Middle and Upper Palaeolithic environments and the calibration of 14C dates beyond 10,000 BP

Antiquity ◽  
1998 ◽  
Vol 72 (275) ◽  
pp. 26-33 ◽  
Author(s):  
Tjeerd H. van Andel
Keyword(s):  
Magnetic Field ◽  
Time Scale ◽  
Archaeological Sites ◽  
Upper Palaeolithic ◽  
Upper Limit ◽  
History Of ◽  
Climatic History ◽  
Quaternary History ◽  
The Last Glacial

Advances in our understanding of the Quaternary history of the earth's magnetic field provide the means to correct the radiocarbon time-scale for long-term (millennia) deviations from the calendrical one beyond the upper limit of the tree-ring-based calibration. The conversion is essential when Middle and Upper Palaeolithic archaeological sites are to be placed within the context of the complex climatic history of the last glacial interval and following deglaciation.

scholarly journals Late-Quaternary Vegetational and Climatic History of the Yellowstone/Grand Teton Region

1988 ◽  
Vol 12 ◽  
pp. 189-192
Author(s):  
Cathy Barnosky
Keyword(s):  
Environmental History ◽  
Late Quaternary ◽  
Sediment Cores ◽  
Sediment Accumulation ◽  
Fire Frequency ◽  
Ice Age ◽  
Sediment Chemistry ◽  
History Of ◽  
Climatic History

The research underway has focused on two different aspects of the environmental history of the Yellowstone/Grand Teton region. One objective has been to examine the long-term vegetational and climatic history of Jackson Hole, the Pinyon Peak Highlands, and Yellowstone Park since the end of late Pinedale glaciation, about 14,000 years ago. Fossil pollen in sediment cores from lakes in the region is being analyzed to clarify the nature and composition of ice-age refugia, the rate and direction of plant migrations in the initial stages of reforestation, and the long-term stability of postglacial communities. Sedimentary charcoal also is being examined to reconstruct fire frequency during different climatic regions and different vegetation types in the past. This information is necessary to assess the sensitivity of plant communities to environmental change and to understand postglacial landscapes of the northern rocky Mountains. The second objective has been a multidisciplinary investigation of the relationship of climate to sedimentation rates in lakes and ponds in Yellowstone, undertaken with Drs. Wright, D.R. Engstrom and S.C. Fritz of the University of Minnesota. This facet of the research examines the relative importance of climate, fire, hillslope erosion induced by overgrazing, and nutrient enrichment in the last 150 years, as recorded in selected lakes in the northern range of Yellowstone. Populations of elk and bison are known to have fluctuated greatly during this interval, and slight climatic changes are suggested from other lines of research. In this study pollen, diatoms, charcoal, sediment chemistry, and sediment accumulation rates are analyzed in short cores from small lakes.

scholarly journals Evaluation of 14C Ages of Organic Fractions of Paleosols from Loess-Paleosol Sequences Near Xian, China

Radiocarbon ◽  
1989 ◽  
Vol 31 (03) ◽  
pp. 680-695 ◽  
Author(s):  
M J Head ◽  
Weijian Zhou ◽  
Mingfu Zhou
Keyword(s):  
Shaanxi Province ◽  
Agricultural Activity ◽  
Agricultural Activities ◽  
The Loess Plateau ◽  
Last Glacial Period ◽  
Period Analysis ◽  
History Of ◽  
Climatic History ◽  
Organic Fractions ◽  
The Last Glacial

The 14C dating of organic fractions from paleosol layers containing <2% carbon in loess-paleosol sequences from the loess plateau in China has yielded results that are quite often much younger than the true age of the sediments. Percolation of modern organic materials from agricultural activities, and binding of these materials within the weathered clays of the paleosols has meant that conventional pretreatment techniques for 14C dating would not isolate a reliable chemical fraction. The total sequence from Bei Zhuang Cun, in Shaanxi Province, reflects the climatic history of the area for ca 30,000 years, ranging from the interstadial of the last glacial period to the postglacial period. Analysis of solvent extracts of organic material from this site indicates that they are mainly composed of carbohydrate residues originating from the relatively recent agricultural activity. Validity of the humic components for dating will be discussed.

