scholarly journals River of Change: a Model for the Development of Terraces Along the Bow River, Alberta

2004 ◽  
Vol 56 (2-3) ◽  
pp. 155-169 ◽  
Author(s):  
Gerald A. Oetelaar
Keyword(s):  
Late Pleistocene ◽  
Rocky Mountains ◽  
Sediment Load ◽  
Younger Dryas ◽  
Early Holocene ◽  
Stream Power ◽  
Independent Variables ◽  
The Past ◽  
Initial Episode ◽  
Alluvial Terraces

Abstract Researchers working in the Bow River valley have identified a minimum of four alluvial terraces, the upper two of which have been designated as paired terraces. Over the past 35 years, they have attempted to correlate these alluvial landforms and to generate models for the development of the terraces along the section of the Bow River between Calgary and the Rocky Mountains. In this study, Mazama ash and an early Holocene paleosol are used to correlate the terrace suites examined by previous researchers and to generate a model which accounts for the development of the upper two sets of paired terraces. These paired terraces reflect major episodes of aggradation and degradation that result from changes in independent variables such as climate and uplift. The initial episode of aggradation, dating from the late Pleistocene, is the result of paraglacial processes in a sparsely vegetated, yet saturated environment. Following a brief episode of degradation at the end of the Younger Dryas, the second episode of aggradation, dating from 9000 to 5000 BP, is caused by increased sediment load and lowered stream power during the Hypsithermal.

scholarly journals How dry was the Younger Dryas? Evidence from a coupled <i>δ</i><sup>2</sup>H–<i>δ</i><sup>18</sup>O biomarker paleohygrometer applied to the Gemündener Maar sediments, Western Eifel, Germany

2019 ◽  
Vol 15 (2) ◽  
pp. 713-733 ◽  
Author(s):  
Johannes Hepp ◽  
Lorenz Wüthrich ◽  
Tobias Bromm ◽  
Marcel Bliedtner ◽  
Imke Kathrin Schäfer ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Younger Dryas ◽  
Late Glacial ◽  
Climatic Conditions ◽  
Leaf Water ◽  
Early Holocene ◽  
Unexpected Finding ◽  
Temperature Dependent ◽  
The Past ◽  
Natural Climate

Abstract. Causes of the Late Glacial to Early Holocene transition phase and particularly the Younger Dryas period, i.e. the major last cold spell in central Europe during the Late Glacial, are considered to be keys for understanding rapid natural climate change in the past. The sediments from maar lakes in the Eifel, Germany, have turned out to be valuable archives for recording such paleoenvironmental changes. For this study, we investigated a Late Glacial to Early Holocene sediment core that was retrieved from the Gemündener Maar in the Western Eifel, Germany. We analysed the hydrogen (δ2H) and oxygen (δ18O) stable isotope composition of leaf-wax-derived lipid biomarkers (n-alkanes C27 and C29) and a hemicellulose-derived sugar biomarker (arabinose), respectively. Both δ2Hn-alkane and δ18Osugar are suggested to reflect mainly leaf water of vegetation growing in the catchment of the Gemündener Maar. Leaf water reflects δ2H and δ18O of precipitation (primarily temperature-dependent) modified by evapotranspirative enrichment of leaf water due to transpiration. Based on the notion that the evapotranspirative enrichment depends primarily on relative humidity (RH), we apply a previously introduced “coupled δ2Hn-alkane–δ18Osugar paleohygrometer approach” to reconstruct the deuterium excess of leaf water and in turn Late Glacial–Early Holocene RH changes from our Gemündener Maar record. Our results do not provide evidence for overall markedly dry climatic conditions having prevailed during the Younger Dryas. Rather, a two-phasing of the Younger Dryas is supported, with moderate wet conditions at the Allerød level during the first half and drier conditions during the second half of the Younger Dryas. Moreover, our results suggest that the amplitude of RH changes during the Early Holocene was more pronounced than during the Younger Dryas. This included the occurrence of a “Preboreal Humid Phase”. One possible explanation for this unexpected finding could be that solar activity is a hitherto underestimated driver of central European RH changes in the past.

