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Middle Holocene (middle + holocene)
Selected AbstractsA Reassessment of the holocene stratigraphy of the Wadi Hasa Terrace and Hasa formation, JordanGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 6 2007Joseph Schuldenrein Vita-Finzi's 1960s model for Mediterranean terrace evolution was once the basis for regional valley histories across much of the Levant. A revisit to the Hasa terrace, formerly considered Early to Middle Holocene in age, resulted in a revised chronostratigraphy. Sedimentological and geochemical analyses bolstered by radiocarbon dating indicate that valley floor construction began shortly after the end of the Middle Holocene, at least 2000 years later than initially proposed. An updated model for floodplain evolution proposes three discrete phases of accretion and alluvial plain formation. A weak cambic soil overprints the alluvium and suggests slightly moister climates than at present for much of the Late Holocene. This model is in accord with settlement data. Intensified uplands agropastoralism accelerated the erosion of slope soils that were recycled and deposited as alluvium across the valley floor. The valley floor sequences of the Hasa are analogous to alluvial chronologies for neighboring wadis of the eastern Jordan Rift and can be tied to key Middle and Late Holocene geomorphic events in the Dead Sea and the southwestern Levant. The data strongly indicate that alluvial fill histories after 1800 cal B.C. were anthropogenically driven, whereas Middle Holocene landscape changes were climatically and structurally triggered. © 2007 Wiley Periodicals, Inc. [source] Soil organic carbon pools in a periglacial landscape: a case study from the central Canadian ArcticPERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2010Gustaf Hugelius Abstract We investigated total storage and landscape partitioning of soil organic carbon (SOC) in continuous permafrost terrain, central Canadian Arctic. The study is based on soil chemical analyses of pedons sampled to 1-m depth at 35 individual sites along three transects. Radiocarbon dating of cryoturbated soil pockets, basal peat and fossil wood shows that cryoturbation processes have been occurring since the Middle Holocene and that peat deposits started to accumulate in a forest-tundra environment where spruce was present (,6000 cal yrs BP). Detailed partitioning of SOC into surface organic horizons, cryoturbated soil pockets and non-cryoturbated mineral soil horizons is calculated (with storage in active layer and permafrost calculated separately) and explored using principal component analysis. The detailed partitioning and mean storage of SOC in the landscape are estimated from transect vegetation inventories and a land cover classification based on a Landsat satellite image. Mean SOC storage in the 0,100-cm depth interval is 33.8,kg C,m,2, of which 11.8,kg C m,2 is in permafrost. Fifty-six per cent of the total SOC mass is stored in peatlands (mainly bogs), but cryoturbated soil pockets in Turbic Cryosols also contribute significantly (17%). Elemental C/N ratios indicate that this cryoturbated soil organic matter (SOM) decomposes more slowly than SOM in surface O-horizons. Copyright © 2010 John Wiley & Sons, Ltd. [source] Holocene Floral and Faunal Remains Revealed Concealed Neotectonic Disturbance (Saria Tal, Kumaun Himalaya, India)ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 1 2010Asha GUPTA Abstract: Palynological and paleontological investigations supported by the radiocarbon dates of the lacustrine sediments of two profiles from the temperate lake Saria Tal, in Nairn Tal District, Kumaun Himalaya, have revealed the presence of a concealed fold at the region. The profile from bore cores represents the upper part of the Late Holocene and the profile from exposed sections from the Middle Holocene to the over middle part of the Late Holocene. The data generated from different investigations have uniformly indicated that the former profile represents normal superposition, while the latter represents the reverse order. The contemporary pollen as well as moüuscan zones of both profiles are situated at different elevations but consist of similar bioremains , indicating continuation of the same strata in two profiles. The presence of reverse order of superposition, continuation