Search results for "Siliciclastic"
showing 10 items of 51 documents
Middle Triassic conodonts from northeastern Spain: biostratigraphic implications
2000
The facies development of the Spanish Triassic corresponds to the typical three-fold subdivision of the Germanic Facies: Buntsandstein, Muschelkalk and Keuper. Two intervals interpreted as epeiric carbonate platforms: lower Muschelkalk (Anisian) and upper Muschelkalk (Ladinian) are recognized during the Middle Triassic of northeastern Spain. These carbonate intervals are separated by one siliciclastic/evaporitic interval interpreted as sabbkha and saline deposits: middle Muschelkalk facies (Lower Ladinian). In northeastern Spain (Catalonian Coastal Ranges), two Middle Triassic sections comprising lower Muschelkalk facies have yielded the following conodont taxa: Paragondolella bulgarica, P.…
The Devonian Stratigraphic Succession and Evolution of the Baltic Sedimentary Basin
2014
Facies analysis, biostratigraphic and taphonomic studies, a re-evaluation of signatures of worldwide events, and a new mathematical model of the Baltic sedimentary basin (BSB) have together enabled a better understanding to be gained of the development of the Devonian basins in the Baltic area. We have established four stages of basin evolution: (a) remnant basin stage (Lochkovian); (b) shallow epeiric basin stage, with mainly siliciclastic sedimentation (Pragian–early Frasnian); (c) shallow epeiric basin stage, with mainly carbonate sedimentation (Frasnian); and (d) infilling stage of the progressively narrowing shallow epeiric basin, with mixed sedimentation (Famennian).
Characterization, provenance, and tectonic setting of Fig Tree greywackes from the Archaean Barberton Greenstone Belt, South Africa
1999
Abstract In this study, mineralogical and geochemical data, as well as Sr and Nd isotopic compositions of early Archaean greywackes from the Fig Tree Group are presented to provide further information about the evolution of the Barberton Greenstone Belt (BGB) of the Kaapvaal Craton, South Africa. The chemical data on the collected greywackes from the BGB suggest limited chemical modification of the source rocks. The Eu/Eu * anomaly is negative with an average value of 0.76 which is slightly higher than that of Eu-depleted crustal rocks (0.65). High Cr and Ni concentrations and a Cr/Ni ratio of about 1.6 indicate derivation from ultramafic sources without fractionation. Although rounded zirc…
Partitioning between “wedge-top” river- and wave-dominated successions: an example from the late Tortonian — early Messinian Terravecchia Formation (…
2011
AbstractDetailed field sedimentological and facies analyses have been performed in the Terravecchia Formation cropping out in NW Sicily, in order to differentiate and describe, for the first time, wave- and river-dominated shallow-marine (deltaic) siliciclastic successions. The latter were deposited filling syntectonic basins, developed between the late Tortonian and early Messinian time, within the wedge-top depozone of the Sicilian Foreland Basin System. It has been observed that river-dominated successions, recording the deposition of small fan-deltas are characterized by fining- to coarsening upward, transgressive-regressive sequences which were mostly deposited filling relatively narro…
Stratigraphy of the Neoproterozoic Damara Sequence in northwest Namibia: Slope to basin sub-marine mass-transport deposits and olistolith fields
2016
Abstract The Neoproterozoic Damara Sequence (>1000 m thick) is composed of siliciclastic and carbonate rocks that crop out in the Damara Belt, Namibia. In Damaraland (including the Vrede, Bethanis, Austerlitz and Toekoms farms), these rocks were deformed and metamorphosed under greenschist facies (biotite zone) conditions during the Damara Orogeny. The stratigraphy and paleoenvironments of the Damara Sequence rocks are debated by the scientific community. We use field data, including detailed 1:25,000 geological mapping, elaboration of stratigraphic profiles and observation of preserved primary structures, textures and composition, to identify lithofacies and lithofacies associations, and t…
Water resource assessment in karst and fractured aquifers of Termini Imerese-Trabia Mts. (Northern central Sicily, Italy).
2014
The carbonatic siliciclastic Mesozoic reliefs of Termini Imerese-Trabia Mts. (Northern central Sicily) were selected in order to investigate groundwater resources, as these fissured to karstic aquifers are used for potable water supply. These reliefs, part of the Sicilian Apennine Chain, consist of a tectonic units (deformed and emplaced during the Miocene-Pleistocene, and collapsed during the Plio-Pleistocene) mostly formed by clayey pelagic limestones (Sicilidi domain) overthrusting Meso-Cenozoic carbonate and silicoclastic rocks (Imerese Basin, Late Triassic-Early Oligocene) and terrigenous covers (Numidian Flysch, Late Oligocene-Early Miocene). The evolution of karstic network and subsu…
Late Archaean foreland basin deposits, Belingwe greenstone belt, Zimbabwe
2001
Abstract The c. 2.65 Ga old sedimentary Cheshire Formation of the Belingwe greenstone belt (BDB), central Zimbabwe, has been studied in detail for the first time to shed some light on the much debated evolution of this classical belt. The Cheshire Formation rests sharply on a mafic volcanic unit (Zeederbergs Formation) and comprises a basal, eastward-sloping carbonate ramp sequence built of shallowing-upward, metre-scale sedimentary cycles. The cycles strongly resemble Proterozoic and Phanerozoic carbonate cycles and might have formed by small-scale eustatic sea level changes. The top of the carbonate ramp is represented by a karst surface. The carbonates are overlain by and grade laterally…
Freshwater discharge and sediment dispersal — Control on growth, ecological structure and geometry of Late Miocene shallow-water coral ecosystems (ea…
2007
Abstract Insolation-driven oceanographic changes are well documented in the Mediterranean deep-sea record and reflect episodes of high precipitation and/or freshwater discharge. In the shallow-water record, however, changes in relative sea-level and sea surface temperature are usually regarded as prime controls on Miocene coral reefs, whereas pulses of freshwater influx represent a hitherto unrecognized factor influencing their growth, ecological structure and geometry. On the island of Crete (NW Messara Basin, Greece) early Tortonian coral biostromes occur associated with deltas along the basin margin and rimming islands formed by large uplifted tectonic blocks. In turbid delta environment…
Lowstand carbonates, highstand sandstones?
2003
The sedimentary facies, sediment dynamics and sequence architecture of modern high-energy shelves in the mid and high latitudes are largely governed by wave abrasion processes. Cool-water carbonates may form there, if the influx and/or net accretion of siliciclastics is kept at a minimum. Little dilution of the carbonate produced in situ is generally promoted by a wide "epicontinental" shelf, subdued topography of the adjacent mainland, the predominance of limestone outcrops, and an arid climate. The aforementioned requirements are rarely met, and thus will automatically lead to the formation of mixed siliciclastic-cool-water carbonates. Such an example is found in the Early to Mid-Miocene …
A siliciclastic shallow-marine turbidite on the carbonate shelf of the Ordovician Baltoscandian palaeobasin
2019
A metre-scale thick siltstone–sandstone lobe is described within the Dapingian outer ramp argillaceous limestone facies of the Baltoscandian palaeobasin. This bed is referred to as the Volkhov Oil Collector in previous studies due to its hydrocarbon accumulation potential. It formed on the palaeoslope of the regional Jelgava Depression, which represents an elongated axial region of the deepest part of the Ordovician Baltoscandian sedimentary basin. Sedimentological and petrological analysis of this siliciclastic bed in core sections shows that it was deposited as a result of a single event of turbidite flow. The internal structure of the turbidite bed follows the classical Bouma divisions o…