Middle Pleistocene Climate Change Recorded in Fossil Mammal Teeth from Tarija, Bolivia, and Upper Limit of the Ensenadan Land-Mammal Age

2000 ◽  
Vol 54 (1) ◽  
pp. 121-131 ◽  
Author(s):  
Bruce J. MacFadden
Keyword(s):  
Middle Pleistocene ◽  
Carbon Isotopic ◽  
Upper Limit ◽  
Pleistocene Climate ◽  
Oxygen Isotope Record ◽  
Isotope Record ◽  
Pleistocene Climate Change ◽  
Age Limits ◽  
Pattern Of Variation ◽  
Land Mammal

Fossiliferous middle Pleistocene sediments of the Tarija basin of southern Bolivia contain a classic Ensenadan land-mammal fauna. New carbon isotopic data reported here for 50 specimens of the grazing mammals Equus (horse) and Cuvieronius (mastodon), documented from eight stratigraphic levels at Tarija, vary significantly in the δ13C values of their teeth. The pattern of variation appears to reflect the proportion of C3 and C4 grasses eaten during colder (more C3) and warmer (more C4) times. Within age limits set by associated magnetostratigraphy, the cold periods can be correlated with particular even-numbered stages in the marine oxygen-isotope record, and the warm periods can be correlated with odd-numbered stages. The oldest fossil teeth analyzed from the Tarija section can thereby be assigned to stage 29, and the youngest to stages 17 or 15, that is; the teeth range in age from about 1.1 myr to as young as 0.7 myr. Based on correlation of the upper part of the Tarija beds to the isotopic stages, the upper limit of the Ensenadan land-mammal age is between 0.7 and 0.6 myr, which is younger than stated in most previous studies.

Hominid colonisation and the Lower and Middle Palaeolithic of the West Midlands

2005 ◽  
Vol 71 ◽  
pp. 63-83 ◽  
Author(s):  
A.T.O. Lang ◽  
D.H. Keen
Keyword(s):  
Raw Materials ◽  
Middle Pleistocene ◽  
The West ◽  
Oxygen Isotope Record ◽  
West Midlands ◽  
Early Humans ◽  
Isotope Record ◽  
The University ◽  
Palaeolithic Archaeology ◽  
New Time

The recognition over the last 20 years that the Quaternary deposits of the West Midlands cover a longer period of time than previously envisaged has led to a re-analysis of their contained Palaeolithic archaeology. Stone tools have been found in the region for over a hundred years and cover most periods of hominid colonisation from the time of the earliest occupants of the country over half a million years ago. Twentieth century research in the West Midlands, often led by Professor F. W. Shotton at the University of Birmingham, correlated the Palaeolithic of the region with the Quaternary geological sequence as it was then understood. Shotton identified the ‘Wolstonian’ glaciation as the key event of the Midlands Pleistocene, around which a chronology for the Palaeolithic could be built and gave an age of less than 250 kyr for this episode. Work since 1985 has compared the Midlands sequence with the oxygen isotope record of the ocean basins and shown that the concept of a relatively recent ‘Wolstonian’ is now untenable and that the former chronology built around it is too short for the observed events in the area. This new time paradigm, with the earliest occupation of the area thought to be c. 500 kyr, has made necessary a reconsideration of the chronology of the Palaeolithic and Middle Pleistocene of the area. This new time framework brings into critical focus the issue of reworking of the archaeology and its true age. The tools themselves present complications of analysis compared to many other areas containing a Palaeolithic record, perhaps most notably through the use of largely non-flint raw materials, some which may have been introduced into the area by early humans or an hither-to unidentified glacial event. This opportunity to present a new chronology of occupation comes out of the work carried out by the ‘Shotton Project’ based at the University of Birmingham, and by the University of Liverpool.

Middle Pleistocene age of the Nome River glaciation, northwestern Alaska

1991 ◽  
Vol 36 (3) ◽  
pp. 277-293 ◽  
Author(s):  
Darrell S. Kaufman ◽  
Robert C. Walter ◽  
Julie Brigham-Grette ◽  
David M. Hopkins
Keyword(s):  
Middle Pleistocene ◽  
Laser Fusion ◽  
Basaltic Lava ◽  
Last Interglacial ◽  
Oxygen Isotope Record ◽  
Isotope Record ◽  
Order Of Magnitude ◽  
Nearshore Sediments ◽  
The Mean ◽  
Basaltic Lava Flow

AbstractDuring the middle Pleistocene Nome River glaciation of northwestern Alaska, glaciers covered an area an order of magnitude more extensive than during any subsequent glacial intervals. The age of the Nome River glaciation is constrained by laser-fusion 40Ar/39Ar analyses of basaltic lava that overlies Nome River drift at Minnie Creek, central Seward Peninsula, that average 470,000 ± 190,000 yr (±1σ). Milligram-size subsamples of the lava were dated to identify and eliminate extraneous 40Ar enrichments that rendered the mean of conventional K-Ar dates on larger bulk samples of the same flow too old (700,000 ± 570,000 yr). While the 40Ar/39Ar analyses provide a minimum limiting age for the Nome River glaciation, maximum ages are provided by a provisional K-Ar date on a basaltic lava flow that underlies the Nome River drift at nearby Lave Creek, by paleomagnetic determinations of the drift itself at and near the type locality, and by amino acid epimerization analysis of molluscan fossils from nearshore sediments of the Anvilian marine transgression that underlie Nome River drift on the coastal plain at Nome. Taken together, the new age data indicate that the glaciation took place between 580,000 and 280,000 yr ago. The altitude of the Anvilian deposits suggests that eustatic sea level during the Anvilian transgression rose at least as high as and probably higher than during the last interglacial transgression; by correlation with the marine oxygen-isotope record, the transgression probably dates to stage 11 at 410,000 yr, and the Nome River glaciation is younger still. Analyses of floor altitudes of presumed Nome River cirques indicate that the Nome River regional snowline depression was at least twice that of the maximum late Wisconsin. The cause of the enhanced snowline lowering appears to be related to greater availability of moisture in northwestern Alaska during the middle Pleistocene.

