Jian-Wei Shen

Guadalupian algae-sponge reefs in siliciclastic environments - the reefs at Lengwu (South China) compared with the reef at Iwaizaki (Japan)

SummaryGuadalupian reefs occur locally in Guangxi, Guizhou, Yunnan and Western Zhejiang, South China. Two types of Guadalupian reefs can be recognized, one is developed in carbonate platforms, e.g. those in the juncture areas of Guangxi, Yunnan and Guizhou; the other occurs in a littoral clastic shelf. The Lengwu reef in Western Zhejiang is a representative of the latter type, which is a major topic of this paper. Lengwu algae-sponge reef, more than one hundred meters in thickness, are composed mainly of sponges, hydrozoans, algae, bryozoans, microbes and lime mud. Reef limestones sit on the mudstone interbedded with fine sandstone of the proximal prodelta facies and are overlain by coarse clasts of the delta front sediments. Lengwu reef displays a lens-shaped relief, dipping and thinning from the reef core, which is remarkably different from the surrounding sediments, showing a protruding relief. Sponges and microbe/algae form bafflestone, bindstone and framestone of the reef core facies. Fore-reef facies is characterized by lithoclastic rudstone and bioclastic packstone. Reef limestone sequence is composed of three cycles and controlled by sea level changes and sediment influx. Such reef is unique among the Guadalupian reefs in South China, but seems similar in some aspects to Iwaizaki reef limestones of south Kitakami in Japan. Algae and microbes growing around sponges to form rigid structure in Lengwu reef are a typical feature, which is distinctly different to Guadalupian reefs in a stable platform facies of Guizhou, Yunnan and Guangxi, South China.

Coral community dynamics and shallow-water carbonate deposition of the reef-flat around Yongxing Island, the Xisha Islands

Microbes and microbial carbonates in reef-flat and coral community dynamics and submarine geomorphologic features in reef crest and fore reef of Yongxing Island, the Xisha Islands, South China Sea, were studied by means of scuba diving, underwater investigation, and line intercept transect survey. Studies indicate a very high coral mortality with few living corals in the reef flat of Yongxing Island. Moreover, macro algae, sea grass and cyanobacteria are common in reef flat. Microbes and microbially induced carbonates occur in reef flat. Living corals grow mainly in the reef crest and fore reef, but are also declined dramatically. From coast to off shore, the southeast reef flat of Yongxing Island can be divided into beach, inner reef flat, outer reef flat, reef flat front (reef crest and fore reef), and fore-reef slope settings. Sedimentary facies include coast, reef flat, reef crest and fore reef, and fore-reef slope. Reefal carbonate sediments are composed of coral skeletons and framework, coral fragments, bioclasts, and lime mud. With the deterioration of environment and water quality, the coral communities tend to be distributed in the reef crest and fore reef with clean sea water, well circulation and moderate water energy. Reef flat is occupied mainly by the macro algae and Heliopora coerulea communities. The coverage statistics on the reef crest demonstrate that the coverage of Acropora cytherea is more than 28% and represents a dominant species with wave-resistant ecological type. Sedimentary characteristics and geomorphologic features are different between the southeast and northwest reef-flat fronts (reef crest and fore reef) of Yongxing Island. The former shows discontinuously tidal channels in outer reef flat and different dimensional and deep reef ponds in reef crest and fore reef, and the latter presents a typical spur-and-groove system. Microbes (cyanobacteria Lyngbya sp.) occur generally in the inner reef flat and reef ponds of reef crest with restricted water circulation. Widely algae growth indicates a eutrophic environment, and the common microbes on the coral surface in the reef flat and reef ponds also demonstrate eutrophication in seawater and deteriorated water quality.

Black band disease as a possible factor of the coral decline at the northern reef-flat of Yongxing Island, South China Sea

