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Hydrographic variation in a tropical coral reef system: The Veracruz Reef System, Gulf of Mexico

Salas-Monreal David, Monreal-Jiménez Rosalinda, Contreras-Tereza Víctor Kevin, Monreal-Gómez Maria Adela, Salas-De-León David Alberto, Riverón-Enzástiga Mayra Lorena

Oceanologia

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2022

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No. 64 (3)

473--488

EN

Three thousand forty-one profiles of temperature, salinity, density, dissolved oxygen, nitrogen and chlorophyll-a were used to study their seasonal variation on a tropical coral reef system, located in the central part, of the reef corridor of the southwestern Gulf of Mexico. The results revealed three seasons according to their hydrographic variations; the northerly wind season from September to April; the dry season from May to June; and the rainy season from July to August. The results of the density ratio during the dry season were ∼1.25 on average, while during the rainy season it had an average value of ∼0.62. Thus, the pycnocline was more influenced by the halocline during the rainy season and by the thermocline during the dry season. There was also an evident variation in chlorophyll-a concentration over the water column, which was not evident in the surface layer. During the summer (rainy season), dissolved oxygen was related to chlorophyll-a concentration; while, during the winter (northern wind season), these values were related to the vertical mixing of the water column due to wind stress. There was evidence of cooler ocean water intrusion into the Veracruz Reef System during the spring-summer season below ∼10 m. Finally, a second halocline, pycnocline, and nitrocline were found near ∼30 m depth during the rainy season.

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Microencruster-microbial framework and synsedimentary cements in the Štramberk Limestone (Carpathians, Czech Republic) : Insights into reef zonation

Hoffmann M., Kołodziej B., Skupien P.

Annales Societatis Geologorum Poloniae

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2017

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Vol. 87, No. 4

325--347

EN

The Štramberk Limestone (Tithonian–lower Berriasian) was developed on a northerly located, isolated intra-Tethyan carbonate platform. It is composed of various facies that can be observed in olistoliths and blocks embedded in the Cretaceous flysch of the Outer Carpathians in Moravia (Czech Republic). Corals, microbialites, microencrusters and synsedimentary cements contributed on various scales to the reef framework. The importance of corals and some microencrusters to the formation of the Štramberk reef complex is well recognized, while other components received less attention in previous studies. Two end members of boundstone types are described from the Kotouč Quarry, near Štramberk. Boundstone type A is dominated by phaceloid (branching-type) corals, encrusted by microbialites and microencrusters, in particular photophile species (“Lithocodium-Bacinella”, Koskinobullina socialis Cherchi et Schroeder, Iberopora bodeuri Granier et Berthou). Boundstone type B is composed of microencrusters, microbialites and synsedimentary isopachous fibrous cements, while corals are absent or subordinate. Microencrusters [Crescentiella morronensis (Crescenti), Labes atramentosa Eliášová, Perturbatacrusta leini Schlagintweit et Gawlick, Radiomura cautica Senowbari-Daryan et Schäfer, thin encrusting calcified sponges] are main biotic components of the microencruster-cement boundstone. Some identified microencrusters are known only or mostly from intra-Tethyan carbonate platforms. Except for C. morronensis, other common microencrusters in the coral-microbial boundstone (type A) are rare in the microencruster-cement boundstone (type B). The depositional setting of boundstone type A corresponds to a low-energy environment of an inner platform. Boundstone type B, until now not recognized in the Štramberk Limestone, was developed in a high-energy, upper fore-reef slope environment. Other important facies in the Kotouč Quarry are reef-derived breccias: matrix-supported breccia and clast-supported breccia with radiaxial-fibrous cement (showing some similarities to Triassic “evinosponges” cement), interpreted as being dominantly synsedimentary (pre-burial). The preliminary studies by the present authors, supported by observations under cathodoluminescence, highlight the significance of synsedimentary cementation for the formation of a boundstone framework (type B) and the stabilization of fore-reef, slope deposits.

3

Wave-induced set-up and flow over shoals and coral reefs. Part 1. A simplified bottom geometry case

Massel S.R., Brinkman R. M.

Oceanologia

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2001

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No. 43 (4)

373-388

EN

An analytical approach was used to model the wave-induced set-up and flow through simple shoal geometry when water depth is a linear function of the distance. Two different approaches were applied to parameterize the energy dissipation due to wave breaking. The resulting set-up height and flow velocity were determined and their dependence on the geometry of the shoal and offshore forcing was demonstrated. The extension of the solution to a more complicated bathymetry and verification against the experimental data will be given in the second part of the paper.