Uranium–Thorium Dating of Speleothems

Elements ◽  
2021 ◽  
Vol 17 (2) ◽  
pp. 87-92 ◽  
Author(s):  
Kathleen A. Wendt ◽  
Xianglei Li ◽  
R. Lawrence Edwards
Keyword(s):  
Asian Monsoon ◽  
Measurement Precision ◽  
Dramatic Reduction ◽  
Earth System ◽  
Sociopolitical Change ◽  
Climate History ◽  
Temporal Precision ◽  
History Of ◽  
Ancient Civilizations ◽  
Earth’S Climate

Speleothems are important timekeepers of Earth’s climate history. A key advantage of speleothems is that they can be dated using U–Th techniques. Mass spectrometric methods for measuring U and Th isotopes has led to vast improvements in measurement precision and a dramatic reduction in sample size. As a result, the timing of past climate, environment, and Earth system changes can be investigated at exceptional temporal precision. In this review, we summarize the principles and history of U–Th dating of speleothems. Finally, we highlight three studies that use U–Th dated speleothems to investigate past changes to the Asian monsoon, constrain the timing of sociopolitical change in ancient civilizations, and develop a speleothem-based calibration of the 14C timescale.

scholarly journals Deglacial temperature history of West Antarctica

2016 ◽  
Vol 113 (50) ◽  
pp. 14249-14254 ◽  
Author(s):  
Kurt M. Cuffey ◽  
Gary D. Clow ◽  
Eric J. Steig ◽  
Christo Buizert ◽  
T. J. Fudge ◽  
...  
Keyword(s):  
Climate Models ◽  
Global Climate ◽  
Ice Core ◽  
Ice Cores ◽  
Temperature History ◽  
West Antarctica ◽  
Climate History ◽  
History Of ◽  
Climate Forcings ◽  
Earth’S Climate

The most recent glacial to interglacial transition constitutes a remarkable natural experiment for learning how Earth’s climate responds to various forcings, including a rise in atmospheric CO2. This transition has left a direct thermal remnant in the polar ice sheets, where the exceptional purity and continual accumulation of ice permit analyses not possible in other settings. For Antarctica, the deglacial warming has previously been constrained only by the water isotopic composition in ice cores, without an absolute thermometric assessment of the isotopes’ sensitivity to temperature. To overcome this limitation, we measured temperatures in a deep borehole and analyzed them together with ice-core data to reconstruct the surface temperature history of West Antarctica. The deglacial warming was 11.3±1.8∘C, approximately two to three times the global average, in agreement with theoretical expectations for Antarctic amplification of planetary temperature changes. Consistent with evidence from glacier retreat in Southern Hemisphere mountain ranges, the Antarctic warming was mostly completed by 15 kyBP, several millennia earlier than in the Northern Hemisphere. These results constrain the role of variable oceanic heat transport between hemispheres during deglaciation and quantitatively bound the direct influence of global climate forcings on Antarctic temperature. Although climate models perform well on average in this context, some recent syntheses of deglacial climate history have underestimated Antarctic warming and the models with lowest sensitivity can be discounted.

Newton and the Origin of Civilization

2012 ◽  
Author(s):  
Jed Z. Buchwald ◽  
Mordechai Feingold
Keyword(s):  
Good Reason ◽  
History Of Mathematics ◽  
Primary Sources ◽  
Ancient History ◽  
Isaac Newton ◽  
History Of ◽  
Ancient Civilizations ◽  
And Mathematics ◽  
One Year ◽  
Radical Ideas

Isaac Newton’s Chronology of Ancient Kingdoms Amended, published in 1728, one year after the great man’s death, unleashed a storm of controversy. And for good reason. The book presents a drastically revised timeline for ancient civilizations, contracting Greek history by five hundred years and Egypt’s by a millennium. This book tells the story of how one of the most celebrated figures in the history of mathematics, optics, and mechanics came to apply his unique ways of thinking to problems of history, theology, and mythology, and of how his radical ideas produced an uproar that reverberated in Europe’s learned circles throughout the eighteenth century and beyond. The book reveals the manner in which Newton strove for nearly half a century to rectify universal history by reading ancient texts through the lens of astronomy, and to create a tight theoretical system for interpreting the evolution of civilization on the basis of population dynamics. It was during Newton’s earliest years at Cambridge that he developed the core of his singular method for generating and working with trustworthy knowledge, which he applied to his study of the past with the same rigor he brought to his work in physics and mathematics. Drawing extensively on Newton’s unpublished papers and a host of other primary sources, the book reconciles Isaac Newton the rational scientist with Newton the natural philosopher, alchemist, theologian, and chronologist of ancient history.

