scholarly journals The (mis)conception of average Quaternary conditions

2021 ◽  
pp. 1-6
Author(s):  
Matteo Spagnolo ◽  
Brice R. Rea ◽  
Iestyn Barr
Keyword(s):  
Landscape Evolution ◽  
Middle Pleistocene ◽  
Extreme Caution ◽  
The Past ◽  
Isotope Record ◽  
Middle Pleistocene Transition ◽  
Clear Change

Abstract The concept of Quaternary average conditions has gained popularity over the past few decades, especially with studies of long-term landscape evolution. In this paper, we critically assess this concept by analyzing the marine isotope record (LR04 δ18O stack) relative to the Quaternary. This shows that the frequency and amplitude of climate glacial-interglacial cycles are not constant throughout the Quaternary, with a clear change during the Middle Pleistocene Transition (MPT), and that many minor oscillations exist within each cycle. For this reason, the identification of pre- and post-MPT most-frequent and, cumulatively, longest-lasting (rather than average) conditions is recommended. The most-frequent pre-MPT δ18O value of 3.725 ± 0.025‰ last occurred during 11.31–11.47 ka, while the most-frequent post-MPT δ18O value of 4.475 ± 0.025‰ last occurred during 14.81–15.04 ka. However, many other δ18O values were almost as frequent throughout the Quaternary and we present geomorphological reasons as to why it is unlikely that the present-day landscape reflects Quaternary average or, indeed, most-frequent conditions. Collectively, our results indicate that extreme caution should be taken when attempting to infer long-term landscape evolution processes (including the buzzsaw hypothesis) based on average Quaternary conditions.

scholarly journals Persistent influence of obliquity on ice age terminations since the Middle Pleistocene transition

Science ◽  
2020 ◽  
Vol 367 (6483) ◽  
pp. 1235-1239 ◽  
Author(s):  
Petra Bajo ◽  
Russell N. Drysdale ◽  
Jon D. Woodhead ◽  
John C. Hellstrom ◽  
David Hodell ◽  
...  
Keyword(s):  
North Atlantic ◽  
North Atlantic Ocean ◽  
Radiometric Dating ◽  
Ice Age ◽  
Middle Pleistocene ◽  
Interglacial Period ◽  
The Past ◽  
Middle Pleistocene Transition ◽  
High Phase ◽  
Age Estimates

Radiometric dating of glacial terminations over the past 640,000 years suggests pacing by Earth’s climatic precession, with each glacial-interglacial period spanning four or five cycles of ~20,000 years. However, the lack of firm age estimates for older Pleistocene terminations confounds attempts to test the persistence of precession forcing. We combine an Italian speleothem record anchored by a uranium-lead chronology with North Atlantic ocean data to show that the first two deglaciations of the so-called 100,000-year world are separated by two obliquity cycles, with each termination starting at the same high phase of obliquity, but at opposing phases of precession. An assessment of 11 radiometrically dated terminations spanning the past million years suggests that obliquity exerted a persistent influence on not only their initiation but also their duration.

scholarly journals Early-Middle Pleistocene Beheading of the River Thames

2007 ◽  
Vol 51 (3) ◽  
pp. 327-336 ◽  
Author(s):  
Colin A. Whiteman ◽  
James Rose
Keyword(s):  
Climate Change ◽  
Recent Work ◽  
Landscape Evolution ◽  
Middle Pleistocene ◽  
Glacial Erosion ◽  
Quaternary Period ◽  
Quaternary Climate ◽  
River Capture ◽  
River Thames

ABSTRACT This paper marks the centenary of the first of three articles by W.M. Davis on the beheading of the Thames, beginning with a statement of his capture hypothesis in 1895 and concluding with attempts to explain anomalous misfit streams in 1899 and 1909. It discusses Davis's classic thesis of river capture by slow, long-term landscape evolution and his apparent reluctance to accept the fact of rapid Quaternary climate change. In contrast, recent work based on lithostratigraphy, biostratigraphy and morphostratigraphy emphasises the dynamism of the Quaternary Period and its influence on river capture. Possible mechanisms for the beheading of the Thames, tectonism, glacial erosion and conventional Davisian river capture, and the timing of the event, are discussed. In conclusion, the paper summarises known and unknown components of the problem of the beheading of the Thames, and discusses the extent of Davis's influence on later Thames studies.

