Triassic Corals Research Articles

Supplemental data on Triassic (Anisian) corals from Upper Silesia (Poland)

About twenty species of scleractinian corals are known from the shallow marine epicontinental deposits (Middle Triassic: Anisian, Muschelkalk) of Krakow-Upper Silesia region. Four of them require taxonomic revision . On the basis of partly preserved micromorphological features and the microstructure of the skeletons two of them are corrected, i.e. Coelocoenia ? assmanni Weissermel, 1925 and C. exporrecta Weissermel, 1925, from Kamien Śląski, near Opole (Upper Silesia). Coelocoenia ? assmanni was incorporated into Eckastraea prisca (Weissermel, 1925), family Eckastraeidae Morycowa, 2006, in Morycowa and Szulc (2006) and C. exporrecta is assigned to a new genus Opolestraea nov. gen., family Eckastraeidae.

Detecting Photosymbiosis in Fossil Scleractinian Corals

The evolutionary success of reef-building corals is often attributed to photosymbiosis, a mutualistic relationship scleractinian corals developed with zooxanthellae; however, because zooxanthellae are not fossilized, it is difficult (and contentious) to determine whether ancient corals harbored symbionts. In this study, we analyze the δ15N of skeletal organic matrix in a suite of modern and fossil scleractinian corals (zooxanthellate- and azooxanthellate-like) with varying levels of diagenetic alteration. Significantly, we report the first analyses that distinguish shallow-water zooxanthellate and deep-water azooxanthellate fossil corals. Early Miocene (18–20 Ma) corals exhibit the same nitrogen isotopic ratio offset identified in modern corals. These results suggest that the coral organic matrix δ15N proxy can successfully be used to detect photosymbiosis in the fossil record. This proxy will significantly improve our ability to effectively define the evolutionary relationship between photosymbiosis and reef-building through space and time. For example, Late Triassic corals have symbiotic values, which tie photosymbiosis to major coral reef expansion. Furthermore, the early Miocene corals from Indonesia have low δ15N values relative to modern corals, implying that the west Pacific was a nutrient-depleted environment and that oligotrophy may have facilitated the diversification of the reef builders in the Coral Triangle.

Upper Triassic reef coral fauna in the Renacuo area, northern Tibet, and its implications for palaeobiogeography

Upper Triassic reef corals from the Riganpeicuo Formation in northern Tibet represent important scleractinian coral fauna that help explain the palaeobiogeography of the eastern Tethys region during the Late Triassic period. The corals were discovered in bedded limestone in patch reefs or biostromes of the Renacuo area. In this paper, 15 genera and 25 species are identified and categorized, the systematic composition of these corals and their relationships with other Triassic coral faunas are also discussed. The results show that these corals are composed of the typical elements of the western Tethys, with the following genera and species that are endemic to China: Radiophyllia cf. astylatus, Margarosmilia zogangensis and Conophyllopsis qamdoensis, and the genera Retiophyllia, Margarosmilia, Hydrasmilia, Procyclolites, Pamiroseris, Araiophyllum, Stylophyllopsis, Stylophyllum and Guembelastraea provide important links to the Tethys province. The coral fauna also highlights the connection between the Qiangtang terrane and the Songpan-Ganzi fold belt, but shows that the areas are distinct from the Himalayan terrane. It has been interpreted that the Qiangtang terrane and the Songpan-Ganzi fold belt were in the vicinity of the gradually-closed Paleo-Tethys Ocean, which resulted in the free transmigration of the benthonic organisms of these areas. On the other hand, the Himalayan terrane was separated from the Qiangtang terrane by a wide ocean–meso Tethys during the Late Triassic period, which made it impossible for the benthonic organisms on both flanks to freely migrate toward the opposite continental margins.

Triassic Scleractinian Corals in China: A Review of Present Knowledge

Scleractinian corals appeared during the Anisian period of the Triassic after the end-Permian mass extinction, which in Triassic were distinct from the Jurassic-Cretaceous scleractinian corals. The study on Triassic scleractinian coral fauna as a separate field is significant for exploring the development and evolution of modern corals and investigating environmental changes since the Mesozoic. The first Triassic coral in China was reported in 1925, and since then, nearly 25 articles dealing with taxonomy and 17 papers about fossil reports on Triassic scleractinian corals in China have been published, which refer to 60 genera and 312 species, 49 localities and 25 strata. In this paper, the history, taxonomy, localities, stratigraphic distribution, current research, and existing knowledge gaps of the Triassic scleractinian corals in China are reviewed. More specifically, the research findings of the Triassic scleractinain coral in China since 1925 are discussed; the species of the Triassic scleractian coral fossil reported in China, has been examined and its synonyms have been sorted out; the geographical distributions of the Middle and Late Triassic scleractinian corals in China are systematically treated; the Triassic coral biostratigraphy in China has been improved; and the stratigraphic ranges of existing genera and species are provided. The above conclusions are presented in the form of complete figures. At the same time, we analyzed shortcomings in current research and identified productive future research directions of the Triassic scleractinian corals in China.

