1,720,978 research outputs found
Morphodynamics and facies architecture of streamflow-dominated, sand-rich alluvial fans, Pleistocene Upper Valdarno Basin, Italy
No full textA progressive unconformity-bounded stratigraphic unit within extensional settings, SE, Volterra Basin, Italy
No full textProvenance, depositional and palaeogeographic insights from the coarse-disorganised deposits of the Macigno turbidite systems (late Oligocene-early Miocene, Northern Apennines)
No full textMorphometric convergence between Proterozoic and post-vegetation rivers
Full text linkProterozoic rivers flowed through barren landscapes, and lacked interactions with macroscopic organisms. It is widely held that, in the absence of vegetation, fluvial systems featured barely entrenched channels that promptly widened over floodplains during floods. This hypothesis has never been tested because of an enduring lack of Precambrian fluvial-channel morphometric data. Here we show, through remote sensing and outcrop sedimentology, that deep rivers were developed in the Proterozoic, and that morphometric parameters for large fluvial channels might have remained within a narrow range over almost 2 billion years. Our data set comprises fluvial-channel forms deposited a few tens to thousands of kilometres from their headwaters, likely the record of basin- to craton-scale systems. Large Proterozoic channel forms present width:thickness ranges matching those of Phanerozoic counterparts, suggesting closer parallels between their fluvial dynamics. This outcome may better inform analy..
Geological map of the Chianti Mts (Northern Apennines, Italy)
No full textA detailed stratigraphical-structural survey combined with classical geological mapping has been performed in the
northern Chianti Mts, part of the Northern Apennines Orogen (central Italy). The study area can be subdivided in
different tectonic and depositional units: (i) the widely outcropping Tuscan Nappe (middle/late Lias–earliest
Miocene), thrusted to the west by (ii) Ligurian units (Cretaceous–Eocene) and unconformably covered by (iii)
post-nappe deposits (Pliocene–Pleistocene). The Chianti Mts are structured as a mega-antiformal fold,
dissected by WSW-ENE transversal lines and by NNW-SSE normal faults linked with the exhumation of the
Northern Apennines Range, developing a basin/ridge structure. As results, (i) a new improved stratigraphic
frame is here proposed; (ii) several tectonic and stratigraphic domains have been newly recognised; (iii) a large
area characterised by severe internal deformation has been recognised and mapped as an imbricate fan thrust
system, linked with transversal lines
Planform-asymmetry and backwater effects on river-cutoff kinematics and clustering
No full textRiver bends occasionally meander to the point of cutoff, whereby a river shortcuts itself and isolates a portion of its course. This fundamental process fingerprints a river's long-term planform geometry, its stratigraphic record, and biogeochemical fluxes in the floodplain. Although meander cutoffs are common in fast-migrating channels, timelapse imagery of the Earth surface typically does not offer a long enough baseline for statistically robust analyses of these processes. We seek to bridge this gap by quantifying cutoff kinematics along the Humboldt River (Nevada) – a stream that, from 1994 to 2019, hosted an exceptionally high number of cutoffs (specifically, 174 of the chute type and 53 of the neck type). A coincidence between major floods and cutoff incidence is first suggestive of hydrographic modulation. Moreover, not just higher sinuosity but also upstream planform skewness is associated with higher cutoff incidence and channel widening for a sub-population of chute cutoffs. We propose a conceptual model to explain our results in terms of channel-flow structure and then examine the distances between adjacent cutoffs to understand the mechanisms governing their clustering. We find that both local and nonlocal perturbations together trigger the clustering of new cutoffs, over distances capped by the backwater length and over yearly to decadal timescales. Our research suggests that planform geometry and backwater controls might sway the occurrence of cutoff clusters – both local and nonlocal – thereby offering new testable hypotheses to explore the evolution of meandering-river landscapes that have significant implications for river engineering and stratigraphic modelling. © 2020 John Wiley & Sons, Ltd
Thrusting strike-slip tectonics and stratigraphic architecture in a thrust-belt belt (Chianti Mts, Northern Apennines)
No full textA detailed stratigraphical-structural geological survey combined with classical geological mapping has been performed in the northern Chianti Mts, part of the Northern Apennines Orogen (central Italy). The study area can be subdivided in some tectonic and depositional units: (i) the widely outcropping Tuscan Nappe (middle/late Lias - earliest Miocene), thrusted from the west by (ii) Ligurian units (Cretaceous-Eocene) and unconformably covered by (iii) post-nappe deposits (Pliocene - Pleistocene). The Chianti Mts are structured as a mega-antiformal fold, dissected by wsw-ene transversal lineaments, that likely forced both the pre-orogenic sedimentation, both the transpressional evolution of this sector of the Northern Apennines, and by nnw-sse normal faults linked with the exhumation of the Northern Apennines Range, developing a basin/ridge structure. As results: (i) a new improved stratigraphic frame is here proposed; (ii) several tectonic and stratigraphic domains, with differentiated stratigraphy and tectonic deformation have been recognised; (iii) a large area characterized by severe internal deformation has been recognised and interpreted as an imbricate fan thrust system, linked and controlled by transversal/strike-slip lineaments and by the stratigraphic architecture
Stratigraphic architecture of an outer ramp/basinal turbidite fan carbonate system in a foreland basin ("Scaglia Toscana" Fm., Chianti Mts, Northern Apennines, Italy)
No full textThe Chianti Mts, part of the Northern Apennines orogen, represent an ideal case study to depict the relationships between outer carbonate ramps and basin plain carbonate turbidite systems in foreland basins. The main object of this research is the "Scaglia Toscana" Fm., a ca. 200 metres thick Eocene-Oligocene succession of polychromous shales, marls, pelagic limestones and turbidite calcarenites, with marked lateral/vertical complexity, having its type-section in the Chianti Mts. During fieldwork, the fm. has been subdivided in four partially interfingered members (from the bottom and northernmost): Sugame Marls; Cintoia Shales; Montegrossi Calcarenites; Dudda Shales and Limestones. The formation relates to three depositional systems: a middle to outer carbonate ramp dominated by hemipelagic deposition; a basinal plain whose sediments distribution was mainly forced by redox/oxic conditions and calcite-lysocline fluctuations; a thinning- and fining-upward, coarse- to fine-grained carbonate turbidite system. The "Scaglia Toscana" basin was located on the Adria continental micro-plate, foreland of the developing Northern Apennines orogen, whose facies distribution was mainly controlled by block faulting and differential subsidence. The Chianti Mts. represent then a crucial sector, since they expose the junction between a northern SSE-dipping ramp and a southern basinal plain with turbidite floor fans. A general southwardand upward-shift from ramp, basinal plain and turbidite fan facies has been recognized and remarked since the pioneering studies of the 1960s. Nonetheless, an exhaustive facies and architectural analysis is still lacking in literature. To fill this gap, the partial and preliminary results of a field logging, integrated with sedimentary facies analysis are reported here. © 2011 Società Geologica Italiana, Roma
Relationships among stratigraphy, fold-and-thrust structures and transversal tectonics in the northern Chianti Mountains (Northern Apennines)
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