Changing Dolomitization Styles from Norian to Rhaetian in the Southern Tethys Realm

Iannace, Alessandro; Frisia, Silvia

doi:10.1002/9781444304077.ch6

Cited by 23 publications

(35 citation statements)

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“…On the whole the Dolomia Principale isotopic values are consistent with those reported by authors in the area (Jadoul et al 1995;Frisia 1994;Iannace and Frisia 1994); a shift toward more depleted 8 18 0 values may be related to water/rock interaction during burial or in presence of hydrothermal fluids (Frisia and Wenk 1994). The dedolomitized fabrics show altered isotopic signatures with a shift of the 8 13C toward more and more depleted values in relation to the increase of calcitization (from a A to B): the most negative carbon values (8 13C about -5 %0) belong to the last calcite cement and internal sediment, which represent the last phase of the dedolomitization.…”

Section: Geochemistry Stable Isotopes Analysessupporting

confidence: 79%

Quaternary dedolomitization along fracture systems in a late triassic Dolomitized platform (Western Southern Alps, Italy)

Ronchi

Jadoul

Savino

2004

Carbonates Evaporites

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The studied area belongs to a south vergent thrust and fold belt of the Southern Alps of central Lombardy where the norian Dolomia Principale crops out. This up to 2 km thick carbonate platform succession has been massively dolomitized from early to shallow burial diagenesis.Dark grey, bedded dolostones (basal Dolomia Principale), outcropping along the both lower slopes of Iseo Lake (lower Camonica Valley), show a complex network of dedolomitized white-grey areas. The calcareous lenses show an irregular, elongated (up to few meters large) shape; they are usually located along fault-fracture systems and extending along the strata bedding. Two main fabrics have been recognized; the fabric A is formed by a reticulate of small fractures filled by calcite and surrounded by fine grained calcitized halos, the fabric B is associated to more intense fracturation process that locally gave rise to breccia fabric; moreover a ochre-reddish internal sediment is locally present in small cavities or as a breccia matrix, a huge speleothem-like cementation is associated to these dedolomitized fabric.This study was aimed to reconstruct the dedolomitization process and to propose a relevant genetic model. The petrographic analyses, integrated using cathodoluminescence and electron scanning microscope allowed to find out that dedolomitization process is composed of a first phase of dolomite dissolution along permeable path ways, both at the macro and at the micro scale, followed by calcite precipitation in the pore spaces.The negative 8 180 and 8 13C values of the calcite cements and the calcitic fraction of the dedolomitized fabrics suggest precipitation in presence of meteoric water derived fluids.Radiometric absolute age determination ( 23°Up14Th) indicates that calcite cements precipitated in the last 100000 years: age during which the area was subject to several advances and retreats of glacial tongues.The field mapping, analytical data and the geomorphology of the areas where the dedolomitized patches are more frequent, in correspondence of a narrow passage of the lower Camonica valley, allowed us to infer that the dedolomitization developed during glacial-interglacial phases particularly active in the region during the Pleistocene. In particular we propose that the fracturation and the first phase of dedolomitization (fabric A) occurred during the glacial period, while extensive calcite precipitation and brecciation (fabric B) formed during the interglacial periods, dominated by a warm climate during which extensive soil cover and karst processes developed.

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Section: Geochemistry Stable Isotopes Analysessupporting

confidence: 79%

Quaternary dedolomitization along fracture systems in a late triassic Dolomitized platform (Western Southern Alps, Italy)

Ronchi

Jadoul

Savino

2004

Carbonates Evaporites

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“…Under the semi-arid conditions prevailing during the early stage of the platform evolution, tidal flat dolomitisation played an active role in lithification (Balog et al 1999;Haas and DemØny 2002) and dolocretes (terrestrial stromatolites; Wright 1989Wright , 1994 formed on the emerged (Balog et al 1997(Balog et al , 1999. Sub-humid conditions during the later stages of platform evolution (Iannace and Frisia 1994;Balog et al 1999;Haas 2002) led to irregular erosional surfaces and the development of typical smallscale but rarely metre-scale karstification. Lens-shaped solution cavities formed beneath the surface at the water table.…”

Section: Discussionmentioning

confidence: 97%

“…The platform limestone deposits were named the Dachstein Limestone while the dolomite was referred to as Dachstein Dolomite or Hauptdolomit. Thick Upper Triassic (Upper Tuvalian-Rhaetian) platform carbonate sequences with features akin to those in the type locality of the Dachstein Limestone and Dachstein Dolomite in the Eastern Alps occur in the Central and Inner Western Carpathians (Michalik 1980(Michalik , 1993, Southern Alps (Bossellini 1967;Bosellini and Hardie 1988;Jadoul et al 1992;Ogorelec and Rothe 1992;Iannace and Frisia 1994;Ogorelec and Buser 1996;Cozzi et al 2003), Dinarides Dimitrijevic 1982, 1991), Hellenides (PomoniPapaioannou et al 1986;Haas and Skourtsis-Coroneou 1995); and also in the northern part of the Pannonian Basin (VØgh-Neubrant 1957, 1960Oravecz 1963;Fülöp 1976;Haas 1982;Gecse 1984;Schwarzacher and Haas 1986;Haas 1991Haas , 1994Haas and Balog 1995;Haas and Budai 1995;Balog et al 1997Balog et al , 1999Mindszenty and Deµk 1999;Haas and DemØny 2002). Although the formal lithostratigraphic names of these formations differ regionally, one can refer them collectively as Dachstein-type platform carbonates.…”

