Coral Limestone Research Articles

Studies on ‘precarious rocks’ in the epicentral area of the AD 1356 Basle earthquake, Switzerland

SUMMARY For the first time precarious rocks have been analysed in the epicentral area of the AD 1356 Basle earthquake in northern Switzerland. Several cliff sites in flat-lying, thickly bedded Upper Jurassic coral limestones in the Jura Mountains were investigated. Seven blocks are regarded as precarious with respect to earthquake strong ground motions. The age of these precarious rocks could not be determined directly as for instance by radiometric dating methods; however, based on slope degradation processes it can be concluded that the formation of these blocks predates the AD 1356 Basle earthquake. The acceleration required to topple a precarious rock from its pedestal is estimated using geometrical data for individual block sections and earthquake strong-motion records from stations on rock sites in the European Strong-Motion Database as input data for the computer program ROCKING V1.0 from the Seismological Laboratory, University of Nevada, Reno. The calculations indicate that toppling of a precarious rock largely depends on earthquake strength but also on the frequency spectrum of the signal. Although most investigated precarious rocks are surprisingly stable for ground motions similar to those expected to have occurred during the AD 1356 Basle earthquake, at least two blocks are clearly precariously balanced, with peak toppling accelerations lower than 0.3 g. Possible reasons why these blocks did not topple during the AD 1356 Basle earthquake include incomplete separation from their base, sliding of precarious rocks, their size, lower than assumed ground accelerations and/or duration of shaking.

The use of microgravity for cavity characterization in karstic terrains

Microgravity is the interpretation of changes in the subsurface density distribution from the measurement of minute variations in the gravitational attraction of the Earth. As a technique, it is particularly suited to the investigation of subsurface structures, mapping of geological boundaries and, most importantly in this case, the location and characterization of voids or cavities. Gravity variations due to the geological/petrophysical changes associated with fracturing and changes in pore composition are superimposed upon much larger variations due to elevation, latitude, topography, Earth tides and regional geological variations. However, these external changes can be modelled or monitored with sufficient accuracy to be removed from the data. With the recent development of high-resolution instruments, careful field acquisition techniques and sophisticated reduction, processing and analysis routines, anomalies as small as 10 microgal can be detected and interpreted effectively. This paper describes the ‘state-of-the-art’ application of the microgravity technique for the detection and characterization of karstic cavities in a variety of limestone terrains, including the Carboniferous Limestone of the United Kingdom and Eire and the coral limestones of the Bahamas. The case study examples show how the recorded gravity anomalies have revealed the location of density variations associated with underground cave systems and, ultimately, provided information on their depths, shapes and morphology from a combined analysis of their spectral content, characteristic gradient signatures and modelling responses. In addition, mass deficiencies have been estimated, directly from the anomaly map, by the use of Gauss's theorem without any prior knowledge of the exact location, or nature, of the causative bodies.

Stratigraphy of the Ryukyu Group in Maeda-misaki area, Okinawa jima, Ryukyu Islands, Japan

The Pleistocene Ryukyu Group consisting mainly of reef-complex deposits is exposed in Maeda-misaki area, central part of Okinawa-jima, Ryukyu Islands, southwestern Japan. The Pleistocene sequence, unconformably overlying pre-Tertiary phyllite of the Nago Formation, comprises the Quaternary Ryukyu Group and Holocene beach and alluvial deposits in this area. The Ryukyu Group consists of the Sobe Formation which is unconformably overlain by younger limestones. The Sobe Formation, the main body of the group, reaches 35m in thickness and crops out at elevations of up to 90m. Five lithologic units have been identified in the carbonate sequence of the Sobe Formation in the neighboring area Yomitan and are numbered sequentially from the base upwards (Units 1-5). Of these, four units (Units 2-5) extend in the study area. Unit 2 is composed chiefly of conglomerate and sandy to gravelly limestone. Each of Units 3 and 4 consists of shallow-water coral limestone grading upward into deep-water deposits (rhodolith, Cycloclypeus-Operculina, and detrital limestones). Unit 5 is composed exclusively of coral limestone. The younger limestones are less than 4m in thickness, rest unconformably on the Sobe Formation, and include detrital and coral limestones. These limestones are found at 3 sites at elevations of <-30m on the coast of the study area. The stratigraphic relationship between the detrital and coral limestones remains unknown due to their limited occurrences. Nannofossil biostratigraphy indicates the sandy limestone of Unit 2 of the Sobe Formation ranges in age from 0.41 to 1.65Ma.

