 12,300 yr B.P. Specific relationship to 14C-dated proglacial Great Lake strands favors occupation during the North Bay Interstade after Greatlakean ice retreat about 11,500 yr B.P. Locality frequency on Lake Algonquin strands suggests contemporaneity with the main stage of this lake about 11,500 to 10,400 yr B.P., with a small number of lake-plain localities indicating minor post-Algonquin persistence. Radiocarbon dates for fluted-point sites elsewhere in the glaciated northeast place occupation coeval with the southwestern Folsom fluted-point tradition of about 10,850 to 10,200 yr B.P. Locality situation in regions dominated by proglacial sediments, on lake-edge features adjacent to strand-dissecting tributaries, within major river valleys, implies selectivity reflecting primary adaptation. Fluted-point associations with caribou and elk remains suggest that “focal” adaptation to cervids, comparable to southwestern Folsom bison exploitation, might underlie the homogeneous nature and distribution of early Palaeo-Indian localities throughout the northeast.  相似文献   

13.
Two approximately 5‐ to 6‐km drainage segments on Black Mesa preserve unusually complete sequences of late Quaternary alluvium and soils. Radiocarbon‐ and tree‐ring‐dated alluvial and soil stratigraphy suggests entrenched paleoarroyos were beginning to aggrade at about >24,260, 11,070, 9660, 8800, 7060, 3500, 2140, and 1870 14C yr B.P. Using the quantity of sediment removal from post‐A.D. 1900 arroyos as analogue, at least 77–200% of total valley alluvium has been removed and replaced by younger sediments during an estimated 11 late Pleistocene and Holocene erosion epicycles. Given that most (59%) of the 150 recorded prehistoric sites in the two study areas occur on valley floors where only about 3% of surface alluvium predates Lolomai phase Basketmaker II occupation (˜1900–1600 yr B.P.), it may be inferred that pre‐Lolomai phase Basketmaker II sites which may have been located along washes have been removed or buried by fluvial erosion. Identification of five buried hearths in alluvial sections, including White Dog and Lolomai phase Basketmaker II sites (dating about 3500 and 1870 14C yr B.P., respectively) and one possible Early Archaic site, supports this conclusion. © 2005 Wiley Periodicals, Inc.  相似文献   

14.
Preliminary phytolith analysis of ephemeral lake fill sediment at Long Pocket, near Toomba, northeast Queensland, Australia, indicates that a C4-dominated grassland with a minor woody component has been present in the region since ca. 8000 cal yr B.P. Based on the modern distribution of C4 and C3 native grasses in Australia, this suggests that mean summer temperatures of at least 14°C (ca. 10°C cooler than present) were maintained since the early Holocene. This interpretation is comparable with previous studies, which together imply that the establishment of C4-dominated grasses in central and northeast Australia occurred between the last glacial maximum (most likely after ca. 16,000 14C yr B.P.) and ca. 7200 14C yr B.P. (ca. 8000 cal yr B.P.). Taxonomic composition of the grassland appears relatively consistent since the early Holocene at Long Pocket and includes phytoliths comparable with those from modern Arundinoideae, Panicoideae, and Chloridoideae. Rare non-grass phytoliths are also present. A gradual decrease in abundance of saddle phytolith forms (attributed to Chloridoideae grasses) from the base of the record at ca. 6500-7000 cal yr B.P. suggests decreasing aridity throughout the Holocene. This trend could reflect a locally drawn out effect of the end of the postglacial arid period due to the well-drained basalt flow catchment maintaining a local arid habitat for the Chloridoideae grasses.  相似文献   

