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 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.

Evolution of Quaternary cave levels in low-relief karst regions: influence of fluvial incision and speleoinception of chalk caves in northern France

2020 ◽  
Author(s):  
Daniel Ballesteros ◽  
Carole Nehme ◽  
Andrew Farrant ◽  
Dominique Todisco ◽  
Diana Sahy ◽  
...  
Keyword(s):  
Laminated Sediments ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Northern France ◽  
Base Level ◽  
River Terraces ◽  
River Incision ◽  
Fluvial Incision ◽  
Relevant Role ◽  
Conduit Development

<p>In many lowland areas, fluvial incision is usually relatively slowly and another factors as the stratigraphical control would play a relevant role. In the lower Seine valley of Northern France, cave systems developed in the sub-horizontal Upper Cretaceous chalk of the Anglo-Paris Basin offer the potential to constrain the Quaternary evolution of the Seine valley and to test the role of speleo-inception theory of conduit development in the chalk aquifer. Six chalk caves, with a combined length of over 5.7 km were studied in detail. In each studied cave, data on the passage morphology, cave deposits (speleothem and sediments) and stratigraphical control were recorded. Cave levels were defined based on geomorphological evidence and altitudinal cave passage analyses. The chronology of cave development and abandonment was constrained by ten U-Th speleothem dates and 144 palaeomagnetic samples collected from laminated sediments within the caves. Four regional cave levels were identified at 10, 40, 75-80, and 85-90 m asl, showing 1% slope to the Seine estuary. Each cave level is formed by phreatic and epiphreatic conduits enlarged by paragenesis, showing branch work or maze patterns. Cave infill corresponds mainly to clayey to silty sediments that occupy the majority of the karst conduits. Locally, sands and pebbles occur, and speleothems are relatively scarce. Palaeomagnetic and U-Th data show that these cave levels developed sequentially from >1.06 ka to c. 300 ka, ca. 78% of them in relation to prominent Turonian, Coniacian and Santonian hardgrounds as well as sheet- and semi-tabular flint bands. Their age correlates with the estimated age of the lower river terraces from limited previously published OSL, palaeontological and U-Th dating, although new age data from the study cave improve the chronology of the higher-level river terraces. The combination of all this data suggests an initial slow rate of incision during the early Pleistocene, followed by a phase of more rapid river incision up to ~ 0.30 m·ka<sup>-1</sup> from ca. 1 to 0.7 Ma. Later, incision rates dropped to ~0.08 m·ka<sup>-1</sup> during Middle Pleistocene, and 0.05 m·ka<sup>-1</sup> since the beginning of the Upper Pleistocene. In conclusion, fluvial incision constitutes also a relevant speleogenic factor in low-gradient areas as the Seine Basin, where conduit development was favoured at sites where suitable lithological inception horizons intercept the contemporary base level.</p>

Cetopirus complanatus (Cirripedia: Coronulidae) from the late Middle Pleistocene human settlement of Pinnacle Point 13B (Mossel Bay, South Africa)

Zootaxa ◽  
2017 ◽  
Vol 4237 (2) ◽  
pp. 393 ◽  
Author(s):  
ALBERTO COLLARETA ◽  
CURTIS W. MAREAN ◽  
ANTONIETA JERARDINO ◽  
MARK BOSSELAERS
Keyword(s):  
South Africa ◽  
Marine Invertebrates ◽  
Indirect Evidence ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Human Consumption ◽  
Right Whale ◽  
Pinnacle Point ◽  
History Of ◽  
Late Middle Pleistocene