A late-Holocene pollen record from the western Qilian Mountains and its implications for climate change and human activity along the Silk Road, Northwestern China

The Holocene ◽  
2018 ◽  
Vol 28 (7) ◽  
pp. 1141-1150 ◽  
Author(s):  
Jun Zhang ◽  
Xiaozhong Huang ◽  
Zongli Wang ◽  
Tianlong Yan ◽  
En’yuan Zhang
Keyword(s):  
Late Holocene ◽  
Qilian Mountains ◽  
Archaeological Sites ◽  
Pollen Record ◽  
Human Environment ◽  
Plant Remains ◽  
Tree Ring Data ◽  
History Of ◽  
The Silk Road

The sparsity of long-term reliable climatic records hampers our understanding of human–environment interactions in the semi-arid Hexi Corridor, NW China. Here, we present a late-Holocene pollen record from a small alpine lake, Tian’E, in the western Qilian Mountains. The chronology is provided by nine accelerator mass spectrometry (AMS) 14C dates from terrestrial plant remains. The ratios of Artemisia and Amaranthaceae (A/C) are used to reconstruct the history of regional humidity: An unstable climate occurred during 1530–1270 BC; there were three relatively wet periods, at 1270 BC–AD 400, AD 1200–1350, and AD 1600–present; and there were two dry periods, from AD 400 to 1200 and from AD 1350 to 1600. Comparison with tree-ring data indicates that continuous droughts were responsible for the abandonment of several archaeological sites and ancient cities in the region, including the major city of Dunhuang, which was abandoned in AD 1372 and AD 1524 for nearly 200 years.

scholarly journals Revisiting the magnetization of comet 67P/Churyumov-Gerasimenko

2019 ◽  
Vol 630 ◽  
pp. A46 ◽  
Author(s):  
P. Heinisch ◽  
H.-U. Auster ◽  
I. Richter ◽  
K. H. Glassmeier
Keyword(s):  
Magnetic Field ◽  
Magnetic Measurements ◽  
Field Observations ◽  
Upper Limit ◽  
Background Magnetic Field ◽  
Surface Magnetization ◽  
Cometary Material ◽  
History Of ◽  
Comet 67P ◽  
The Magnetic Field

Context. The landing of the Philae probe as part of the ESA Rosetta mission made it possible to study the magnetization of comet 67P/Churyumov-Gerasimenko (67P) by combining observations from the lander and orbiter. In this work, we revisit the magnetic properties with information gained during the progression of the mission for a comprehensive understanding of the circumstances of Philae’s descent and landing. Aims. The aim is to derive a limit for any possible magnetization of the cometary material on the surface of 67P. To achieve this, the surface contacts of Philae were analyzed. Combined with a more detailed understanding of the background magnetic field, this allows us to interpret the underlying magnetic measurements in detail. Methods. We combined magnetic field observations from the ROMAP magnetometer on board Philae with observations from the RPC-MAG instrument on board the Rosetta orbiter. To facilitate this, a correlation analysis was used to correct phase shifts between the observed signals. Additionally, in-flight calibration of the ROMAP offsets was performed using information about the dynamics of Philae during flight. These corrections made it possible to use the orbiter measurements as reference for the comet-based Philae observations. We assumed a simple dipole model and used the magnetic field observations to derive an upper limit for the magnetization of the cometary material. Results. An upper limit of 0.9 nT for the observed magnetic field on the surface of 67P was derived for any contribution from surface magnetization. For homogeneously magnetized pebbles with a size of typical aggregates in the range of ~5 cm, this translates into an upper limit of ~5 × 10−5 Am2 kg−1 for the specific magnetic moment. Depending on the exact history of formation, this results in an upper limit of 4 μT for the magnitude of the magnetic field in the solar nebula during the formation of comet 67P.

AI and HCI: Two Fields Divided by a Common Focus

AI Magazine ◽  
2009 ◽  
Vol 30 (4) ◽  
pp. 48 ◽  
Author(s):  
Jonathan Grudin
Keyword(s):  
Time Scale ◽  
Short Time Scale ◽  
Intelligent Behavior ◽  
History Of ◽  
Short Time ◽  
Competition For Resources

Although AI and HCI explore computing and intelligent behavior and the fields have seen some cross-over, until recently there was not very much. This article outlines a history of the fields that identifies some of the forces that kept the fields at arm’s length. AI was generally marked by a very ambitious, long-term vision requiring expensive systems, although the term was rarely envisioned as being as long as it proved to be, whereas HCI focused more on innovation and improvement of widely-used hardware within a short time-scale. These differences led to different priorities, methods, and assessment approaches.  A consequence was competition for resources, with HCI flourishing in AI winters and moving more slowly when AI was in favor. The situation today is much more promising, in part because of platform convergence: AI can be exploited on widely-used systems.

