Assessments of reef sediments in the North Ari Atoll (Maldives) were conducted in 2015 and 2018 on reefs of three islands with different management strategies: community, resort, and uninhabited. Indices applied were the Foraminifera in Reef Assessment and Monitoring Index (FI) and the Sediment Constituents Index (SI). Both indices are based on shells or fragments of functional groups, which for the FI are foraminiferal shells and for the SI are sediment components. The FI is considered to be an indicator of water quality and the SI an indicator of water quality, community structure, and processes such as grazing and bioerosion. Both indices indicated that environmental deterioration occurred between 2015 and 2018, likely related to the intense temperature anomaly in March-June 2016 that caused widespread coral bleaching and mortality. Median FI declined from 5.1 to 4.0 overall, indicating that water quality still supports reef accretion, though the replacement of coral cover by algae and sponges likely provides more food sources for smaller, faster-growing foraminiferal species. The median SI values similarly declined from 3.8 to 3.0, reflecting a decrease in identifiable coral fragments and an increase in unidentifiable clasts, likely indicative of increased bioerosion. Although a minor component, molluscan fragments also increased by 25%, likely in response to more algal cover for grazers. In 2015, the FI and SI data indicated that the island management regime contributed to the reef health status. Uninhabited islands were associated with higher indices compared to resort and community islands. A clear distinction between management regimes was not observed in 2018, because a major decrease in FI (median: 4.9 in 2015, 2.9 in 2018) was recorded offshore from an agricultural settlement on the previously "uninhabited" island surveyed. These observations support the usefulness of these indices in reef assessment, and provide additional understanding that the FI can respond to a coral-mortality event that alters food sources in the benthic community. 1. Introduction Coral reefs are among the most diverse, complex and vulnerable ecosystems on Earth, and their status is influenced by a wide range of environmental variables (e.g.

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The Pennsylvanian is characterized by intense paleoenvironmental changes related to glacio-eustatic sea-level fluctuations and major tectonic events, which affected the evolution of biocommunities. Most known Pennsylvanian tropical reefs and mounds are predominantly composed of calcareous algae (e.g. phylloid algae, Archaeolithophyllum), calcareous sponges, fenestrate bryozoans, Tubiphytes, and microbialites. However, in Houchang (southern China), the Late Pennsylvanian carbonate platform records a large coral reef lacking any analogs in age (Gzhelian), size (80–100 m thick) and composition (high biodiversity). The large coral reef developed at the border of the Luodian intraplatform basin. The intraplatform basin is characterized by the deposition of green algal grainstone, coated grain grainstone and bioclastic packstone, grainstone, floatstone and rudstone in shallow-waters. In the deep-water shelf, lithofacies are composed of burrowed bioclastic wackestone, microbioclastic peloidal packstone, grainstone, and fine-grained burrowed wackestone and packstone. In this context, the coral reef developed on a deep-shelf margin, in a moderate to low energy depositional environment, below the FWWB. The scarcity of Pennsylvanian coral reefs suggests global unfavorable conditions, which can be attributed to a complex pattern of several environmental factors, including seawater chemistry (aragonite seas), paleoclimatic cooling related to continental glaciation, and the biological competition with the more opportunistic and adaptive phylloid algal community that occupied similar platform margin paleoenvironments. The existence of the large Bianping coral reef in southern China, as well as a few additional examples of Pennsylvanian coralliferous bioconstructions, provides evidence that coral communities were able to endure the Late Paleozoic fluctuating paleoenvironmental conditions in specific settings. One of such settings appears to have been the deep shelf margin, where low light levels decreased competition with the phylloid algal community.

Low-and very low-grade metamorphic studies investigating the alteration and reaction progress of clay minerals are powerful tools to decipher the thermal evolution of sedimentary and inverted meta-sedimentary basins. Sheet silicates such as illite and chlorite are very common in sedimentary basin sequences. They can be used to determine the grade of diagenesis and low-temperature metamorphism as measured through the XRD: illite Kübler-Index (KI; illite "crystallinity" in older literature) and the chlorite Árkai-Index (ÁI; chlorite "crystallinity" in older literature), respectively. Although the ÁI method is considered to be slightly less sensitive than the KI method, a reliable correlation between both methods is often observed in metamorphic domains with a uniform heat-flow history and minor tectono-structural complexity. Complementary to these methods, the K-white mica b cell dimension provides a robust estimate of pressure facies reached in very low-to low-grade temperature domains.Here, we present a case-study from the Markstein basin located in the Southern Vosges.The lithostratigraphic units in the basin are characterized by deep marine flysch sequences of Upper Devonian to Upper Visean age and volcano-clastic sediments, respectively. The Markstein basin is surrounded by granitoids with intrusion ages between 340 and 326 Ma. A previous study showed orogenic deformation characterized by regional folding, and a contact metamorphism found in an outer halo of the granitoids up to 1500 m away from the contact (delineated by the occurrence of biotite and andalusite). Here we present a multidisciplinary study combining mineral assemblages, illite and chlorite "crystallinity indices", and K-white mica b cell dimension. Our approach allows to (i) map in (great) detail the areal extent of both regional/burial metamorphic and contact metamorphic domains; (ii) reveal the metamorphic zonation within both domains; and (iii) better constrain regional/burial and contact metamorphic history. The contact metamorphic domain is characterized by the occurrence of biotite and/or actinolite and low K-white mica b cell dimensions, whereas the zone of incipient orogenic metamorphism yields KI and ÁI values of the high-grade diagenesis and anchizone with intermediate K-white b cell dimensions.

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