scholarly journals Revisions and Extension of the Hohenheim Oak and Pine Chronologies: New Evidence About the Timing of the Younger Dryas/Preboreal Transition

Radiocarbon ◽  
1998 ◽  
Vol 40 (3) ◽  
pp. 1107-1116 ◽  
Author(s):  
Marco Spurk ◽  
Michael Friedrich ◽  
Jutta Hofmann ◽  
Sabine Remmele ◽  
Burkhard Frenzel ◽  
...  
Keyword(s):  
Calibration Curve ◽  
Younger Dryas ◽  
Ice Cores ◽  
Early Holocene ◽  
Proxy Data ◽  
The Past ◽  
Varve Chronology ◽  
New Evidence ◽  
Radiocarbon Calibration

Oak and pine samples housed at the Institute of Botany, University of Hohenheim, are the backbone of the early Holocene part of the radiocarbon calibration curve, published in 1993 (Becker 1993; Kromer and Becker 1993; Stuiver and Becker 1993; Vogel et al. 1993). Since then the chronologies have been revised. The revisions include 1) the discovery of 41 missing years in the oak chronology and 2) a shift of 54 yr for the oldest part back into the past. The oak chronology was also extended with new samples as far back as 10,429 BP (8480 BC). In addition, the formerly tentatively dated pine chronology (Becker 1993) has been rebuilt and shifted to an earlier date. It is now positioned by 14C matching at 11,871-9900 BP (9922–7951 BC) with an uncertainty of ±20 yr (Kromer and Spurk 1998). With these new chronologies the 14C calibration curve can now be corrected, eliminating the discrepancy in the dating of the Younger Dryas/Preboreal transition between the proxy data of the GRIP and GISP ice cores (Johnsen et al. 1992; Taylor et al. 1993), the varve chronology of Lake Gościąż (Goslar et al. 1995) and the pine chronology (Becker, Kromer and Trimborn 1991).

Late-Glacial to Holocene Changes in Winds, Upwelling, and Seasonal Production of the Northern California Current System

1992 ◽  
Vol 38 (3) ◽  
pp. 359-370 ◽  
Author(s):  
Constance Sancetta ◽  
Michell Lyle ◽  
Linda Heusser ◽  
Rainer Zahn ◽  
J.Platt Bradbury
Keyword(s):  
Late Pleistocene ◽  
Climate Model ◽  
Current System ◽  
Younger Dryas ◽  
California Current ◽  
Late Glacial ◽  
California Current System ◽  
The Past ◽  
Northern California Current ◽  
Continental Interior

AbstractA core 120 km off the coast of southern Oregon was examined for changes in lithology, diatoms, and pollen over the past 30,000 yr. Primary production during the late Pleistocene was about half that of the Holocene. Evidence from diatoms and pollen indicates that summer upwelling was much weaker, implying an absence of strong northerly winds. Early Pliocene diatoms found throughout the late Pleistocene section were probably derived from diatomites east of the Cascades and provide evidence for strong easterly winds over a dry continental interior. The findings verify predictions of a climate model based on glacial maximum conditions. There is no compelling evidence for a climatic reversal corresponding to the European Younger Dryas chron. During the early Holocene (9000−7000 yr B.P.) there may have been years when winds were insufficiently strong to support upwelling, so that warm stratified waters lay closer to the coast.

scholarly journals Geoconservation of Vertebrate and Human Ancient Fossils Site, The South TulungagungArea East Java

2019 ◽  
Vol 20 (4) ◽  
pp. 187
Author(s):  
Erick Setiyabudi ◽  
Agus Trihascaryo ◽  
Tutik Koesbarditi ◽  
Rusyad Adi Suriyanto ◽  
Delta Bayu Murti
Keyword(s):  
Early Modern ◽  
Late Pleistocene ◽  
Mining Area ◽  
Geological Heritage ◽  
Early Holocene ◽  
The Past ◽  
Early Modern Humans ◽  
Past Life ◽  
Fossil Site ◽  
And Migration

The paleontology and archeology sites in southern Tulungagung, East Java are part of the geodiversity and geological heritage that has significance for the process of evolution and migration of early modern humans. The sites are Wajak Cave, Song Gentong, and Tenggar Cave (Late Pleistocene to Early Holocene) located in the marble and limestone ornaments mining area of the Campurdarat Formation. Geoconservation of the geological heritage continues to be carried out by research or excavation in these fossil sites to reveal the past life and paleoenvironment, where the fossil site is susceptible to the threat of damage due to surrounded mining activities.Keyword: Wajak Cave, Song Gentong, Tenggar Cave, limestone, marble, Campurdarat Formation.

