Beschreibung: Publication date: 15 July 2018 Source: Quaternary Science Reviews, Volume 192

Beschreibung: Publication date: 15 July 2018 Source: Quaternary Science Reviews, Volume 192 Author(s): G.T.H. Jenkins, G.A.T. Duller, H.M. Roberts, R.C. Chiverrell, N.F. Glasser In recent years luminescence dating has increasingly been applied to date glaciofluvial sediments, but uncertainties about the degree of bleaching of the luminescence signal at deposition make dating of such sediments challenging. Here we test a new approach for luminescence dating of glaciofluvial sediments, based on the analysis of rock cores drilled from granite cobbles, and compare the luminescence ages generated against independent age control. Luminescence measurements from rock slices in cobble-sized clasts can be used to reconstruct the extent of bleaching, thereby giving greater confidence in the ages produced. This study illustrates that another important advantage of using cobbles is that at depths of 2 mm or more below the cobble surface >90% of the total dose rate arises from the cobble itself, making the dose rate insensitive to the water content of the sediment matrix. Ordinarily, uncertainties in estimating water content during burial are one of the largest sources of uncertainty in luminescence dating methods, and hence reducing the reliance upon the dose rate could be particularly advantageous for glacial deposits, where water contents can potentially be large and highly variable. Measurements of cobbles from Orrisdale Head, Isle of Man, demonstrate that the luminescence signal was completely bleached to depths of up to 12 mm into the cobble. Sampling of orientated cobbles from lithofacies diagnostic of bar-top environments was used to maximise the chances of exposure to sunlight. The upper-faces of these orientated cobble surfaces appear to be bleached to a greater depth than the lowermost faces. Data from 45 rock slices from these cobbles were tightly clustered, yielding a mean age of 20.7 ± 0.3 ka that is in agreement with independent age control. One of the well-bleached cobbles shows evidence of two discrete exposure events, potentially recording both the advance at 26.2 ± 0.8 ka, and retreat at 20.7 ± 0.3 ka, of the Irish Sea Ice Stream.

Beschreibung: Publication date: 1 August 2018 Source: Quaternary Science Reviews, Volume 193 Author(s): Kantapon Suraprasit, Hervé Bocherens, Yaowalak Chaimanee, Somsak Panha, Jean-Jacques Jaeger Paleoecological and paleoclimatic records based on the stable isotopes of mammalian tooth enamel are poorly known in mainland Southeast Asia during the Pleistocene. Khok Sung in Northeastern Thailand is a late Middle Pleistocene terrace deposit, tentatively dated either as 213 ka or 188 ka, yielding 15 described mammalian taxa with especially abundant and complete fossil remains. To investigate paleodiets and habitats of these ancient mammals and to understand the corresponding regional climate, we performed an analysis of stable carbon and oxygen isotopes extracted from tooth enamel carbonate of various mammalian taxa, coupled with the cenogram method. The enamel δ 13 C values of Khok Sung mammals indicate a variety of diets, ranging from pure C 3 to C 4 plants, suggesting that C 4 grasses were a major component of local Thai ecosystems during the late Middle Pleistocene. The stable isotopic distinction between C 3 and C 4 plants suggests that the Pleistocene wildlife habitats ranged from closed forests to open grasslands for the Khok Sung area. Moreover, differences within sympatric Pleistocene herbivores such as proboscideans, rhinoceroses, and cervids characterize possible niche partitioning by minimizing interspecific overlap. Paleoclimatic interpretations based on the intra-tooth variability in enamel δ 18 O values from large mammals and on the cenogram analysis reflect significant seasonal variations in precipitation and temperature, and humid conditions, for the Khok Sung locality. Compared to modern environments in Thailand, it is apparent that C 4 -dominated grasslands were more widespread at that time when anthropic impacts on the ecosystems were presumably absent or minimal.

