scholarly journals LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from <sup>10</sup>Be surface exposure dating

2007 ◽  
Vol 3 (3) ◽  
pp. 839-869 ◽  
Author(s):  
R. Zech ◽  
Ch. Kull ◽  
P. W. Kubik ◽  
H. Veit
Keyword(s):  
North Atlantic ◽  
Late Quaternary ◽  
Late Glacial ◽  
Tropical Andes ◽  
Surface Exposure Dating ◽  
Exposure Dating ◽  
The North ◽  
Innovative Tool ◽  
Cordillera Real ◽  
Exposure Ages

Abstract. Surface exposure dating (SED) is an innovative tool being already widely applied for moraine dating and for Late Quaternary glacier and climate reconstruction. Here we present exposure ages of 28 boulders from the Cordillera Real and the Cordillera Cochabamba, Bolivia. Our results indicate that the local Last Glacial Maximum (LGM) in the Eastern Cordilleras occurred at ~22–25 ka and thus synchronous to the global temperature minimum. We were also able to date several Late Glacial moraines to ~11–13 ka, which likely document lower temperatures and increased precipitation ("Coipasa" humid phase). Additionally, we recognize the existence of older Late Glacial moraines re-calculated to ~15 ka from published cosmogenic nuclide data. Those may coincide with the cold Heinrich 1 event in the North Atlantic region and the pronounced "Tauca" humid phase. We conclude that (i) exposure ages in the tropical Andes may have been substantially overestimated so far due to methodological uncertainties, and (ii) although precipitation plays an important role for glacier mass balances in the tropical Andes, it becomes the dominant forcing for glaciation only in the drier and thus more precipitation-sensitive regions further west and south.

scholarly journals LGM and Late Glacial glacier advances in the Cordillera Real and Cochabamba (Bolivia) deduced from <sup>10</sup>Be surface exposure dating

2007 ◽  
Vol 3 (4) ◽  
pp. 623-635 ◽  
Author(s):  
R. Zech ◽  
Ch. Kull ◽  
P. W. Kubik ◽  
H. Veit
Keyword(s):  
North Atlantic ◽  
Late Quaternary ◽  
Late Glacial ◽  
Tropical Andes ◽  
Surface Exposure Dating ◽  
Exposure Dating ◽  
The North ◽  
Innovative Tool ◽  
Cordillera Real ◽  
Exposure Ages

Abstract. Surface exposure dating (SED) is an innovative tool already being widely applied for moraine dating and for Late Quaternary glacier and climate reconstruction. Here we present exposure ages of 28 boulders from the Cordillera Real and the Cordillera Cochabamba, Bolivia. Our results indicate that the local Last Glacial Maximum (LGM) in the Eastern Cordilleras occurred at ~22–25 ka and was thus synchronous to the global temperature minimum. We were also able to date several Late Glacial moraines to ~11–13 ka, which likely document lower temperatures and increased precipitation ("Coipasa" humid phase). Additionally, we recognize the existence of older Late Glacial moraines re-calculated to ~15 ka from published cosmogenic nuclide data. Those may coincide with the cold Heinrich 1 event in the North Atlantic region and the pronounced "Tauca" humid phase. We conclude that (i) exposure ages in the tropical Andes may have been overestimated so far due to methodological uncertainties, and (ii) although precipitation plays an important role for glacier mass balances in the tropical Andes, it becomes the dominant forcing for glaciation only in the drier and thus more precipitation-sensitive regions farther west and south.

