bibliography - various topics
Reefs / 9th December 2016
ABDEL-FATTAH Z. A., ASSAL E. M. 2016. Bioerosion in the Miocene Reefs of the northwest Red Sea, Egypt. Lethaia 49, 3: 398-412.
[keywords: Egypt; Miocene reefs; Red Sea; Um Mahara Formation]
Macroborings provide detailed information on the bioerosion, accretion and palaeoenvironment of both modern and fossil reefs. Dolomitized reefal carbonates in the Um Mahara Formation exhibit an outstanding example of spatially distributed, well-preserved bioerosion structures in tropical to subtropical syn-rift Miocene reefs. Ten ichnospecies belonging to five ichnogenera are identified; three belonging to the bivalve-boring ichnogenus Gastrochaenolites, three attributed to the sponge-boring ichnogenus Entobia, and four ichnospecies assigned to three worm-boring ichnogenera Trypanites, Maeandropolydora and Caulostrepsis. The distribution of the reported borings is strongly linked to the palaeo-reef zones. Two distinctive ichnological boring assemblages are recognized. The Gastrochaenolites-dominated assemblage reflects shallower-marine conditions, under water depths of a few metres, mostly in back-reef to patch-reef zones of a back-reef lagoon. The Entobia-dominated assemblage signifies relatively deeper marine conditions, mostly in reef core of the fringing Miocene reefs. These ichnological assemblages are attributed herein to the Entobia sub-ichnofacies of the Trypanites ichnofacies. This ichnofacies indicates boring in hard carbonate substrates (such as corals, rhodoliths, carbonate cements and hardgrounds) during periods of non-sedimentation or reduced sediment input. [original abstract; Wrzolek]
ALEXANDROFF S. J., ZUSCHIN M., KROH A. 2016. Quantitative comparison of Pleistocene and Recent coral reef habitats in the northern Red Sea (El Quseir, Egypt). Facies 2016 (62); 15.
[keywords: Taphonomy; Paleoecology; Invertebrates; Coral composition; Reefs]
Fossil reefs have the potential to provide important data for studies of climate and environmental change. This is particularly true for Pleistocene-Holocene coral reefs, which predominantly consist of communities undisturbed by anthropogenic impact and therefore provide a baseline for evaluating the status of modern reefs. We used photo transects and point-counting to quantitatively compare two Pleistocene reef terraces of two Pleistocene sites, tentatively assigned to marine isotope stage 5e, with habitats (reef flat, reef edge, reef slope at 5- and 10-m water depth) of a modern reef near El Quseir, Egypt. The modern reef exhibits a clear trend of increasing taxonomic richness and diversity from the reef flat towards the reef slope at 10-m water depth. The most abundant genera are Pocillopora, Acropora, Millepora, and massive Porites, but strong differences between individual habitats were evident. The most abundant genera in the fossil reefs are massive Porites and Dipsastraea. With regard to quantitative composition, all modern reef habitats differed significantly from each other as well as from the fossil reefs. The fossil reef composition is most similar to the modern reef slope habitat at 10-m water depth. There are two conflicting hypotheses on geodynamic processes for this area - these are tectonic uplift and tectonic stability. Considering tectonic stability, the fossil reefs would have to be interpreted as lagoonal patch reefs, for which no modern counterparts exist in the study area. However, in the case of tectonic uplift, we conclude that the fossil reefs studied were once situated at around 10-m water depth. [original abstract; Wrzolek]
BAARLI B. G., WEBB G. E., JOHNSON M. E., COOK A. G., WALSH D. R. 2016. Shoal-water dynamics and coastal biozones in a sheltered-island setting: Upper Devonian Pillara Limestone (Western Australia). Lethaia 49, 4: 507-523. (online: 25 November 2015)
Along the Canning Basin's Lennard Shelf in Western Australia, the 80-km-long Oscar Range is composed of folded Palaeoproterozoic quartzite and phyllite and surrounded by limestones of the Great Devonian Barrier Reef including reef complex, related back-reef and lagoonal deposits of the Frasnian Pillara Limestone. The range represents an exhumed cluster of palaeoislands. Near the east end of the Oscar Range, a palaeoislet is encircled by the Pillara Limestone showing outward dips that dramatically shallow to expose nearly horizontal bedding planes offshore. From shore and outward, the facies zones observed in the Pillara Limestone include unfossiliferous laminated sediments followed by biozones with abundant Amphipora and Stachyodes, and domal stromatoporoids. An additional outermost lagoonal facies with a diverse molluscan fauna preserved in fine limestone / dolostone is described in this study. High-spired Murchisonia in a time-averaged assemblage with other gastropods, bivalves, brachiopods and scaphopods dominate this zone. Uneven distribution of biozones is due to intermittent shoals controlled by the complex relief of basement rocks or recent erosion into underlying layers. The orientations of dendroid stromatoporoids and high-spired gastropods were analysed to appraise the dynamics of prevailing shoal-water settings on the inner, more sheltered side of the Oscar Range facing the Devonian mainland to the north. Oscillatory wave action is interpreted as the main agent of transport. Palaeocurrent data for the lighter dendroid stromatoporoids suggest that fair-weather prevailing winds originated from the SE. Pebble clasts, oncoids, bivalves and gastropods indicate episodes of wave agitation and stronger wind from a SE and southerly direction. [original abstract; Wrzolek]
BERESI M. S., CABALERI N. G., LOESER H., ARMELLA C. 2017. Coral patch reef system and associated facies from southwestern Gondwana: paleoenvironmental evolution of the Oxfordian shallow-marine carbonate platform at Portada Covunco, Neuquen Basin, Argentina. Facies 63: 4. doi:10.1007/s10347-016-0486-4
[keywords: Middle Oxfordian; La Manga Formation; Coral reefs; Facies/microfacies; Paleoenvironments; Argentina; Neuquen Basin]
During the Middle Oxfordian, the epicontinental shelf of the Neuquen Basin was a site of major coralline evolution and reef building. This work expounds the studies performed on the La Manga patch reefs at Portada Covunco locality, near Zapala city, Neuquen province. Based on the results of 12 facies/microfacies types and the vertical succession of coral morphotypes a shallowing-upward trend ranging from a shallow subtidal-lagoon- to intertidal settings is inferred. The microfacies model suggests an ooidal shoal area in the highest energy zone and various patch reefs on the shallow carbonate platform. Autochthonous reefal facies comprise a low diversity of platy coral and mixed coral-siliceous sponge framestone, ramose coral bafflestone, and microbial bindstone. Non-reefal facies are composed of ooidal packstone, bedded bioclastic wackestone-packstone, and marl levels. Several shallowing-upward episodes are evidenced by local erosional surfaces (main exposure surface-MES). The succession of platy corals (exclusively Australoseris) followed by ramose corals (Etallonasteria, Stelidioseris, and Stephanastrea rollieri) probably reflects local environmental changes. The upward change in reefal composition is best interpreted in response to extrinsic physical parameters (local, relatively minor sea-level fluctuations). Siliceous sponges occur in low percentages. The La Manga reefal succession could be correlated with the "global carbonate reef event". This event occurred in most basins associated with the Tethyan oceanic belt and the North Atlantic Ocean, in low paleolatitude. The Portada Covunco reefs grew at higher paleolatitudes (nearly 39° south), within an embayment of the Neuquen Basin, with open circulation to the paleo-Pacific Ocean on the southwestern margin of the Gondwana realm. [original abstract; Wrzolek]
BRACCHI V. A., NALIN R., BASSO D. 2016. Morpho-structural heterogeneity of shallow-water coralligenous in a Pleistocene marine terrace (Le Castella, Italy). Palaeogeography, Palaeoclimatology, Palaeoecology 454: 101-112.