Long-term nivation rates, Cathedral Massif, northwestern British Columbia

2020 ◽  
Vol 57 (11) ◽  
pp. 1305-1311 ◽  
Author(s):  
Kelsey E. Nyland ◽  
Frederick E. Nelson
Keyword(s):  
British Columbia ◽  
Contemporary Literature ◽  
Short Term ◽  
Denudation Rates ◽  
History Of ◽  
Aerial Vehicle ◽  
The Last Glacial Maximum ◽  
East West ◽  
The Last Glacial

Cryoplanation terraces (CTs) are large (3000–800 000 m2) erosional landforms found in upland periglacial environments. Two hypotheses for the formation of CTs are supported in contemporary literature: (1) CT formation is controlled primarily by geologic structure; and (2) CTs are climatically controlled through nivation, a suite of erosional processes associated with late-lying snowbanks. A persistent question in periglacial geomorphology is whether nivation can produce CT-scale landforms. This paper examines the unusual deglaciation history of “Frost Ridge” on the Cathedral Massif, northwestern British Columbia, to estimate long-term denudation attributable to nivation processes active since the last glacial maximum. Frost Ridge forms one flank of an east–west-oriented glacial valley. During deglaciation, marginal drainage created V-shaped erosional notches on both valley walls. Minimization of solar radiation on the steep north-facing wall (Frost Ridge) allowed snowbanks to accumulate and persist in the marginal drainage features and nivation processes to erode the slope. Today, several large nivation hollows (incipient CTs) are present near the summit of Frost Ridge, while the V-shaped marginal drainage features are preserved at lower elevations and on the opposite, south-facing valley wall. A high-resolution survey using an unmanned aerial vehicle (UAV) allowed volumes of marginal drainage and incipient terrace features to be compared. Based on this volumetric comparison, denudation rates are estimated to range from 4.2 to 125.8 mm/kyr, which are comparable with relatively short-term nivation rates reported from Antarctica and mid-latitude alpine periglacial areas.

The late Quaternary history of lodgepole and jack pines

1985 ◽  
Vol 15 (5) ◽  
pp. 749-772 ◽  
Author(s):  
William B. Critchfield
Keyword(s):  
Late Quaternary ◽  
Jack Pine ◽  
The North ◽  
Last Glaciation ◽  
Variation Patterns ◽  
History Of ◽  
Quaternary History ◽  
Fossil Records ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Lodgepole and jack pines (Pinuscontorta Dougl. ex. Loud. and Pinusbanksiana Lamb.), components of the North American boreal forest, have pioneering roles after major disturbances such as fire or glaciation. These species are closely related and hybridize in western Canada, but their fossil records and contemporary variation patterns suggest they had completely different late Quaternary histories. Several taxonomically recognized geographic races of lodgepole pine apparently survived the last glaciation without drastic modification, the northern races either persisting in far-northern refugia or migrating from the south. The uneven influence of jack pine on northern lodgepole populations implies repeated genetic contacts, but less marked introgression in the other direction could be of post-Pleistocene origin. Jack pine occupied its entire range after the last glacial maximum and lacks taxonomically recognized races. In the Great Lakes region, however, the presence of regionally distinct populations suggests the species had at least two Midwestern refugia. This hypothesis is contrary to the widely held view that jack pine occupied most or all of its range from a well-documented refugium in southeastern North America, but is supported by limited fossil evidence that pine persisted in the Midwest during the last glaciation.

scholarly journals Observations of GRO J1744–28 in quiescence with XMM-Newton

2020 ◽  
Vol 643 ◽  
pp. A62
Author(s):  
V. Doroshenko ◽  
V. Suleimanov ◽  
S. Tsygankov ◽  
J. Mönkkönen ◽  
L. Ji ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Binary System ◽  
Galactic Center ◽  
Optical Counterpart ◽  
X Ray ◽  
Upper Limit ◽  
Dipole Term ◽  
The Magnetic Field