Section: Introductionmentioning

confidence: 97%

Characteristics of peritidal facies and evidences for subaerial exposures in Dachstein-type cyclic platform carbonates in the Transdanubian Range, Hungary

Haas

2004

Facies

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In the Late Triassic, an extremely large carbonate platform system (Dachstein-type platforms) developed on the margin of the Neotethys. On the wide inner platform cyclic peritidal, lagoonal successions were deposited. In the Transdanubian Range (Hungary), the lower part of the 1.5-2-km-thick cyclic succession (Upper Tuvalian-mid-Norian) is pervasively dolomitised, the upper part (Upper Norian-Rhaetian) is non-dolomitised; there is a transitional interval between them made up of partially dolomitised cycles. The peritidal-lagoonal cycles are commonly bounded by well-developed disconformity surfaces reflecting subaerial erosion that punctuated the marine carbonate accumulation. Truncation of the cycles was preceded by pervasive cementation of the previously deposited cycle. In the early stage of the platform evolution, tidal flat dolomitisation under semiarid conditions led to the consolidation of the previously deposited sediments. The truncation surfaces were commonly covered by dolocretes. During the more humid Late Norian-Rhaetian period, the early cementation was followed by karstification, accumulation of wind-blown dust and pedogenesis. Erosion during regularly recurring subaerial exposure that commonly reached the previously deposited subtidal beds suggests eustatic control of the cyclicity and supports the application of an allocyclic model, even if the Milankovitch signal is imperfect.

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“…This Late Triassic carbonate platform is the well‐known Dolomia Principale, which has been the subject of several studies on dolomitization processes (e.g. Frisia & Wenk, ; Frisia, ; Iannace & Frisia, ; McKenzie & Vasconcelos, ; Meister et al ., ).…”

Section: Palaeogeographic and Environmental Settingmentioning

confidence: 99%

Primary dolomite in the Late Triassic Travenanzes Formation, Dolomites, Northern Italy: Facies control and possible bacterial influence

et al. 2014

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In the late Carnian (Late Triassic), a carbonate-clastic depositional system including a distal alluvial plain, flood basin and sabkha, tidal flat and shallow carbonate lagoon was established in the Dolomites (Northern Italy). The flood basin was a muddy supratidal environment where marine carbonates and continental siliciclastics interfingered. A dolomite phase made of sub-micrometre euhedral crystals with a mosaic microstructure of nanometre-scale domains was identified in stromatolitic laminae of the flood basin embedded in clay. This dolomite is interpreted here as primary and has a nearly stoichiometric composition, as opposed to younger early diagenetic (not primary) dolomite phases, which are commonly calcian. This primary dolomite was shielded from later diagenetic transformation by the clay. The stable isotopic composition of dolomite was analyzed along a depositional transect. The δ13C values range between ca -6‰ and +4‰, with the most 13C-depleted values in dolomites of the distal alluvial plain and flood basin, and the most 13C-enriched in dolomites of the tidal flat and lagoon. Uniform δ18O values ranging between 0‰ and +3‰ were found in all sedimentary facies. It is hypothesized that the primary dolomite with mosaic microstructure nucleated on extracellular polymeric substances secreted by sulphate reducing bacteria. A multi-step process involving sabkha and reflux dolomitization led to partial replacement and overgrowth of the primary dolomite, but replacement and overgrowth were facies-dependent. Dolomites of the landward, clay-rich portion of the sedimentary system were only moderately overgrown during late dolomitization steps, and partly retain an isotopic signature consistent with bacterial sulphate reduction with δ13C as low as -6‰. In contrast, dolomites of the marine, clay-free part of the system were probably transformed through sabkha and reflux diagenetic processes into calcian varieties, and exhibit δ13C values of ca +3‰. Major shifts of δ13C values strictly follow the lateral migration of facies and thus mark transgressions and regressions. © 2014 International Association of Sedimentologists

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Changing Dolomitization Styles from Norian to Rhaetian in the Southern Tethys Realm

Cited by 23 publications

References 0 publications

Quaternary dedolomitization along fracture systems in a late triassic Dolomitized platform (Western Southern Alps, Italy)

Quaternary dedolomitization along fracture systems in a late triassic Dolomitized platform (Western Southern Alps, Italy)

Characteristics of peritidal facies and evidences for subaerial exposures in Dachstein-type cyclic platform carbonates in the Transdanubian Range, Hungary

Primary dolomite in the Late Triassic Travenanzes Formation, Dolomites, Northern Italy: Facies control and possible bacterial influence

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