Black band disease (BBD), characterized by the Cyanobacterial dominated pathogenic consortium, is thought to play a key role in the global decline of the coral reef ecosystems. The present paper originally documents a case of BBD from Yongxing Island (Xisha Islands, South China Sea), and further probes the reasons of this abnormal phenomenon. Prior to 2007, corals at northern reef-flat of Yongxing Isand were in healthy growth. Catastrophic coral mortality occurred between 2007 and 2008. The 16S rRNA gene sequencing and PCR amplification, with universally conserved primers, were applied to detect the contagious bacterial community of the microbial mat. The results demonstrated that six bacterial divisions constituted the clone libraries derived from the BBD mat, and that Cyanobacteria are the most diversely represented group that inhabit BBD bacterial mats, despite the fact that species in five others divisions (α-Proteobacteria, γ-Proteobacteria, Bacteroidetes, Verrucomicrobia and Actinobacteria) are also consistently diverse within the BBD mats of diseased coral. Other factors such as coral bleaching, typhoons, ocean acidification and crown-of-thorns starfish outbreaks, are not primarily responsible for the coral mortality within such a short time interval. The disaster expansion of BBD associated with Cyanobacterial blooms is a more likely mechanism impacting these coral reefs. Excessive human activity enhances the eutrophication of the marine water of the reefal region and may result in occurrence of the BBD.

Calcimicrobes and microbialites in lagoonal sediments from Mississippian Midale Beds, Williston Basin, southeastern Saskatchewan, Canada

Carbonates of Mississippian age (Viséan) in the Midale Beds, Charles Formation of southeastern Saskatchewan, Canada, produce significant amounts of hydrocarbons. The Midale Beds represent deposition in a shallow-water, periodically restricted, epeiric setting. The sedimentation is characterized by a variety of shallow-water carbonate lithologies ranging from wackestone, packstone, grainstone, to microbial boundstone. Algae, calcimicrobes, and related microbial fabrics are common features in these limestones. Cores and thin sections through the Midale Beds in the Glen Ewen and Midale pools of southeastern Saskatchewan were examined in order to study the contribution of calcimicrobes and microbial fabrics to the sedimentation of Mississippian carbonate rocks in southeastern Saskatchewan. Calcimicrobes and microbial fabrics are the important components in the grainstones and microbial boundstone. The calcimicrobes are commonly found as porostromate forms, including Garwoodia sp. and Ortonella sp., and other forms such as Archaeolithoporella-like, Girvanella-like, Wetheredella-like, and problematic microbes also occur but are not common. Microbial fabrics are characterized by microstromatolites, microbial laminations, thrombolite, clotted peloids, and fenestrate forms. Calcimicrobes stabilized grains and modified and created sediments, and the related syndepositional microbial fabrics affected the development of porosity/permeability of Midale carbonates. Calcimicrobes and microbial fabrics in Midale Beds highlighted a significant account of microbial facies associated with the Mississippian carbonates worldwide.

Mixed carbonate-clastic facies in the Eocene Kalatar Formation of the southwest Tarim Basin (NW China): tectonic and climatic controls

During the Eocene, the southwest Tarim Basin was a large epicontinental sea as a part of the Turun Sea in the eastern Paratethys. The marine succession of the Kalatar Formation is exposed along the piedmonts of the southern Tian Shan and western Kunlun Shan, and can be subdivided into three members. On the southern side of the Tarim Basin, a non-barrier shore-to-shelf, siliciclastic-dominated system, locally with carbonates and oyster biostromes, developed along the western Kunlun Shan, where river input led to a seaward arrangement of alluvial fan, foreshore, shoreface, and offshore facies. In contrast, on the northern side of the Tarim Basin, a carbonate ramp system formed along the southern Tian Shan, including shallow bioclastic-oolitic grainstone shoals, oyster beds, and red algal rudstones along with a number of evaporite units, which formed under hypersaline tidal-flat and lagoonal conditions. The basin center was a largely moderate deep and low-energy embayment facies. Deposition of the mixed carbonate-siliciclastic Kalatar Formation was controlled by tectonic activity, in particular the development of the Himalayan orogeny with the closure of Paratethys sea-level fluctuations, and arid-humid climate variations.

Serpulids and their paleoecology of the Paleogene Kalatar Formation in southwest Tarim Basin of China