General History of Africa, Vol. II: Ancient Civilizations of Africa

1981 ◽  
Vol 24 (4) ◽  
pp. 135
Author(s):  
J. Jeffrey Hoover ◽  
G. Mokhtar ◽  
UNESCO
Keyword(s):  
History Of ◽  
Ancient Civilizations

scholarly journals Lake-level variability in Salar de Coipasa, Bolivia during the past ∼40,000 yr

2018 ◽  
Vol 91 (2) ◽  
pp. 881-891 ◽  
Author(s):  
J. Andrew Nunnery ◽  
Sherilyn C. Fritz ◽  
Paul A. Baker ◽  
Wout Salenbien
Keyword(s):  
Lake Level ◽  
Sediment Accumulation ◽  
Geochemical Data ◽  
South American ◽  
Climate History ◽  
Oxygen Isotope Stage ◽  
The Past ◽  
History Of ◽  
Diatom Stratigraphy ◽  
The Last Glacial

AbstractVarious paleoclimatic records have been used to reconstruct the hydrologic history of the Altiplano, relating this history to past variability of the South American summer monsoon. Prior studies of the southern Altiplano, the location of the world’s largest salt flat, the Salar de Uyuni, and its neighbor, the Salar de Coipasa, generally agree in their reconstructions of the climate history of the past ∼24 ka. Some studies, however, have highly divergent climatic records and interpretations of earlier periods. In this study, lake-level variation was reconstructed from a ∼14-m-long sediment core from the Salar de Coipasa. These sediments span the last ∼40 ka. Lacustrine sediment accumulation was apparently continuous in the basin from ∼40 to 6 ka, with dry or very shallow conditions afterward. The fossil diatom stratigraphy and geochemical data (δ13C, δ15N, %Ca, C/N) indicate fluctuations in lake level from shallow to moderately deep, with the deepest conditions correlative with the Heinrich-1 and Younger Dryas events. The stratigraphy shows a continuous lake of variable depth and salinity during the last glacial maximum and latter stages of Marine Oxygen Isotope Stage 3 and is consistent with environmental inferences and the original chronology of a drill core from Salar de Uyuni.

Vegetation and climate history of Quebec’s mixed boreal forest suggests greater abundance of temperate species during the early- and mid-Holocene

Botany ◽  
2018 ◽  
Vol 96 (7) ◽  
pp. 437-448 ◽  
Author(s):  
Émilie Larochelle ◽  
Martin Lavoie ◽  
Pierre Grondin ◽  
Pierre-Luc Couillard
Keyword(s):  
Boreal Forests ◽  
Regional Scale ◽  
Plant Macrofossils ◽  
Habitat Characteristics ◽  
Temperate Species ◽  
White Pine ◽  
Yellow Birch ◽  
Climate History ◽  
History Of ◽  
Suitable Habitats

Today, scattered disjunct stands of two temperate species, yellow birch and white pine, are present north of their continuous distributional range in southern Quebec (Canada) at topographical locations that offer protection from severe fires. This study tested whether these species had populations more numerous and widespread millennia ago when the climate was presumably warmer. Specifically, this research involved the analyses of pollen, plant macrofossils, and charcoal fragments of two sites within the western part of Quebec’s balsam fir – paper birch bioclimatic domain: a forest humus deposit from a yellow birch stand (local scale), and a peatland (regional scale). Fossil data suggest that white pine was more abundant regionally between 7500 and 5000 cal. BP, before coming rare under subsequent cooler conditions. Likewise, yellow birch was more abundant regionally between 7700 and 1500 cal BP. Its subsequent decline and the local disappearance of white pine by ∼200 cal. BP may both be explained by the severe fires that occurred in recent centuries, as well as the rarity of suitable habitats for these species. The sustained presence of temperate species in mixed boreal forests is the result of the combined action of climate, natural disturbances and habitat characteristics.

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