scholarly journals Μελέτη των μικροθηλαστικών των τεταρτογενών αποθέσεων του σπηλαίου Α των Λουτρών Αλμωπίας Πέλλας

2013 ◽  
Author(s):  
Αικατερίνη Χατζοπούλου
Keyword(s):  
Last Glacial Maximum ◽  
Younger Dryas ◽  
Glacial Maximum ◽  
Lepus Timidus ◽  
Arvicola Terrestris ◽  
Last Glacial

Στην παρούσα διατριβή μελετήθηκαν τα μικρά θηλαστικά από δύο θέσεις του Σπηλαίου Λουτρών Αλμωπίας. Πρόκειται για έναν απολιθωματοφόρο ορίζοντα στα ιζήματα του δαπέδου του σπηλαίου (θέση LAC) και έναν ορίζοντα που βρίσκεται σε υπερυψωμένο θάλαμο (θέση LAC Ia). Μετά από λεπτομερή ανασκαφική διαδικασία και επεξεργασία των ιζημάτων βρέθηκε πληθώρα δοντιών και οστών μικροθηλαστικών. O προσδιορισμός βασίστηκε στα μορφολογικά και μετρικά χαρακτηριστικά 3209 δειγμάτων. Συνολικά προσδιορίστηκαν 30 διαφορετικά είδη μικροθηλαστικών, εκ των οποίων 29 είδη (8 Εντομοφάγα, 19 τρωκτικά, 2 λαγόμορφα) στη θέση LAC και 26 είδη (6 Εντομοφάγα, 17 τρωκτικά, 3 λαγόμορφα) στη θέση LAC Ia. Επτά από τα είδη που βρέθηκαν στο σπήλαιο Λουτρών Αλμωπίας προσδιορίζονται για πρώτη φορά σε απολιθωμένες πανίδες της Ελλάδας και άλλα επτά είδη δεν αναφέρονται στη σύγχρονη πανίδα της Ελλάδας. Οι πανίδες LAC και LAC Ia χρονολογούνται ως νεότερες της τελευταίας μεσοπαγετώδους περιόδου Riss-Würm από την παρουσία του Arvicola terrestris και παλαιότερες του Ολοκαίνου από την παρουσία του Ochotona pusilla. Ειδικότερα, η πανίδα LAC μπορεί να είναι σύγχρονη ή λίγο νεότερη της πανίδας των μεγάλων θηλαστικών του δαπέδου του σπηλαίου αντιπροσωπεύοντας το Μέσο Würm ως Last Glacial Maximum, ενώ η πανίδα LAC Ia είναι νεότερη αντιπροσωπεύοντας το Younger Dryas. Η σύνθεση των πανίδων LAC και LAC Ia φανερώνει ότι έζησαν σε περιπαγετώδεις συνθήκες, πιο ήπιες από τις τυπικές των Άλπεων κατά την τελευταία παγετώδη περίοδο. Η σύγκριση των ποσοστών συμμετοχής των ειδών δείχνει ότι η πανίδα LAC έζησε σε θερμότερες συνθήκες από την πανίδα LAC Ia. Η παρουσία του Lepus timidus στο θάλαμο LAC Ia σχετίζεται με το μέγιστο ψύχος στο τέλος της τελευταίας Παγετώδους περιόδου και αποτελεί τη νοτιότερη καταγραφή του είδους στην Ευρώπη. Από τις περιβαλλοντικές προτιμήσεις των ειδών που μελετήθηκαν προκύπτει ότι στην ευρύτερη περιοχή υπήρχαν κωνοφόρα και φυλλοβόλα δάση, λειμώνες και αρκετές συγκεντρώσεις νερού. Το κλίμα ήταν ξηρότερο από το σημερινό. Η ταφονομική μελέτη έδειξε ότι τα μικροθηλαστικά των δύο πανίδων αποτέλεσαν τη λεία θηρευτών (μπούφου, πετρίτη και κάποιου σαρκοφάγου θηλαστικού) και συγκεντρώθηκαν μέσα στο σπήλαιο με pellets ή περιττώματα του θηρευτή και τη δράση του νερού. Η μελέτη των ιζημάτων έδειξε ότι πρόκειται για ποτάμιες αποθέσεις με εμφανή επεισόδια έντονων υδραυλικών συνθηκών που αποτέθηκαν κοντά στην πηγή προέλευσής τους.