scholarly journals The “missing glaciations” of the Middle Pleistocene

2020 ◽  
Vol 96 ◽  
pp. 161-183 ◽  
Author(s):  
Philip D. Hughes ◽  
Philip L. Gibbard ◽  
Jürgen Ehlers
Keyword(s):  
High Amplitude ◽  
Middle Pleistocene ◽  
Volume Changes ◽  
The West ◽  
Feedback Mechanisms ◽  
West Antarctic Ice Sheet ◽  
Ice Volume ◽  
West Antarctic ◽  
Middle Pleistocene Transition

AbstractGlobal glaciations have varied in size and magnitude since the Early–Middle Pleistocene transition (~773 ka), despite the apparent regular and high-amplitude 100 ka pacing of glacial–interglacial cycles recorded in marine isotope records. The evidence on land indicates that patterns of glaciation varied dramatically between different glacial–interglacial cycles. For example, Marine Isotope Stages (MIS) 8, 10, and 14 are all noticeably absent from many terrestrial glacial records in North America and Europe. However, globally, the patterns are more complicated, with major glaciations recorded in MIS 8 in Asia and in parts of the Southern Hemisphere, such as Patagonia, for example. This spatial variability in glaciation between glacial–interglacial cycles is likely to be driven by ice volume changes in the West Antarctic Ice Sheet and associated interhemispheric connections through ocean–atmosphere circulatory changes. The weak global glacial imprint in some glacial–interglacial cycles is related to the pattern of global ice buildup. This is caused by feedback mechanisms within glacial systems themselves that partly result from long-term orbital changes driven by eccentricity.

scholarly journals Long-term landscape evolution of the Molise sector of the central-southern Apennines, Italy

2017 ◽  
Vol 68 (1) ◽  
pp. 29-42 ◽  
Author(s):  
Vincenzo Amato ◽  
Pietro P.C. Aucelli ◽  
Vito Bracone ◽  
Massimo Cesarano ◽  
Carmen Maria Rosskopf
Keyword(s):  
Late Pleistocene ◽  
Landscape Evolution ◽  
Temporal Distribution ◽  
Structural Data ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Southern Apennines ◽  
Geomorphological Evolution ◽  
Present Setting

AbstractThis paper concerns the reconstruction of the main stages of the long-term landscape evolution of the Molise portion of the central-southern Apennines along a transect divided into three sectors (SW, Central and NE). Analysis mainly focused on geomorphological, stratigraphical and structural data supported by chronological constraints, coming from an overall review of past literature and several studies carried out by the authors of the paper during the last 20 years. The results obtained allowed the elaboration of a conceptual model of the long-term evolution of the Molise sector of the central-southern Apennines. Starting from the Pliocene, the emersion of the Molise area occurred gradually from SW to NE, allowing a polycyclic landscape to evolve under the major controls first of compression then transtensional to extensional tectonics as well as climatic variations. Principal markers of the Quaternary geomorphological evolution of the Molise area are represented by the infill successions of the intermontane tectonic depressions located in its internal, SW sector and by four orders of palaeosurfaces that developed between the Early Pleistocene and the beginning of the Late Pleistocene across the region. These markers testify to the alternation of phases of substantial tectonic stability and uplift whose spatial-temporal distribution could be assessed along the investigated transect. Results highlight that the most important stages of landscape evolution occurred during the Early and Middle Pleistocene. At the beginning of the Late Pleistocene, the Molise sector of the Apennine chain had already reached its present setting and further landscape evolution occurred under the major control of climate and land-use.