Late Quaternary glaciation of the Tianshan, Central Asia, using cosmogenic 10Be surface exposure dating

2009 ◽  
Vol 72 (2) ◽  
pp. 229-233 ◽  
Author(s):  
Ping Kong ◽  
David Fink ◽  
Chunguang Na ◽  
Feixin Huang
Keyword(s):  
Electron Spin Resonance ◽  
Central Asia ◽  
Late Quaternary ◽  
Glacial Retreat ◽  
Surface Exposure Dating ◽  
Exposure Dating ◽  
Quaternary Glaciation ◽  
Spin Resonance ◽  
Cosmogenic 10Be ◽  
Exposure Ages

AbstractGlacial deposits are present at the head of the Ürümqi River valley, Tianshan, Central Asia. 10Be surface exposure ages of 15 boulders from three sites along a 12 km valley transect range from 9 to 21 ka suggesting emplacement by glacial retreat and advance commencing at the global last glacial maximum (LGM) and most likely abating in the early Holocene. Although the age spread for a given locality is not small, perhaps indicating post-depositional reworking, maximum ages per site are either coeval with or are post-LGM and inconsistent with previous pre-LGM electron spin resonance ages.

Cosmogenic Cl-36 surface exposure dating of late Quaternary glacial events in the Cordillera de Talamanca, Costa Rica

2019 ◽  
Vol 92 (1) ◽  
pp. 216-231 ◽  
Author(s):  
Rebecca Potter ◽  
Yingkui Li ◽  
Sally P. Horn ◽  
Kenneth H. Orvis
Keyword(s):  
Costa Rica ◽  
Late Quaternary ◽  
Age Dating ◽  
Complete Disappearance ◽  
Surface Exposure Dating ◽  
Exposure Dating ◽  
Glacial Chronology ◽  
Tropical America ◽  
Exposure Ages ◽  
Cordillera De Talamanca

AbstractGeomorphic evidence of past glaciation, such as U-shaped valleys, aretes, glacial lakes, and moraines, is preserved in the highland surrounding Cerro Chirripó in the Cordillera de Talamanca, Costa Rica. Previous work to establish a glacial chronology has focused on relative age dating of moraines and on radiocarbon dating of basal lake sediments to infer the timing of deglaciation. We used cosmogenic 36Cl surface exposure dating to constrain the ages of moraines within two formerly glaciated valleys, the Morrenas and Talari valleys. Forty-nine boulder samples were processed and measured from four moraine complexes in the Morrenas Valley and two moraine complexes in the Talari Valley. The exposure ages of these samples indicate a major glacial event occurred in this area from ~25 to 23 ka, broadly synchronous with the global last glacial maximum. Our results also indicate periods of glacial retreats and standstills from the deglacial period to the Early Holocene (~16–10 ka) before the complete disappearance of glaciers in this highland. These findings provide important insights into the glacial chronology and paleoclimate of tropical America.

Late Quaternary glacial chronology on Nevado Illimani, Bolivia, and the implications for paleoclimatic reconstructions across the Andes

2011 ◽  
Vol 75 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Colby A. Smith ◽  
Thomas V. Lowell ◽  
Lewis A. Owen ◽  
Marc W. Caffee
Keyword(s):  
Late Quaternary ◽  
Marked Change ◽  
Late Glacial ◽  
Eastern Cordillera ◽  
The Andes ◽  
Western Cordillera ◽  
Glacial Chronology ◽  
The Pacific ◽  
Cordillera Real ◽  
Exposure Ages

Abstract10Be terrestrial cosmogenic nuclide surface exposure ages from moraines on Nevado Illimani, Cordillera Real, Bolivia suggest that glaciers retreated from moraines during the periods 15.5–13.0 ka, 10.0–8.5 ka, and 3.5–2.0 ka. Late glacial moraines at Illimani are associated with an ELA depression of 400–600 m, which is consistent with other local reconstructions of late glacial ELAs in the Eastern Cordillera of the central Andes. A comparison of late glacial ELAs between the Eastern Cordillera and Western Cordillera indicates a marked change toward flattening of the east-to-west regional ELA gradient. This flattening is consistent with increased precipitation from the Pacific during the late glacial period.