of the same strata in two profiles at different elevations, and the orientation of biozones, have indicated that the revealed folding is of syncline type. The present study has also given an idea about the origin of this lake. [source] Past distribution and ecology of the cork oak (Quercus suber) in the Iberian Peninsula: a pollen-analytical approachDIVERSITY AND DISTRIBUTIONS, Issue 1 2000J. S. Carrión Abstract., This study presents pollen-analytical data from continental and offshore Iberian Peninsula sites that include pollen curves of Quercus suber, to provide information on the past distribution and ecology of the cork oak (Q. suber). Results centre on a new pollen record of Navarrés (Valencia, eastern Spain), which shows that the cork oak survived regionally during the Upper Pleistocene and was important during a mid-Holocene replacement of a local pine forest by Quercus -dominated communities. This phenomenon appears linked to the recurrence of fire and reinforces the value of the cork oak for reforestation programmes in fire-prone areas. In addition to Navarrés, other Late Quaternary pollen sequences (Sobrestany, Casablanca-Almenara, Padul, SU 8103, SU8113, 8057B) suggest last glacial survival of the cork oak in southern and coastal areas of the Peninsula and North Africa. Important developments also occur from the Late Glacial to the middle Holocene, not only in the west but also in the eastern Peninsula. It is suggested that, in the absence of human influence, Q. suber would develop in non-monospecific forests, sharing the arboreal stratum both with other sclerophyllous and deciduous Quercus and Pinus species. [source] The geoarchaeological and paleoenvironmental context of Paleoindian sites in western Middle Park, Colorado, USAGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 2 2010James H. Mayer 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. [source] The effects of temporal and spatial patterns of Holocene erosion and alluviation on the archaeological record of the Central and Eastern Great Plains, U.S.A.GEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 2 2002E. Arthur Bettis III Patterns of erosion and deposition act as a filter that strongly influences the disposition of the archaeological record of the Central and Eastern Plains of the North American Midcontinent. Detailed studies of alluvial valley stratigraphy in four drainage basins in the region reveal temporal and spatial patterns of fluvial system behavior that control the preservation and visibility of past human activity. These basins are located on a 600-km-long longitudinal gradient extending from semiarid southwestern Kansas to moist-subhumid central Iowa. Despite significant environmental variability along this transect, basin-wide patterns of Holocene erosion and deposition are similar across the study area. From ca. 11,000 to 8000 yr B.P., aggradation, punctuated by slow alluviation and/or stability around 10,000 yr B.P., was the dominant process in large and some small valleys. The early and middle Holocene (ca. 8000,5000 yr B.P.) was a period of net erosion and sediment movement in small valleys, sediment storage in large valleys, and episodic aggradation on alluvial fans. During the late Holocene (post-5000 yr B.P.), alluvial fans stabilized, small valleys became zones of net sediment storage, and aggradation slowed in large valleys. Basin-wide aggradation followed by entrenchment and channel migration characterizes fluvial activity during the Historic period. Consideration of the effects of these temporal and spatial patterns of Holocene erosion and alluviation on the archaeological record is crucial for developing efficient cultural resource sampling strategies and for accurately interpreting the archaeological record. © 2002 John Wiley & Sons, Inc. [source] A geochronological approach to understanding the role of solar activity on Holocene glacier length variability in the Swiss AlpsGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 4 2006Anne Hormes ABSTRACT. We present a radiocarbon data set of 71 samples of wood and peat material that melted out or sheared out from underneath eight presentday mid-latitude glaciers in the Central Swiss Alps. Results indicated that in the past several glaciers have been repeatedly less extensive than they were in the 1990s. The periods when glaciers had a