Photosymbiosis and the expansion of shallow-water corals.

Roughly 240 million years ago (Ma), scleractinian corals rapidly expanded and diversified across shallow marine environments. The main driver behind this evolution is uncertain, but the ecological success of modern reef-building corals is attributed to their nutritional symbiosis with photosynthesizing dinoflagellate algae. We show that a suite of exceptionally preserved Late Triassic (ca. 212 Ma) coral skeletons from Antalya (Turkey) have microstructures, carbonate 13C/12C and 18O/16O, and intracrystalline skeletal organic matter 15N/14N all indicating symbiosis. This includes species with growth forms conventionally considered asymbiotic. The nitrogen isotopes further suggest that their Tethys Sea habitat was a nutrient-poor, low-productivity marine environment in which photosymbiosis would be highly advantageous. Thus, coral-dinoflagellate symbiosis was likely a key driver in the evolution and expansion of shallow-water scleractinians.

Upper Triassic reef corals from the Sambosan Accretionary Complex, Kyushu, Japan

Reef-building and dwelling scleractinian corals attained worldwide distribution in the Late Triassic and are best known from the former Tethys but some taxa also occur in the collage of displaced terranes now comprising the circum-Pacific rim. Among these are Upper Triassic corals from Japan, which have received little systematic study during the past 40 years but hold keys for resolving crucial questions about the depositional history and paleogeography of this region. Ten Upper Triassic coral taxa are here described from limestone rocks of the Sambosan Accretionary Complex, of Japan—a tectonically mobile belt extending from the Okinawa Islands to south of Tokyo on the island of Honshu. This belt contains the remains of reefs and carbonate sediment deposited on volcanic atolls formed at unknown tropical paleogeographic positions. The paleogeographic relationship of the Sambosan Accretionary Complex (SAC) relative to the Tethys and terranes of the circum-Pacific is not well constrained. The Upper Triassic corals of Japan occur within isolated carbonate blocks and extensive breccia deposits of the SAC. Corals and other organisms contain mixed Carnian and Norian taxa, many of which are known to build reefs and appear to have been derived from reef facies. Here we describe and discuss solitary and colonial, potentially reef-building corals from the SAC that come from the island of Kyushu and from Nara and Kochi Prefectures. Three new species described for the first time are: Retiophyllia tosaensis n. sp., Margarosmilia mizukamia n. sp., and Guembelastraea kanmerae n. sp. Other corals are taxonomically reevaluated from previous work: Craspedophyllia japonica n. sp., Thamnasteriamorpha okudai n. sp., Khytrastrea ominensis (Okuda and Yamagiwa), Craspedophyllia ramosa Roniewicz, Protoheterastraea konosensis (Kanmera), and Seriastraea furukawai (Kanmera). Two additional taxa, Retiophyllia cf. R. frechi Roniewicz and Volzeia cf. V. badiotica (Volz) show relationships with Carnian to Norian corals of the former Tethys. Results, when compared with previous taxa, increase knowledge of the composition of Upper Triassic corals of Japan. It shows a high degree of endemism among the Triassic corals of the SAC with some paleogeographic connection to the western Tethys and Pamir Mountains and Timor. The presence of many reef-building coral taxa and reef-type carbonate microfacies along with their paleogeographic distribution suggests a location in the southwestern Panthalassa.