石垣島の現成サンゴ礁浅海域におけるナガウニによる堆積物生産

Sea urchins graze on limestone and at the same time, they also produce sediments by discharging various intakes into the sea bottom of the coral reefs.This study was done on the Shiraho and Arakawashita reefs, the Ishigaki Island, Ryukyus. There are some differences in reef topographies and sediment composition between the 2 reefs. In this study, the author mainly analyzed the gut contents of Echinometra mathaei distributed predominantly within the 2 study reefs.The result are as follows; 1) E. mathaei produces the fine sediment of less than 1 mm in diameter into the sea bottom of the coral reef. The grain size distribution of the gut contents of E. mathaei is different from that of bottom sediments near the area inhabited by E. matheaei. It is thought that the fine sediment ingested by E. mathaei moved from the inhabited area to the other locations by wave and tidal currents. This indicates that E. matehaei discharges calcium carbonate accumulated by reef builders and moves to another place. 2) Comparing the results obtained from 2 coral reefsites, the contents ingested by E. mathaei change according to geographical zone. The intake of E. mathaei contains not only fragments eroding coral limestone but also sediments from the nearby sea floor. 3) There has been no research on the characteristics of intake materials to quantify erosion by E. mathaei. The erosion rates reported in the previous research seem to be over estimats than the actual rate. 4) E. mathaei yields fine sediments by crushing and discharging coral limestone produced by reef builders. Moreover, it is thought that the sediments from E. mathaei have a little influence on the total amount of sediment produced by other organisms in the whole coral reef.

Fish otoliths from the Paleocene of Denmark

Fish otoliths are described from the Lower Paleocene (Danian) and Middle Paleocene (Selandian) from Sjælland in Denmark. A total of 44 species are described, 23 as newly established and nine in open nomenclature. Twelve species (including seven new species) have been obtained from the Danian poorly consolidated coral limestone at Fakse and 39 species (including 19 new species) from the Selandian at localities near Copenhagen. Both stages have previously been poorly known for otoliths in the North Sea Basin, and are described from only two previous publications, i.e. Koken in 1885 from the Selandian of Copenhagen and Roedel in 1930 who described otoliths from erratic ice age boulders in north-east Germany. The original material of both workers has been revised in this bulletin. Otoliths are well known elsewhere in the North Sea Basin since Upper Paleocene (Thanetian) times and are described from the London Basin and from Belgium. Palaeographic, palaeoecological and biostratigraphic implications of the otolith findings in the Paleocene of the North Sea Basin are discussed. Two new genera and 23 new species are introduced and described. The new taxa are: Genartina hauniensis n. sp., genus Anguillidarum semisphaeroides n. sp., Conger illaesus n. sp., Rhechias angulosus n. sp., genus Clupeidarum rectiventralis n. sp., genus Salmonidarum n. sp., Protargentinolithus procerus n. sp., Argentina longistrostris n. sp., Aulopus tortus n. sp., genus Myctophidarum schnetleri n. sp., genus ?Percopsiformorum enigmaticus n. sp., Palaeogadus sinangulatus n. sp., Molvia palaeomorpha n. sp., Protocolliolus amorphus n. sp., Coryphaenoides amager n. sp., Hymenocephalus rosenkrantzi n. sp., genus Bythitidarm rasmussenae n. sp., genus Veliferidarum harderi n. sp., genus Zeiformorum janni n. sp., Centroberyx fragilis n. sp., Scorpaena corallophilus n. sp., genus Gempylidarum merus n. sp. and Ostracion pergravis n. sp.