The late Middle Pleistocene cave site of Pinnacle Point 13B (PP13B, South Africa) has provided the archaeologically oldest evidences yet known of human consumption of marine resources. Among the marine invertebrates recognised at PP13B, an isolated whale barnacle compartment was tentatively determined as Coronula diadema and regarded as indirect evidence of human consumption of a baleen whale (likely Megaptera novaeangliae). In this paper we redetermine this coronulid specimen as Cetopirus complanatus. This record significantly extends the fossil history of C. complanatus back by about 150 ky, thus partially bridging the occurrence of Cetopirus fragilis in the early Pleistocene to the latest Quaternary record of C. complanatus. Since C. complanatus is currently known as a highly specific phoront of right whales (Eubalaena spp.), we propose that the late Middle Pleistocene human groups that inhabited PP13B fed on a stranded southern right whale. Therefore, the whale barnacle from PP13B suggests the persistence of a southern right whale population off South Africa during the predominantly glacial MIS 6, thus evoking the continuity of cetacean migrations and antitropical distribution during that global cold phase. Interestingly, the most ancient evidence of humans feeding on a whale involves Eubalaena, historically the most exploited cetacean genus, and currently still seriously threatened with extinction due to human impact. 

scholarly journals Anatomy, Age and Origin of an Intramontane Top Basin Surface (Sorbas Basin, Betic Cordillera, SE Spain)

2018 ◽  
Author(s):  
Martin Stokes ◽  
Anne E. Mather ◽  
Ángel Rodés ◽  
Samantha H. Kearsey ◽  
Shaun Lewin
Keyword(s):  
Growth Patterns ◽  
Alluvial Fan ◽  
Betic Cordillera ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Surface Erosion ◽  
Se Spain ◽  
Surface Formation ◽  
Base Level ◽  
Basin Surface

Collisional mountain belts commonly develop intramontane basins from mechanical and isostatic subsidence during orogenic development. These frequently display a relict top surface, evidencing a change interval from basin infilling to erosion often via capture or overspill. Such surfaces provide markers that inform on orogenic growth patterns via climate and base level interplay. Here, we describe the top surface from the Sorbas Basin, a key intramontane basin within the Betic Cordillera (SE Spain). The surface is fragmentary comprising high elevation hilltops and discontinuous ridges developed onto the variably deformed final basin infill outcrop (Gochar Formation). We reconstruct surface configuration using DEM interpolation and apply 10Be/26Al cosmonuclides to assess surface formation timing. The surface is a degraded Early Pleistocene erosional pediment developed via autogenic switching of alluvial fan streams under stable dryland climate and base level conditions. Base level lowering since the Middle Pleistocene focused headwards incision up interfan drainages, culminating in fan head capture and fan morphological preservation within the abandoned surface. Post abandonment erosion has lowered the basin surface by 31 m (average) and removed ~5.95 km3 of fill. Regional basin comparisons reveal a phase of Early Pleistocene surface formation, marking landscape stability following the most recent Pliocene-Early Pleistocene mountain building. Post-surface erosion rate quantification is low and in accordance with 10Be denudation rates typical of the low uplift Betic Cordillera.

scholarly journals Long-term landscape evolution of the Molise sector of the central-southern Apennines, Italy

2017 ◽  
Vol 68 (1) ◽  
pp. 29-42 ◽  
Author(s):  
Vincenzo Amato ◽  
Pietro P.C. Aucelli ◽  
Vito Bracone ◽  
Massimo Cesarano ◽  
Carmen Maria Rosskopf
Keyword(s):  
Late Pleistocene ◽  
Landscape Evolution ◽  
Temporal Distribution ◽  
Structural Data ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Southern Apennines ◽  
Geomorphological Evolution ◽  
Present Setting

AbstractThis paper concerns the reconstruction of the main stages of the long-term landscape evolution of the Molise portion of the central-southern Apennines along a transect divided into three sectors (SW, Central and NE). Analysis mainly focused on geomorphological, stratigraphical and structural data supported by chronological constraints, coming from an overall review of past literature and several studies carried out by the authors of the paper during the last 20 years. The results obtained allowed the elaboration of a conceptual model of the long-term evolution of the Molise sector of the central-southern Apennines. Starting from the Pliocene, the emersion of the Molise area occurred gradually from SW to NE, allowing a polycyclic landscape to evolve under the major controls first of compression then transtensional to extensional tectonics as well as climatic variations. Principal markers of the Quaternary geomorphological evolution of the Molise area are represented by the infill successions of the intermontane tectonic depressions located in its internal, SW sector and by four orders of palaeosurfaces that developed between the Early Pleistocene and the beginning of the Late Pleistocene across the region. These markers testify to the alternation of phases of substantial tectonic stability and uplift whose spatial-temporal distribution could be assessed along the investigated transect. Results highlight that the most important stages of landscape evolution occurred during the Early and Middle Pleistocene. At the beginning of the Late Pleistocene, the Molise sector of the Apennine chain had already reached its present setting and further landscape evolution occurred under the major control of climate and land-use.

