scholarly journals Geochemical characteristics of the infilling of ground wedges at Puerto Deseado (Santa Cruz, Argentina): palaeoenvironmental and chronological implications

2018 ◽  
Vol 45 (2) ◽  
pp. 130 ◽  
Author(s):  
Giovanni Zanchetta ◽  
Adriano Ribolini ◽  
Matteo Ferrari ◽  
Monica Bini ◽  
Ilaria Isola ◽  
...  
Keyword(s):  
Late Quaternary ◽  
Volcanic Glass ◽  
Late Glacial ◽  
Major Elements ◽  
Chemical Analyses ◽  
The North ◽  
Xrd Patterns ◽  
Bulk Chemistry ◽  
Deseado Massif ◽  
Glass Shards

Ground wedge structures of cryogenic origin are common in the Quaternary sediments along the coast of the Patagonia, and their formation is related to climatic cold events experienced by this area in the Late Quaternary. The infilling sediments of two wedges generations were analyzed in the area of Puerto Deseado. Bulk chemistry (major elements), X-ray diffraction (XRD), morphoscopic observations with Scanning Electronic Microscope (SEM) and chemical analyses of volcanic glass shards were undertaken to provide indications about infilling sediment provenience, along with chronological constraint for wedge formation. Bulk chemistry and XRD patterns indicate a significant SiO2-enriched composition of the sediment infilling compared to the most of the loess deposits of the North Argentina and the present day dust originated in Patagonia. This was interpreted as due to the nature of the bedrock present over the Deseado Massif. SEM morphoscopic characteristics of glass shards evidence typical aeolian reworking features, with impact structures and indented edges of the volcanic fragments. Chemical analyses of the glass shards indicate that they were probably generated by the H0 eruption (17,300-17,400 cal yr BP) of the Hudson volcano. Volcanological data indicate that H0 eruption dispersed toward NE, but volcanic glasses were available for reworking due to a WNW component in the western wind direction. Over the Deseado Massif structural high the glass shards mixed with sediments enriched in SiO2, and were eventually deflated further to SE reaching the present coastal area and infilling the frost cracks. The age of the glass shards (17,300-17,400 cal yr BP) and that of the sandy layer affected by cryogenic structures (14,670±750 yr BP) well constrain to the Late Glacial both wedge generations.

scholarly journals Geochemical trends in central and western North Greenland

1987 ◽  
Vol 133 ◽  
pp. 123-132
Author(s):  
A Steenfelt
Keyword(s):  
Cross Sections ◽  
Sedimentary Environment ◽  
Distribution Patterns ◽  
Major Elements ◽  
Tectonic Activity ◽  
Chemical Analyses ◽  
The North ◽  
Platform Margin ◽  
Vein Type ◽  
North Greenland

Geochemical maps and geochemical cross-sections, based on chemical analyses of the < 0.1 mm fraction of stream sediment samples collected at a density of approximately 1 sample per 30 km2 in central and western North Greenland, show that the distribution patterns for the major elements and some trace elements reflect the main lithological units of the North Greenland Palaeozoic platform and trough. By contrast the distribution patterns for S and Sr are different. High S values are correlated with zones of tectonic activity and are thought to indicate migration of H2S along faults. High Sr values are correlated with evaporitic rocks in the platform sequence and with deep sea carbonates. High BaO values occurring along the Silurian platform margin and in the Ordovician platform-slope sequence are the result of Ba enrichment in the sedimentary environment, combined with epigenetic vein-type baryte mineralisation.

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.

A submerged late-Quaternary deposit at Roddans Port on the north-east coast of Ireland

1965 ◽  
Vol 249 (758) ◽  
pp. 221-255 ◽  
Keyword(s):  
Local Development ◽  
Late Quaternary ◽  
Algal Species ◽  
Late Glacial ◽  
Red Clay ◽  
Quaternary Deposit ◽  
Radiocarbon Dates ◽  
North East ◽  
The North ◽  
Pollen Analyses

