Preservation of Internal Reef Porosity and Diagenetic Sealing of Submerged Early Holocene Barrier Reef, Southeast Florida Shelf

Lighty, Robin G.

doi:10.2110/pec.85.36.0123

Cited by 63 publications

(61 citation statements)

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“…A higher cementation rate characterizes reefs with higher rates of water agitation and a lower sedimentation rate (Lighty 1985). This is well confirmed by the studied low-growing Tubiphytes micro-encrusters.…”

Section: Depositional Environmentsupporting

confidence: 81%

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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Section: Depositional Environmentsupporting

confidence: 81%

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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“…9) are similar to the spheres described by Lighty (1985). Lighty (1985) interpreted that the pore water movement in carbonates formed and developed such radiating type crystals of carbonates. Early diagenetic processes must be occurring in some surficial unconsolidated carbonates of Manza Beach.…”

Section: Microscopic Observationsupporting

confidence: 76%

Scanning electron microscopic observation of lime mud recovered from a coral reef lagoonal basin, Manza Beach, the Okinawa Island, Japan

Yamamoto

1997

Jour. Sed. Soc. Japan

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Lime mud was isolated from calcareous sands in the lagoonal basin of Manza Beach, the Okinawa Island. The lagoonal basin is enriched by both mud content and carbonate content towards the center, indicating that lime mud is enriched in the central portion of the low-energy lagoonal basin. Observation by the scanning electron microscopy (SEM) on the lime mud shows that it is composed by detrital, authigenic (precipitated), and cement crystals. Aragonite needles, as fragments of Halimeda, were occasionally observed to be present in the lime mud. Some spheres of radiating crystals were formed due to pore-water diagenetic processes. Lime mud deposited in the low-energy lagoonal basin may be an important material, which consolidates into limestone and which help to build up coral reefs.

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“…Note the overall similarity between the muddy matrix and the resulting peloids (e.g., the small inclusions in both components). Sample #DU 4 or fuzzy rims around an initial center (Land and Goreau 1970;Macintyre 1977Macintyre , 1985Lighty 1985). Dentate rims, as described in previous studies, are not visible in the SEM images of peloids studied.…”

Section: Discussionmentioning

confidence: 53%

Origin of peloids in Early Cretaceous deposits, Dorset, South England

Samankassou

Tresch

Strasser

2005

Facies

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Peloids are ubiquitous components in modern and fossil carbonates. The term peloid is non-genetic because the origin of these grains and the pathways of their formation are not fully understood. Based on Berriasian material originating from Dorset, southern England, we report here on peloids that result from the more or less in-place breakdown of previously micritized bivalve shells. The continuum from shell breakdown to peloids is documented by petrography and observation by scanning electron microscopy. The identical elemental composition of peloids and micritized shells confirms the petrographic observation and interpretation. Bivalve shells that were previously entirely micritized appear to be the preferential source for the formation of peloids. Obviously, the micritization weakened the shells, facilitating their breakdown and abrasion. This result identifies the fragmentation of micritized shells as a process leading to the formation of distinct peloids, adding to the categories of peloids recognized to date. Mold, mud, and microbial peloids observed in the studied sections and documented herein are distinct from peloids derived from bivalve shells.

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Preservation of Internal Reef Porosity and Diagenetic Sealing of Submerged Early Holocene Barrier Reef, Southeast Florida Shelf

Cited by 63 publications

References 0 publications

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

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

Scanning electron microscopic observation of lime mud recovered from a coral reef lagoonal basin, Manza Beach, the Okinawa Island, Japan

Origin of peloids in Early Cretaceous deposits, Dorset, South England

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