scholarly journals Incomplete similarity of the ice-climate system

2021 ◽  
Author(s):  
Mikhail Verbitsky
Keyword(s):  
Climate System ◽  
Middle Pleistocene ◽  
Physical Processes ◽  
Physical Similarity ◽  
Future Scenario ◽  
The Past ◽  
Proxy Records ◽  
Climate Evolution ◽  
Incomplete Similarity ◽  
Middle Pleistocene Transition

Abstract. Reconstruction and explanation of past climate evolution using proxy records is the essence of paleoclimatology. In this study, we use dimensional analysis and concepts of similarity to recognize theoretical limits of such forensic inquiries. Specifically, we demonstrate that incomplete similarity in the dynamical ice-climate system implies the absence of physical similarity in conglomerate similarity parameters. It means that major events of the past such as, for example, the middle-Pleistocene transition could have been produced by different physical processes, and, therefore, the task of disambiguation of the historical paleo-records may be fundamentally difficult, if not impossible. It also means that any future scenario may not have a unique cause and, in this sense, the orbital time-scale future may be to some extent insensitive to specific physical circumstances.

The middle Pleistocene transition: characteristics, mechanisms, and implications for long-term changes in atmospheric pCO2

2006 ◽  
Vol 25 (23-24) ◽  
pp. 3150-3184 ◽  
Author(s):  
Peter U. Clark ◽  
David Archer ◽  
David Pollard ◽  
Joel D. Blum ◽  
Jose A. Rial ◽  
...  
Keyword(s):  
Middle Pleistocene ◽  
Long Term Changes ◽  
Middle Pleistocene Transition ◽  
Atmospheric Pco2

Estimating the style and duration of former glaciation in the mountains of Britain and Ireland

2020 ◽  
Author(s):  
Iestyn Barr ◽  
Jeremy Ely ◽  
Matteo Spagnolo ◽  
Ian Evans ◽  
Matt Tomkins
Keyword(s):  
Landscape Evolution ◽  
Ice Core ◽  
Balance Model ◽  
Glacial Cycle ◽  
Regional Variability ◽  
Model Driven ◽  
The Past ◽  
Simple Mass ◽  
Core Project

<p>With a view to better understanding landscape evolution, we model the style and duration of former mountain glaciation in Britain and Ireland during the Quaternary (i.e., the past 2.6 Ma). We use a simple mass balance model, driven by published temperature depression data from the Greenland Ice Core Project (for the past 120 ka), and from a benthic δ18O stack (for the Quaternary as a whole). Though there are limitations to this approach, results provide first-order estimates and indicate that during the Quaternary as a whole, the mountains of Britain and Ireland were glacier-free for 1.1 ± 0.5 Ma; occupied by small (cirque) glaciers for 0.3 ± 0.2 Ma; and occupied by large glaciers for 1.1 ± 0.4 Ma. During the most recent glacial cycle specifically (i.e., the last 120 ka), these areas were glacier-free for an average of 52.0 ± 21.2 ka; occupied by small (cirque) glaciers for 16.2 ± 9.9 ka; and occupied by large glaciers, including ice sheets, for 51.8 ± 18.6 ka. Here, we investigate some of the regional variability in these estimates, and consider implications for long-term landscape evolution.</p>

scholarly journals The "Shackleton Site" (IODP Site U1385) on the Iberian Margin

2013 ◽  
Vol 16 ◽  
pp. 13-19 ◽  
Author(s):  
D. A. Hodell ◽  
L. Lourens ◽  
D. A. V. Stow ◽  
J. Hernández-Molina ◽  
C. A. Alvarez Zarikian ◽  
...  
Keyword(s):  
Climate Variability ◽  
Ice Cores ◽  
Middle Pleistocene ◽  
Ocean Drilling Program ◽  
Integrated Ocean Drilling Program ◽  
Oxygen Isotope Record ◽  
Isotope Record ◽  
Middle Pleistocene Transition ◽  
Iberian Margin ◽  
Millennial Scale