Stable carbon and oxygen isotope record in the Paleogene La Meseta Formation, Seymour Island, Antarctica

1992 ◽  
Vol 4 (4) ◽  
pp. 461-468 ◽  
Author(s):  
Andrzej Gaździcki ◽  
Michał Gruszczyński ◽  
Antoni Hoffman ◽  
Krzysztof Małkowski ◽  
Sergio A. Marenssi ◽  
...  
Keyword(s):  
Middle Part ◽  
Weddell Sea ◽  
Stable Carbon ◽  
Carbon Isotopic ◽  
Early Oligocene ◽  
Oxygen Isotope Record ◽  
Carbon And Oxygen Isotope ◽  
La Meseta Formation ◽  
Isotope Record ◽  
Oxygen Isotopic

Stable carbon and oxygen isotopic relations have been analysed in brachiopod, gastropod, and bivalve fossils from the La Meseta Formation (Eocene-?early Oligocene), Seymour (Marambio) Island, West Antarctica. The results indicate a shift in δ13C by 6 permil beginning in the middle part of the Unit II of the formation. This shift may imply a change from a largely stratified to a vigorously mixed ocean. Such an interpretation is corroborated by changes in the elemental proportions in the shell material. Alternatively, the carbon isotopic shift may be regarded as reflecting a change in the local depositional enviornment. Such an interpretation agrees with isotopic data from the Weddell Sea, which do not confirm the pattern observed in the La Meseta Formation. In any event, the oxygen isotopic curve does not decline parallel to the carbon curve and may thus imply a considerable climatic cooling event. This effect is so profound that it might be interpreted as evidence for glaciation, especially when taking into account the fact that this phenomenon coincides with the well-known cooling trend throughout the Eocene. If this interpretation is correct, the hypothesized Glaciation may possibly be correlated with the Polonez Glaciation, the largest Cenozoic glaciation known in the Antarctic Peninsula sector. Alternatively, it may be regarded as a local phenomenon, predating development of the icesheet.

Middle Pleistocene Climate Change in the Colorado Rocky Mountains Indicated by Fossil Mammals from Porcupine Cave

1994 ◽  
Vol 41 (3) ◽  
pp. 366-375 ◽  
Author(s):  
David L. Wood ◽  
Anthony D. Barnosky
Keyword(s):  
Solar Radiation ◽  
Rocky Mountains ◽  
Middle Pleistocene ◽  
Temperature Extremes ◽  
Seasonal Precipitation ◽  
Seasonal Temperature ◽  
Pleistocene Climate ◽  
Glacial Stage ◽  
Pleistocene Climate Change ◽  
Colorado Rocky Mountains

AbstractFossiliferous sediments from The Pit Locality in Porcupine Cave, Park County, Colorado, span multiple glacial and interglacial cycles between ca. 800,000 and 400,000 yr B.P. at 2900 m elevation. The uppermost cycle probably represents oxygenisotope glacial Stage 12 (stratigraphic Levels 4 and 3) and interglacial Stage 11 (Levels 3, 2, and 1) as determined by arvicoline biostratigraphic data that place the sequence between 487,000 and 365,000 yr B.P. A no-analog assemblage comprising the bog lemming Mictomys meltoni (of the M. borealis lineage) and the sagebrush vole Lemmiscus curtatus (=Lagurus curtatus) characterizes both the glacial and the interglacial deposits. Climatographs for these two species suggest that, compared to present conditions, the following local climatic limits can be imposed on oxygenisotope Stages 12 and 11: (1) January effective moisture was greater, resulting from average temperatures of at least 5°C cooler and/or at least 15 mm more precipitation; (2) January solar radiation was lower by at least 75 Langleys; (3) effective July solar radiation might have been lower by at least 50 Langleys. Seasonal temperature extremes were not necessarily different from those of the present, but seasonal precipitation was more equable. Relative abundance of mammal taxa and sedimentological data indicate that aridity increased at the onset of the interglacial.

scholarly journals A Paleoclimatic Model of the Mid-Pleistocene Climate Transition

1990 ◽  
Vol 14 ◽  
pp. 47-50
Author(s):  
G. Deblonde ◽  
W.R. Peltier
Keyword(s):  
Ice Sheet ◽  
Feedback Mechanism ◽  
Ice Volume ◽  
Ice Load ◽  
The Earth ◽  
Pleistocene Climate ◽  
Oxygen Isotope Record ◽  
Isotope Record ◽  
Climate Transition ◽  
Time Lead

A one-dimensional time-dependent ice-sheet model is employed to simulate ice-volume variations throughout the Pleistocene epoch of Earth history. The model is based upon the explicitly-described physics of ice-sheet accumulation and flow and the physics of the viscoeleastic relaxation of the Earth under the weight of the ice load. The model of the viscoelastic relaxation of the Earth incorporates the vertical variation of density and viscosity of its interior in great detail. An abrupt variation of some of the parameters that govern the height of the ice-sheet equilibrium line, and a gradual increase in the strength of a generalized feedback mechanism that is turned on after mid-Pleistocene time, lead to simulation of ice volume that has the general features of observed δ18O records, in particular the new high-resolution oxygen-isotope record from site ODP 677 (Peltier and others, 1989).

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.

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