Carbonate platform growth influenced by contemporaneous basaltic intrusion (Albian of Larrano, Spain)

Abstract Carbonate platform growth in active tectonic settings may be strongly influenced by the structural evolution of the basin, including volcanic activity. In this paper, the sedimentary–tectonic evolution of the Duranguesado carbonate platform (Larrano) in northern Spain is described, and an evolutionary depositional model is presented. The Albian Duranguesado carbonate platform deposits are dominated by rudist and coral limestones with small intervening argillaceous limestone‐filled troughs (10–30 m deep). The platform succession is divided into two parts. The lower platform deposits were intruded by volcanics and tilted before the deposition of the upper platform succession. A volcanic vent plug filling an upward‐flaring pipe occurs in the lower carbonate platform succession. The timing of intrusion is well constrained to the early Albian. Tectonic extension and active deep‐seated strike‐slip faults induced magma ascent at a fault intersection. Sedimentological analysis of these areas indicates that, before volcanic intrusion, they acted as weakened zones of extension, and were slightly more subsident basinal areas. These sites contain anomalous accumulations of siliceous sponge spicule deposits, linked to the release of hydrothermal fluids on the sea floor. After the phase of intrusion, tilting and erosion of the platform and its associated volcanic products occurred. As the intrusion cooled, the platform downwarped, leading to the formation of an overlying perched capping basin bordered by carbonate platforms. Over the volcanic plug, carbonate mounds grew on local palaeohighs. The presence of strike‐slip and magma emplacement in the Duranguesado platform is related to movements between the Iberian and European lithospheric plates, which were accommodated by rotation and lateral movement of the crust along wrench faults.

Is sulphur acidifying cashew soils of South Eastern Tanzania?

Cashew nut, a major cash crop of Tanzania, is mainly produced in the South Eastern part of the country. Sulphur dust is widely used for controlling powdery mildew disease caused by Oidium anacardii Noack. This can cause acidification of soils and thus, may threaten the productivity of cashew and its intercrops. To assess the extent and magnitude of the current acidification, pH of topsoil (0–20 cm) and subsoil (20–40 cm) of 70 farmers’ cashew groves where sulphur had been applied for up to 12 years, was compared to 70 similar undusted groves. On average topsoil pH of sulphur dusted groves on the Makonde plateau was 0.2 U lower than of undusted groves; subsoil pH was 0.1 U lower. However, in 29% of the groves the difference in topsoil pH between dusted and undusted groves was between 0.5 and 0.9 U. For groves of the inland plains, no effect could be established. Soil pH on the Makonde plateau decreased with increasing number of years of sulphur use while it remained stable in the inland plains. Soils of the Makonde plateau have a high risk for acidifying to pH levels between 4.5 and 4.0 which could affect the cashew nut production and would be detrimental to intercrops such as sorghum, finger millet, and maize. This is due to the soils’ inherently low pH and low buffering capacity which is linked to their high sand content. Lime could be used to mitigate the effect of sulphur and can be obtained locally from fossil coral limestone, not exploited yet. Alternatively, the incidence of powdery mildew could be reduced by crop husbandry techniques or by using organic fungicides; the first alternative has the disadvantage of requiring farmers to understand aspects of the epidemiology, the second of being more costly and more toxic than sulphur and of requiring water for its application which is scarce on the Makonde plateau.

Pleistocene reef development in the southwest Ryukyu Islands, Japan

Calcareous nannofossil and sedimentological studies of the Pleistocene Ryukyu Group, based on 13 cores and surface outcrops on Irabu-jima and Shimoji-jima, the Ryukyu Islands, southwestern Japan, suggest that these sediments were deposited at 1.5–0.3 Ma and unconformably overlie the Pliocene Shimajiri Group. The Ryukyu Group consists mainly of reef complex deposits, which accumulated in a wide range of depositional environments, from shallow reef flat to deep insular shelf. Carbonate lithofacies representing 10 depositional environments were delineated by comparison with the present-day marine sediments and biota around the Ryukyus. Five coral assemblages were defined by species composition and the morphology of fossil forms within the coral limestone, each indicating a particular environment. The Ryukyu Group in the study area is composed of 13 lithologic units. A complete succession of units commences with coral limestone (LST or TST) grading upward into rhodolith and larger foraminiferal limestones (TST) overlain by coral limestone (HST). Episodic subaerial exposure and subordinate karstification commonly occurred after deposition. The study area subsided during the deposition of units 1–12 and then was uplifted during deposition of unit 13. Reef development may have been dominated by obliquity or precessional cycles (sixth- and seventh-order cycles, respectively) for the first 0.5 million years (∼1.5–1 Ma), after which it may have responded to fifth-order (eccentricity) cycles.