[keywords: Algal reefs; Shallow-water carbonates; Substrate type; Water turbidity; Morpho-structural heterogeneity; Mediterranean Sea]
[highlights: * We describe coralligenous (C) build-ups from an Upper Pleistocene paleo-shelf area. * Extensive C bioconstructions developed in shallow, possibly infralittoral, waters. * C shows notable variation in size, composition and framework over short distances. * Large blocks on mobile substrate affect inception and spatial distribution of C. * Turbidity and sediment input affect growth style and demise of infralittoral C.]
COULSON K. P., BRAND L. R. 2016. Lithistid sponge-microbial reef-building communities construct laminated upper Cambrian (Furongian) 'stromatolites'. Palaios 31, 7: 358-370.
Laminoid, weakly fused sponge spicule networks are intercalated between convex stromatolitic laminae in an upper Cambrian (Furongian) reef. Sponges are small, millimeter to centimeter-sized lithistids that encrusted automicritic laminae and in turn were encrusted by microbial biofilms, eventually leading to columnar, crudely laminated 'stromatolites'. Weakly fused desmas, now replaced with fine, blocky calcite, possess an arcuate geometry along the medial to distal ray axes. Minimal decay and separation of sponge tissue from these spicules produced arcuate, filament-like cavities that obscure the former presence of spicule networks when viewed in cross-section. Further deterioration produced peloidal networks and voids. These observations have important implications when reconstructing middle to late Cambrian reef-building communities. Until recently, these periods were assumed to be virtually devoid of calcified metazoan reefal components. An increasing number of recent studies, however, are demonstrating that metazoan reef-builders were more prevalent. This paper adds a unique element to the nature of framebuilding by demonstrating that lithistid sponge-microbial reef-building communities constructed laminated 'stromatolites', and thus may have had a flourishing ecology within late Cambrian microbial buildups. [original abstract; Wrzolek]
DECHNIK B., WEBSTER J. M., WEBB G. E. NOTHDURFT L., ZHAO Jian-xin 2017. Successive phases of Holocene reef flat development: evidence from the mid- to outer Great Barrier Reef. Palaeogeography, Palaeoclimatology, Palaeoecology 466, 15 January 2017, pp 221-230; http://dx.doi.org/10.1016/j.palaeo.2016.11.030
A re-examination of 46 recently published U/Th reef flat ages from Heron and One Tree reefs in the southern Great Barrier Reef (GBR) identified several distinct Holocene reef growth phases with a clear 2.3-kyr hiatus in lateral reef accretion from 3.9 ka to 1.5 ka. An analysis of all available published radiocarbon reef flat ages (165) from 27 other mid-outer platform reefs revealed a similar hiatus between 3.6 ka and 1.6 ka for the northern, south-central and southern GBR. However, no hiatus in reef flat growth was observed in reefs from the central GBR with ages ranging from 7.6 ka to 0.9 ka. Increased upwelling, turbidity and cyclone activity in response to increased sea-surface temperature (SST's), precipitation and El-Nino Southern Oscillation variability have been ruled out as possible mechanisms of reef turn-off for the mid-outer platform reefs. Rather, a fall (~0.5m) in relative sea level at 4-3.5 ka is the most likely explanation for why reefs in the northern and southern regions turned off during this time. Greater hydro-isostatic adjustment of the central GBR and long term subsidence of the Halifax Basin may have provided greater vertical accommodation for the mid-outer reefs of the central GBR, thus allowing these reefs to continue to accrete vertically despite a fall in sea level ~ 4–3.5 ka. Further evidence for greater subsidence in this region includes the lack of senile reefs and dominance of incipient and juvenile reefs in the central GBR. This suggests that these reefs approached sea level considerably later than the northern and southern reefs, consistent with their deeper antecedent substrates. Thus, these results not only provide important information about possible reef flat demise in response to natural environmental factors, but also provide insights into regional subsidence that affected relative sea level along the east Australian margin during the Holocene.
EICHHOLT S., BECKER R. T. 2016. Middle Devonian reef facies and development in the Oued Cherrat Zone and adjacent regions (Moroccan Meseta). Facies 2016 (62); 7.
[keywords: Middle Devonian; Reefs; Microfacies; Paleoecology; Morocco; Meseta]
Middle Devonian reefs were widespread on the various synsedimentary tectonic blocks of the Moroccan Meseta, which formed the southern external Variscides. So far, poorly studied biostromes and small to medium-sized bioherms have grown in the southern subtropics, separated by the ca. 3000-km-wide Prototethys from the well-known reefs of the southern Laurussian shelf. Autochthonous, displaced, and reworked Givetian reefal limestones of the Oued Cherrat Zone south of Rabat and from adjacent regions were studied by outcrop facies logging and microfacies analysis. The new data are used to reconstruct their paleoecology, developments in time and space, and contribute to the understanding of reef facies differences along a paleolatitudinal gradient. Eighteen microfacies (sub) types are recognized, described, and illustrated. They represent thick inner-reef platforms (Ain Khira South, Jennabia), different parts of a synsedimentarily tectonized bioherm (Ain-Al-Aliliga), a small, open neritic biostrome/low bioherm (Ain-as-Seffah), the episodically retro-and prograding outer margin of a thick biostrome to bioherm sequence (Sidi Mohamed Smaine), and reworked reef remnants preserved in proximal to distal olistolith units (Ain Dakhla, Sidi Ahmed Lhemdoun, Biar Setla Conglomerate). Meseta reefs differed from those of stable northern Gondwana (western Anti-Atlas to southern Algeria) but show many similarities with the more distant Rhenish organic buildups. This suggests a very low Givetian paleoclimatic gradient in the southern hemisphere. The lack of facies types dominated by calcimicrobes / calcareous algae is distinctive for the study area. [original abstract; Wrzolek]
HINESTROSA G., WEBSTER J. M., BEAMAN R. J. 2016. Postglacial sediment deposition along a mixed carbonate-siliciclastic margin: New constraints from the drowned shelf-edge reefs of the Great Barrier Reef, Australia. Palaeogeography, Palaeoclimatology, Palaeoecology 446: 168-185 (15 March 2016).
[keywords: Last Glacial Maximum; Submerged reefs; Sequence stratigraphy; Seismic stratigraphy; Sea level change; Quaternary reefs]
A seismic stratigraphy analysis was conducted at two sites, Hydrographers and Noggin passages, separated by about 540km on the shelf-edge of the central Great Barrier Reef (GBR), Australia. We used recently available seismic and bathymetry data and a new synthesis of downhole logs and lithological, petrophysical and radiometric data from cores recovered by the Integrated Ocean Drilling Program Expedition 325 (Great Barrier Reef Environmental Changes). We compared the stratigraphy of both sites, identifying a full depositional sequence with deposits from at least 28ka BP to ~7ka BP, bounded by two marine flooding surfaces. Within this sequence, each systems tract is represented by unique depositional features characteristic of the shelf-edge systems. Despite the broad environmental and geomorphic similarities between the two sites, differences in postglacial reef development were remarkable. These contrasts can be explained as a result of: (1) local antecedent substrate variations and (2) the interplay of shelf physiography with Late Quaternary sea level fluctuations, which favoured changes in biological production and sediment flux as the palaeo-shoreline evolved from linear to complex during intermediate sea levels. During these intermediate sea levels, the northern estuarine coast and its steep substrate at shelf-edge locations contrasted strongly with the protected palaeo-lagoons and the extensive, gentle marginal terraces found at the southern central GBR. This setting enhanced the regional differences in sediment transport and reef development through the last transgression. The conceptual model presented here provides a broader depositional framework and improves the understanding of the main processes controlling the spatial and temporal depositional patterns on the shelf-edge of mixed siliciclastic-carbonate margins. [original abstract; Wrzolek]
HU Mingyi, HU Zhonggui, QIU Xiaosong, ZHAO Enzhang, WANG Dan 2012. Platform edge reef and bank structure and depositional model of Changxing formation in Panlongdong section, Xuanhan, northeastern Sichuan. Journal of Earth Science 23, 4: 431-441.