Recent coastal erosion has cut into the filling of a former inter-drumlin lake and exposed an excellent sequence of Late-glacial deposits. These have been investigated by pollen analyses, identification of seeds, Mollusca, ostracods, and Algae; by stratigraphic studies and by radiocarbon dating. The coincidence of all this evidence strongly confirms that the greater part of the depositional sequence embraces the north-west European Late-glacial stages of the Older and Younger Dryas or Salix herbacea clays, with the intervening milder Allerod oscillation. This sequence is overlain by a small thickness of Post-glacial peat. The Late- and Post-glacial filling is shown to be sandwiched between deposits laid down during two phases of marine submergence; the earlier transgression is represented by a red marine clay which had a widespread occurrence on the Co. Down coast, and the later transgression is represented by the local development of the Postglacial raised beach. The pollen analyses from the close sampling of the organic Allerød phase muds have yielded unusually detailed data on vegetational conditions in the Late-glacial period. The radiocarbon dates, while fully confirming the age attribution, have not enough precision to give a close measure of the duration of the Allerød phase. The pollen evidence on vegetation and climate is augmented and clarified by identifications of seeds, shells, ostracods and Algae. The ostracods confirm the marine character of the early red clay, and freshwater shells were found in the overlying Allerød mud. The algal species from the Late-glacial layers have been compared with recent algal floras from Ireland, and with those found in Late- and Inter-glacial sediments elsewhere. The most notable feature is the prominence of species representative of a base-rich habitat.

A Late-Quaternary Pollen Record from Ka‘au Crater, O‘ahu, Hawai‘i

1999 ◽  
Vol 52 (1) ◽  
pp. 115-128 ◽  
Author(s):  
Sara Hotchkiss ◽  
James O. Juvik
Keyword(s):  
Last Glacial Maximum ◽  
Late Quaternary ◽  
Late Glacial ◽  
Glacial Maximum ◽  
Pollen Record ◽  
Forest Species ◽  
Subtropical Anticyclone ◽  
Last Glacial ◽  
Mesic Forest ◽  
The North

A pollen record from Ka‘au Crater, O‘ahu, Hawai‘i contains evidence for changes in vegetation and climate since about 28,000 14C yr B.P. Zone 1 (ca. 28,100–ca. 22,800 14C yr B.P.) has pollen of dry to mesic forest species, including Pipturus-type, Dodonaea viscosa, Acacia koa, Chenopodium oahuense, Claoxylon sandwicense, Myrsine, and Metrosideros-type. In zone 2 (ca. 22,800–ca. 16,200 14C yr B.P.) Myrsine and Coprosma increase, with herbs, fern allies, and Grammitidaceae suggesting open canopies. Zone 3 (ca. 16,200–ca. 9700 14C yr B.P.) has pollen of wet forest species, including Freycinetia arborea, abundant Pritchardia, and Metrosideros-type. Zone 4 (ca. 9700–ca. 7000 14C yr B.P.) is similar, with less Pritchardia and more Metrosideros-type.Climate reconstruction was based on modern climatic ranges of flowering plants and an index derived from abundance of pollen in surface samples. Both methods agree on a qualitative reconstruction, although the ages are poorly constrained: 28,000–25,000 14C yr B.P. cool and dry; 25,000–23,000 14C yr B.P. dry and warmer; 23,000–20,000 14C yr B.P. moderately dry with declining temperature; 20,000–16,000 14C yr B.P. moderately dry and cool; 16,000–9000 14C yr B.P. warm and wet; 9000–7000 14C yr B.P. warm and possibly drier. Lower precipitation at Ka‘au Crater during the late glacial period and last glacial maximum is consistent with the interpretation that the North Pacific subtropical anticyclone was south of its present position. The pollen-derived temperature index yields an estimate of 3°–5°C temperature depression during the last glacial maximum.