Pleistocene coral reef deposits (the Ryukyu Group) on Kume-jima, Okinawa Prefecture, Japan

The Ryukyu Group, composed of Pleistocene reef-complex deposits that pass laterally into terrigenous sediments, crops out on Kume-jima and its adjacent islet, Ohajima, Ryukyu Islands, southwestern Japan. We propose a major revision of the previous stratigraphic scheme for the Ryukyu Group, based on new investigations, and provide a formal stratigraphic description. These Pleistocene deposits comprise the Nakandakari, Kumejima, and Torishima Formations, in ascending order, on Kume-jima. The lowest of these, the Nakandakari Formation, consists of pumice-bearing detrital limestone (<20m thick); its surface exposure is confined to the type locality, which is on the coast to the northwest of Nakandakari. The unconformably overlying Kumejima Formation exceeds 30m in thickness and is exposed in the northwestern part of Kume-jima at elevations less than ca. 50m. It is divisible into at least three units, each comprising coral limestone and overlying rhodolith, Cycloclypeus-Operculina, and detrital limestones. The Torishima Formation rests unconformably on the Kumejima Formation, and is characteristically thin (<15m thick) and composed of well-sorted detrital and coral limestones that are thought to have been deposited in a shallow lagoon (moat). The Oha Limestone is limited in its distribution to Oha-jima and consists of diagenetically altered, reddish to brownish, coral limestone. The stratigraphic relationship between limestones on Kume-jima and those on Oha-jima remains unknown, as does the geological age of these limestones. It is evident from the stratigraphic succession and configuration of lithofacies that the reefs grew in response to at least three repeated cycles of sea-level change with amplitudes of up to 80m during deposition of the Kume-jima Formation. Subsequently, a relatively small reef now assigned to the Torishima Formation grew to fringe the older reefs.

宮古島における窒素負荷発生量と地下水窒素濃度の長期的推移

Groundwater pollution by nitrogen is a common environmental problem in the islands covered with coral limestone. Total annual emission of nitrogen from fertilizers, livestock wastes, and domestic wastes at Miyako Island, Okinawa was examined from 1977 to 1998, and compared with the concentration of nitrogen in groundwater. The trend of nitrogen emission was reflected on the groundwater concentration with the delay of seven years. This suggests that the velocity of nitrogen permeating down to the groundwater is 3 m per year. The amount of nitrogen leaching into the groundwater was 39% of the total nitrogen emission on the ground. These results emphasize the importance of data collection on nitrogen emission in order to predict the future nitrogen concentration of groundwater in coral islands.

GIS-based landslide hazard mapping in the Scotland District, Barbados

Rationale The Scotland District occupies an area of approximately 60 km 2 forming the northeast coastline of Barbados (Fig. 1). The district is geologically and topographically distinct from the rest of Barbados in that the coral limestone cap that covers the remainder of Barbados is absent. The underlying Tertiary rocks exposed in the Scotland District are soft and erodible, and are themselves prone to landsliding and erosion. Land use in the district comprises forest, sugar cane, fruit and vegetable growing and pasture, and the district has high landscape value and eco-tourism potential. Low rise, low density housing has developed over the decades, predominantly along cart tracks and roads with alignments that tend to follow ridge and spur lines in an attempt to avoid potentially unstable side-long ground. However, there are numerous locations where erosion and ground movements have caused significant distress to road pavements, and where foundations to residential buildings have been undermined to the extent that some areas have been abandoned altogether. The Soil Conservation Unit (Ministry of Agriculture and Rural Development) has been tackling slope instability and erosion problems in the district for over half a century. A number of useful projects have been commissioned to examine and remediate areas of known ground instability, and several schemes involving drainage and earthworks have proved successful. However, realizing that there were several geological, topographical, drainage and land use factors distributed throughout the district that had a role to play in the pattern of ground instability and erosion.