[keywords: northeastern Sichuan; Changxing Formation; reef bank; depositional model]
The Changxing Formation has two sequences (sq1 and sq2) in the Panlongdong Section, Xuanhan, northeastern Sichuan . It belongs to the platform edge facies belt, rich in reefs and banks, which were developed in the highstand system tract (HST) of sq1 and sq2, respectively. During third-order relative sea level dropping, the platform edge reef bank were mainly developed in the overall progradation parasequence sets. The platform edge reefs were developed in three phases, while platform edge banks in two phases. Outcrop observation and microscopic identification for platform egde reefs and banks in the section show that the three-phase-reefs are all composed of reef base and reef core, with string of tube sponge as the major reef-building organisms and fiber sponge, hydrazoan and bryozoans as the minor, while the reef-attached organisms mainly being foraminifera, brachiopod, echinoderm and ostracod. The first-phase-reef rock type is baffling reefs, the second phase baffling reefs and framework reefs assembles, the third phase framework reefs. Typically, the second phase reefs were developed with the maximum sedimentary scale and thickness, with the most abundant reef-building organisms and reef-attached organisms, showing best physical properties for reservoirs. The platform edge banks mainly consists of gravel debris and ooide grains, mostly dolomized. The dolomitizition in the second phase was relatively intense, favoring good reservoirs. [original abstract; Wrzolek]
JIAO Yangquan, WU Liqun, RONG Hui, WANG Yongbiao, WANG Rui 2012. Paleoecology of the Ordovician reef-shoal depositional system in the Yijianfang outcrop of the Bachu area, West Tarim Basin. Journal of Earth Science 23,4: 408-420.
[keywords: paleoecology; reef-shoal depositional system; Ordovician; Tarim basin]
The reef-shoal depositional system of the Ordovician carbonate platform margin is well exposed in the Yijianfang outcrop of the Bachu uplift region, which offers an advantageous condition to study their paleoecology. Using a detailed field geologic survey and illustrated profiles of typical depositional systems, three types of genetic facies associations can be recognized in the reef-shoal depositional system: an organic reef, an organic shoal, and an upper slope. The organic reef is composed of three types of genetic facies (a reef base, a reef core, and fore-reef breccias); the organic shoal is formed from five types of genetic facies (tide channels, fore-reef inner shoals, fore-reef outer shoals, back-reef inner shoals, and back-reef outer shoals). The studies of the paleontological assemblage in each genetic facies of the depositional system indicate that the fauna preserved in each genetic facies are varied. The Calathium, Archaeoscyphia, bryozoan, and calcareous alga are well preserved in the organic reefs. The organisms preserved in the organic shoals are generally fragmented, while well-preserved Girvanella and Nuia siberica with a content of about 15% in the back-reef outer shoals are the most characteristic and different from others. The Sinoceras, trilobites, and gastropods are well preserved in the upper slope deposits. The studies will demonstrate that the reef-shoal complexes developed above the base of the fair-weather wave base and that the original hydrodynamic conditions for the reef core forming is the stronger and become more and more low-energy from the inner part to outer part of the organic shoals. [original abstract; Wrzolek]
LEE Jeong-Hyun, HONG Jongsun, CHOH Suk-Joo, LEE Dong-Jin, WOO Jusun, RIDING R. 2016. Early recovery of sponge framework reefs after Cambrian archaeocyath extinction: Zhangxia Formation (early Cambrian Series 3), Shandong, North China. Palaeogeography, Palaeoclimatology, Palaeoecology 457: 269-276.
[keywords: Cambrian; Metazoan-microbial reef; Sponge; Rankenella; Reef framework]
Reefs dominated by the anthaspidellid sponge Rankenella zhangxianensis, the calcimicrobe Epiphyton and the stem-group cnidarian Cambroctoconus orientalis, together with encrusting microstromatolites occur early in the middle Cambrian (Series 3, late Stage 5) of Shandong, eastern China. In the Zhangxia Formation, these in situ components created a tight framework, with centimeter-scale growth cavities mainly filled by fine-grained matrix. Among them, R. zhangxianensis and C. orientalis mutually attached and locally formed metazoan-dominated frameworks. These metazoan-microbial reefs form thin lenses < 2 m wide within microbial mounds, and probably developed at least a few centimeters of synoptic relief above these surrounding structures. With an age of > 505 Ma, these Rankenella reefs indicate recovery of framework-building metazoans within ~ 5 million years of the archaeocyath reef decline. In structure, they resemble archaeocyath reefs as well as Early Ordovician lithistid sponge-microbial reefs, having conjoined conical macroskeletons thickly veneered by calcimicrobes and microbial carbonate with largely matrix-filled intervening cavities. In combination with other sponge-microbial reefs reported from Australia, Iran, Korea and the USA, they demonstrate that an anthaspidellid sponge-microbial reef consortium was widespread throughout the mid-late Cambrian. [original abstract; Wrzolek]
LEE Jeong-Hyun, HONG Jongsun, LEE Dong-Jin, CHOH Suk-Joo 2016. A new Middle Ordovician bivalve-siliceous sponge-microbe reef-building consortium from North China. Palaeogeography, Palaeoclimatology, Palaeoecology 457, 1 September 2016, pp 23-30; http://dx.doi.org/10.1016/j.palaeo.2016.05.034
[keywords: Reef; Bivalve; Siliceous sponge; Middle Ordovician; North China Platform]
A new reef-building consortium from a Middle Ordovician succession of the western North China Platform is described, consisting mainly of bivalves, siliceous sponges, and microbial carbonates (Epiphyton-like, Renalcis-like and Girvanella calcified microbes, and microcrystalline microstromatolites), in addition to minor brachiopods, Amsassia and Rhabdotetradium. The bivalves are thin-walled and mostly articulated, indicating in situ preservation. The siliceous sponges are characterized by regularly spaced spicule networks embedded within micrite, which partly grade into peloidal textures. Three main types of bivalve-sponge associations are found: (1) larger bivalves (2-13 mm) encrusted by sponges, (2) sponges occupying internal spaces of larger bivalves, and (3) smaller (0.2-0.4 mm) bivalves embedded within sponge spicule networks. Microbial carbonates either cover the upper surfaces of siliceous sponges and bivalves, or occur independently as centimeter-scale patches. The reefal boundstones were constructed mainly by bivalves, siliceous sponges and microbes, which were subsequently encrusted and stabilized by additional sponges and microbes. Extensive early marine cementation forming fibrous cement helped stabilize the reef framework. The co-occurrence of bivalves and siliceous sponges is possibly analogous to modern-day counterparts in which sponges encrust bivalves or bivalves are living within sponges, suggesting a symbiotic relationship. The bivalve-siliceous sponge-microbial reefs of this study, together with other Ordovician reefs, represent the changeover from microbial- to skeletal-dominated reefs during the Middle Ordovician. The current example may represent an ancestral association of bivalve-siliceous sponge-microbe reefs, similar to those in the Mesozoic and Cenozoic, thus shedding light on the roots of such associations.