Cosmogenic nuclide constraints on late Quaternary glacial chronology on the Dalijia Shan, northeastern Tibetan Plateau

2013 ◽  
Vol 79 (3) ◽  
pp. 439-451 ◽  
Author(s):  
Jie Wang ◽  
Christine Kassab ◽  
Jonathan M. Harbor ◽  
Marc W. Caffee ◽  
Hang Cui ◽  
...  
Keyword(s):  
Tibetan Plateau ◽  
Last Glacial Maximum ◽  
Younger Dryas ◽  
Glacial Maximum ◽  
The Tibetan Plateau ◽  
Last Glacial ◽  
Cosmogenic Nuclide ◽  
Mis 3 ◽  
Northeastern Tibetan Plateau ◽  
Exposure Ages

AbstractCosmogenic nuclide (CN) apparent exposure dating has become a widely used method for determining the age of glacial landforms on the Tibetan Plateau with > 1200 published ages. We present the first 10Be exposure ages from the Dalijia Shan, the most northeastern formerly glaciated mountain range on the Tibetan Plateau. The moraine groups identified from field and remote sensing imagery mapping record four glacial events at 37.07 ± 3.70 to 52.96 ± 4.70 ka (MIS 3), 20.17 ± 1.79 to 26.99 ± 2.47 ka (MIS 2), 16.92 ± 1.49 to 18.76 ± 1.88 ka (MIS 2), and 11.56 ± 1.03 to 11.89 ± 1.06 ka (Younger Dryas). These ages indicate that glaciation in the northeastern Tibetan Plateau is much younger than previously thought. In addition, this record is consistent with many other regions on the Tibetan Plateau, with a local last glacial maximum during MIS 3 asynchronous with Northern Hemisphere last glacial maximum during MIS 2. The Dalijia Shan might also include an event of Younger Dryas age, but this needs to be tested in future studies.

Last-glacial-maximum North Atlantic deep water: on, off or somewhere in-between?

1995 ◽  
Vol 348 (1324) ◽  
pp. 243-253 ◽  
Keyword(s):  
Last Glacial Maximum ◽  
North Atlantic ◽  
Deep Water ◽  
Younger Dryas ◽  
Glacial Maximum ◽  
Nutrient Concentrations ◽  
Last Glacial ◽  
The North ◽  
The North Atlantic ◽  
Intermediate Waters

Various papers have been published during the past decade concerning Last Glacial Maximum (LGM) North Atlantic Deep Water (NADW) flow. Using somewhat different methods, they have produced somewhat contradictory results. This review considers both apparent and real conflicts concerning the data and their interpretation, and attempts to resolve them. Despite the earlier (contradictory) interpretations, currently there is a widespread belief that nutrient concentrations in deep cores from the North Atlantic increased during glacial times and that concentrations in the upper-deep and intermediate waters decreased at least slightly. It is also clear that further north in the basin (particularly at upper-deep and intermediate depths), nutrient concentrations were as low or perhaps even lower than those seen today. Data from the Caribbean Sea, ventilated by intermediate waters through an approximately 1800 m sill, indicate that lower nutrient levels were also found at intermediate depths in the North and Tropical Atlantic; this data is supported by continental margin data. The recontoured 8 13 C data of Duplessy et al. ( Paleoceanography 3, 343—360 (1988)) remain a valid expression of the broadscale LGM Atlantic nutrient distribution. Data from the South Atlantic has been the most contradictory to date, but recent 8 13 c evidence from a low-productivity South Atlantic site supports Cd data indicating a relative stability in the nutrient chemistry of waters that are presently influenced by low-nutrient NADW. Sedimentary 231 Pa/ 230 Th data appear to require the continued export of Atlantic-generated 231 Pa from the Atlantic into the Southern Ocean. Finally, radiocarbon evidence from paired planktonic/benthic foraminifera indicates that the ventilation time of the North Atlantic remained low and that the ventilation time of the entire ocean did not change much beyond the uncertainty of the 14 C data. Taken together, this evidence suggests that the NADW became ‘Glacial North Atlantic Deep/Intermediate Water’ (GNAIDW) during glacial times, with perhaps a greater flux through intermediate waters than currently combined with a lesser flux through deeper waters. Although one cannot say much with confidence about the total GNAIDW flux, the data are consistent with a persistent but perhaps somewhat diminished role for NADW in the global thermohaline circulation during glacial times. A review of recent evidence concerning the response of the deep North Atlantic during the Younger Dryas concludes that there is no inconsistency between the new evidence and the occurence of a Younger Dryas NADW event in the deep western North Atlantic.