Beschreibung: Publication date: 15 July 2018 Source: Quaternary Science Reviews, Volume 192 Author(s): Jia Deng, Zhaohua Wu, Min Zhang, Norden E. Huang, Shizhu Wang, Fangli Qiao Astronomical forcing (obliquity and precession) has been thought to modulate Dansgaard-Oeschger (DO) events, yet the detailed quantification of such modulations has not been examined. In this study, we apply the novel Holo-Hilbert Spectral Analysis (HHSA) to five polar ice core records, quantifying astronomical forcing's time-varying amplitude modulation of DO events and identifying the preferred obliquity phases for large amplitude modulations. The unique advantages of HHSA over the widely used windowed Fourier spectral analysis for quantifying astronomical forcing's nonlinear modulations of DO events is first demonstrated with a synthetic data that closely resembles DO events recorded in Greenland ice cores (NGRIP, GRIP, and GISP2 cores on GICC05 modelext timescale). The analysis of paleoclimatic proxies show that statistically significantly more frequent DO events, with larger amplitude modulation in the Greenland region, tend to occur in the decreasing phase of obliquity, especially from its mean value to its minimum value. In the eastern Antarctic, although statistically significantly more DO events tend to occur in the decreasing obliquity phase in general, the preferred phase of obliquity for large amplitude modulation on DO events is a segment of the increasing phase near the maximum obliquity, implying that the physical mechanisms of DO events may be different for the two polar regions. Additionally, by using cross-spectrum and magnitude-squared analyses, Greenland DO mode at a timescale of about 1400 years leads the Antarctic DO mode at the same timescale by about 1000 years. Graphical abstract

Beschreibung: Publication date: 1 July 2018 Source: Quaternary Science Reviews, Volume 191

Beschreibung: Publication date: 15 July 2018 Source: Quaternary Science Reviews, Volume 192 Author(s): Daryl Fedje, Duncan McLaren, Thomas S. James, Quentin Mackie, Nicole F. Smith, John R. Southon, Alexander P. Mackie A refined relative sea level (RSL) history spanning the past 14,300 calendar years is described for the Quadra Island area in the northern Strait of Georgia on the Pacific coast of Canada. Here marine shorelines dating to the time of earliest post-glacial emergence are at least 197 m above present-day sea-level at 14,300 years ago. RSL fell rapidly, reaching two to three metres above present-day by 12,000 years ago. A series of raised marine terraces at ca. 4, 10 and 30 m above present day high tide level suggest the rapid fall in RSL during early post-glacial time may have been briefly interrupted by factors such as regional ice advances and recessions and global meltwater pulses generated by climatic variations. A possible minor sea-level transgression of 1–2 m around 12,000 to 11,400 years ago was followed by slow regression to modern levels. This sea-level reconstruction is providing critical input for efficient discovery and cataloging of late Pleistocene and early Holocene archaeological sites on ancient raised shorelines in the region. Integration of the sea-level history with LiDAR imagery has proven successful in locating a number of archaeological sites on these ancient shorelines.

Beschreibung: Publication date: 15 July 2018 Source: Quaternary Science Reviews, Volume 192 Author(s): Xia Wang, Yi-Feng Yao, Alexandra H. Wortley, Hui-Jie Qiao, Stephen Blackmore, Yu-Fei Wang, Cheng-Sen Li The Younger Dryas (YD) is one of the most abrupt climatic events in Earth's recent history. The warming at the end of the YD, in particular, is considered to be comparable to the global warming seen in the 21 st century. However, the YD termination has received little attention, particularly in the Hengduan Mountains of Southwestern China, a low latitude temperate biodiversity hotspot. Here we present evidence for a rapid response in the diversity and composition of vegetation to the warming at the YD termination, based on a continuous, well-dated pollen sequence and loss-on-ignition data (12.9–9.2 cal. ka BP) from Haligu wetland in the Hengduan Mountains. Our data indicate that variations in plant diversity were correlated with relative humidity during this period, and suggest a distinct shift from Pinus-Abies-Picea forest to Pinus -dominated forest at the YD-Holocene transition, accompanied by an increase in coverage of generally temperate taxa such as Salix and Betula . This finding provides insights that may be of relevance to biodiversity conservation under future warming scenarios in similar mountain ecosystems worldwide. Graphical abstract