Synchronization of late-glacial vegetation changes at Crystal Lake, Illinois, USA with the North Atlantic Event Stratigraphy

2009 ◽  
Vol 72 (2) ◽  
pp. 234-245 ◽  
Author(s):  
Leila M. Gonzales ◽  
Eric C. Grimm
Keyword(s):  
North Atlantic ◽  
Late Quaternary ◽  
Ice Core ◽  
Late Glacial ◽  
Vegetation Changes ◽  
Pollen Record ◽  
Climate Conditions ◽  
The North ◽  
Event Stratigraphy ◽  
The North Atlantic

AbstractLate-glacial (17–11 cal ka BP) pollen records from midwestern North America show similar vegetation trends; however, poor dating resolution, wide-interval pollen counts, and variable sedimentation rates have prevented the direct correlation with the North Atlantic Event Stratigraphy as represented in the Greenland ice-core records, thus preventing the understanding of the teleconnections and mechanisms of late-Quaternary events in the Northern Hemisphere. The widespread occurrence of late-glacial vegetation and climates with no modern analogs also hinders late-glacial climate reconstructions. A high-resolution pollen record with a well-controlled age model from Crystal Lake in northeastern Illinois reveals vegetation and climate conditions during the late-glacial and early Holocene intervals. Late-glacial Crystal Lake pollen assemblages, dominated by Picea mariana and Fraxinus nigra with lesser amounts of Abies and Larix, suggest relatively wet climate despite fluctuations between colder and warmer temperatures. Vegetation changes at Crystal Lake are coeval with millennial-scale trends in the NGRIP ice-core record, but major shifts in vegetation at Crystal Lake lag the NGRIP record by 300–400 yr. This lag may be due to the proximity of the Laurentide ice sheet, the ice sheet's inherent slowness in response to rapid climate changes, and its effect on frontal boundary conditions and lake-effect temperatures.

scholarly journals Timing and extent of late pleistocene glaciation in the arid Central Andes of Argentina and Chile (22°-41°S)

2017 ◽  
Vol 43 (2) ◽  
pp. 697 ◽  
Author(s):  
J. Zech ◽  
C. Terrizzano ◽  
E. García-Morabito ◽  
H. Veit ◽  
R. Zech
Keyword(s):  
Southern Oscillation ◽  
Co2 Concentration ◽  
Late Glacial ◽  
Central Andes ◽  
The North ◽  
Eastern Equatorial Pacific ◽  
Southern Central ◽  
Study Sites ◽  
Increasing Temperature ◽  
Exposure Ages

The arid Central Andes are a key site to study changes in intensity and movement of the three main atmospheric circulation systems over South America: the South American Summer Monsoon (SASM), the Westerlies and the El Niño Southern Oscillation (ENSO). In this semi-arid to arid region glaciers are particularly sensitive to precipitation changes and thus the timing of past glaciation is strongly linked to changes in moisture supply. Surface exposure ages from study sites between 41° and 22°S suggest that glaciers advanced: i) prior to the global Last Glacial Maximum (gLGM) at ~40 ka in the mid (26°- 30°S) and southern Central Andes (35°-41°S), ii) in phase with the gLGM in the northern and southern Central Andes and iii) during the late glacial in the northern Central Andes. Deglaciation started synchronous with the global rise in atmospheric CO2 concentration and increasing temperature starting at ~18 ka. The pre-gLGM glacial advances likely document enhanced precipitation related to the Southern Westerlies, which shifted further to the North at that time than previosuly assumed. During the gLGM glacial advances were favored by decreased temperatures in combination with increased humidity due to a southward shifted Intertropical Convergence Zone (ITCZ) and SASM. During the late-glacial a substantial increase in moisture can be explained by enhanced upper tropospheric easterlies as response to an intensified SASM and sustained La Niña-like conditions over the eastern equatorial Pacific that lead to glacial advances in the northern Central Andes and the lake level highstand Tauca (18-14 ka) on the Altiplano. In the southernmost Central Andes at 39º-41°S, further north at 31°S and in the northernmost Central Andes at 22°S glacial remnants even point to precipitation driven glaciations older than ~115 ka and 260 ka.

