Reef-Platform Coral Boulders

2013 ◽  
Author(s):  
James P Terry ◽  
A Y Annie Lau ◽  
Samuel Etienne
Keyword(s):  
Reef Platform

Diagenetic evolution of a Late Silurian reef platform, Gaspé Basin, Quebec, based on cathodoluminescence petrography

1989 ◽  
Vol 26 (4) ◽  
pp. 791-806 ◽  
Author(s):  
Martine Savard ◽  
Pierre-André Bourque
Keyword(s):  
Organic Matter ◽  
Stable Isotope ◽  
Light Microscope ◽  
West Point ◽  
Burial Depth ◽  
Back Reef ◽  
Diagenetic Evolution ◽  
Reef Platform ◽  
Colour Alteration ◽  
Stable Isotope Data

Carbonate units of two facie of the platformal upper reef complex of the Late Silurian West Point Formation, Gaspé Peninsula, Quebec, were studied to decipher their diagenetic evolution. The two facies were a reef-margin facies and a back-reef to lagoonal facies. Under the light microscope, only three broad cement phases were recognized. In contrast, cathodoluminescence observation revealed seven distinct generations of cements and a plethora of additional diagenetic features such as fracturing, internal brecciation, sulfatization, and stylolitization. The first four generations of cement were early marine and confined to the reef-margin facies. The subsequent three cement generations evolved in shallow to deeper burial environments and affected the reef-margin facies and the back-reef to lagoonal facies. C and O stable-isotope data support these deductions. Fracturing, internal brecciation, stylolitization, sulfatization, and the generation of the latest cements occurred during compaction and postcompaction stages. Lithification of the facies was rapid, with the pores completely occluded before a maximum burial depth of about 1 km was attained (based on conodont colour-alteration indices, organic-matter maturation data, and overall post-Silurian paleogeography).

Diurnal changes in oxygen content of the water over the coral reef platform at Heron I

1967 ◽  
Vol 18 (1) ◽  
pp. 23 ◽  
Author(s):  
DW Kinsey ◽  
E Kinsey
Keyword(s):  
Oxygen Content ◽  
High Tide ◽  
Spring Tide ◽  
Algal Species ◽  
Coral Growth ◽  
Diurnal Changes ◽  
Oxygen Levels ◽  
Production And Consumption ◽  
Early Afternoon ◽  
Reef Platform

Heron I., in the Australian Great Barrier Reef, is a small sand cay situated near the western end of a reef 6.5 miles long. The area investigated was south-west of the cay and approximately level, with extensive areas of living coral in the seaward half. Larger algal species were common near the cay but were not in evidence in the areas of active coral growth. Oxygen levels were determined without sampling using a membrane-enclosed polarographic probe. Results are presented as profiles across the platform and also as time sequences in the main draining channel. Some deep water results are included. Oxygen production and consumption were associated primarily with areas of rich coral growth and hence larger algae seemed unimportant in the overall oxygen exchange. Low tide oxygen levels in less than 1 ft of water ranged from 2.1 mg O2/l for a spring tide after midnight to more than 10.8 mg O2/l (the limit of the instrument) in the early afternoon. High tide levels in more than 6 ft of water ranged from 9.0 mg O2/l in the early afternoon to 6.4 mg O2/l 2hr after sunset. High tide readings were not taken late at night. There is some evidence that water already reduced or enriched in oxygen content on the previous tide was returned in significant quantities to the reef platform.

Carbonate production rates of encruster communities on a lagoonal patch reef: Vabbinfaru reef platform, Maldives

2014 ◽  
Vol 65 (8) ◽  
pp. 720 ◽  
Author(s):  
K. M. Morgan ◽  
P. S. Kench
Keyword(s):  
Coral Cover ◽  
Patch Reef ◽  
Coralline Algae ◽  
Carbonate Production ◽  
Sedimentary Environments ◽  
Reef Health ◽  
Global Estimates ◽  
Range Of Values ◽  
Encrusting Organisms ◽  
Reef Platform

Coral reefs are formed by the growth and calcification of primary coral framework and secondary encrusting organisms. Future scenarios of reef health predict global declines in coral cover and an increase in the relative importance of encrusting organisms to gross reef calcification. Numerous coral growth studies are available; however, there are few quantitative estimates of secondary carbonate production on reefs. The present study used vertically orientated PVC pipe to generate rates of carbonate production (g cm–2 year–1) by encruster communities on Vabbinfaru reef platform, Maldives (4°18′35″N, 73°25′26″E). Maximum carbonate production by encrusters was 0.112 g cm–2 year–1 (mean ± s.d.: 0.047 ± 0.019 g cm–2 year–1). Encruster community composition was dominated by non-geniculate coralline algae (mean ± s.d.: 76 ± 14.2%), with other encrusting taxa being quantitatively unimportant to total substrate cover (mean ± s.d.: 9 ± 16.7%). Rates of encruster calcification at Vabbinfaru fell within the range of values reported for other reef-building provinces. There is a particular need for more quantitative field-based measurements of reef-organism calcification rates because such values strengthen regional and global estimates of gross carbonate production and have direct implications for net reef accretion and the development of reef sedimentary environments.

Pliocene to Pleistocene carbonate systems of the Guadeloupe archipelago, French Lesser Antilles: a land and sea study (the KaShallow project)

2013 ◽  
Vol 184 (1-2) ◽  
pp. 99-110 ◽  
Author(s):  
Philippe Münch ◽  
Jean-Frédéric. Lebrun ◽  
Jean-Jacques Cornée ◽  
Isabelle Thinon ◽  
Pol Guennoc ◽  
...  
Keyword(s):  
Coral Reefs ◽  
Late Pleistocene ◽  
Late Miocene ◽  
Lesser Antilles ◽  
Carbonate Platforms ◽  
Bank Deposits ◽  
Extensional Tectonic ◽  
Red Algal ◽  
Reef Platform

AbstractThis work presents a synthesis of the present-day knowledge on both emerged and submerged carbonate platforms of the Guadeloupe archipelago. Onshore and offshore data acquired during the KaShallow project are presented. Since the early Zanclean, some isolated platforms developed onto a Jurassic to Tortonian basement which displayed reliefs inherited from a major extensional tectonic episode dated from −8 to −5 Ma. Marie-Galante, Grande Terre and the southern shelf of Grande-Terre show strong similarities with Zanclean to Gelasian red-algal facies upward changing into early Calabrian coral facies. A major erosional unconformity (SB2) was recognized and allows to distinguish two early Calabrian formations (Calcaires à Agaricia Formation and Calcaires à Acropora Formation). The final emersion of these platforms is late Calabrian. The La Désirade platform displays Zanclean to early Piacenzian red-algal facies upward changing into coral facies. This platform emerged as soon as in the late Piacenzian. The island subsided again in relation with later extensional tectonic episode and early Calabrian reef platform then unconformably deposited. The Colombie bank deposits comprise Pliocene basinal deposits overlain by late Calabrian coral reefs. The Flandre bank might have emerged synchronously with La Désirade but was drowned only in the late Pleistocene-Holocene interval. Four extensional tectonic episodes have been identified in the late Miocene-Recent interval. Their effects depend on the location of the platforms within the fore-arc.

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