We report on the deep observations of the “bursting pulsar” GRO J1744–28, which were performed with XMM-Newton and aimed to clarify the origin of its X-ray emission in quiescence. We detect the source at a luminosity level of ∼1034 erg s−1 with an X-ray spectrum that is consistent with the power law, blackbody, or accretion-heated neutron star atmosphere models. The improved X-ray localization of the source allowed us to confirm the previously identified candidate optical counterpart as a relatively massive G/K III star at 8 kpc close to the Galactic center, implying an almost face-on view of the binary system. Although we could only find a nonrestricting upper limit on the pulsed fraction of ∼20%, the observed hard X-ray spectrum and strong long-term variability of the X-ray flux suggest that the source is also still accreting when not in outburst. The luminosity corresponding to the onset of centrifugal inhibition of accretion is thus estimated to be at least two orders of magnitude lower than previously reported. We discuss this finding in the context of previous studies and argue that the results indicate a multipole structure in the magnetic field with the first dipole term of ∼1010 G, which is much lower than previously assumed.

scholarly journals Could clonality contribute to the northern survival of grey alder [Alnus incana (L.) Moench] during the Last Glacial Maximum?

2016 ◽  
Vol 86 (1) ◽  
Author(s):  
Monika Dering ◽  
Małgorzata Latałowa ◽  
Krystyna Boratyńska ◽  
Piotr Kosiński ◽  
Adam Boratyński
Keyword(s):  
Gene Diversity ◽  
Phylogeographic Structure ◽  
Alnus Incana ◽  
Postglacial History ◽  
Northern Latitudes ◽  
Northern Regions ◽  
History Of ◽  
The Last Glacial

Reconstruction of the glacial and postglacial history of a species, including life-history traits, provides valuable insights into the relationships between ecological and genetic factors shaping phylogeographic patterns. Clonality appears as a trait of high importance for survival in northern refugia. In the present study, the phylogeographic structure of 24 <em>Alnus incana</em> (grey alder) populations and clonal structure in seven populations were analyzed utilizing four microsatellites markers. Palaeobotanical data were collected and combined with the genetic results in order to support the possibility that this species survived in northern refugia. Our study indicated that: (i) Balkan populations are the most divergent, which likely reflects their long-term in-situ existence, (ii) Western Alpine populations are genetically different from other European populations, which corresponds with palaeobotanical data, suggesting that this region served as a refugium for this species, (iii) the macrofossil data indicate that the Scandinavian and northeastern Polish populations are likely derived from the refugia located in northern latitudes, (iv) Western and Eastern Carpathian populations form separate groups, which indicate that both regions could serve as refugia. Clonality was an important factor in allowing grey alder to survive in northern regions during the last glaciation. However, this mode of reproduction has also influenced the population genetic structure, as we noted rather low level of gene diversity, <em>H</em><span><sub>E</sub></span> = 0.386 and low allelic variability, <em>A</em> = 3.8, in this species.

The Quaternary history of vegetation in the South Atlantic islands

1960 ◽  
Vol 152 (949) ◽  
pp. 516-529 ◽  
Keyword(s):  
South Africa ◽  
New Zealand ◽  
South America ◽  
History Of Vegetation ◽  
Gough Island ◽  
History Of ◽  
Antarctic Continent ◽  
Climatic History ◽  
Quaternary History ◽  
The Antarctic

My contribution to the exploration of the southern temperate zone is the pollenanalytical investigation of a number of peat cores, collected by Dr Christophersen, the leader of the Norwegian scientific expedition to Tristan da Cunha 1937/38, and by Mr N. M. Wace, the botanist on the British Gough Island survey 1955/56. I am most grateful to these explorers, especially to Mr Wace, for placing this valuable material at my disposal. Since von Post, on receiving the Vega medal in 1944, gave his famous lecture ‘The prospect for pollen analysis in the study of the earth’s climatic history’ (published in English in 1946), a number of pollen-analytical investigations have been carried out in the Southern Hemisphere. In extreme South America, especially by Auer; in New Zealand, by Cranwell-Smith, Deevey, Harris, Moar, Moore and others; in Australia, by Cookson, Duigan and others; in South Africa, by van Zinderen Bakker, Coetzee, Martin and others; and also in some of the isolated islands around the Antarctic continent.

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