Polychaete serpulids are globally distributed tubeworms mostly in marine environments from Late Triassic to modern time. These calcareous tubeworms could be rock-forming, reef-building, or a principal fouling organism in harbor and bays. Carbonates of the Paleogene Kalatar Formation in southwest Tarim Basin yield abundant serpulid fossils, which, together with oyster fossils, constitute the characteristic fossil assemblage of the Kalatar Formation. Other common fossils include bivalves, gastropods, ostracods, echinoderms, and bryozoans. Lithologies that yielded serpulid fossils are characterized by micritic bioclastic limestone, sandy limestone, and shelly limestone, indicating a semi-restricted to open shallow marine environment with medium to low water energy. The research data about serpulids and their fossil materials from China are relatively rare. Based on the studies of fossils taxonomy, community palaeoecology, and fossil taphonomy, this paper analyzed and studied the types, occurrence, distribution, and morphological characteristics of serpulids and their palaeoecological features in the Kalatar Formation. Two serpulid community compositions were recognized in the Kalatar Formation, including a rock-forming Ditrupa community and a cluster-growth Propomatoceros community. The Ditrupa community was distributed in coastal environment of the west Kunlun piedmont, lived on sandy hard substrates with little mud, and rarely occurred in lagoon and tidal settings. The Propomatoceros community occurred in offshore middle carbonate ramp in the piedmont of the south Tianshan Mountains and in offshore shelf in the piedmont of the west Kunlun Mountains. According to the analysis on the host-rock lithologies, preservation and symbionts, it is inferred that serpulids in the Kalatar Formation grew on the oyster shell or other hard substrate, and they did not form reefs or bioherms.

REE DISTRIBUTION PATTERN IN THE XIAODONGHAI FRINGING REEF-FLAT SEDIMENTS OFF SANYA, HAINAN ISLAND AND ITS ENVIRONMENTAL IMPLICATIONS: REE DISTRIBUTION PATTERN IN THE XIAODONGHAI FRINGING REEF-FLAT SEDIMENTS OFF SANYA, HAINAN ISLAND AND ITS ENVIRONMENTAL IMPLICATIONS

REE in the sediments of the northeast Xiaodonghai fringing reef-flat off Sanya City,Hainan Island were systematically analyzed using Inductively coupled palsma mass spectrometry(ICP-MS).A high resolution record of rare earth elements(REEs) were obtained.The REE content averages 80.22 mg/kg,and the Chondrite-normalized REE pattern of the reef-flat sediments is characterized by the enrichment of light REE(LREE) and deficiency of heavy REE(HREE),significantly negative Eu,normal Ce and low Y/Ho ratio(27.80).It indicates that the terrigenous influx is the major source of the reef-flat surface sediments.In addition,the sediments show a geomorphologic and ecological zonations from large massive corals zone,to inner reef flat zone to outer reef flat zone seaward,indicating the influence of marine and biological effects.However,the REEs content and distribution pattern show little change in the zones.It is believed that the REE pattern mentioned above represents a specific tropical fringing reef-flat REEs distribution pattern.It is probably related to the sediments from the bedrock around the reef-flat,and the joint affect of tropical marine climate.

REEF-BUILDING CORAL COMMUNITY AND EVOLUTIONARY CHARACTERISTICS OF THE FRINGING REEFS ON THE WEST COAST OF XUWEN COUNTY, LEIZHOU PENINSULA: REEF-BUILDING CORAL COMMUNITY AND EVOLUTIONARY CHARACTERISTICS OF THE FRINGING REEFS ON THE WEST COAST OF XUWEN COUNTY, LEIZHOU PENINSULA

Fringing reefs are well developed on the southwest coast of Xuwen County at the Leizhou Peninsula,southernmost tip of China mainland.They are the only fringing coral reefs remaining on the coast of the mainland.Living corals in the fringing coral reefs consist of Porites,Favia,Acropora,Favite,Montipora,Platygyra and Pavona,dominated by Acropora-Favia-Porites community.Molluscs and arthropods are the main dwelling organisms.According to the coral ecology and reef-flat topographic features,the Dengloujiao fringing reef on the west coast of Xuwen County can be divided into 4 zones from the shore to the sea: 1) the intertidal zone covered by sand and gravel,2) the subtidal inner reef-flat with coral fragment and bioclast deposits,3) the subtidal outer reef-flat with sparse living corals,and 4) the subtidal reef-flat rim of living corals.Goniopora is the dominant species in subtidal outer reef-flat and reef-flat rim.Relative sea-level changes,sea surface temperature variations and coastal eutrophication influx significantly affect the growth of coral reefs.The fringing coral reefs are primarily formed in the mid-Holocene based on the analysis of reef development and evolution.Recent surveys on the coral reefs indicate that the environmental changes caused by climate changes,coastal civil construction and population increase resulted in the changes in dominant coral species in reefal area,and the dynamic changes in the coral community.