smaller volume and shorter length persisted between 320 and 2500 years. This data set provides greater insight into glacier variability than previously possible, especially for the early and middle Holocene. The radiocarbon-dated periods defined with less extensive glaciers coincide with periods of reduced radio-production, pointing to a connection between solar activity and glacier melting processes. Measured long-term series of glacier length variations show significant correlation with the total solar irradiance. Incoming solar irradiance and changing albedo can account for a direct forcing of the glacier mass balances. Long-term investigations of atmospheric processes that are in interaction with changing solar activity are needed in order to understand the feedback mechanisms with glacier mass balances. [source] Holocene vegetation and climate change on the Colorado Great Plains, USA, and the invasion of Colorado piñon (Pinus edulis)JOURNAL OF BIOGEOGRAPHY, Issue 12 2009R. Scott Anderson Abstract Aim, To reconstruct the last c. 7000 years of vegetation and climate change in an unusual region of modern Great Plains grassland and scarp woodland in south-east Colorado (USA), and to determine the late Holocene biogeography of Colorado piñon (Pinus edulis) at its easternmost extent, using a series of radiocarbon-dated packrat (Neotoma sp.) middens. Location, The West Carrizo Canyon drains the Chaquaqua Plateau, a plateau that projects into the western extent of the southern Great Plains grasslands in south-eastern Colorado, USA. Elevations of the study sites are 1448 to 1525 m a.s.l. Today the plateau is mostly Juniperus scopulorum,P. edulis woodland. Methods, Plant macrofossils and pollen assemblages were analysed from 11 14C-dated packrat middens. Ages ranged from 5990 yr bp (6839 cal. yr bp) to 280 yr bp (485 cal. yr bp). Results, The results presented here provide information on the establishment and expansion of Juniperus,P. edulis woodland at its eastern limits. The analysis of both plant macrofossils and pollen from the 11 middens documents changes in plant communities over the last 7000 years, and the establishment of P. edulis at its easternmost limit. Though very minor amounts of P. edulis pollen occur as early as the middle Holocene, plant macrofossils were only recovered in middens dating after c. 480 cal. yr bp. Main conclusions, Originally, midden research suggested a late glacial refuge to the north-east of the Carrizo Canyon site, and a middle Holocene expansion of P. edulis. Results reported here are consistent with a late Holocene expansion, here at its eastern limits, but noted elsewhere at its northern and north-eastern limits. In general, this late Holocene expansion is consistent with pollen data from sediments in Colorado and New Mexico, and suggests that P. edulis is still expanding its range at its present extremes. This has implications for further extension of its range due to changing climatic conditions in the future. [source] Holocene pollen records from the central Arctic Foothills, northern Alaska: testing the role of substrate in the response of tundra to climate changeJOURNAL OF ECOLOGY, Issue 6 2003W. Wyatt Oswald Summary 1To explore the role of edaphic controls in the response of arctic tundra to climate change, we analysed Holocene pollen records from lakes in northern Alaska located on glaciated surfaces with contrasting soil texture, topography and tundra communities. Using indicator taxa, pollen accumulation rates (PARs) and multivariate comparison of fossil and modern pollen assemblages, we reconstructed the vegetational changes at Upper Capsule Lake (Sagavanirktok surface) and Red Green Lake (Itkillik II surface) in response to increased effective moisture between the early and middle Holocene. 2In the Red Green record, low PARs and the continuous presence of taxa indicative of prostrate-shrub tundra (PST; Equisetum, Polypodiaceae, Thalictrum and Rosaceae) indicate that the vegetation resembled PST throughout the Holocene. During the warm, dry early Holocene (11 300,10 000 cal years BP), PST also occurred on Sagavanirktok surfaces, as evidenced by PST indicators (Bryidae, Polypodiaceae, Equisetum and Rosaceae) in this interval of the Upper Capsule record. However, PARs increased, suggesting increased vegetation cover, PST taxa declined and taxa indicative of dwarf-shrub tundra (DST; Rubus chamaemorus and Lycopodium annotinum) increased between 10 000 and 7500 cal years BP. 3We hypothesize that between the early and middle Holocene the fine-textured soils and smooth topography of Sagavanirktok surfaces led to increased soil moisture, greater vegetation cover, permafrost aggradation, anoxic and acidic soil conditions, slower decomposition and the development of a thick organic layer. In contrast, soil moisture remained low on the better-drained Itkillik II surface, and vegetational changes were minor. 