scholarly journals The Distal and Local Volcanic Ash in the Late Pleistocene Sediments of the Termination I Interval at the Reykjanes Ridge, North Atlantic, Based on the Study of the Core AMK-340

Geosciences ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 379
Author(s):  
Matul ◽  
Gablina ◽  
Khusid ◽  
Libina ◽  
Mikhailova
Keyword(s):  
North Atlantic ◽  
Volcanic Ash ◽  
Late Quaternary ◽  
Central Zone ◽  
Younger Dryas ◽  
Quaternary Sediments ◽  
Reykjanes Ridge ◽  
Volcanic Material ◽  
The North ◽  
Russian Research

We made the geochemical analysis of the volcanic material from the sediment core AMK-340 (the Russian research vessel “Akademik Mstislav Keldysh” station 340), the central zone of the Reykjanes Ridge. Two ash-bearing sediment units within the interval of the Termination I can be detected. They correlate with the Ash Zone I in the North Atlantic Late Quaternary sediments having an age of 12,170–12,840 years within the Younger Dryas cold chronozone and 13,600–14,540 years within the Bølling–Allerød warm chronozone. The ash of the Younger Dryas unit is presented mostly by the mafic and persilicic material originated from the Icelandic volcanoes. One sediment sample from this unit contained Vedde Ash material. The ash of the Bølling–Allerød unit is presented mostly by the mafic shards which are related to the basalts of the rift zone on the Reykjanes Ridge, having presumably local origin. Possible detection of Vedde Ash could help to specify the timing of the previously reconstructed paleoceanographic changes for the Termination I in the point of the study: significant warming in the area might have occurred as early as 300 years before the end of the conventional Younger Dryas cold chronozone.

Progressive glacial retreat in the Southern Altiplano (Uturuncu volcano, 22°S) between 65 and 14 ka constrained by cosmogenic 3He dating

2014 ◽  
Vol 82 (1) ◽  
pp. 209-221 ◽  
Author(s):  
Pierre-Henri Blard ◽  
Jérôme Lave ◽  
Kenneth A. Farley ◽  
Victor Ramirez ◽  
Nestor Jimenez ◽  
...  
Keyword(s):  
Late Pleistocene ◽  
Late Glacial ◽  
Glacial Period ◽  
Tropical Andes ◽  
Equilibrium Line Altitude ◽  
Glacial Retreat ◽  
Late Glacial Period ◽  
Cold Episode ◽  
Glacial Landforms ◽  
Exposure Ages

AbstractThis work presents the first reconstruction of late Pleistocene glacier fluctuations on Uturuncu volcano, in the Southern Tropical Andes. Cosmogenic 3He dating of glacial landforms provides constraints on ancient glacier position between 65 and 14 ka. Despite important scatter in the exposure ages on the oldest moraines, probably resulting from pre-exposure, these 3He data constrain the timing of the moraine deposits and subsequent glacier recessions: the Uturuncu glacier may have reached its maximum extent much before the global LGM, maybe as early as 65 ka, with an equilibrium line altitude (ELA) at 5280 m. Then, the glacier remained close to its maximum position, with a main stillstand identified around 40 ka, and another one between 35 and 17 ka, followed by a limited recession at 17 ka. Then, another glacial stillstand is identified upstream during the late glacial period, probably between 16 and 14 ka, with an ELA standing at 5350 m. This stillstand is synchronous with the paleolake Tauca highstand. This result indicates that this regionally wet and cold episode, during the Heinrich 1 event, also impacted the Southern Altiplano. The ELA rose above 5450 m after 14 ka, synchronously with the Bolling–Allerod.