Late Pleistocene/Early Holocene Archaeology of the Southeastern Atlantic Slope

2018 ◽  
pp. 299-308
Author(s):  
David G. Anderson
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Late Pleistocene ◽  
Younger Dryas ◽  
Early Holocene ◽  
Social Dimensions ◽  
Early Archaic ◽  
The Social ◽  
Impact Hypothesis

In recent decades, great progress has been made in perennial topics and questions in the Southeast such as the existence and nature of Pre-Clovis and Clovis occupations; the role of sea level rise and fall and its affects on prehistoric peoples; the need for effective prospecting for possible inundated sites; the studies of the nature of the Younger Dryas climatic reversal and its affects on climate, environment, and humans, including the proposed cosmic impact hypothesis; and the expansion of more sophisticated methodologies for analysing Early Archaic, notched-point attributes to reveal the social dimensions of these widespread early Holocene societies.

Potential for14C Dating of Biogenic Carbonate in Hackberry (Celtis) Endocarps

1997 ◽  
Vol 47 (3) ◽  
pp. 337-343 ◽  
Author(s):  
Yang Wang ◽  
A.Hope Jahren ◽  
Ronald Amundson
Keyword(s):  
Late Pleistocene ◽  
North American ◽  
Mineral Content ◽  
Early Holocene ◽  
Archaeological Sites ◽  
Past Century ◽  
Quaternary Sediments ◽  
Biogenic Carbonate ◽  
The Past ◽  
Suitable Substrate

Hackberry endocarp (Celtissp.) contains significant amounts (up to 70 wt%) of biogenic carbonate that is nearly pure aragonite (CaCO3). Because of their high mineral content, hackberry endocarps are found abundantly in Tertiary and Quaternary sediments and are very common in many North American archaeological sites. We analyzed the14C content of different components of modern hackberries including the biogenic carbonate in hackberry endocarps collected at known times over the past century. The14C content of the endocarp carbonate accurately records the14C content of the atmosphere.14C dates of fossil endocarp carbonates compared favorably with dates obtained by other means at archaeological and geological sites ranging in age from the late Pleistocene through the early Holocene. We therefore suggest that hackberry endocarp is a suitable substrate for14C dating provided that its morphological and mineralogical integrity is preserved.

scholarly journals Calibration of Radiocarbon Dates for the Late Pleistocene Using U/Th Dates on Stalagmites

Radiocarbon ◽  
1997 ◽  
Vol 39 (1) ◽  
pp. 27-32 ◽  
Author(s):  
John C. Vogel ◽  
Joel Kronfeld
Keyword(s):  
South Africa ◽  
Magnetic Dipole ◽  
Satisfactory Agreement ◽  
Late Pleistocene ◽  
Calibration Curve ◽  
Dipole Field ◽  
Radiocarbon Dates ◽  
The Past ◽  
The Earth ◽  
Magnetic Dipole Field

Twenty paired 14C and U/Th dates covering most of the past 50,000 yr have been obtained on a stalagmite from the Cango Caves in South Africa as well as some additional age-pairs on two stalagmites from Tasmania that partially fill a gap between 7 ka and 17 ka ago. After allowance is made for the initial apparent 14C ages, the age-pairs between 7 ka and 20 ka show satisfactory agreement with the coral data of Bard et al. (1990, 1993). The results for the Cango stalagmite between 25 ka and 50 ka show the 14C dates to be substantially younger than the U/Th dates except at 49 ka and 29 ka, where near correspondence occurs. The discrepancies may be explained by variations in 14C production caused by changes in the magnetic dipole field of the Earth. A tentative calibration curve for this period is offered.

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