LI Qijian, LI Yue, ZHANG Yuandong, MUNNECKE A. 2016. Dissecting Calathium-microbial frameworks: the significance of calathids for the Middle Ordovician reefs in the Tarim Basin, northwestern China. Palaeogeography, Palaeoclimatology, Palaeoecology, available online 3 August 2016; http://dx.doi.org/10.1016/j.palaeo.2016.08.005
[keywords: Calathium reef; Microbialite; Darriwilian; Tarim Basin; Northwestern China]
As an obconical macrofossil with porous double-wall, Calathium was commonly present in reefs of Early to early Middle Ordovician age. The Calathium-bearing reefs thrived globally during the Early Ordovician, but this ecosystem collapsed in Middle Ordovician. A rare case of Calathium-microbial reefs was found from the middle part of the Yijianfang Formation (Darriwilian, late Middle Ordovician) of the Bachu area, located in the northwestern margin of the Tarim Basin, northwestern China. Surrounded by bioclastic grainstones, patch reefs here are well-developed and vary in size, with 1–4 m in thickness and 2–18 m in diameter. Three facies types are distinguished within the reef limestones: (1) Calathium-microbial framestone, (2) echinoderm-Calathium bafflestone, and (3) bryozoan-microbial bindstone. As a dominant type, the Calathium-microbial framestone shows a three-dimensional skeletal framework that is mainly constructed by Calathium and stabilized by microbialites. Although most specimens are toppled, Calathium displays well-developed lateral outgrowths, which connected individuals of the same species. Morphological characters of Calathium in thin sections show that calathids are hypercalcified sponges rather than receptaculitid algae. Unlike the Early Ordovician lithistid sponge-Calathium reefs, the Tarim reefs studied herein contain very few lithistid sponges. Instead, bryozoans are fairly common and act as the most important non-microbial encrusters, attaching to the walls of Calathium. Noticeably, the co-occurrence of pelmatozoans and Calathium is similar to those reported from Late Ordovician calathids-echinoderm reef communities from Tennessee. The presence of Calathium-microbial reefs in Tarim indicates that locally calathids were major reef builders, at least before the latest Middle Ordovician.
LIPPS J. H., STANLEY G. D. Jr 2016. Photosymbiosis in the past and present reefs. In Coral Reefs at the Crossroads. Coral Reefs of the World 6. Hubbard et al. (eds). Springer Science Publishers, Dordrecht; pp 47-68. doi 10.1007/978-94-017-7567-0_3
Reef organisms are well known for engaging in photosymbiosis in which a heterotrophic protist or animal host partners with one or more kinds of photosynthetic microbes. This relationship provides metabolic advantages in nutrition and rapid calcification, often leading to secretion of massive skeletons in the host. In turn the symbiont receives protection, physical stability in the photic zone and direct access to the sun's energy. On an evolutionary scale, this relationship provided strong selective pressures for producing the algal-host relationship and has occurred multiple times in geological history. Today, different kinds of algae (dinoflagellates, diatoms, chlorophytes, rhodophytes, and cyanobacteria) inhabit various hosts (foraminifera, corals, mollusks) in modern reefs, and multiple phylogenetically separate algae may have also inhabited phylogenetically distinct ancient animals and protists. The modern dinoflagellate photosymbiont Symbiodinium occurs in a wide variety of unrelated host organisms from protists to mollusks. Molecular data indicate this genus first evolved either after the end-Cretaceous mass extinction 65 my ago or in the Early Eocene some 55 my ago. Encysted dinoflagellates related to Symbiodinium have been traced to the Triassic, and photosymbiosis may have been involved in even earlier reef associations. In all fossils, however, the identity of ancient photosymbionts is difficult to establish because they rarely, if ever, fossilize. Nevertheless, indirect evidence indicates that photosymbiotic ecosystems existed at least as far back as the Cambrian. Inferential lines of evidence, including large colony size, massive skeletons, unusual or complex morphology, the biogeographic distribution of possible hosts and skeletal geochemistry are all consistent with active photosynthesis. In the following pages, we develop the hypothesis that photosymbiosis best explains both the successes and failures of reefs through geologic time. We then review the evidence that suggests photosymbiosis in reef organisms played significant roles through geologic time in both the evolution and extinction of organisms and the reefs they constructed. [original abstract; Stanley]
LIPPS J. H., STANLEY G. D. Jr 2016. Coral Reefs at the Crossroads. Coral Reefs of the World 6. Hubbard et al. (eds). Springer Science Publishers, Dordrecht; pp 175-196. doi 10.1007/978-94-017-7567-0_8
Although reef-like structures formed in the Neoproterozoic, reefs built by metazoans did not appear until the early Paleozoic. From then until the Recent, reefs diversified, underwent extinctions many times and then diversified again. Reef-inhabiting organisms included many different groups from algae to vertebrates as well as enigmatic, extinct suprageneric taxa. Evolution of these groups continued unabated and sometimes resulted in significant changes in the communities making up reefs. These reef groups varied over geologic time with extinction events commonly marking dramatic changes in the biotas. Paleozoic reefs consisted of sponges, corals, foraminifera, algae, bryozoans, and brachiopods, among others. The major extinction event at the end of the Paleozoic eliminated these forms as reef constituents and new groups (e.g., the first scleractinian corals) appeared in the Triassic. The Mesozoic was dominated by sponges, corals, rudist bivalves, and algae, most of which were eliminated in the end-Cretaceous extinction event. The Cenozoic reef biotas included red algae, foraminifera, sponges, corals, various invertebrates, and fish. Throughout the Phanerozoic, these biotas were eliminated by extinction events of differing magnitude. Each event corresponded to warming due to rising greenhouse gases (CO2 and CH4), and ocean acidification caused by lowered pH and anoxia of shallow waters that took severe tolls on reef organisms. These extinction events caused the decline of reef organisms and the reefs they built, resulting in decreased diversity and slower carbonate deposition. Photosymbiotic reef ecosystems failed during extinctions and these failures may have been driven, at least in part, by either the demise of the symbiosis or the extinction of symbionts. Reefs were generally absent in post-extinction times due to different ecologies. The ancestors of the next radiation of reef organisms must have been present somewhere - perhaps in deeper water, remote seamounts or isolated shallow seas. These ancestral faunas gave rise to radiations of reef organisms following several million years of depauperate and unusual biotas. Once underway, these radiations were relatively rapid and were responses to an amelioration of the extinction conditions and an increase in ecological opportunities. They did not restore the same taxa; rather new organisms at the familial or generic levels commonly diversified in most groups. [original abstract; Stanley]
LUO C., REITNER J. 2016. 'Stromatolites' built by sponges and microbes – a new type of Phanerozoic bioconstruction. Lethaia 49, 4: 555-570.
[keywords: Carboniferous, keratose demosponge, microbialite, stromatolite, Triassic]
Two 'stromatolites' from Carboniferous and Triassic carbonates previously regarded as microbial bioconstructions are analysed and reinterpreted as sponge-microbial build-ups. The automicritic aggregations in these build-ups are similar to the previously reported fossils of keratose demosponges in showing moulded anastomosing filamentous structures. All the studied columnar or domal constructions were formed in turbulent water with high sedimentation rate. The Carboniferous build-ups were constructed in the shallow subtidal zone of an open shelf or a ramp. The laminations within the stromatolite-like columns are composed of alternating dark micritic laminae of sponge fossils and pale laminae of neomorphic microspars. The accretion of these columns is probably related to the repeated cycles of sponge growth, rapid lithification after burial, re-exposure and erosion, and settlement of new generations. The Triassic rocks are presumed to have been precipitated in a slightly evaporitic environment based on lithological features. They show a transition from planar laminae, which were formed under the influence of microbial mats, to stromatolitic columnar or domal build-ups, which are dominated by stacked micritic clumps of probable sponge fossils. The sponge-microbe alternation may have been controlled by variation of salinity. Comparable with a recent study, this work shows that sponge-related bioconstructions can be morphologically similar to microbialites in the level of mega- and mesostructures. [original abstract; Wrzolek]
MARTINDALE R. C., CORSETTI F. A., JAMES N., BOTTJER D. J. 2015. Paleogeographic trends in Late Triassic reef ecology from northeastern Panthalassa. Earth-Science Reviews 142: 18-37.