15.
This synthesis integrates recently acquired archaeological and geological data with earlier documented observations to shed light on the subsidence of ancient Greek coastal facilities in southern Italy. These are now positioned between former shorelines and inner shelf sectors at five Calabrian margin localities. Submergence of coastal to inner shelf facilities has resulted in part from sea‐level rise by about 2 m associated with glacio‐hydro‐isostatic factors since archaic to classic Greek time. This phenomenon alone, however, does not explain the wide variation of measured subsidence rates from site‐to‐site. The marked lowering of coastal site substrates by seismo‐tectonic activity (including extensional fault motion), stratal readjustments at depth, and compaction of underlying sediment sequences is significant. Four of the subsided facilities are positioned near emerged Calabrian areas where prevailing Holocene average annual land uplift rates range to ˜1.0 mm/yr; at the fifth, near Hipponion, terrains have risen by nearly 2 mm/yr. In marked contrast, submerged and/or buried structures record the following late Holocene long‐term average rates of coastal margin subsidence: Sybaris‐Thuri on the Taranto Gulf margin (˜0.5–1.0 mm/yr); Hipponion‐Vibo Valentia along the Tyrrhenian coast (˜0.8 to ˜3.2 mm/yr); and Locri‐Epizefiri, Kaulonia, and Capo Colonna on Calabria's Ionian margin (˜1.6, ˜1.6–2.4, and ˜4.0 mm/yr, respectively). © 2012 Wiley Periodicals, Inc.  相似文献   

16.
Microlithic artifacts, some found in situ, are abundant in the Zhongba archaeological site in southwestern Tibet. The site environment consists of extant wetlands and paleo‐wetland deposits found in depressions between sand dunes derived from the Yarlung Tsangpo floodplain. Constraining 14C dates from wetland vegetation and shell from one site fall between ca. 6600–2600 cal. yr B.P., while a second site is dated 3400–1200 cal. yr B.P. A significant and variable 14C reservoir effect—up to 1400 14C yr—limits these ranges to terminus post quem constraints. The in situ artifacts are supplemented by surface collections fully characterizing raw material and typological variability for each site. Raw material found at Zhongba is chert and chalcedony likely sourced from Cretaceous bedrock near the site. Typologically, microblades are nongeometric and are derived from conical and wedge‐shaped cores similar to those identified in the Qinghai Lake Basin and the Chang Tang Nature Reserve of similar or greater age. The later occupation period at Zhongba is broadly contemporaneous with sites on the Qinghai‐Tibet Plateau containing bronze and iron artifacts, indicating microlithic technology remained an important tool‐making strategy in western Tibet late into the protohistoric period.  相似文献   

17.
New stratigraphic and geochronologic data from the Killpecker Dunes in southwestern Wyoming facilitate a more precise understanding of the dune field’s history. Prior investigations suggested that evidence for late Pleistocene eolian activity in the dune field was lacking. However, luminescence ages from eolian sand of ∼15,000 yr, as well as Folsom (12,950-11,950 cal yr B.P.) and Agate Basin (12,600-10,700 cal yr) artifacts overlying eolian sand, indicate the dune field existed at least during the latest Pleistocene, with initial eolian sedimentation probably occurring under a dry periglacial climate. The period between ∼13,000 and 8900 cal yr B.P. was characterized by relatively slow eolian sedimentation concomitant with soil formation. Erosion occurred between ∼8182 and 6600 cal yr B.P. on the upwind region of the dune field, followed by relative stability and soil formation between ∼5900 and 2700 cal yr B.P. The first of at least two latest Holocene episodes of eolian sedimentation occurred between ∼2000 and 1500 yr, followed by a brief (∼500 yr) episode of soil formation; a second episode of sedimentation, occurring by at least ∼700 yr, may coincide with a hypothesized Medieval warm period. Recent stabilization of the western Killpecker Dunes likely occurred during the Little Ice Age (∼350-100 yr B.P.). The eolian chronology of the western Killpecker Dunes correlates reasonably well with those of other major dune fields in the Wyoming Basin, suggesting that dune field reactivation resulted primarily due to departures toward aridity during the late Quaternary. Similar to dune fields on the central Great Plains, dune fields in the Wyoming Basin have been active under a periglacial climate during the late Pleistocene, as well as under near-modern conditions during the latest Holocene.  相似文献   

