scholarly journals New Chronological Constraints from Hypogean Deposits for Late Pliocene to Recent Morphotectonic History of the Alpi Apuane (NW Tuscany, Italy)

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 65
Author(s):  
Ilaria Isola ◽  
Francesco Mazzarini ◽  
Giancarlo Molli ◽  
Leonardo Piccini ◽  
Elena Zanella ◽  
...  
Keyword(s):  
Radiometric Dating ◽  
Early Pleistocene ◽  
Late Pliocene ◽  
Mountain Ranges ◽  
Fluvial Deposits ◽  
Fine Grained ◽  
Base Level ◽  
Cave System ◽  
Cave Sediments ◽  
History Of

A sedimentary sequence of fluvial deposits preserved in the Corchia Cave (Alpi Apuane) provides new chronological constraints for the evolution of the cave system and the timing and rate of uplift of this sector of the Alpi Apuane since the late Pliocene. Supported by magnetostratigraphic analysis performed on fine-grained fluvial deposits, and by radiometric dating of speleothems, we suggest that the deposition of fluvial sediments occurred between ~1.6–1.2 Ma. This implies that the host volume of rock was already located close to the local base level, adding key information about the recent tectonic evolution of the Alpi Apuane. A few before ~1 Ma, an erosive phase occurred due to the base-level lowering, followed by continuous speleothem deposition since at least 0.97 Ma. From that time, Monte Corchia uplifted at a maximum rate of ~0.5 mm/year, which is consistent with isostatic uplift mainly driven by erosional unloading. The petrographical study of the fluvial deposits highlights the presence of material derived from the erosion of rocks that today are absent in the cave’s catchment area, suggesting a different surface morphology during the Early Pleistocene. This study highlights the potential of cave sediments as archives for reconstructing the uplift history of mountain ranges.

scholarly journals Cosmogenic burial dating of in cave-deposited alluvium: unravelling long-term incision rates and complex speleogenesis in multi-level cave systems

2020 ◽  
Author(s):  
Gilles Rixhon ◽  
Didier L. Bourlès ◽  
Régis Braucher ◽  
Alexandre Peeters ◽  
Alain Demoulin
Keyword(s):  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Fluvial Terrace ◽  
Base Level ◽  
Cave System ◽  
River Incision ◽  
Order Of Magnitude ◽  
History Of ◽  
Multi Level

<p>Multi-level cave systems record the history of regional river incision in abandoned alluvium-filled phreatic passages which, mimicking fluvial terrace sequences, represent former phases of fluvial base-level stability. In this respect, cosmogenic burial dating of in cave-deposited alluvium (usually via the nuclide pair <sup>26</sup>Al/<sup>10</sup>Be) represents a suitable method to quantify the pace of long-term river incision. Here, we present a dataset of fifteen <sup>26</sup>Al/<sup>10</sup>Be burial ages measured in fluvial pebbles washed into a multi-level cave system developed in Devonian limestone of the uplifted Ardenne massif (eastern Belgium). The large and well-documented Chawresse system is located along the lower Ourthe valley (i.e. the main Ardennian tributary of the Meuse river) and spans altogether an elevation difference exceeding 120 m.</p><p>The depleted <sup>26</sup>Al/<sup>10</sup>Be ratios measured in four individual caves show two main outcomes. Firstly, computed burial ages ranging from ~0.2 to 3.3 Ma allows highlighting an acceleration by almost one order of magnitude of the incision rates during the first half of the Middle Pleistocene (from ~25 to ~160 m/Ma). Secondly, according to the relative elevation above the present-day floodplain of the sampled material in the Manants cave (<35 m), the four internally-consistent Early Pleistocene burial ages highlight an “anomalous” old speleogenesis in the framework of a gradual base-level lowering. They instead point to intra-karsting reworking of the sampled material in the topographically complex Manants cave. This in turn suggests an independent, long-lasting speleogenetic evolution of this specific cave, which differs from the <em>per descensum</em> model of speleogenesis generally acknowledged for the regional multi-level cave systems and their abandoned phreatic galleries. In addition to its classical use for inferring long-term incision rates, cosmogenic burial dating can thus contribute to better understand specific and complex speleogenetic evolution.</p>

scholarly journals Neogene Vertebrate Paleontology and Stratigraphy of Nepal

1981 ◽  
Vol 1 (1) ◽  
Author(s):  
Robert M. West ◽  
Jens Munthe
Keyword(s):  
Radiometric Dating ◽  
Early Pleistocene ◽  
Vertebrate Paleontology ◽  
Kathmandu Valley ◽  
Late Pliocene ◽  
The Past ◽  
Group A ◽  
Physical Stratigraphy ◽  
Siwalik Group ◽  
The Himalaya