The Late Triassic was a pivotal period in reef evolution, but the majority of information about reef ecology during this time comes from buildups in the Alps (e. g., the Tethys Ocean ). Recent studies of reefs in western North America have recognized unique ecologies along the eastern margin of the Panthalassa Ocean. Although there are numerous (twenty-five) localities with putative reef builders, only four buildups had syndepositional relief and a rigid framework (i.e. true reefs). The most paleo-northern true reefs were microbial patch reefs with only a few large skeletal bioconstructors; hypercalcified sponges and spongiomorphs built the mid- latitude reefs, with secondary microbial encrustation and branching, phaceloid Retiophyllia corals. Corals are the primary bioconstructors in Panthalassa's most paleo-equatorial reefs and calcareous microbes are sparse. When all reefal deposits are analyzed, the N-S gradient is also present, with microbial and bivalve deposits in the north, spongecoral deposits in the mid latitudes, and coral deposits near the equator. This ecological gradient is not apparent in the Tethys Ocean. Tethyan reefs thrived in oligotrophic, tropical waters without strong latitudinal gradients; by contrast, paleoceanographic considerations suggest that cool, nutrient-rich waters swept south along the western North American borderlands in the Late Triassic. The eastern boundary current is interpreted to have created a strong north-south differentiation of environments in northeastern (NE) Panthalassa that was manifested in both the biotic and abiotic characteristics of eastern Panthalassic reefs. Reefs from equatorial Panthalassa are similar to Tethyan reefs (warm-water, photozoan, coral reef structures), whereas higher paleo-latitude reefs from Panthalassa are interpreted as cool-water (heterozoan) buildups, with abundant calcareous microbes, diminutive biocalcifiers, and few large, framework-building corals. [original abstract; Löser]
MATYSIK M. 2010. Reefal environments and sedimentary processes of the Anisian Karchowice Beds in Upper Silesia, southern Poland. Annales Societatis Geologorum Poloniae 80, 2: 123-145.
[keywords: Middle Triassic; palaeoenvironments; sponge-coral reefs; Upper Silesia]
The Anisian shallow-marine Karchowice Beds of the Upper Silesia represent reefal habitats and circum-reefal environments, where biological-mechanical interactions determine sedimentary processes and facies pattern. The purpose of this study was recognition of the interaction between biological and mechanical controls of carbonate deposition. Such interdependence resulted in considerable lateral variability of thickness and lithological features, observed at a distance of 25km. The western part of the basin is dominated by proximal facies (reefal facies), whereas the eastern one represents distal facies (fore-reef). Sedimentary succession in the western area is twice as thick than the eastern one. It resulted from different rate of subsidence owing to block tectonics, controlled by reactivated ancestral Silesian-Moravian Fault. Small-scale synsedimentary faults confirm syndepositional tectonic activity in the region. * Palaeogeographical position caused that the Upper Silesia was strongly affected by monsoon climate, generating storms. These storms contributed to episodic deposition, prevailing during the sedimentation of Karchowice Beds. However, most of time was represented by prolonged non-deposition periods, recorded as interstratal hiatuses, but also by forming of firmgrounds, micritization and coating of bioclasts or substrate recolonisation by organisms. [original abstract; Wrzolek]
PERYT T. M., RACZYNSKI P., PERYT D., CHLODEK K., MIKOLAJEWSKI K. 2016. Sedimentary history and biota of the Zechstein Limestone (Permian, Wuchiapingian) of the Jablonna Reef in Western Poland. Annales Societatis Geologorum Poloniae 86: 00-00. [in press]
[keywords: Wuchiapingian, reefs, Zechstein, bryozoans, stromatolites, aragonite cementation, neptunian dykes, carbon and oxygen isotopes]
The Jablonna Reef, one of the reefs formed in Wuchiapingian time in the western part of the Wolsztyn palaeo-High (SW Poland), is characterized by quite irregular outlines and consists of three separate reef bodies (ca. 0.5-1.5 km2 each; the thickness of the reef complex is usually >60 m). It is penetrated by four boreholes, which show two distinct phases of bryozoan reef development during deposition of the the Zechstein Limestone. The first one occurred early in the depositional history and botryoidal aragonitic cementation played a very important role in reef formation. This phase of bryozoan reef development terminated suddenly; one possible reason was that a relative change of sea level - first a fall and then a rise - disturbed the upwelling circulation. Consequently, bioclastic deposition predominated for a relatively long time until the second phase of bryozoan reef development occurred, but the latter was not accompanied by dubious early cementation. During this second phase, reticular fenestellid bryozoans were predominant. Subsequently, microbial reefs developed and abound in the upper part of the Zechstein Limestone sections. The general shallowing-upward nature of deposition in the Jablonna Reef area resulted in reef-flat conditions with ubiquitous, microbial deposits, in the central part of the Jablonna Reef. Then, the reef-flat started to prograde and eventually the entire Jablonna Reef area became the site of very shallow, subaqueous deposition [first part of an extensive abstract; Wrzolek]
PEYBERNES C., CHABLAIS J., ONOUE T., ESCARGUEL G., MARTINI R. 2016. Paleoecology, biogeography, and evolution of reef ecosystems in the Panthalassa Ocean during the Late Triassic: Insights from reef limestone of the Sambosan Accretionary Complex, Shikoku, Japan. Palaeogeography, Palaeoclimatology, Palaeoecology 457: 31-51.
[keywords: Upper Triassic; Reef; Sambosan Accretionary Complex; Japan; Panthalassa; Biostratigraphy; Multivariate analyses]
Upper Triassic reefs from the Panthalassa Ocean have been understudied in comparison to their Tethyan counterparts and are therefore pivotal to understanding the global reef evolution during the Late Triassic. To fill this gap, Upper Triassic reef limestone from ten localities of the Sambosan Accretionary Complex at Shikoku Island (Japan) has been investigated. Biotic assemblages, quantitative microfacies analysis, and integrated biostratigraphy allow us to characterize two types of reefs, those attributed to the Ladinian?-Early Carnian and those attributed to the Late Carnian-Rhaetian? At the regional scale, our data refine the biostratigraphic framework of the Upper Triassic Sambosan limestone. At the global scale, multivariate analyses support a strong paleobiogeographic affinity of the Western Panthalassa reef biota with those of the South Tethys Ocean during the Ladinian-Carnian and Norian-Rhaetian. Additionally, they indicate connections with East Panthalassa reefs during the Norian-Rhaetian. [original abstract; Wrzolek]
PRETKOVIC V., BRAGA J. C., NOVAK V., ROSLER A., RENEMA W. 2016. Microbial domes and megaoncoids in Miocene reefs in the Mahakam Delta in East Kalimantan, Indonesia. Palaeogeography, Palaeoclimatology, Palaeoecology 449, 1 May 2016, pp 236-245; http://dx.doi.org/10.1016/j.palaeo.2016.02.019
* Microbialites occur in Langhian patch reefs within delta deposits in East Kalimantan.
* Microbialites appear as low-relief domes and as large nodules, here named megaoncoids.
* Flat-domed microbialites formed at the transition from reefs to fine siliciclastics.
* Megaoncoids accumulated in a breccia laterally changing into coral boundstones.
* Both types formed in shallow, turbid waters of the Miocene Mahakam delta.
RODRIGUEZ S. 2014. Los Santos de Maimona: un arrecife del Carbonífero. Memorias de la Real Sociedad Espanola de Historia Natural 12: 73-81.