Abstract. Nick Shackleton's research on piston cores from the Iberian margin highlighted the importance of this region for providing high-fidelity records of millennial-scale climate variability, and for correlating climate events from the marine environment to polar ice cores and European terrestrial sequences. During the Integrated Ocean Drilling Program (IODP) Expedition 339, we sought to extend the Iberian margin sediment record by drilling with the D/V JOIDES Resolution. Five holes were cored at Site U1385 using the advanced piston corer (APC) system to a maximum depth of ~155.9 m below sea floor (m b.s.f.). Immediately after the expedition, cores from all holes were analyzed by core scanning X-ray fluorescence (XRF) at 1 cm spatial resolution. Ca/Ti data were used to accurately correlate from hole-to-hole and construct a composite spliced section, containing no gaps or disturbed intervals to 166.5 m composite depth (mcd). A low-resolution (20 cm sample spacing) oxygen isotope record confirms that Site U1385 contains a continuous record of hemipelagic sedimentation from the Holocene to 1.43 Ma (Marine Isotope Stage 46). The sediment profile at Site U1385 extends across the middle Pleistocene transition (MPT) with sedimentation rates averaging ~10 cm kyr−1. Strong precession cycles in colour and elemental XRF signals provide a powerful tool for developing an orbitally tuned reference timescale. Site U1385 is likely to become an important type section for marine–ice–terrestrial core correlations and the study of orbital- and millennial-scale climate variability.

Enabling Community Well-being Self-Monitoring in the Context of Mining: The Naskapi Nation of Kawawachikamach

2016 ◽  
Vol 1 (2) ◽  
Author(s):  
Robert Klinck ◽  
Ben Bradshaw ◽  
Ruby Sandy ◽  
Silas Nabinacaboo ◽  
Mannie Mameanskum ◽  
...  
Keyword(s):  
Indigenous Peoples ◽  
Well Being ◽  
Aboriginal Community ◽  
Self Monitoring ◽  
Community Engaged Research ◽  
The Past ◽  
Mineral Development ◽  
Iron Deposits ◽  
Term Monitoring

The Naskapi Nation of Kawawachikamach is an Aboriginal community located in northern Quebec near the Labrador Border. Given the region’s rich iron deposits, the Naskapi Nation has considerable experience with major mineral development, first in the 1950s to the 1980s, and again in the past decade as companies implement plans for further extraction. This has raised concerns regarding a range of environmental and socio-economic impacts that may be caused by renewed development. These concerns have led to an interest among the Naskapi to develop a means to track community well-being over time using indicators of their own design. Exemplifying community-engaged research, this paper describes the beginning development of such a tool in fall 2012—the creation of a baseline of community well-being against which mining-induced change can be identified. Its development owes much to the remarkable and sustained contribution of many key members of the Naskapi Nation. If on-going surveying is completed based on the chosen indicators, the Nation will be better positioned to recognize shifts in its well-being and to communicate these shifts to its partners. In addition, long-term monitoring will allow the Naskapi Nation to contribute to more universal understanding of the impacts of mining for Indigenous peoples.

Courting the Youth Vote in 2008: The Obama Effect

2009 ◽  
Vol 5 ◽  
Author(s):  
Lindsey C Bohl
Keyword(s):  
Presidential Elections ◽  
Voter Registration ◽  
The Internet ◽  
The Past ◽  
Several Variables ◽  
High Turnout ◽  
Short And Long Term ◽  
Use Of The Internet ◽  
Youth Vote

This paper examines a few of the numerous factors that may have led to increased youth turnout in 2008 Election. First, theories of voter behavior and turnout are related to courting the youth vote. Several variables that are perceived to affect youth turnout such as party polarization, perceived candidate difference, voter registration, effective campaigning and mobilization, and use of the Internet, are examined. Over the past 40 years, presidential elections have failed to engage the majority of young citizens (ages 18-29) to the point that they became inclined to participate. This trend began to reverse starting in 2000 Election and the youth turnout reached its peak in 2008. While both short and long-term factors played a significant role in recent elections, high turnout among youth voters in 2008 can be largely attributed to the Obama candidacy and campaign, which mobilized young citizens in unprecedented ways.

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