ABSTRACT For the past 150 years, the Siwalik Group, a Miocene through Pleistocene molasse along the flank of the Himalaya has been studied intensively stratigraphically and paleontologically in both India and Pakistan. This work recently has been extended into Nepal, where a presumably complete Siwalik section is present, and a modest number of vertebrate fossils have been found. All but one of Nepalese Siwalik vertebrates hare been collected along the southern edge of the Dang Valley in western Nepal. Two assemblages are now known. The older is of presumed Miocene age and likely equivalent to the fauna of the Chinji Formation in Pakistan. The other is of late Pliocene to early Pleistocene age and similar to the Indian Pinjor fauna. In addition, Plio-Pleistocene vertebrates have been reported from fluvial intermontane deposits in the Kathmandu Valley. As studies of radiometric dating, magnetostratigraphy, physical stratigraphy and fossil distributions are extended into Nepal, the place of the Nepalese Siwaliks and basin deposits will become increasingly clear.

Linking source to stratigraphy through sediment transport: The importance of spatially variable climate on the evolution of the Argentine Andes

2020 ◽  
Author(s):  
Rebekah Harries ◽  
Linda Kirstein ◽  
Alex Whittaker ◽  
Mikael Attal ◽  
Boris Gailleton ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Geomorphic Mapping ◽  
Mountain Ranges ◽  
Base Level ◽  
Source Regions ◽  
Sediment Deposits ◽  
Mountain Front ◽  
History Of ◽  
River Profiles ◽  
Sediment Export

<p>Over geological timescales, we often assume the export of sediment, from mountainous source regions to depositional basins, is relatively instantaneous. As such, stratigraphic units are thought to capture erosional trends in their upstream catchment. The export of sediment from mountain basins, however, is a process heavily modified by sediment transport.</p><p>Here, we exploit a well-constrained field site in the Argentine Andes to demonstrate how the connectivity between hillslopes and mountain rivers modulates long-term sediment export in post glacial landscapes. We map out erosion trends in upstream catchments by combining an analysis of river profiles with geomorphic mapping of sediment deposits. We then use a comprehensive catalogue of clast lithology data to test to what extent upstream erosion trends are recorded downstream.</p><p>Despite their proximity to each other, we find adjacent catchments supplying sediment to the Iglesia basin have distinctly different degrees of hillslope-river connectivity, evident from the morphology of terraced and fan deposits within the catchments. Catchments with good hillslope-river channel connectivity also have a higher abundance of clasts sourced from the upper cordillera downstream of their mountain front. We place these observations within the context of a strong precipitation gradient across the cordillera and demonstrate the importance of climate and climate-controlled base-level on the spatial distribution of erosion within mountain catchments and fundamentally, on sediment export.</p><p>This work has implications for those using gravels to reconstruct the history of mountain ranges. Furthermore, it highlights the need to better constrain the potential for a disproportionate increase in sediment export to populated areas under future climate scenarios</p>

Le karst des plateaux jurassiques de la moyenne valee de l'Ardeche; datation par paleomagnetisme des phases d'evolution plio-quaternaires (aven de la Combe Rajeau)

2001 ◽  
Vol 172 (1) ◽  
pp. 121-129 ◽  
Author(s):  
Philippe Audra ◽  
Hubert Camus ◽  
Pierre Rochette
Keyword(s):  
Radiometric Dating ◽  
Base Level ◽  
Cave System ◽  
Knowing That ◽  
Precise Knowledge ◽  
Recent Part ◽  
Piezometric Surface ◽  
Underground River ◽  
Karst Systems ◽  
Level Lowering