scholarly journals Climate-induced speleothem radiocarbon variability on Socotra Island from the Last Glacial Maximum to the Younger Dryas

2020 ◽  
Vol 16 (1) ◽  
pp. 409-421
Author(s):  
Steffen Therre ◽  
Jens Fohlmeister ◽  
Dominik Fleitmann ◽  
Albert Matter ◽  
Stephen J. Burns ◽  
...  
Keyword(s):  
Soil Carbon ◽  
Carbon Cycling ◽  
Last Glacial Maximum ◽  
Younger Dryas ◽  
Glacial Maximum ◽  
Last Glacial ◽  
Soil Carbon Cycling ◽  
Socotra Island ◽  
The Last Glacial Maximum ◽  
The Last Glacial

Abstract. In this study, the dead carbon fraction (DCF) variations in stalagmite M1-5 from Socotra Island in the western Arabian Sea were investigated through a new set of high-precision U-series and radiocarbon (14C) dates. The data reveal an extreme case of very high and also climate-dependent DCF. For M1-5, an average DCF of 56.2±3.4 % is observed between 27 and 18 kyr BP. Such high DCF values indicate a high influence of aged soil organic matter (SOM) and nearly completely closed-system carbonate dissolution conditions. Towards the end of the last glacial period, decreasing Mg∕Ca ratios suggest an increase in precipitation which caused a marked change in the soil carbon cycling as indicated by sharply decreasing DCF. This is in contrast to the relation of soil infiltration and DCF as seen in stalagmites from temperate zones. For Socotra Island, which is influenced by the East African–Indian monsoon, we propose that more humid conditions and enhanced net infiltration after the Last Glacial Maximum (LGM) led to dense vegetation and thus lowered the DCF by increasing 14CO2 input into the soil zone. At the onset of the Younger Dryas (YD) a sudden change in DCF towards much higher, and extremely variable, values is observed. Our study highlights the dramatic variability of soil carbon cycling processes and vegetation feedback on Socotra Island manifested in stalagmite DCF on both long-term trends and sub-centennial timescales, thus providing evidence for climate influence on stalagmite radiocarbon. This is of particular relevance for speleothem studies that aim to reconstruct past atmospheric 14C (e.g., for the purposes of 14C calibration), as these would rely on largely climate-independent soil carbon cycling above the cave.

Reconstructing Last Glacial Maximum and Younger Dryas paleolandscapes through subsurface paleosol stratigraphy: An example from the Po coastal plain, Italy

Geomorphology ◽  
2017 ◽  
Vol 295 ◽  
pp. 790-800 ◽  
Author(s):  
Agnese Morelli ◽  
Luigi Bruno ◽  
David M. Cleveland ◽  
Tina M. Drexler ◽  
Alessandro Amorosi
Keyword(s):  
Last Glacial Maximum ◽  
Coastal Plain ◽  
Younger Dryas ◽  
Glacial Maximum ◽  
Last Glacial
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