The Siphonodendron Limestone at Los Santos de Maimona Carboniferous Basin is regarded as a reef structure built mainly by rugose corals. It is not a complex reef, but a reef-flat in which few building organisms (rugose and tabulate corals) are combined with highly diverse secondary components, such as brachiopods, calcareous algae, echinoderms, bryozoans, molluscs, foraminifers, ostracods, etc. Many examples of interaction between organisms and ecological successions are visible in that limestone, which consequently have a very high paleontological value. [original abstract; Rodriguez]
RYAN E. J., SMITHERS S. G., LEWIS S. E., CLARK T. R., ZHAO J.-X. 2016. Chronostratigraphy of Bramston Reef reveals a long-term record of fringing reef growth under muddy conditions in the central Great Barrier Reef. Palaeogeography, Palaeoclimatology, Palaeoecology 441, 4: 734-747 (1 January 2016).
[keywords: Reef accretion; Palaeo-ecology; Great Barrier Reef; Inshore coral reef; Holocene; U-Th dating]
Inshore reefs on Australia's Great Barrier Reef (GBR) are widely argued to be in decline, although recent reports suggest that some may be more resilient than traditionally assumed. Resolution of this debate requires long-term insights into past reef development and variability to provide context for the assessment of present reef condition. Long-term reef growth histories can preserve extended records of reef growth and condition, however they are rare, especially for mainland-attached fringing reefs, which are themselves uncommon on the GBR. We examined the internal structure and ecology at Bramston Reef, a mainland-attached fringing reef located in a protected bay on the central GBR. Eight reef matrix cores were collected across the reef flat. Sedimentological and palaeo-ecological analyses coupled with U-Th dating were used to develop the first reef growth history for a shore-attached fringing reef in this region. Twenty-five hard coral genera were identified in the palaeo-ecological analyses. The key reef-building genera (including Acropora, Montipora, Euphyllia, Porites and Goniopora) have contributed to reef growth since initiation and are represented in the extant coral community, despite a change in accretion 'mode' during the late Holocene. Sedimentological and stratigraphic investigations demonstrate Bramston Reef has always grown in a mud-rich setting. U-Th ages indicate that reef initiation occurred at or before 5400 yBP in a palaeo-water depth of 2-3m. Bramston Reef reached sea level by 4256 yBP when sea level was approximately 1m higher than present, after which rapid seaward progradation occurred until around 3000 yBP (~19 cm/yr on average). Between approximately 3000 and 1000 yBP seaward progradation of the reef flat slowed (to ~9.8 cm/yr on average). This deceleration of reef growth occurred long before European settlement of the Queensland coast and was driven by natural constraints, probably associated with limited accommodation space due to late-Holocene sea-level fall. Our results demonstrate that mainland-attached reef initiation and accretion can occur in muddy inshore environments over long timeframes (centuries to millennia). [original abstract; Wrzolek]
SHEN Jian-Wei, WANG Yue, ZHAO Na, YANG Hong-Qiang, FU Fei-Xue, JIN Yong-Bin 2016. Carbonate sedimentary characteristics of the beach rocks around Qilian Islets and Cays, Xisha Islands: implication for coral reef development and decline. Palaeogeography, Palaeoclimatology, Palaeoecology, available online 6 May 2016; http://dx.doi.org/10.1016/j.palaeo.2016.05.005
[keywords: Beach rocks; Sedimentary characteristics; Cementation; Microbial carbonate; Coral reef]
* Beachrocks on a coral reef coast were studied in detail. The results promote the knowledge of beach rock formation mechanism.
* The constituent of skeletal grains in beach rocks were estimated, and the depositional patterns were established.
* The cementation of beach rocks was examined; the microbial activities in micritization of skeletal grains were documented.
* Factors controlling the formation of beach rocks were discussed, and links between beach rocks and reef growth were probed.
SHEN Jian-Wei, ZHAO Na, YOUNG A., MAO Ying-Jiang, WANG Yue 2016. Upper Devonian reefs and microbialite at Maoying, South China - implications for paleoenvironmental changes. Palaeogeography, Palaeoclimatology, Palaeoecology, available online 5 July 2016; http://dx.doi.org/10.1016/j.palaeo.2016.07.005
[keywords: Carbonate platform; Patch reef; Stromatoporoid; Stromatolite; Thrombolite; Frasnian-Famennian]
Reefal carbonate deposits in South China preserve a record of community structure and environmental change across the Frasnian-Famennian boundary and through the Late Devonian, detailing a regional response to one of the largest mass extinction events in Earth history. The Upper Devonian (Frasnian to Famennian) limestone outcrops in the Maoying area of northern Ziyun County, South China, record a carbonate platform depositional setting with some patch reef development. The Upper Devonian carbonate deposits in Maoying area are distinctive from those in correlative sections in Dushan County with rare argillaceous limestone and dolomitic limestone as well as less dolostone. Exposures to the south in the Guilin area of northeastern Guangxi Province are similar to those seen in the study area. Upper Devonian carbonates in the Maoying area are divided into two lithologic groups, reef limestones or dolostone beds, composed of five lithologically distinctive intervals. The Upper Devonian strata have a cumulative thickness of 530 m. The Upper Devonian reefs in the Maoying area were developed on a shell pavement of brachiopod- and bivalve-shell shoal packstones and evolved into patch reefs in the interior of the carbonate platform. Patch-reef development was limited to early Frasnian time. Reef-building organisms are dominated by massive and tabular stromatoporoids, Amphipora sp., Stachyodes sp., and coral Thamnopora sp., while brachiopods and algae accumulated between stromatoporoid skeletal frameworks. Three evolutionary stages of the Frasnian patch reefs, including an initial development stage, maturity stage and demise stage, can be recognized according to sedimentary structures and fossil assemblage characteristics. The Frasnian strata overlying the patch reefs represent a well-bedded back-reef depositional setting and are mainly composed of Amphipora floatstone and packstone containing a few bulbous stromatoporoids and small fasciculate corals. Famennian strata are characterized by laminated limestone and fenestrate limestone that are interbedded with infrequent mudstone and argillaceous limestone horizons. A prominent microbialite bed developed in the laminated limestone of the Famennian carbonate platform consists of stromatolite and thrombolite framestone. This bed can be correlated, in horizon and age, with microbial reefs and mounds in the Famennian offshore carbonate platform in the Huanan Epeiric Sea (such as Famennian microbial reefs and mounds in Guilin). This represents a biogenic carbonate formation characterized by microbial fabrics that accumulated in a nearshore carbonate platform setting after the global Frasnian/Famennian biotic extinction event, which promoted the growth of microbialites during the latest Devonian in South China.
SHI Zhiqiang, PRETO N., JIANG Haishui, KRYSTYN L., ZHANG Yang, OGG J. G., JIN Xin, YUAN Jinling, YANG Xiaokang, DU Yixing 2016. Demise of Late Triassic sponge mounds along the northwestern margin of the Yangtze Block, South China: related to the Carnian Pluvial Phase? Palaeogeography, Palaeoclimatology, Palaeoecology, available online 24 October 2016 http://dx.doi.org/10.1016/j.palaeo.2016.10.031
[keywords: Sponge mound; Triassic; Tethys; Carnian Pluvial Phase; Ammonoid; Conodont]
Upper Triassic (Carnian) marine successions in the northwestern margin of Upper Yangtze Region (Sichuan Basin, China) show a lithological change from grey oolitic into a sponge-mound limestone (Units 1 and 2 of the lower member of the Ma'antang Formation), then overlain by greyish black to dark grey sandy shale and siltstone (Units 3 and 4 of the upper member of the Ma'antang Formation). Siliceous sponge mounds were built by Hexactinellida, and this succession was examined in three localities: Jushui section in Anxian (JS), and Guanyinya (HWG) and Qingyangou sections (HWQ) in Hanwang, Mianzhu. The conodont Quadralella polygnathiformis confirms a Carnian age for the biolithite and oolitic limestone of the lower Ma'antang Formation. Abundant ammonoids identified as belonging to the Discotropitid and Juvavitid families suggest a Tuvalian 1 (early Late Carnian) age for the lowermost part of the greyish black sandy shale that overlies the sponge mound at the Jushui Section. Field investigations and microfacies analysis suggest that sponge mounds had two stages of growth in relatively deeper water with low energy. The first sponge-growth mound stage ended in a regional karstified omission surface, and was followed by a sudden increase of siliciclastic input. Greyish black shales containing plant fossils cover a second Upper Carnian sponge mound stage, which is mainly recorded in HWG. The onset of these shales may be related to the Carnian Pluvial Phase (CPP) documented in the western Tethys region (e.g., in Italy, Austria and Hungary). The demise of the sponge mounds at all three sections may have been triggered by the joint effect of climatic changes associated with the fresh water input caused by CPP and with a relative sea-level change caused by local tectonic movements in the course of the Indosinian orogeny.