Abstract Thanks to its immunity, karst is an excellent recorder of environmental change, which also offers the possibility for dating. Karst records position of old base levels, in particular to which were linked horizontal underground drains located near the piezometric surface. After a base level lowering, a new drain appears at a lower level, the old perched drain being abandoned. If base level lowering is slow, the initial drain is progressively entrenched, forming a canyon. The "Combe Rajeau" cave system corresponds to this last type: a 100 m high underground canyon, continuously entrenched during the Ardeche valley downcutting. The underground river left several terraces during the entrenchment. Knowing that speleothem U/Th radiometric dating method covers only the most recent part of karst systems history, which spans over several million years, paleomagnetism has been applied to date the Combe Rajeau sediments. A more precise knowledge of the evolution phases of this system provides a better understanding of the middle Ardeche valley evolution upon which it depends.

Extirpations and extinctions: a plant microfossil-based history of the demise of rainforest and wet sclerophyll communities in the Lake George basin, Southern Tablelands of NSW, south-east Australia

2020 ◽  
Vol 68 (3) ◽  
pp. 208 ◽  
Author(s):  
Mike Macphail ◽  
Brad Pillans ◽  
Geoff Hope ◽  
Dan Clark
Keyword(s):  
Water Levels ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Temperate Rainforest ◽  
Late Pliocene ◽  
Eastern Australia ◽  
History Of ◽  
Lake George ◽  
Plant Microfossil

Sites recording the extinction or extirpation of tropical–subtropical and cool–cold temperate rainforest genera during the Plio–Pleistocene aridification of Australia are scattered across the continent, with most preserving only partial records from either the Pliocene or Pleistocene. The highland Lake George basin is unique in accumulating sediment over c. 4 Ma although interpretation of the plant microfossil record is complicated by its size (950km2), neotectonic activity and fluctuating water levels. A comparison of this and other sites confirms (1) the extinction of rainforest at Lake George was part of the retreat of Nothofagus-gymnosperm communities across Australia during the Plio–Pleistocene; (2) communities of warm- and cool-adapted rainforest genera growing under moderately warm-wet conditions in the Late Pliocene to Early Pleistocene have no modern analogues; (3) the final extirpation of rainforest taxa at Lake George occurred during the Middle Pleistocene; and (4) the role of local wildfires is unresolved although topography, and, elsewhere, possibly edaphic factors allowed temperate rainforest genera to persist long after these taxa became extinct or extirpated at low elevations across much of eastern Australia. Araucaria, which is now restricted to the subtropics–tropics in Australia, appears to have survived into Middle Pleistocene time at Lake George, although the reason remains unclear.

scholarly journals The Crati River Basin: geomorphological and stratigraphical data for the Plio–Quaternary evolution of northern Calabria, South Apennines, Italy

2017 ◽  
Vol 68 (1) ◽  
pp. 68-79 ◽  
Author(s):  
Gaetano Robustelli ◽  
Francesco Muto
Keyword(s):  
Network Evolution ◽  
Early Pleistocene ◽  
Drainage Network ◽  
Fluvial Deposits ◽  
South Italy ◽  
Eastern Side ◽  
Base Level ◽  
Sedimentary Evolution ◽  
Depositional Systems ◽  
Coastal Range

Abstract In this paper, we present the results of an integrated geomorphological and stratigraphical study carried out in the eastern side of the Crati River valley (northern Calabria, South Italy). This area is characterized by the occurrence of three order palaeosurfaces that, along with low-sloping palaeovalleys and structural landforms, are striking features of the landscape. The relationships between morpho-tectonic and sedimentary evolution of the Crati Basin has been assessed through sandstone detrital modes, morphostratigraphy and geomorphological correlation with adjacent areas. The two main unconformity surfaces that typify the Quaternary fill were correlated to different steps of landscape evolution. The presence of both erosional and depositional palaeosurfaces has been a useful marker for reconstructing sedimentary and morphogenetic events, and hence to detect drainage network evolution and changes in source sediment area. In particular, we recognized that the study area experienced, during the late Pliocene–Early Pleistocene a period of sub-aerial landscape modelling as suggested by low-sloping palaeovalleys and related fluvial deposits (1st Order Palaeosurface). At that time, the source of the detrital constituents of the PPS Unit sandstones was mainly from the Sila Massif. The onset of Coastal Range identification and uplift (Early Pleistocene) marks a change in the geomorphic scenario with tectonic driven stream incision and valley development along the eastern side of Coastal Range, along with the occurrence of depositional and erosional landsurfaces (2nd Order Palaeosurface) at footslopes. During this period, the Coastal Range and Sila Massif were the sources for the detrital constituents of the PlS Unit sandstones. The progressive uplift of Coastal Range during late Early Pleistocene and the marked backstepping of the depositional systems along the Sila footslope was accompanied by alternating phases of down-cutting and base-level stability resulting in the development of a step-like distributed 3rd Order Palaeosurface. The presence of dolostone in detrital modes is clear evidence of stream piracy phenomena of ancient palaeovalleys by the Crati valley-facing drainage network.