Upper Triassic corals from Nevada, western North America, and the implications for paleoecology and paleogeography

Late Carnian–early Norian corals from the Luning and Osobb formations in west-central Nevada represent an important Late Triassic fauna for understanding the paleoecology and the paleogeography of the eastern Panthalassa region during Late Triassic time. The corals occur in bedded limestone representing biostromes and patch reefs and their composition presages the important global changeover of faunas of the intra-Norian interval. A taxonomic analysis of over 60 specimens reveals a majority of colonial corals ranging from cerioid, astreoid (i.e., cerioid-plocoid lacking walls), meandroid and thamnasterioid types. Surprisingly, remnants of the original aragonite microstructure remain in some specimens, allowing a better comparison with more remote Tethyan corals. In total, 14 genera have been identified from Nevada while two genera remain undetermined. The fauna is composed of species considered typical of both the North American Cordillera and cratonal South America. The following genera and species are new and endemic to the Americas: Khytrastrea silberlingi and K. cuifiamorpha, Flexastrea serialis, Nevadoseris punctata, Areaseris nevadaensis and a new genus Minasteria (with Astrocoenia shastensis Smith, 1927 as type species). Likewise are the new species: Margarogyra silberlingi and Curtoseris dunlapcanyonae. Genera Meandrovolzeia, Margarogyra, Ceriostella, Ampakabastraea, Retiophyllia, Distichomeandra, Curtoseris, Thamnasteria and Astraeomorpha provide important links to the former Tethys province. The revised coral fauna changes previous views of the close taxonomic similarity with the Tethys, instead producing a paleogeographic pattern emphasizing a much greater degree of endemism. This pattern emphasizes the isolation of Nevada from the Tethys and the similarities with some outboard terranes of the Cordillera.

MIDDLE TRIASSIC CORAL GROWTH BANDS AND THEIR IMPLICATION FOR PHOTOSYMBIOSIS

In living zooxanthellate corals, photosymbiosis explains increased metabolism and accelerated skeletal growth, accounting for the success of these corals in shallow-water tropical reefs. Mesozoic corals of the order Scleractinia appeared in the geologic record during the Middle Triassic, but it was not until the Late Triassic that these corals became prominent reef builders—a change hypothesized to coincide with the advent of photosymbiosis. There is considerable discussion, however, concerning algal symbiosis and the timing of their co-evolution with corals. Thus, the beginning of photosymbiosis in the earliest corals of the Middle Triassic has not been established, nor whether their paleoecology was similar to that of modern corals. Many massive colonial reef-building corals lay down thick, discrete bands in their skeletons that record annual growth. We discovered and illustrate here growth bands in Middle Triassic corals from central Nevada, in particular Ceriostella variabilis, whose skeletal structure and bands are well-preserved in Middle Triassic biostromes of central Nevada. To test the photosymbiosis hypothesis we studied colony growth forms in these fossil corals and performed a quantitative analysis of the bands, both in C. variabilis and in a morphologically similar living zooxanthellate reef coral, Montastraea faveolata. Results of these analyses revealed growth bands and colony shapes almost identical in both living and fossil corals. These findings suggest that photosymbiosis was present in Middle Triassic corals at a very early stage in their Mesozoic history. Scleractinians were also likely zooxanthellate from the onset of their Middle Triassic occurrence but for unexplained reasons were not as efficient as modern corals in building reefs.

Uniform habit spectrum vs. taxonomic discrepancy between two succeeding Triassic coral faunas: A proof of the intra-Norian faunal turnover

Triassic coral fauna from the Tethys Ocean contains, besides colonial cerioid, meandroid and thamnasterioid corals, a high percentage of solitary and pseudocolonial, phaceloid corals with exclusively epithecal walls, about one-fifth of the genera with micromorphology of septa having pennules or menianes. These features are significant indications of moderate depth environments of low energy level and reduced illumination. Despite a uniform spectrum of growth forms, microstructural criteria allow discriminating a middle Anisian-early Norian (A2-N1) fauna from the middle/late Norian-Rhaetian (N2/3-R) one. Taxonomy of the two faunas shows meaningful differences: of four families that dominated in A2-N1 fauna, Volzeiidae, Conophylliidae, and Tropiastraeidae are absent from the N2/3-R fauna and Margarophylliidae are present in a considerably reduced volume. As a consequence of reduction of the earlier corals, particular morphologies were eliminated. In the N2/3-R fauna, five families are abundant: the solitary and phaceloid Reimaniphyllidae and Stylophyllidae, along with colonial Cuifastraeidae, Pamiroseriidae and Astraeomorphidae, all known as rare and rudimentary elements in the earlier fauna. This change in faunal content in the Tethys during the Norian was controlled by environmental factor(s) hardly identifiable by simple observation, as this is not connected with any obvious facies or change in coral growth form.