Response of triassic reef coral communities to sea-level fluctuations, storms and sedimentation: Evidence from a spectacular outcrop (Adnet, Austria)

The Upper Rhaetian coral limestone of Adnet, southeast of Salzburg Austria has been repeatedly referred to as one of the most spectacular examples of an ancient ‘autochthonous’ coral reef structure. The ‘Tropfbruch’ quarry is probably the best outcrop for interpreting the distributional patterns of biotic successions and communities of a late Triassic patch reef. Our study is based on the interpretation of a) outcrop photographs, b) reef maps resulting from quadrat transects, and c) the analysis of quantitative data describing the distribution and frequency of reef organisms and sediment. A new methodological approach (combination of reef mapping and photo-transects) is used to obtain quantitative field data which can be compared in greater detail with data from modern coral reefs investigated by corresponding quantitative surveys. Three unconformities and three well-defined ‘reef growth stages’ reflecting the vertical and lateral development of the reef structure were differrentiated using transects: Stage 1, representing the reef growth optimum, is characterized by laterally differentiated coral reef knobs with corals in growth position. Criteria supporting this interpretation are the extraordinary size of the corals, their preservation in situ and the great thickness of this interval. The massive coralPamiroseris grew under higher energy conditions at the rim of the reef knob, whereas branchingRetiophyllia colonies preferred less agitated water in the center. Vertical changes are reflected by an increase in frequency of the dasycladacean algaDiplopora adnetensis and by the decreasing size ofRetiophyllia. These sedimentological and biological criteria together with the unconformity above indicate a fall in the sea level as a major control mechanism. Stage 2, separated from stage 1 by an unconformity caused by partial subaerial exposure and karstification, is characterized by vertically stacked coral successions with diverse reef debris. Facies heterogeneity is reflected by differences in the diversity, taphonomy and packing density of reef-building organisms as well as by differences in sediment input from the platform. Water depths and accommodation space were lower, therefore minor sea level fluctuations had a stronger effect on the biotic composition. The high percentage of coral debris and corals reworked by storms and the increase in the input of platform sediment led to a reduction of reef growth. Stage 3, again separated at the base by an unconformity associated with karstification, is characterized by bioclastic sediments with isolated reefbuilders forming a level-bottom community. The distribution of different coral morphotypes suggests that sea level fluctuations were not the only controlling factor. Variations in the substrate were caused by differences in the input of platform sediment. The three-step development seen in Adnet documents the response of low-diverse coral associations to variations caused by small-scale sea level changes, storm activity and sedimentation. The vertical changes in reef community structures correspond to a sequence of ‘allogenic replacements’. The Adnet reef structure should not be regarded as a general model of Alpine Upper Rhaetian reefs, because of the particular setting of the patch reef. Only the ‘capping beds’ of the Upper Rhaetian Reef Limestone of the Steinplatte exhibit criteria similar to Adnet. Potential modern analogues of features seen in the coral communities of Adnet are the internal structure of theRetiophyllia thickets, the key role of branching corals within the communities, the scattered distribution and low and even diversity of corals subsequent to breaks in settlement, segration patterns of corals indicating ‘contact avoidance’, toppling of large coral colonies by intensive boring, and decreasing coral coverage from deeper and sheltered settings to more shallower water depths.

THE ORIGIN AND DEVELOPMENT OF NEOGENE BASINS IN THE SE BETIC CORDILLERA (SE SPAIN): A CASE STUDY OF THE TABERNAS‐SORBAS AND HUERCAL OVERA BASINS