The Eyjafjallajökull AD 2010 eruption and the preservation of medium-sized eruptions in marine surface sediment offshore southern Iceland

2017 ◽  
Vol 87 (3) ◽  
pp. 386-406
Author(s):  
Christina Bonanati ◽  
Heidi Wehrmann ◽  
Maxim Portnyagin ◽  
Kaj Hoernle
Keyword(s):  
North Atlantic ◽  
Surface Sediment ◽  
Volcanic Glass ◽  
Volcanic Eruptions ◽  
Major Element Composition ◽  
Geochemical Fingerprinting ◽  
The North ◽  
Marine Surface ◽  
Glass Shards

AbstractThe recent volcanic eruptions of Eyjafjallajökull 2010 and Grímsvötn 2011 demonstrated the risks that mediumsized explosive Icelandic eruptions pose to the North Atlantic region. Using the Eyjafjallajökull 2010 eruption as a case study, we assess how traceable such eruptions are in the marine sedimentary record at medial distances from the source and investigate which factors have affected the particle transport to the marine sedimentary archive. During R/VPoseidoncruise 457, we recovered 13 box cores at 100–1600 m water depths and distances of 18–180 km southwest, south, and east of Iceland. Volcanic glass shards from the uppermost surface sediment were analyzed for their major element composition by electron microprobe and assigned to their eruptive source by geochemical fingerprinting. The predominantly basaltic particles are mostly derived from the Katla, Grímsvötn-Lakagígar, and Bárðarbunga-Veiðivötn volcanic systems. We also identified rhyolitic particles from the Askja 1875 and Öræfajökull 1362 eruptions. Only three out of almost 900 analyzed glass shards are derived from the recent Eyjafjallajökull 2010 eruption, suggesting that medium-sized eruptions are only poorly preserved in marine sediments located at medial distances southwest to east of Iceland. We conclude that the frequency of past medium-sized eruptions is likely higher than detectable in this archive.

scholarly journals Late-Glacial and Postglacial Vegetation and Climate of Jackson Hole and the Pinyon Peak Highlands, Wyoming

1987 ◽  
Vol 11 ◽  
pp. 55-59
Author(s):  
Cathy Barnosky
Keyword(s):  
Environmental Changes ◽  
Late Quaternary ◽  
Late Glacial ◽  
Ice Age ◽  
Plant Migration ◽  
Critical Gap ◽  
Long Term Stability ◽  
The North ◽  
Jackson Hole ◽  
Central Rocky Mountains

The objective of this study has been to describe the late-Quaternary vegetation of the Jackson Hole region and vicinity in order to clarify the nature and composition of ice-age communities, the rate and direction of plant migration during the recession of glaciers from the region, and the long-term stability of communities in the Park to environmental changes in the postglacial period. This information is necessary to assess the sensitivity of the Park's communities to environmental change and fill a critical gap in our understanding of the vegetational, climatic, and glacial history of the north-central Rocky Mountains as a whole.

A palynological investigation of true-moss (Bryidae) spores: morphology and occurrence in modern and late Quaternary lake sediments of Alaska

1998 ◽  
Vol 76 (12) ◽  
pp. 2145-2157 ◽  
Author(s):  
L B Brubaker ◽  
P M Anderson ◽  
B M Murray ◽  
D Koon
Keyword(s):  
Boreal Forest ◽  
Late Quaternary ◽  
Late Glacial ◽  
North Slope ◽  
Wall Structure ◽  
Herbarium Specimens ◽  
Glacial Sediments ◽  
The North ◽  
True Moss ◽  
Southwestern Alaska

This study describes (i) spore morphology of 121 Alaskan species of true moss (Bryidae) and (ii) percentages of Bryidae and Sphagnum spores in mud-water interface samples from 46 Alaskan lakes and a late-Quaternary sediment core from Idavain Lake in southwestern Alaska. Bryidae spores were collected from herbarium specimens, prepared by standard palynological chemical treatment and described under light microscopy. An identification key based on spore shape, wall structure, and size recognized 11 major morphological groups. Although family, genus, or species identifications were not possible for most groups, spores of a few genera and species were distinctive. Bryidae spores occurred in 80% of the modern sediment samples, representing boreal forest and three areas of tundra (North Slope, Seward Peninsula, and southwestern Alaska). Bryidae and Sphagnum spore percentages showed greatest differences between the North Slope tundra and other vegetation types, whereas pollen percentages distinguished boreal forest from tundra regions as a group. Bryidae spores were present throughout the Idavain Lake record but were most common in late-glacial sediments. Variations in the abundance of Bryidae spores are consistent with or enhance paleoenvironmental interpretations based on pollen and other spore types.Key words: Bryidae, palynology, spores, Alaska, Quaternary, paleoenvironment.

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.

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.

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