scholarly journals Late Pleistocene sea-level changes recorded in tidal and fluvial deposits from Itaubal Formation, onshore portion of the Foz do Amazonas Basin, Brazil

2015 ◽  
Vol 45 (suppl 1) ◽  
pp. 63-78 ◽  
Author(s):  
Isaac Salém Alves Azevedo Bezerra ◽  
Afonso César Rodrigues Nogueira ◽  
José Tasso Felix Guimarães ◽  
Werner Truckenbrodt
Keyword(s):  
Sea Level ◽  
Late Pleistocene ◽  
Sea Level Changes ◽  
Fluvial Deposits ◽  
Base Level ◽  
Lower Unit ◽  
Basement Rocks ◽  
History Of ◽  
Floodplain Deposits ◽  
The Last Glacial

ABSTRACTThe Pleistocene deposits exposed in the Amapá Coastal Plain (onshore portion of the Foz do Amazonas Basin, northeastern South America) were previously interpreted as Miocene in age. In this work, they were named as "Itaubal Formation" and were included in the quaternary coastal history of Amazonia. The study, through facies and stratigraphic analyses in combination with optically stimulated luminescence (single and multiple aliquot regeneration), allowed interpreting this unit as Late Pleistocene tidal and fluvial deposits. The Itaubal Formation, which unconformably overlies strongly weathered basement rocks of the Guianas Shield, was subdivided into two progradational units, separated by an unconformity related to sea-level fall, here named as Lower and Upper Units. The Lower Unit yielded ages between 120,600 (± 12,000) and 70,850 (± 6,700) years BP and consists of subtidal flat, tide-influenced meandering stream and floodplain deposits, during highstand conditions. The Upper Unit spans between 69,150 (± 7,200) and 58,150 (± 6,800) years BP and is characterized by braided fluvial deposits incised in the Lower Unit, related to base-level fall; lowstand conditions remained until 23,500 (± 3,000) years BP. The studied region was likely exposed during the Last Glacial Maximum and then during Holocene, covered by tidal deposits influenced by the Amazon River.

scholarly journals The Kvabebi Canidae record revisited (late Pliocene, Sighnaghi, eastern Georgia)

2017 ◽  
Vol 91 (6) ◽  
pp. 1258-1271 ◽  
Author(s):  
Lorenzo Rook ◽  
Saverio Bartolini Lucenti ◽  
Maia Bukhsianidze ◽  
David Lordkipanidze
Keyword(s):  
Central Asia ◽  
Evolutionary History ◽  
Western Europe ◽  
Niche Partitioning ◽  
Early Pleistocene ◽  
Raccoon Dog ◽  
Late Pliocene ◽  
Early Pliocene ◽  
First Occurrence ◽  
History Of

AbstractUnlike the Asian and North American Pliocene record, fossil occurrences of Canidae in Europe (and Africa) are uncommon and fragmentary. The revision of canid material from the late Pliocene site of Kvabebi (eastern Georgia) revealed the contemporaneous occurrence of three different taxa: (1)Nyctereutes megamastoides(a derived species of the Eurasian Pliocene raccoon dog-like canids); (2)Vulpescf.V.alopecoides(representing the first occurrence of a member of the vulpine taxonV.alopecoides, a species that was the most widespread fox in the early Pleistocene in western Europe); and (3)Eucyonsp. The latter occurrence at Kvabebi completes our knowledge of the late Pliocene evolutionary history of the latest representatives of the genus in Western Europe and Central Asia. Our revision of Kvabebi canids registers a previously undocumented case of established niche partitioning among early Pliocene sympatric Canidae.

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