Terminology of long-term geomorphology: a Scandinavian perspective

2009 ◽  
Vol 33 (2) ◽  
pp. 163-182 ◽  
Author(s):  
Karin Ebert
Keyword(s):  
Sea Level ◽  
Land Surface ◽  
Large Scale ◽  
Ice Sheets ◽  
Stepped Surfaces ◽  
Base Level ◽  
History Of ◽  
Land Surfaces ◽  
Over Time

In this paper the terminology used in long-term geomorphology is evaluated. Long-term geomorphology is the study of landforms that are of mostly pre-Quaternary, Cenozoic, Mesozoic or even Palaeozoic age. Many terms have been introduced to name the long-term large-scale landforms that persist to the present. The definitions of many of these terms are ambiguous, have changed over time, and their use and meaning is consequently often unclear. An attempt is made to clarify definitions, when possible, and to facilitate more concise usage of these terms. Long-term geomorphology deals in great parts with the lowering of a land surface to the base level (mostly sea level), leaving a new land surface. The largest group of terms concerns descriptions and genetic models for these kinds of new land surfaces collectively called `base level surfaces' here. Other terms discussed here relate to relict and preglacial landforms and regional terms for stepped surfaces. Terminology is discussed with particular reference to examples from and its use in Scandinavia. There is a long history of long-term geomorphology study in this region. Scandinavia is unique in the respect that pre-Quaternary landforms were repeatedly covered by Quaternary ice sheets but often survived with different degrees of glacial modification.

scholarly journals Leaky salt: pipe trails record the history of cross-evaporite fluid escape in the northern Levant Basin, Eastern Mediterranean

2021 ◽  
Author(s):  
Davide Oppo ◽  
Sian Evans ◽  
Christopher A-L Jackson ◽  
David Iacopini ◽  
SM Mainul Kabir ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Tectonic Evolution ◽  
Eastern Mediterranean ◽  
Early Pleistocene ◽  
Salt Tectonics ◽  
Messinian Salinity Crisis ◽  
Seal Failure ◽  
History Of ◽  
Levant Basin

<p>Hydrocarbon escape systems can be regionally active on multi-million-year timescales. However, reconstructing the timing and evolution of repeated escape events can be challenging because their expression may overlap in time and space. In the northern Levant Basin, eastern Mediterranean, distinct fluid escape episodes from common leakage points formed discrete, cross-evaporite fluid escape pipes, which are preserved in the stratigraphic record due to the coeval Messinian salt tectonics.</p><p>The pipes consistently originate at the crest of prominent sub-salt anticlines, where thinning and hydrofracturing of overlying salt permitted focused fluid flow. Sequential pipes are arranged in several kilometers-long trails that were progressively deformed due to basinward gravity-gliding of salt and its overburden. The correlation of the oldest pipes within 12 trails suggests that margin-wide fluid escape started in the Late Pliocene/Early Pleistocene, coincident with a major phase of uplift of the Levant margin. We interpret that the consequent transfer of overpressure from the deeper basin areas triggered seal failure and cross-evaporite fluid flow. We infer that other triggers, mainly associated with the Messinian Salinity Crisis and compressive tectonics, played a secondary role in the northern Levant Basin. Further phases of fluid escape are unique to each anticline and, despite a common initial cause, long-term fluid escape proceeded independently according to structure-specific characteristics, such as the local dynamics of fluid migration and anticline geometry.</p><p>Whereas cross-evaporite fluid escape in the southern Levant Basin is mainly attributed to the Messinian Salinity Crisis and compaction disequilibrium, we argue that these mechanisms do not apply to the northern Levant Basin; here, fluid escape was mainly driven by the tectonic evolution of the margin. Within this context, our study shows that the causes of cross-evaporite fluid escape can vary over time, act in synergy, and have different impacts in different areas of large salt basins.</p>