4Landscape-scale substrate variations have an effect on how tundra responds to climate change, suggesting that the response of arctic ecosystems to future variability may be spatially heterogeneous. [source] Late Devensian and Holocene relative sea-level changes on the Isle of Skye, Scotland, UK,JOURNAL OF QUATERNARY SCIENCE, Issue 2 2007Katherine A. Selby Abstract Detailed litho- and biostratigraphical analyses from three coastal sites in contrasting coastal settings on the Isle of Skye, Scotland, UK, reveal evidence for several changes in relative sea level during the Late Devensian and Holocene. At the start of the record, relative sea level in the area was high at ca. 12,500 14C (ca. 14,800,cal.) yr,BP but then fell, reaching a low point during the Younger Dryas, at ca. 11,000,10,000 14C (ca. 13,000,11,600,cal.) yr,BP, when a rock platform, correlated with the Main Rock Platform, was formed. In the early,middle Holocene, relative sea level was rising by ca. 8000 14C (ca. 8800,cal.) yr,BP and in northeast Skye a lagoonal surface, correlated with the Main Postglacial Shoreline, was formed at ca. 6600 14C (ca. 7500,cal.) yr,BP. By the late Holocene, relative sea level was again falling, but a rise, registered at at least two sites, began probably before ca. 4000 14C (ca. 4500,cal.) yr,BP, and a second lagoonal surface in northeast Skye, correlated with the Blairdrummond Shoreline, was formed, although by ca. 3000 14C (ca. 3200,cal.) yr,BP relative sea level in the area had resumed its downward trend. The pattern of relative sea-level changes disclosed is compared with evidence elsewhere in Scotland. Copyright © 2006 John Wiley & Sons, Ltd. [source] Changing marine productivity off northern Chile during the past 19,000 years: a multivariable approachJOURNAL OF QUATERNARY SCIENCE, Issue 4 2004M. Mohtadi Abstract A multivariable approach utilising bulk sediment, planktonic Foraminifera and siliceous phytoplankton has been used to reconstruct rapid variations in palaeoproductivity in the Peru,Chile Current System off northern Chile for the past 19,000,cal.,yr. During the early deglaciation (19,000,16,000,cal.,yr,BP), our data point to strongest upwelling intensity and highest productivity of the past 19,000,cal.,yr. The late deglaciation (16,000,13,000,cal.,yr,BP) is characterised by a major change in the oceanographic setting, warmer water masses and weaker upwelling at the study site. Lowest productivity and weakest upwelling intensity are observed from the early to the middle Holocene (13,000,4000,cal.,yr,BP), and the beginning of the late Holocene (<4000,cal.,yr,BP) is marked by increasing productivity, mainly driven by silicate-producing organisms. Changes in the productivity and upwelling intensity in our record may have resulted from a large-scale compression and/or displacement of the South Pacific subtropical gyre during more productive periods, in line with a northward extension of the Antarctic Circumpolar Current and increased advection of Antarctic water masses with the Peru,Chile Current. The corresponding increase in hemispheric thermal gradient and wind stress induced stronger upwelling. During the periods of lower productivity, this scenario probably reversed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Pollen- and diatom based environmental history since the Last Glacial Maximum from the Andean core Fúquene-7, ColombiaJOURNAL OF QUATERNARY SCIENCE, Issue 1 2003Maria Isabel Vélez Abstract The late Pleistocene,Holocene ecological and limnological history of Lake Fúquene (2580 m a.s.l.), in the Colombian Andes, is reconstructed on the basis of diatom, pollen and sediment analyses of the upper 7 m of the core Fúquene-7. Time control is provided by 11 accelerator mass spectrometry (AMS) 14C dates ranging from 19 670 ± 240 to 6040 ± 60 yr BP. In this