Neogene— Quaternary sedimentary basins in SE Spain contain a record of the geodynamic evolution of the Internal Zone of the Betic Cordillera. The basement of the Internal Zone is composed of Palaeozoic and Mesozoic metasediments which have undergone variable degrees of metamorphism. The External Zones consist of largely unmetamorphosed sedimentary rocks which were deposited on the SE margin of the Iberian Plate during the Mesozoic and Early Cenozoic. Westward tectonic emplacement of these terranes onto the Iberian Plate took place between the end of the Palaeogene and the middle Miocene. In this paper, we investigate the late Miocene (Tortonian‐Messinian) stratigraphy of two basins in the Internal Zone — the Tabernas‐Sorbas and Huercal Overa Basins. We also consider some recently‐acquired structural data.The Tabernas‐Sorbas and Huercal Overa Basins are east‐west trending depressions bounded to north and south by sierras in which basement rocks are exposed. The basins contain very similar sedimentary successions in which planktonic foraminifera have been preserved. However, the faunal composition is very variable, and the observed sporadic and abrupt changes in foraminiferal populations imply palaeo‐ecologic and palaeo‐oceanographic instabilities which may be associated with local tectonism. Stratigraphic markers were affected by these changes, making precise dating difficult near the Tortonian‐Messinian boundary.Our data indicate that Messinian rocks are more widely distributed than has hitherto been suspected. A Messinian age for the prominent coral limestones in the Tabernas‐Sorbas Basin has long been accepted; similar coral limestones in the Huercal Overa Basin have previously been dated as Tortonian. However, our data show that these carbonates are of Messinian age in both basins.The origin and development of the Tabernas‐Sorbas and Huercal Overa Basins have previously been interpreted in a number of ways. Many (but not all) models favour strike‐slip movement on NE‐SW or east‐west trending basin‐bounding faults. The formation and deformation of the basins occurred during the Tortonian and Messinian, at the same time as the uplift of the sierras. The sierras are here interpreted to represent structural culminations above westward‐verging, deep‐seated thrust faults, and the basins to be lateral folds (or lateral ramps, i.e. oriented parallel to the thrust transport direction). The east‐west trending strike‐slip faults at the margin of the Sorbas‐ Tabernas Basin may be compatible with such a model.Major NE‐SW trending, left‐lateral wrench faults have been described in this area. These faults cut through late Miocene and Pliocene deposits, and are still active at the present day. Although these faults were initiated during the late Miocene, they do not appear to have influenced the development of the Tabernas‐Sorbas and Huercal Overa Basins during the early Tortonian.

Three-dimensional simulation of the Home Island freshwater lens: preliminary results

Home Island is one of the two main inhabited islands of the Cocos (Keeling) Islands, situated about 2800 km north-west of Perth. The island has an average elevation of approximately 2 m above MSL and supports a population of about 450. The geology of the island consists of coral sediments overlying a volcanic seamount. The upper sediments are of primary importance from a hydrogeological viewpoint. These sediments consist of unconsolidated coral sands and other fragments and coral limestone. An unconformity between the younger (Holocene) unconsolidated sediments and older (Pleistocene) coral limestone was found at depths between 10 m to more than 17 m. The island has a long term average annual rainfall of 1950 mm. Water supply is based primarily on groundwater extraction from a local freshwater lens and supplementary rainwater is collected from roofs. Groundwater is currently extracted via seven galleries. A recent study based on a two dimensional model (using the SUTRA package), simulating impacts of various level of pumping up to 200 m 3 day −1 determined the sustainable yield as 140 m 3 day −1. This paper describes progress regarding the development of a three-dimensional model of the freshwater lens using the SALTFLOW package, by discretising the aquifer to about 90 000 nodes and 83 000 elements. This is followed by the steady-state calibration of the model, estimation of the parameters affecting the system and assessing the sustainable yield of the lens. Preliminary results of the three dimensional modelling suggest that the sustainable extraction rate is less than 200 m 3 day −1, which is consistent with the results of the two dimensional modelling. This research project is continuing towards simulation of tidal forces, transient calibration of the model over a 10 year period from January 1988 to December 1997, estimation of sustainable yield of freshwater lens and simulation of various management options.

Application of GPR for 3-D visualization of geological and structural variation in a limestone formation

Ground-penetrating radar (GPR) offers a simple and rapid means of providing valuable information for mapping of geological and structural variations in limestone. Data from closely spaced radar sections were gathered in two areas in Faxe Kalk's limestone quarry on the island of Zealand, Denmark. A `pulseEKKO 100' GPR system with 100 MHz antennas was used for data gathering. In this paper we describe the steps required to obtain three-dimensional (3-D) data. Data were collected in continuous mode with readings every 20 cm. The 3-D cubes were prepared for visualization by using several processing routines. Various data presentations, including chair views, and multiple and single slices, were generated from the 3-D cube to enhance the outline and distribution of flint-free limestone in the surveyed areas. Animation of 3-D data was found to be a very powerful way of visualizing the geological structures in the surveyed areas. The limestone formation in the quarry is of middle Danian age (approx. 63 million years old) and is divided into two main deposition facies—coral limestone and bryozoan limestone. The coral limestone appears as reef structures in the more abundant bryozoan limestone. In the bryozoan limestone frequent flint layers appear often delineating mound-like structures. Coral limestone and areas of bryozoan limestone without flint are quarried selectively and used for high quality products. Division of the limestone formation into areas of coral reefs and bryozoan mounds and separation of flint-free areas is made possible through distinctive reflection patterns and differing penetration depths between the rock units. The 3-D visualization allows estimation of potential volumes of limestone for selective exploitation.