Meteoric diagenesis in carbonates below karst unconformities: heterogeneity and control factors

Abstract The combination of sedimentological and diagenetic data is important for the characterization of carbonate pore systems. This is particularly true for carbonates that were affected by meteoric diagenesis during sub-aerial exposure, for instance at sea-level lowstands. This diagenetic environment is commonly believed to be associated with increases in porosity, permeability and pore-throat diameters. Using data from three localities, improvement or deterioration of reservoir parameters below karst unconformities were analysed with a three-fold approach. In the first step, meteoric dissolution was characterized and early to late diagenetic products were described. In the second step, sedimentological and diagenetic data were converted to petrophysical data. In the third step, modelled climate data, in particular the occurrence of monsoon cells, in conjunction with other control mechanisms, were considered to understand the processes that controlled meteoric dissolution and later pore infill. Three case studies were analysed: (1) Lower Triassic oolites (sedimentary rocks dominated by ooids) and microbialites of the Calvörde Formation (Buntsandstein Group, Germany); (2) stacked shallowing-upward cycles of carbonate platform deposits in the Middle–Upper Triassic Mahil Formation (Arabian plate, Oman), capped by palaeosols; and (3) an Upper Triassic coral patch reef and overlying strata (Adnet, Salzburg region, Austria). Data integration allowed the establishment of three scenarios of significantly different processes related to meteoric diagenesis below unconformities: (1) increase of porosity and permeability and their preservation through time; (2) increase of porosity and permeability and subsequent pore system occlusion; and (3) decrease of porosity and permeability and creation of a barrier for pore fluids. Knowledge of the time span involved in meteoric diagenesis and the nature of the climatic regime helped to explain the origins and control mechanisms of the meteoric pore systems. The study provided evidence that a well-connected, large karst system, typical of a humid climate, is likely to be sealed subsequently by sediment and cement. Under arid climatic conditions, tight palaeosols developed at the unconformity and small karst pore systems developed which had the potential to remain open during basin evolution. Depending on the aforementioned parameters, carbonates affected by meteoric diagenesis may either become tight rocks or reservoirs.

Noriphyllia, a new Tethyan Late Triassic coral genus (Scleractinia)

Noriphyllia gen. n. is a distinctive coral representing the Coryphylliidae, a group of Late Triassic scleractinian corals. Coral faunas of this age are poorly known. The new coral is distinguished from related corals belonging to the reimaniphylliids by key features of septal microstructure as discerned in thin sections. This microstructure consists of a straight/wavy midseptal zone and lateral septal stereome organized into thin fascicles of fibres, producing a fine and sharp micromorphology of the septal sides. The solitary genus Noriphyllia gen. n. contains two Early Norian species: N. anatoliensis sp. n. chosen as the type species and N.dachsteinae sp. n., and a Carnian species referred to as N. monotutoensis sp. n. The new genus is widely distributed in the Late Triassic, Early Norian reef facies of the Tethys region (Northern Calcareous Alps, Austria; Taurus Mountains, Turkey) and it also occurs in the Carnian of Timor. Noriphyllia gen. n. is unique and details of its microstructural features add new understanding to the composition of both Late Carnian and Early Norian corals.

Late Triassic (Carnian) corals from Timor-Leste (East Timor): their identity, setting, and biogeography

Four scleractinian coral taxa are described from limestones within a sandstone-shale séquence correlated with the Late Triassic Babulu Formation, Manatuto township, on the northern coast of Timor-Leste (East Timor). The coral fauna consists of three phaceloid taxa, Paravolzeia tìmorìca gen. et sp. nov., Craspedophyll ramosa sp. nov., Margarosmilia confluens (Münster), and a generically indeterminate solitary taxon attributed to the family Margarophylliidae. Ali four corals are related at various taxonomie levels to Carnian faunas from the Dolomites of northern Italy. Previously, only Norian coral faunas were known from the Triassic of Timor. The fauna exhibits both similarities to and differences from Carnian faunas of the Dolomites and helps confirm palaeogeographic affinities with the western Tethys, although during Late Triassic time Timor lay in the distant southeastern portai of the Tethys. Despite isolation from the western Tethys, the presence of two species foundalso in the Dolomites indicates that larvai dispersai occurred between the two areas.