paper we present the evolution of the lake and its surroundings. Glacial times were cold and dry, lake-levels were low and the area was surrounded by paramo and subparamo vegetation. Late-glacial conditions were warm and humid. The El Abra Stadial, a Younger Dryas equivalent, is reflected by a gap in the sedimentary record, a consequence of the cessation of deposition owing to a drop in lake-level. The early Holocene was warm and humid; at this time the lake reached its maximum extension and was surrounded by Andean forest. The onset of the drier climate prevailing today took place in the middle Holocene, a process that is reflected earlier in the diatom and sediment records than in the pollen records. In the late Holocene human activity reduced the forest and transformed the landscape. Climate patterns from the Late-glacial and throughout the Holocene, as represented in our record, are similar to other records from Colombia and northern South America (the Caribbean, Venezuela and Panama) and suggest that the changes in lake-level were the result of precipitation variations driven by latitudinal shifts of the Intertropical Convergence Zone. Copyright © 2003 John Wiley & Sons, Ltd. [source] Upper limb musculoskeletal stress markers among middle Holocene foragers of Siberia's Cis-Baikal regionAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2009Angela R. Lieverse Abstract This evaluation of musculoskeletal stress markers (MSMs) in the Cis-Baikal focuses on upper limb activity reconstruction among the region's middle Holocene foragers, particularly as it pertains to adaptation and cultural change. The five cemetery populations investigated represent two discrete groups separated by an 800,1,000 year hiatus: the Early Neolithic (8000,7000/6800 cal. BP) Kitoi culture and the Late Neolithic/Bronze Age (6000/5800,4000 cal. BP) Isakovo-Serovo-Glaskovo (ISG) cultural complex. Twenty-four upper limb MSMs are investigated not only to gain a better understanding of activity throughout the middle Holocene, but also to independently assess the relative distinctiveness of Kitoi and ISG adaptive regimes. Results reveal higher heterogeneity in overall activity levels among Early Neolithic populations,with Kitoi males exhibiting more pronounced upper limb MSMs than both contemporary females and ISG males,but relative constancy during the Late Neolithic/Bronze Age, regardless of sex or possible status. On the other hand, activity patterns seem to have varied more during the latter period, with the supinator being ranked high among the ISG, but not the Kitoi, and forearm flexors and extensors being ranked generally low only among ISG females. Upper limb rank patterning does not distinguish Early Neolithic males, suggesting that their higher MSM scores reflect differences in the degree (intensity and/or duration), rather than the type, of activity employed. Finally, for both Kitoi and ISG peoples, activity patterns,especially the consistently high-ranked costoclavicular ligament and deltoid and pectoralis major muscles,appear to be consistent with watercraft use. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc. [source] Holocene vegetation and climate changes in Hoton-Nur basin, northwest MongoliaBOREAS, Issue 2 2000PAVEL TARASOV Radiocarbon-dated pollen and diatom records from Hoton-Nur lake (48°40'N, 88°18'E), northwest Mongolia are used to reconstruct Holocene vegetation and climate changes. Steppe, which covered the area some time before 9000 BP (all ages are given in 14C BP), was replaced by boreal conifer forest-steppe by 9000,8500 BP. At the same time, planktonic diatoms increased in abundance from 5 to 45%. After 4000 BP there was a sharp reduction in forest and re-establishment of steppe. Changes in the pollen composition were accompanied by a decrease in the abundance of planktonic diatoms from 35,50% (between 9000 and 5500 BP) to less than 10% soon after 4000 BP. These and other published data from Mongolia suggest wetter conditions during the early and middle Holocene than those of today. This pattern probably reflects an expansion of the Pacific monsoon recorded in geological data from China and simulated in climate-model experiments, and suggests that the summer monsoon influenced a larger area than might appear if the Chinese records only are taken into consideration. [source] | ||||||||||||||||