Beschreibung: Publication date: 15 July 2018 Source: Quaternary Science Reviews, Volume 192 Author(s): Mohammed Allan, Adrien Deliège, Sophie Verheyden, Samuel Nicolay, Yves Quinif, Nathalie Fagel We present a decadal-centennial scale Holocene climate record based on trace elements contents from a 65 cm stalagmite from Belgian Père Noël cave. “Père Noël” (PN) stalagmite covers the last 12.7 ka according to U/Th dating. High spatial resolution measurements of trace elements (Sr, Ba and Mg) were done by Laser-Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Trace elements profiles were interpreted as environmental and climate changes in the Han-sur-Lesse region. Power spectrum estimators and continuous wavelet transform were applied on trace elements time series to detect any statistically significant periodicities in the PN stalagmite. Spectral analyses reveal decadal to millennial periodicities (i.e., 68–75, 133–136, 198–209, 291–358, 404–602, 912–1029 and 2365–2670 yr) in the speleothem record. Results were compared to reconstructed sunspot number data to determine whether solar signal is presents in PN speleothem. The occurrence of significant solar periodicities (i.e., cycles of Gleissberg, de Vries, unnamed 500 years, Eddy and Hallstatt) supports for an impact of solar forcing on PN speleothem trace element contents. Moreover, several intervals of significant rapid winter change were detected during the Holocene at 10.3, 9.3–9.5, around 8.2, 6.4–6.2, 4.7–4.5, and around 2.7 ka BP. Those intervals are similar to the cold winter events evidenced in different natural paleoclimate archives, suggesting common climate forcing mechanisms related to changes in solar irradiance.

Beschreibung: Publication date: 15 July 2018 Source: Quaternary Science Reviews, Volume 192 Author(s): Thijs van Kolfschoten, Alexey S. Tesakov, Christopher J. Bell The Beringian Land Bridge is a well-documented dispersal corridor between the Eurasian continent and North America. Episodic sub-aerial exposure of the land bridge during the Late Cenozoic resulted from climatic oscillations and concomitant lowering of sea level. For much of the Pleistocene, dispersal was predominantly west-to-east (e.g., from Eurasia to North America), but a new discovery of the North American rodent Phenacomys from deeply buried sediments in The Netherlands documents an Early Pleistocene east-to-west invasion. The discovery reinforces earlier suggestive hints of an integrated Holarctic mammal fauna in the Early Pleistocene and provides a unique opportunity to establish a direct correlation of the classic mammal zonations of Europe and North America. Phenacomys is traditionally conceptualized as an endemic North American radiation of voles, and all extant taxa are exclusively North American. The first European remains of Phenacomys were recovered as part of the Zuurland Drilling Project from earliest Pleistocene (ca, 2.3–2.1 Ma) strata. The specimens were found in stratigraphic association with species that are well-known from more southern European assemblages of Early Pleistocene age, but also with contemporaneous taxa traditionally associated with more northern latitudes. The recognition of Phenacomys within the Zuurland assemblage demonstrates that the Bering Land Bridge served as a corridor for dispersal of mammal species during the earliest Pleistocene, and served as a physiographic mechanism for the integration of a circumpolar biogeographic province at that time.

Beschreibung: Publication date: 15 July 2018 Source: Quaternary Science Reviews, Volume 192 Author(s): Hazel Reade, Tamsin C. O'Connell, Graeme Barker, Rhiannon E. Stevens Oxygen isotope analysis (δ 18 O) of caprine and bovine tooth enamel carbonates from the Haua Fteah cave (Gebel Akhdar massif, northeast Libya) reveals significant differences in palaeoseasonality during the last c. 70 ka. Data indicate different phases of human occupation of the region occurred under notably different climatic conditions. During the last glacial period, prior to the Last Glacial Maximum, a gradual increase in climate aridity occurred. This was followed in the late glacial (c. 16.6–14.7 ka) by considerably more arid conditions and much greater climate seasonality, which was likely produced by changing winter precipitation amounts and a strengthening of arid summer air masses. The high seasonality in the late glacial coincides with a period when human activity at the Haua Fteah greatly intensified. Significant changes in subsistence strategies and the seasonal exploitation of food resources also occurred at this time. The results presented here suggest that changes in the seasonal climate may have affected the seasonal supply of floral and faunal resources available to local human populations at the time, which resulted in changing subsistence practices.