Triassic roots of the amphiastraeid scleractinian corals

The Early Carnian (Upper Triassic) phaceloid coral originally described by Volz (1896) asHexastraea fritschi, type species ofQuenstedtiphylliaMelnikova, 1975, reproduced asexually by “Taschenknospung” (pocket-budding), a process documented herein for the first time. This type of budding is recognized only in the Amphiastraeidae, a family thus far recorded only from Jurassic-Cretaceous strata. Similar to amphiastraeids,Quenstedtiphyllia fritschi(Volz, 1896) has separate septal calcification centers and a mid-septal zone built of serially arranged trabeculae. The most important discriminating characters of the new amphiastraeid subfamily Quenstedtiphylliinae are one-zonalendotheca and radial symmetry of the corallite in the adult stage (in contrast to two-zonal and bilateral symmetry in the adult stage in Amphiastraeinae).Quenstedtiphyllia fritschishares several primitive skeletal characters (plesiomorphies) with representatives of Triassic Zardinophyllidae and, possibly, Paleozoic plerophylline rugosans: e.g., thick epithecal wall and strongly bilateral early blastogenetic stages with the earliest corallite having one axial initial septum. To interpret the phylogenetic status of amphiastraeid corals, we performed two analyses using plerophylline rugosans and the solitary scleractinianProtoheterastraea, respectively, as the outgroups. The resulting phylogenetic hypotheses support grouping the Zardinophyllidae with the Amphiastraeidae in the clade Pachythecaliina (synapomorphy: presence of pachytheca). Taschenknospung is considered an autapomorphy for the Amphiastraeidae. This study is the first attempt to analyze the relationships of the Triassic corals cladistically.

TRIASSIC ROOTS OF THE AMPHIASTRAEID SCLERACTINIAN CORALS

The Early Carnian (Upper Triassic) phaceloid coral originally described by Volz (1896) as Hexastraea fritschi, type species of Quenstedtiphyllia Melnikova, 1975, reproduced asexually by “Taschenknospung” (pocket-budding), a process documented herein for the first time. This type of budding is recognized only in the Amphiastraeidae, a family thus far recorded only from Jurassic-Cretaceous strata. Similar to amphiastraeids, Quenstedtiphyllia fritschi (Volz, 1896) has separate septal calcification centers and a mid-septal zone built of serially arranged trabeculae. The most important discriminating characters of the new amphiastraeid subfamily Quenstedtiphylliinae are one-zonalendotheca and radial symmetry of the corallite in the adult stage (in contrast to two-zonal and bilateral symmetry in the adult stage in Amphiastraeinae). Quenstedtiphyllia fritschi shares several primitive skeletal characters (plesiomorphies) with representatives of Triassic Zardinophyllidae and, possibly, Paleozoic plerophylline rugosans: e.g., thick epithecal wall and strongly bilateral early blastogenetic stages with the earliest corallite having one axial initial septum. To interpret the phylogenetic status of amphiastraeid corals, we performed two analyses using plerophylline rugosans and the solitary scleractinian Protoheterastraea, respectively, as the outgroups. The resulting phylogenetic hypotheses support grouping the Zardinophyllidae with the Amphiastraeidae in the clade Pachythecaliina (synapomorphy: presence of pachytheca). Taschenknospung is considered an autapomorphy for the Amphiastraeidae. This study is the first attempt to analyze the relationships of the Triassic corals cladistically.

Origins and relationships of Paleozoic coral groups and the origin of the Scleractinia

Two major groups of corals have essentially continuous records from the Early Ordovician (Tabulata) and Middle Ordovician (Rugosa) to the end of the Permian. A third major group, the living Scleractinia, range from Middle Triassic to Holocene. Additional groups have shorter ranges within the Paleozoic. The origins and relationships of these groups have been discussed for over 100 years. Relations between the Rugosa and Scleractinia have attracted the greatest interest because of their morphologic similarities and the time sequence. Arguments involve the significance of serial versus cyclic septal insertion, calcitic versus aragonitic skeletal mineralogy, and the time gap between the last rugosans and first scleractinians (there are no known Lower Triassic corals). Discussions of relationships among the various Paleozoic groups are commonly based on detailed morphological comparisons because of their overlapping stratigraphic ranges.Recent work on the living corals and anemones supports a closer relationship between groups than is suggested by placing them in different orders or suborders. The paleontological record of “anemones” is slight, but it is reasonable to assume that one or more groups of skeletonless zoantharians persisted through long parts of the Phanerozoic. It is suggested that the major groups of zoantharian corals originated through the development of skeletons in various anemone groups at several different times.