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 Anatomy, Age and Origin of an Intramontane Top Basin Surface (Sorbas Basin, Betic Cordillera, SE Spain)

2018 ◽  
Author(s):  
Martin Stokes ◽  
Anne E. Mather ◽  
Ángel Rodés ◽  
Samantha H. Kearsey ◽  
Shaun Lewin
Keyword(s):  
Growth Patterns ◽  
Alluvial Fan ◽  
Betic Cordillera ◽  
Early Pleistocene ◽  
Middle Pleistocene ◽  
Surface Erosion ◽  
Se Spain ◽  
Surface Formation ◽  
Base Level ◽  
Basin Surface

Collisional mountain belts commonly develop intramontane basins from mechanical and isostatic subsidence during orogenic These frequently display a relict top surface, evidencing a change  interval from basin infilling  to erosion often via  capture  or overspill.  Such surfaces provide  markers  that  inform  on orogenic  growth patterns  via  climate  and  base level Here, we describe the top surface from the Sorbas Basin, a key intramontane basin within the Betic Cordillera (SE Spain). The surface is fragmentary comprising high elevation hilltops and discontinuous ridges developed onto the variably deformed final basin infill outcrop (Gochar Formation). We reconstruct surface configuration using DEM interpolation and apply 10Be/26Al cosmonuclides to assess surface formation The surface is an Early Pleistocene erosional pediment developed via autogenic switching of alluvial fan streams under stable dryland climate and base level Base level lowering since the Middle Pleistocene focused headwards incision up interfan drainages, culminating in fan head capture and fan morphological preservation within the abandoned Post abandonment erosion has lowered the basin surface by 31 m (average) and removed ~5.95 km3 of fill. Regional basin comparisons reveal a phase of Early Pleistocene surface formation, marking landscape stability following the most recent Pliocene-Early Pleistocene mountain Post-surface erosion rate quantification is low and in accordance with 10Be denudation rates typical of the low uplift Betic

scholarly journals The role of mutational spectrum in the selection against mutator alleles

2019 ◽  
Author(s):  
Alejandro Couce ◽  
Olivier Tenaillon
Keyword(s):  
Bacterial Genome ◽  
Clinical Settings ◽  
Disruptive Effect ◽  
Genome Wide ◽  
Complex Picture ◽  
Order Of Magnitude ◽  
Evolution Experiment ◽  
History Of

AbstractRapidly adapting microbe and cancer cell populations often evolve high mutation rates. Yet, once adaptive opportunity declines, antimutator alleles are expected to take over as a result of indirect selection against deleterious mutations. Theory indicates that the most important determinant of antimutator invasions is the extent of mutation rate reduction. However, inconsistent results from evolution experiments suggest that additional factors may also play a major role in antimutator dynamics. Here we show that the idiosyncratic mutation bias exhibited by different mutators – a previously unrecognized factor – can greatly alter mutator susceptibility to antimutator invasions. Using a simulation model calibrated to mimic a well-known long-term evolution experiment with bacteria, we show that differences in average deleterious load can account for order-of-magnitude changes in antimutator fitness for a realistic range of parameters. Since these parameters are known to vary with the environment, our results reveal an unanticipated source of variability in antimutator dynamics. Finally, we estimated the genome-wide average disruptive effect on proteins of mutations caused by different mutators, and found marked and systematic differences emerging across mutators and species with different genomic GC compositions. Taken together, our results suggest that antimutator dynamics may be highly dependent on the specific genetic, ecological and evolutionary history of a given population. Such dependence reveals a more complex picture than anticipated, being relevant for understanding mutators in clinical settings, as well as how hypermutability shapes the evolution of bacterial genome size and composition.

Sign in / Sign up

Export Citation Format

Share Document