Please cite this article as: Pomar, L., Baceta, J.I., Hallock, P., Mateu-Vicens, G., Basso, D., Reef building and carbonate production modes in the west-central Tethys during the Cenozoic, Marine and Petroleum Geology (2017), ABSTRACTChanging components, rock textures, lithofacies, platform types and architecture throughout time are unique characteristics of carbonate rocks. Characterizing these attributes has been approached by 1) building reference models for specific Phanerozoic intervals, 2) recognizing the climatic impact in modulating carbonate production, and 3) analyzing the influence of changing bio-geochemical conditions. The reference-model approach is mostly based on biological evolution, the climaticimpact approach emphasizes temperature, and the bio-geochemical approach considers the changes in Mg/Ca ratios and Ca ++ concentrations in the oceans. To date, however, an analysis integrating all of these factors is still missing. The analysis presented here includes all these factors but also CO 2 , which is fundamental for both photosynthesis and CaCO 3 precipitation.Here we analyze the waxing and waning of Cenozoic reef limestones from the central Tethys region through several steps: 1) on the basis of rock volume, rock textures, associated sediments and light-dependent skeletal components, as records of light penetration and wave energy (depth); 2) on global environmental conditions (δ 13 C, δ 18 O, pCO 2 , temperature); and 3) on the basis of functionality, nutritional requirements and available resources.Through the Cenozoic, water motion, whether induced by surface or internal waves or by currents, increased as the thermal gradients strengthened, both with depth and with latitude. Active water motion is essential for plankton catchers such as corals, but less so for many larger benthic foraminifers (LBF). Pycnoclines in the meso-oligophotic zone would then favor the benthic plankton catchers such as corals, but would be detrimental for many LBF. Warm temperatures favored LBF. The Eocene LBF families predominated during lowering of atmospheric pCO 2 by using respiratory CO 2 to enhance the symbiont production of photosynthates under oligotrophic conditions and limited turbulence, whereas the Miocene families had to adapt to a progressive increase in turbulence. The eurythermal coralline red algae, however, became preponderant producers in the mesophotic zone during times when the δ 13 C was relatively high. This explains two apparent paradoxes: 1) corals thrive best when the Earth's high latitudes cool, and 2) the dominance of corals and LBF is inversely correlated, despite they both require tropical conditions and have similar trophic strategies (mixotrophy).

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The paper presents the characteristics of surface sediments in a seagrass-dominated environment of the inner shelf of the Pontinian Islands (Tyrrhenian Shelf, Central Mediterranean). The aims of this work are to characterize the carbonate production and sedimentary processes of a representative high-latitude, temperate Posidonia oceanica-dominated area, to discuss the role of seagrass in the siliciclastic-carbonate mixing processes, which provide analogs for interpreting the occurrence and importance of these types of deposits in the rock record.The majority of sediments are poorly sorted siliciclastic skeletal sand. Based on grain type and abundance and carbonate content, these deposits include six subfacies. The different subfacies reflect environmental changes within the seagrass environment associated with variations in light penetration and hydrodynamic conditions.Additionally, the seagrass facies range from purely carbonate to mixed carbonate-siliciclastic, depending on the amount of siliciclastic input and on the capacity of seagrasses to trap allochthonous sediments while hosting carbonate-producing biota. The type of substrate and the erosion and transport processes control the siliciclastic input. In these Pontinian seagrass meadows, sedimentary facies contain abundant siliciclastic grains produced by erosion of the volcanic substrate and trapped by seagrass blades and rhizomes. This Pontinian example illustrates that in heterozoan-dominated seagrass settings, mudproducing green algae are not present or are not calcifying, and consequently, seagrass deposits are much more grainy than photozoan counterparts. Ancient heterozoan tropical seagrass deposits likely will be discriminated from their temperate or subtropical counterparts only by careful taxonomic analysis of skeletal grains.