Steep microbial boundstone-dominated platform margins—examples and implications

Kenter, J.A.M.; Harris, Paul M.; Porta, Giovanna Della

doi:10.1016/j.sedgeo.2004.12.033

Cited by 116 publications

(85 citation statements)

References 42 publications

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“…These differ from later coral-reefdominated Mesozoic and Cenozoic platforms in that the carbonate factory was not shallow and light dependent but may have extended to hundreds of metres in depth. This has a consequence for platform architecture in that platform slopes are stabilized and steep, and progradation may not be interrupted by sea-level falls (Kentner et al 2005). Jenkins et al (2013) characterize such microbialdominated slopes from the supergiant Tengiz and smaller Korolev fields (Visean to Serpukhovian) from the Caspian Basin, Kazakhstan.…”

Section: Palaeozoicmentioning

confidence: 99%

Microbial carbonates in space and time: introduction

Bosence

Gibbons²,

Heron

et al. 2015

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Section: Palaeozoicmentioning

confidence: 99%

Microbial carbonates in space and time: introduction

Bosence

Gibbons²,

Heron

et al. 2015

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“…It is inferred, however, that it was analogue to known examples, such as the Latemar platform in the Italian Dolomites (Marangon et al 2011), the Siera del Cuera, in Spain, and some recent flat-topped systems (Della Porta et al 2003). By analogy, the microbialites from the Middle Triassic of North Dobrogea could have extended on a steep slope to depths of ~200-300 m (Kenter et al 2005). …”

Section: Depositional Environmentmentioning

confidence: 99%

“…Microbial boundstones, as Tubiphytes-dominated facies, are also the main constituents of the Carboniferous upper slopes in the Cantabrian Mountains in northern Spain (Della Porta et al 2003;2004;Kenter et al 2005;Bahamonde et al 2007).…”

Section: Comparison With Other Tubiphytes-buildups Known In the Geolomentioning

confidence: 99%

An early Middle Anisian (Middle Triassic) Tubiphytes and cement crusts-dominated reef from North Dobrogea (Romania): facies, depositional environment and diagenesis

Popa¹,

Panaiotu²,

Grădinaru³

2014

Acta Geologica Polonica

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ABSTRACT:Popa, L., Panaiotu, C.E. and Grădinaru, E. 2014. An early Middle Anisian (Middle Triassic) Tubiphytes and cement crusts-dominated reef from North Dobrogea (Romania): facies, depositional environment and diagenesis. Acta Geologica Polonica, 64 (2), 189-206. Warszawa.A well-developed Triassic carbonate platform is exposed in the eastern part of the Tulcea Unit, in the Cimmerian North Dobrogean Orogen, southeastern Romania. Facies analysis of the 200 m thick succession of lower Middle Anisian limestones exposed in a large limestone quarry south of the village of Mahmudia suggests a transition from upper slope towards toe-of-slope carbonate facies, reflecting sea-level fluctuations and tectonic tilting. The slope is dominated by in situ microbialites in the upper portion, consisting of reefal boundstone facies, and by molluscan coquina and cement boundstones. A key role is played by the cosmopolitan micro-encruster Tubiphytes, which became common in the aftermath of the mass extinction at the Permian/Triassic boundary, and by autochthonous micrite and synsedimentary marine cement. The absence of metazoan reef builders, such as sponges and corals, reflects the fact that microbes were the first organisms to recover after the Permian/Triassic crisis under unusual marine conditions and that their main role in reef formation was sediment stabilization along the upper slopes. The lower slope is mostly detrital, being dominated by platform-derived bioclastic rudstones and crinoidal floatstones, which are interbedded with basinal carbonate hemipelagics. The toe-of-slope is composed of pelagic wackestones framed by thin tongues of intraclast breccia. All these observations are in agreement with the slopeshedding model described for the Pennsylvanian microbial margin in Asturias (northern Spain) and the AnisianLadinian flat-topped, steep-rimmed Latemar platform (Dolomites, Italy).As most of the Anisian reefs were described from western and eastern Tethys (Southern Alps, Hungary, China), the occurrence of the early Middle Anisian Tubiphytes-reef from North Dobrogea (Romania) contributes to resolving the puzzle of the geographic distribution of reef recovery in the Middle Triassic.

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“…This was a period of high-amplitude cyclic glacioeustatic sea-level variations, which favoured reworking of carbonates. Similar, time-equivalent stylolitised 'welded' microbial carbonate breccias are observed in the fractured slope sediments of the Caspian region (Kenter et al, 2005;Harris et al, 2008).…”

Section: Bhg-01mentioning

confidence: 59%

Seismic stratigraphy of Dinantian carbonates in the southern Netherlands and northern Belgium

Reijmer

Veen²,

Jaarsma

et al. 2017

Netherlands Journal of Geosciences

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Due to their potential as a petroleum or geothermal system, the Dinantian carbonates of the Netherlands have recently attracted renewed interest because of the identified presence of excellent reservoir properties. This notion contrasts with the general assumption that these carbonates are tight. Therefore, in order to give the current knowledge state, this paper re-examines the sparse publicly available well and seismic data and literature to assess the distribution and reservoir properties of the Dinantian carbonates.Dinantian carbonate deposition occurred throughout the study area (southern onshore and offshore of the Netherlands and northern Belgium), which is situated on the northern margin of the London-Brabant Massif, progressively onlapping the latter structure. This study confirms the presence of three carbonate facies types in the study area: a Tournaisian low-gradient carbonate ramp system, succeeded by a succession in which the carbonate ramp system evolved to a rimmed shelf setting. Subsidence of the northern margin of the London-Brabant Massif resulted in a landward shift of the shallow-marine facies belts, while the formation of normal faults resulted in a 'staircase'-shaped shallow-water platform-slope-basin profile, associated with large-scale resedimentation processes. After deposition, the limestone deposits were frequently exhumed and reburied. A first period of regional exhumation occurred at the end of the Dinantian, which seems to be associated with porosity-enhancing meteoric karstification, possibly limited to the palaeo-shelf edge. The most intense alterations seem to be present as a deep leached horizon below the Cretaceous unconformity at the top of the Dinantian sequences. In addition, clear evidence for hydrothermal fluid migration is found locally, enhancing reservoir properties at some places while occluding porosity at others. The timing of these phases of hydrothermal fluid circulation is poorly understood.Whereas in the United Kingdom hydrocarbons have been produced from karstified Dinantian carbonates, this petroleum play has received little attention in the Netherlands. This paper shows that, also for the Netherlands, a karstic reservoir probably existed before the start of hydrocarbon generation from the onlapping basal Namurian shales. The hydrocarbon prospectivity of these sediments, however, is primarily controlled by the presence of both a karst-related reservoir and migration routes from a decent-quality source rock. Two geothermal projects producing from this reservoir in the southern onshore Netherlands have shown the potential of the Dinantian carbonates for ultra-deep geothermal projects. To conclude, the findings presented herein are relevant for studies of the hydrocarbon prospectivity and studies of the geothermal potential of Dinantian carbonates in the Dutch on-and offshore.

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Steep microbial boundstone-dominated platform margins—examples and implications

Cited by 116 publications

References 42 publications

Microbial carbonates in space and time: introduction

Microbial carbonates in space and time: introduction

An early Middle Anisian (Middle Triassic) Tubiphytes and cement crusts-dominated reef from North Dobrogea (Romania): facies, depositional environment and diagenesis

Seismic stratigraphy of Dinantian carbonates in the southern Netherlands and northern Belgium

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