Stratigraphy and timing of eolianite deposition on Rottnest Island, Western Australia

2003 ◽  
Vol 60 (2) ◽  
pp. 211-222 ◽  
Author(s):  
Paul J. Hearty
Keyword(s):  
North Atlantic ◽  
Late Quaternary ◽  
The West ◽  
Oxygen Isotope Stage ◽  
Amino Acid Racemization ◽  
Marine Deposits ◽  
The North ◽  
The North Atlantic ◽  
Radiometric Ages ◽  
Mis 5E

AbstractOver 100 whole-rock amino acid racemization (AAR) ratios from outcrops around Rottnest Island (32.0° S Latitude near Perth) indicate distinct pulses of eolian deposition during the late Quaternary. Whole-rock d-alloisoleucine/l-isoleucine (A/I) ratios from bioclastic carbonate deposits fall into three distinct modal classes or “aminozones.” The oldest, Aminozone E, averages 0.33 ± 0.04 (n = 21). Red palaeosol and thick calcrete generally cap the Aminozone E deposits. A younger Aminozone C averages 0.22 ± 0.03 (n = 63); comprising two submodes at 0.26 ± 0.01 (n = 14) and 0.21 ± 0.02 (n = 49). Multiple dune sets of this interval are interrupted by relatively weak, brown to tan “protosols.” A dense, dark brown rendzina palaeosol caps the Aminozone C succession. Ratios from Holocene dune and marine deposits (“Aminozone A”) center on 0.11 ± 0.02 (n = 15), comprising submodes of 0.13 ± 0.01 (9) and 0.09 ± 0.01 (6). Calibration of A/I averages from Aminozones E and A are provided by U/Th and 14C radiometric ages of 125,000 yr (marine oxygen isotope stage (MIS) 5e and 2000–6000 14C yr B.P. (MIS 1), respectively. The whole-rock A/I results support periodic deposition initiated during MIS 5e, continuing through MIS 5c, and then peaking at the end of MIS 5a, about 70,000–80,000 yr ago. Oceanographic evidence indicates the area was subjected to much colder conditions during MIS 2–4 (10,000 to 70,000 yr ago), greatly slowing the epimerization rate. Eolianite deposition resumed in the mid Holocene (∼6000 yr ago) up to the present. The A/I epimerization pathway constructed from Rottnest Island shows remarkable similarity to that of Bermuda in the North Atlantic (32° N Latitude). These findings suggest that, like Bermuda, the eolian activity on Rottnest occurred primarily during or shortly after interglacial highstands when the shoreline was near the present datum, rather than during glacial lowstands when the coastline was positioned 10–20 km to the west.

Variability of Monsoon Climate in East Asia at the End of the Last Glaciation

1996 ◽  
Vol 46 (3) ◽  
pp. 219-229 ◽  
Author(s):  
Zhou Weijian ◽  
Douglas J. Donahue ◽  
Stephen C. Porter ◽  
Timothy A. Jull ◽  
Li Xiaoqiang ◽  
...  
Keyword(s):  
North Atlantic ◽  
Asian Monsoon ◽  
East Asian Monsoon ◽  
Climatic Variability ◽  
Late Glacial ◽  
Proxy Records ◽  
The North ◽  
Last Glaciation ◽  
Eolian Sand ◽  
Dry Conditions

High-resolution paleomonsoon proxy records from peat and eolian sand–paleosol sequences at the desert–loess transition zone in China denote a rapid oscillation from cold–dry conditions (11,200–10,600 14C yr B.P.) to cool–humid conditions (10,600–10,200 14C yr B.P.), followed by a return to cold–dry climate (10,200–10,000 14C yr B.P.). Variations in precipitation proxies suggest that significant climatic variability occurred in monsoonal eastern Asia during the Younger Dryas interval. Late-glacial climate in the Chinese desert–loess belt that lies downwind from Europe was strongly influenced by cold air from high latitudes and from the North Atlantic via the westerlies. The inferred precipitation variations were likely caused by variations in the strength of the Siberian high, which influenced the pressure gradient between land and ocean and therefore influenced the position of the East Asian monsoon front.

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