SREMAC J., JURKOVSEK B., ALJINOVIC D., KOLAR-JURKOVSEK T. 2016. Equatorial Palaeotethys as the last sanctuary for late Permian metazoan reef-builders: New evidence from the Bellerophon Formation of Slovenia. Palaeogeography, Palaeoclimatology, Palaeoecology 454, 15 July 2016, pp 91-100; http://dx.doi.org/10.1016/j.palaeo.2016.04.028
[keywords: Sponge biostrome; Microfacies; Palaeoecology; Late Changshingian; Western Palaeotethys]
The rise and demise of warm-temperate Permian reefs and biostromes reflect the complex geologic history of this dynamic period. Environments suitable for reef-builders were devastated by the Guadalupian/Lopingian crisis, and Lopingian reefs have only been recorded at a small number of localities. The uppermost Permian limestones of the Bellerophon Formation, on the Vojsko Plateau (Slovenia), contain small, lenticular biostromes within a bioclastic wackestone/packstone lithofacies. The major biostrome builders are medium-sized coralline sponges (Demospongea and Calcarea), encrusted by smaller sponges, tube worms, sessile foraminifera, calcareous algae (Archaeolithoporella) and Shamovella (i.e., Tubiphytes), all of which are typically covered by microbial crusts. The biostromes are characteristically composed of bafflestone and bindstone, incorporating sporadic framestone. Narrow belts of floatstone surround the buildups, and sponge debris is also present in lenses within the mud matrix between metazoan bafflestones. The fossils are generally well-preserved, although the fine skeletal microstructure has been partially recrystallized. Sponges are heavily calcified, and ontogenic thickening of the skeleton can be observed in some encrusters. Framboidal pyrite, forming thin films on the inner walls of sponge chambers, suggests the presence of sulphate-reducing bacteria. These microbial symbionts may have enabled the sponges to survive in the anoxic marine environments of the uppermost Permian. The Changshingian sponge biostromes of the Vojsko Plateau represent the westernmost known occurrence of contemporary metazoan boundstones in the Palaeotethys.
STANLEY G. D. 2015. Geologic history of reefs. In McGraw-Hill Yearbook of Science and Technology 2015, pp 124-126. McGraw-Hill, New York.
Reefs in the geologic sense are ancient marine ecosystems which have experienced profound change during 500 million years of prosperity and collapse. Reefs experienced high levels of CO2 during their geologic history. Buildup of this greenhouse gas leads to global warming and ocean acidification. Ancient reefs responded to change as shown by their frequent collapse followed by long reef gaps. Reefs today and in the past were controlled by nutrient level, sedimentation, sunlight and temperature. They are best developed in tropical settings between 30° N-S of the equator. This is because of an important relationship with symbiotic algae living in the tissues of corals and other reef organisms. These algae exploit photosymbiosis, providing substantial nutritional benefit to their reef hosts while also greatly accelerating calcification rates. Photosymbiosis explains why reefs exist today and may well explain their successes and failures through time. Understanding the dynamics of ancient reef systems is central to understanding the current reef crisis. [original abstract; Stanley]
TERRY J. P., GOFF J. 2016. Comment on "Late Cenozoic sea level and the rise of modern rimmed atolls" by Toomey et al. (2016), Palaeogeography, Palaeoclimatology, Palaeoecology 451: 73–83. Palaeogeography, Palaeoclimatology, Palaeoecology, available online 18 November 2016 (in press, corrected proof); http://dx.doi.org/10.1016/j.palaeo.2016.11.027
Toomey et al. (2016) present a credible new model to explain variations in the formation of Pacific Ocean atolls through the Late Cenozoic, thus accounting for contemporary differences in atoll morphology. While we do not contradict the primary influences of dissolution and sedimentation processes, we suggest that the influence of submarine landsliding should not be ignored. Multiple slope failures exist on the flanks of many atolls. When large submarine landslides affected a significant portion of a palaeo-atoll rim, this had the potential to open up an atoll lagoon allowing much freer circulation between the lagoon and the ocean. Our atoll flank collapse model therefore provides an additional mechanism for an enclosed atoll lagoon to become a 'leaking bucket' system and an atoll more likely to evolve into the 'empty bucket' form with later sea-level rise. Submarine landsliding adds additional support for the new model of atoll formation proposed by Toomey et al.
TOOMEY M. R., ASHTON A. D., RAYMO M. E., PERRON J. T. 2016. Late Cenozoic sea level and the rise of modern rimmed atolls. Palaeogeography, Palaeoclimatology, Palaeoecology 451: 73-83.
[keywords: Reef; Coral; Dissolution; Late Miocene; Oxygen isotope stack]
Sea-level records from atolls, potentially spanning the Cenozoic, have been largely overlooked, in part because the processes that control atoll form (reef accretion, carbonate dissolution, sediment transport, vertical motion) are complex and, for many islands, unconstrained on million-year timescales. Here we combine existing observations of atoll morphology and corelog stratigraphy from Enewetak Atoll with a numerical model to (1) constrain the relative rates of subsidence, dissolution and sedimentation that have shaped modern Pacific atolls and (2) construct a record of sea level over the past 8.5 million years. Both the stratigraphy from Enewetak Atoll (constrained by a subsidence rate of ~ 20 m/Myr) and our numerical modeling results suggest that low sea levels (50–125 m below present), and presumably bi-polar glaciations, occurred throughout much of the late Miocene, preceding the warmer climate of the Pliocene, when sea level was higher than present. Carbonate dissolution through the subsequent sea-level fall that accompanied the onset of large glacial cycles in the late Pliocene, along with rapid highstand constructional reef growth, likely drove development of the rimmed atoll morphology we see today. [original abstract; Wrzolek]
TOSTI F., RIDING R. 2017. Current molded, storm damaged, sinuous columnar stromatolites: Mesoproterozoic of northern China. Palaeogeography, Palaeoclimatology, Palaeoecology 465, Part A, 1 January 2017, pp 93-102; http://dx.doi.org/10.1016/j.palaeo.2016.10.019
* Curved and sinuous Tieling Formation stromatolites reflect changes in current direction.
* They formed by agglutination, and accreted towards oncoming sediment: clastitropism.
* They show no clear evidence of heliotropism (growth towards the sun).
* Currents locally removed sufficient matrix to break and topple columns.
* Similar Mesoproterozoic columns occur in Siberia and North America.