Evolution of the coral-zooxanthellae symbiosis during the Triassic: a geochemical approach

Scleractinian corals first appeared during Triassic time in tropical shallow water environments. Controversy surrounds the paleoecology of scleractinian corals of the Late Triassic. Were they like their living counterparts, capable of supporting reefs, or had they not yet coevolved the important association with zooxanthellae that facilitated reef growth and construction? Indirect evidence suggests that some Upper Triassic corals from the Tethys played important constructional roles as reef builders within tropical carbonate complexes of the Tethys. To evaluate this idea, we have employed a geochemical approach based on isotope fractionation to ascertain if Late Triassic corals once possessed zooxanthellae.We have determined evidence for the ancient presence of algal symbiosis in 13 species of Triassic scleratinians from reef complexes in Turkey and northern Italy. In contrast, two higher latitude Jurassic species used as a control group for isotope analysis, lacked isotopic indications of symbiosis. These findings, together with stratigraphic and paleoecologic criteria, support the contention that Late Triassic scleractinian corals inhabiting shallow-water carbonate complexes of the Tethys were predominantly zooxanthellate, like their living counterparts from present day reefs.We view the zooxanthellate condition in calcifying reef organisms as a necessary prerequisite for constructional reef development. Our results emphasize the power of stable isotope studies in helping to answer paleobiological questions.

Upper Triassic corals from Peru

Upper Triassic corals from Peru

Combined quantitative analysis and microfacies studies of ancient reefs: An integrated approach to Upper Permian and Upper Triassic reef carbonates (Sultanate of Oman)

The internal architecture of Upper Permian calcisponge reefs, Upper Triassic coral thickets, and Upper Triassic coral reef communities of the Oman Mountains have been investigated. In order to gain comparable data sets, investigations were carried out at different scales comprising quantitative data from outcrops and descriptions from thin-sections. Methods of quantitative outcrop investigations were modified with reference to standard investigation techniques used in the study of communities of modern reefs. Data evaluation comprises mapping of reef fabric in natural scale on plastic sheets in the field. Data calculation was carried out utilizing the digitized image analysis system Vidas. Measurement parameter are the total detrital framework coverage, coverage of reefbuilder taxa, mean diameter of taxa, and mean distance. In addition, measured plastic sheets were printed for paleoecological interpretation. Thin-section analysis reveal microfacies types, sedimentological criteria and taxonomic inventory of reef organisms.

A coral reef in the Telkwa Range, British Columbia: the earliest Jurassic example

An end-Triassic mass extinction profoundly affected reef ecosystems that flourished in the Late Triassic Tethys seaway. The collapse of Late Triassic coral–sponge reefs was followed by an Early Jurassic (Hettangian–Sinemurian) perturbation interval with a near-global absence of reefs and sharp reductions in diversity. A Jurassic (Sinemurian) reef in the Hazelton Group of central British Columbia appears to fill the gap. Its paleoecology and composition show it to be the first large-framework example in North America and perhaps the world. It demonstrates that the reef-building Triassic coral, Phacelostylophyllum, survived the extinction event and was constructing reefs in Early Jurassic time during a global reef eclipse. The reef is a 48 m thick bioherm that grew within the island-arc complex of Stikinia. Following a decrease in volcanism, reef building began with bivalves growing upon water-lain tuffs. The reef was dominated by large dendroid–phaceloid corals, primarily Phacelostylophyllum rugosum, a species known from the Upper Triassic of Italy, which produced extensive constructional framework. Other fossils include bivalves, solitary and colonial corals, and a variety of dwellers and reef destroyers. Three stages of growth are present. During siliciclastic deposition, the reef mound grew into a bioherm with steep relief and flanking beds. Two intervals of arrested growth marked by pyroclastic lenses and hard grounds punctuated the reef's history. The reef was finally overwhelmed by volcaniclastic sediment, was uplifted, and developed paleokarst. The reef is unique in understanding the dynamics of recovery after the end-Triassic mass extinction.

Evolution des Scleractiniaires: Diversité des architectures poreuses au Trias supérieur

Among Triassic Scleractinia, three distinct architectural types of porous skeletons can be recognized: discontinuity between adjacent trabeculae in Araiophyllum; contraction of the septal plan in the Spongiomorphid family; occurrence of lacunae in the vertical growth of septa in representatives of the genus Seriastraea. The comparison of structural and microstructural features between these three architectural organizations provides evidences for their very inequal values from taxonomic point of view. However, the presence of these various trends to realize porous, architectures among Triassic corals, demonstrates the importance of the evolutionary process at this period, before the strong taxonomic collapse of the Trias/Lias boundary.