Distribution of the Carboniferous coral limestone belt in the eastern part of North China and its geological significance

Distribution of the Carboniferous coral limestone belt in the eastern part of North China and its geological significance

Bryozoaires récoltés dans les unités messiniennes de sondages offshore dans le Golfe de Gabès (Tunisie)

Two offshore borings in the Gulf of Gabes (Tunisia) yielded 37 bryozoan species. Most species are from the coral limestones of the Melqart Formation (early Messinian). The proportions of the 7 zoarial forms represented — together with the ecology of extant species — indicate depths of deposition of a few meters down to about ten meters, in warm tropical waters. A comparison with bryozoan faunas from Messinian coral reefs in Morocco and Algeria shows similar diversities and specific compositions, but stronger affinities with Morocco. Data on Recent coral reefs bryozoans also suggest an open environment inside a well-developed carbonate platform.

Late Quaternary paleolandslides on the coral terraces of Huon Peninsula, Papua New Guinea

Many landslides disrupt the coral terraces at northeast Huon Peninsula, Papua New Guinea. Each landslide is younger than the youngest terrace which it intersects and is older than the oldest coral reef or shoreline that overlies it. The ages of the raised coral reefs and terraces were established by previous studies using radiocarbon and uranium-series dating. The times of occurrence of 26 late Quaternary landslides are reported here; 7 are based on new radiocarbon dates from in situ corals or molluscs associated with landslide deposits, and the remainder are based on terrace ages that were established previously. The landslides include slumps, block slides and block flows which mostly involve failure of coral limestones of the terraces, and debris flows which originate from large landslides that cut through the coral limestones into underlying fan-delta and tuffaceous sedimentary rocks. The proportion of terrace area affected by Late Quaternary landslides ranges from < 1% to > 50% per km2 and depends on average gradient of the landsurface, tectonic uplift rate, and the thickness and geometry of the raised reefs and terraces. Clusters of landslides, which occurred at about 800–1250 and 6300–7800 yr BP, may have been triggered by large earthquakes which also caused metre-scale coseismic uplift. However, we did not identify landslides that could have been associated with every large coseimic uplift that has been documented in this region.

Adsorption of Inorganic and Organic Arsenic Compounds by Aluminium-loaded Coral Limestone

Coral limestones were treated with an aqueous solution of aluminium sulfate and thereby aluminium-loaded coral limestones (Al-CL) were prepared. By use of Al-CL as an adsorbent, the adsorption of inorganic arsenic compounds (arsenate [As(V)] and arsenite [As(III)] and of organic arsenic compounds (methylarsonic acid, dimethylarsinic acid, and arsenobetaine) was examined. The adsorption ability of Al-CL is superior to that of iron(III)-loaded coral limestone (Fe-CL) for As(V), As(III), methylarsonic acid and dimethylarsinic acid. The adsorption of As(V) and As(III) is almost independent of the initial pH over a wide range (2 or 3 to 11). The addition of other anions, such as chloride, nitrate, sulfate and acetate, in the solution does not affect the adsorption of As(V) and As(III), whereas the addition of phosphate greatly interferes with the adsorption. Arsenic adsorption is effectively applied to a column-type operation and the adsorption capability for As(V) is 150 μg/g coral limestone.

Middle Bathonian Foraminifers from the Patcham Formation, Jumara Dome, Kachchh, western India

The Patcham Shell Limestone and Coral Limestone of Jumara Dome have yielded a rich foraminiferal assemblage including species of Garantella, Epistomina, Reinholdella, Pseudomarssonella, and Reyadhella. On this basis middle Bathonian age is assigned to the fossil yielding basal part (Patcham Shell - Coral Limestone) of the Jumara Dome.