WANG Jianpo, LI Yue, ZHANG Yuanyuan, KERSHAW S. 2016. A Middle Ordovician (Darriwilian) Calathium reef complex on the carbonate ramp of the northwestern Tarim Block, northwest China: a sedimentological approach. Palaeogeography, Palaeoclimatology, Palaeoecology, available online 6 November 2016; http://dx.doi.org/10.1016/j.palaeo.2016.11.002
[keywords: Morphological variation; Reef complex; Yijianfang formation; Bachu; Northwest China]
Middle Ordovician carbonates are exposed for 25km along the Lianglitag Mountains in the Tarim Basin, northwest China. They reflect platform carbonate and reef deposition along the ancient Central Tarim Uplift. The Darriwilian Yijianfang Formation, ~70m thick, was deposited in a shallow carbonate ramp setting, deepening seaward to the north in current geography. Reefal and biostromal units are constructed primarily by sessile Calathium of possible sponge affinity in the Middle Member of the formation. Patch reefs, ~10m in thickness and tens of meters in diameter, are common in the northern region. Associated shelly faunas, including trilobites, bivalves, and brachiopods, are diverse and preserved as coarse bioclastic materials together with intraclasts. Towards the south, patch reefs are smaller, <1m in thickness and with low relief. A biostrome formed by in situ Calathium framework is interpreted to act as a baffle for fine sediments, with smaller amounts of bioclasts and intraclasts. The biostrome is only ~3m thick in the southernmost section suggesting a calmer leeward setting initially. Tempestite beds composed of Calathium and nautiloid floatstones are abundant through the section, with monospecific brachiopod layers in the tempestite beds. This work demonstrates previously unrecognized paleogeographic variations of the Darriwilian Calathium reef complexes, which have larger patch reefs generally developing in the north area, smaller patch reefs dominating southward, and biostromes occurring in the southernmost locations. The reef complex was drowned due to sea-level rise, which is recorded in the upper Yijianfang Formation.
WU Liqun, JIAO Yangquan, RONG Hui, WANG Rui, LI Rong 2012. Reef types and sedimentation characteristics of Changxing formation in Manyue-Honghua Section of Kaixian, Northeastern Sichuan Basin. Journal of Earth Science 23, 4: 490-505.
[keywords: northeastern Sichuan; Manyue-Honghua Section; Changxing Formation; reef]
In Changxing stage, Manyue-Honghua Section of Kaixian, northeastern Sichuan Province was located in the platform-margin slope, which was the advantage area of reef-shoal depositional system developing. The strata of Changxing Formation are continuously exposed on both Honghua Section and Manyue Section. Four and two depositional cycles can be identified in Honghua Section and Manyue Section, respectively. They are all platform-margin reef-shoal deposits. Their lithologic associations have obvious sequence, which is as follows: micrite bioclast limestone, bafflestone, bindstone, framestone, and bioclast limestone, in order from below. The paleontological assemblages are controlled by water depth and genetic facies. Six paleontological assemblages can be identified in Honghua Section and Manyue Section; they are coral-calcareous algae-calcareous sponge assemblage, calcareous sponge-calcareous algae assemblage, calcareous sponge-calcareous algae-coral-bryozoan assemblage, calcareous sponge-calcareous algae-hydra assemblage, calcareous sponge-calcareous algae-hydra-bryozoan assemblage, and calcareous sponge-calcareous algae-hydra-bryozoan-coral assemblage. The study of lithologic associations and paleontological assemblages indicates that the water body shallowed upward in both the growth cycle of a single reef and the higher-grade depositional cycle. According to the water depth types of reef (bioherm) developing, three different reef-shoal depositional systems can be identified in study area: deep-water-type bioherm, transitional-type reef (bioherm), and more shallow-water-type reef. [original abstract; Wrzolek]
YAN Xian-qin 2015. The morphological characteristic code of Neoproterozoic stromatolotes in China. Acta Palaeontologica Sinica 2015, 4: 444-452.
[keywords: morphological characteristic code; stromatolites; Neoproterozoic]
"The morphological characteristic code of stromatolites" documented in this paper is composed of 10 items: shape of columns, average diameter and height of columns, style and frequency of branching, shape of laminae, style of lamina arrangement, surface features of columns, form of cross section and microstructure. The sequence of these items in this code is constant, with each item consisting of 5-9 divisions, and each division representing a definite morphological characteristic. On the basis of this coding system, each of Neoproterozoic columnar stromatolites in China can get a morphological characteristic number, which consists of 10 digits (see Table II Table V).
YAO Le, WANG Xiangdong, LIN Wei, LI Yue, KERSHAW S., QIE Wenkun 2016. Middle Visean (Mississippian) coral biostrome in central Guizhou, southwestern China and its palaeoclimatological implications. Palaeogeography, Palaeoclimatology, Palaeoecology 448: 179-194 (15 April 2016).
[keywords: Coral biostrome; Composition; Growth and demise; Middle Visean; Southwestern China]
A middle Visean (Mississippian) coral biostrome is reported for the first time from the Shangsi Formation in Yashui area, central Guizhou Province, southwestern China (palaeogeographically located in eastern Palaeotethys). The biostrome, which is about 500m across and 2.5-3.9m thick, is laterally variable and composed of rugose and tabulate corals with low taxonomic diversity comprising 4 rugose and 1 tabulate coral species belonging to 5 genera. Three growth stages of the biostrome are distinguished, based on different compositions of coral taxa. Average coral contents of the biostrome increase from 38.7% to 72.0% upward and the main builders are Siphonodendron pentalaxoidea, Syringopora sp. and Kueichouphyllum sinense. Associated fossils include abundant brachiopods, crinoids and common foraminifers together with rare calcareous algae, bryozoans, gastropods and ostracods. Relative sea-level changes are interpreted to have controlled growth and demise of the biostrome, which grew continuously during sea-level rise and decreasing water energy, as evident from the gradually increasing of micrite content and in situ coral colonies. However, the biostrome declined and died as the sea level fell and hydrodynamic energy strengthened, indicated by an increase of bioclasts and sparry calcite cement (indicating lack of micritic matrix due to higher energy) overlying the biostrome. This coral biostrome has similar biotic composition to middle to late Visean coral biostromes in Europe and North Africa (western Palaeotethys). The approximately coeval occurrence of coral biostromes in both eastern and western Palaeotethys suggests that a relatively global warm episode existed during the Visean Stage. [original abstract; Wrzolek]
ZHANG Yuanyuan, WANG Jianpo, MUNNECKE A., LI Yue 2015. Ramp morphology controlling the facies differentiation of a Late Ordovician reef complex at Bachu, Tarim Block, NW China. Lethaia 48, 4: 509-521.
[keywords: Bachu; Late Ordovician; Lianglitag Formation; NW China; reef complex; Tarim Block]
A carbonate ramp in the shallow-marine northwestern part of the Central Tarim Uplift, Bachu, NW China, exhibits an extraordinary Late Ordovician reef complex along the Lianglitag Mountains, exposed for a distance of about 25km. Seven localities within the 'Middle Red Limestone' of the Upper Member of the Lianglitag Formation (Katian, Late Ordovician) illustrated the changes in biofacies and lithofacies: northern, seaward-directed patch reefs are replaced towards the south by coeval grain banks. The patch reef units are dominated by microbial and calcareous algal components. The reefs at the northernmost locality are knoll-shaped, kalyptra-shaped or irregularly shaped with sizes of individual reefs increasing from about 2m in height and diameter. Stratigraphically upward, reefs notably expand to larger structures by several mounds coalescing; they are generally about 10m thick and tens of metres in lateral extent. The maximum thickness of the main patch reef is more than 30m, and its diameter is around 100m. The reefal units turn into biostromes with gentler relief southward and still further south grade into banks composed of peloids and coated grains. The southernmost locality is still a shallow-water bank, and the coastline is not documented in the study area. The present evidence indicates that the Late Ordovician palaeo-oceanography provided a number of environments for the optimal growth of carbonate build-ups; microbial-calcareous algal communities could thrive in areas where the innovative metazoan reef frameworks consisting of corals and stromatoporoids did not play a significant role. The ramp morphology, especially changes in water depth, controlled the configuration of the reef complex. [original abstract; Wrzolek]