18.
Sedimentological, faunal, and archaeological investigations at the Sunshine Locality, Long Valley, Nevada reveal a history of human adaptation and environmental change at the last glacial–interglacial transition in North America's north-central Great Basin. The locality contains a suite of lacustrine, alluvial, and eolian deposits associated with fluvially reworked faunal remains and Paleoindian artifacts. Radiocarbon-dated stratigraphy indicates a history of receding pluvial lake levels followed by alluvial downcutting and subsequent valley filling with marsh-like conditions at the end of the Pleistocene. A period of alluvial deposition and shallow water tables (9,800 to 11,000 14C yr B.P.) correlates to the Younger Dryas. Subsequent drier conditions and reduced surface runoff mark the early Holocene; sand dunes replace wetlands by 8,000 14C yr B.P. The stratigraphy at Sunshine is similar to sites located 400 km south and supports regional climatic synchroneity in the central and southern Great Basin during the terminal Pleistocene/early Holocene. Given regional climate change and recurrent geomorphic settings comparable to Sunshine, we believe that there is a high potential for buried Paleoindian features in primary association with extinct fauna elsewhere in the region yet to be discovered due to limited stratigraphic exposure and consequent low visibility.  相似文献   

19.
The St. Louis site, located in the Plains–Parkland transition zone along the South Saskatchewan River, in Saskatchewan, Canada, is a multiple‐component site consisting of stratified floodplain alluvium with multiple, weakly developed soils. Human occupation at the site spans the Late Paleoindian to Middle Precontact periods (10,000–5,000 14C yr B.P.), a time poorly represented archaeologically on the Northern Plains. The dearth of early–middle Holocene‐age archaeological sites is often attributed to reduced inhabitability of the Northern Plains during the Hypsithermal, a period of maximum aridity and limited water availability. Stable isotope and phytolith data from the site indicate increased temperatures during the Hypsithermal and an expansion of Northern Plains grasslands into north‐central Saskatchewan. Although characterized by increased xeric conditions, human occupation at the St. Louis site, as well as the predominance of C3 grasses, attests to the habitability of Northern Plains river systems during this time period. © 2011 Wiley Periodicals, Inc.  相似文献   

20.
Pollen analysis on a 9.54-m sediment core from lake Chignahuapan in the upper Lerma basin, the highest intermontane basin in Central Mexico (2570 m asl), documents vegetation and limnological changes over the past ∼23,000 14C yr. The core was drilled near the archaeological site of Santa Cruz Atizapán, a site with a long history of human occupation, abandoned at the end of the Epiclassic period (ca. 900 AD). Six radiocarbon AMS dates and two well-dated volcanic events, the Upper Toluca Pumice with an age of 11,600 14C yr B.P. and the Tres Cruces Tephra of 8500 14C yr B.P., provide the chronological framework for the lacustrine sequence. From ca. 23,000 14C yr B.P. to ca. 11,600 14C yr B.P. the plant communities were woodlands and grasslands based on the pollen data. The glacial advances MII-1 and MII-2 correlate with abundant non-arboreal pollen, mainly grasses, from ca. 21,000 to 16,000 14C yr B.P., and at ca. 12,600 14C yr B.P. During the late Pleistocene, lake Chignahuapan was a shallow freshwater lake with a phase of lower level between 19,000 and 16,000 14C yr B.P. After 10,000 14C yr B.P., tree cover in the area increased, and a more variable lake level is documented. Late Holocene (ca. 3100 14C yr B.P.) deforestation was concurrent with human population expansion at the beginning of the Formative period (1500 B.C.). Agriculture and manipulation of the lacustrine environment by human lakeshore populations appear at 1200 14C yr B.P. (550 A.D.) with the appearance of Zea mays pollen and abundant charcoal particles.  相似文献   

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