Coral Limestone Research Articles

Laboratory Studies on Compressive Strength of Normal Concrete Using Coral Limestone on Timor Island, East Nusa Tenggara Province as a Substitute for Coarse Aggregate

Laboratory Studies on Compressive Strength of Normal Concrete Using Coral Limestone on Timor Island, East Nusa Tenggara Province as a Substitute for Coarse Aggregate

Impact of landslide on geoheritage: Opportunities through integration, geomorphological classification and machine learning

Landslides are widely understood to cause damage to the geological features and the surrounding environment. Our study focuses on the northern region of the Karangsambung-Karangbolong Geopark (KKNG), characterized by diverse lithology and multi-phase tectonics. This study aims to explore (i) landslide susceptibility assessment, (ii) geomorphological characteristics and distribution of landslide susceptibility, and (iii) identification of landslide impacts on geosites. We mapped morphogenesis, morphology, materials, and processes to understand the geomorphological context, identifying three primary landforms: structural, pediments, and fluvial. For landslide susceptibility mapping, we used the XGBoost algorithm with cross-validation and utilized the area under the receiver operating characteristic curve (AUROC) for model validation. The XGBoost model revealed a high susceptibility classification for 10 geosite points. Landslides have negative impacts, such as Olistoliths of coral limestones, Exotic-blocks of chert, and calcareous red claystone that change landforms and damage outcrops. Nevertheless, some landslides have positive impacts on the geosite, such as Exotic-blocks of phyllites, and Exotic-blocks of pillow lava and radiolarian chert, because landslides can reveal fresher outcrops and rock structures, and the outcrop area becomes larger. Landslide mapping has successfully identified geosites that are highly vulnerable and have adverse impacts, especially those with certain lithological characteristics. This research on viewing disaster as a harmful process has evolved into a more holistic view of the disaster. This view includes various positive aspects that involve understanding the complex interactions between geology and geomorphology towards the geosite. By understanding the relationship between geomorphologic features (morphology, material, process, morpho-arrangement) and landslide occurrence, effective management strategies can be implemented to develop geological heritage further.

Development and chronology of the Late Jurassic shallow-water carbonate deposits of the Holy Cross Mountains area, central Poland

The Late Jurassic shallow-water carbonates with intervening clayey-marly deeper-water deposits in the Holy Cross Mts. area formed over large bank of the elevated part of the Northern Tethyan Shelf during about 12 myr. They comprise three main successions (I, II and III) deposited partly in different environmental conditions, controlled by tectonic and climatic factors, and still preserved in the north-eastern margin, the north-western margin and the south-western margin of the Holy Cross Mountains. The history of sedimentation is presented according to the concept of the large tectono-stratigraphic units COK, LUK and KVB, which owe their origin to variable rates of tectonic subsidence, as introduced by Kutek (1994) for the area of central Poland. The studied deposits of the COK megasequence corresponding to the Upper Oxfordian and the Lower Kimmeridgian up to the Hypselocyclum Zone consist of coral limestones, various grained (including oolitic) limestones, and micritic limestones formed over the gradually enlarging shallow-water carbonate platform of the Holy Cross Mts. This platform was subsequently subdivided into two elevated areas, separated by a depressed zone in the middle, bounded by the Nowe Miasto–Iłża–Bałtów Fault Zone in the north-east and the Holy Cross Fault System in the south. The younger megasequence LUK with it strongly transgressive character marks the successive stages of the marine transgression which entered the central, lowered part of the area of the Holy Cross Mts. from the west, where it appeared already in the early Hypselocyclum Chron. It successively spread across the Holy Cross Mts. area towards the north-east and south bringing everywhere the deposition of various oyster lumachelles and marls with ammonites at the end of the Hypselocyclum Chron and during the Divisum Chron of the Early Kimmeridgian to the Acanthicum/Mutabilis Chron of the earliest Late Kimmeridgian. The following megasequence KVB is represented by the detrital lumachelles and chalky limestones with nereineids of the Eudoxus Chron of the Late Kimmeridgian marking the development of still younger shallow-water carbonate platform in the uplifted areas in the north-eastern and possibly the south-western margins of the mountains, allegedly subdivided by a deeper area of sedimentation of marly deposits. The youngest Late Jurassic deposits of the Holy Cross Mts., are very fragmentarily preserved, mostly because of Early Cretaceous uplift and erosion. They suggest an initial episode of complete drowning of the carbonate platform which became covered by marly deposits during the Early Tithonian, and the subsequent restoration of shallow-water carbonate sedimentation at the end of the Early Tithonian.

Petrographic analysis of Oligocene carbonates of Kachchh basin

The Kachchh basin is located on the northwestern margin of India. The basin consists of a relatively continuous sequence of sediments from the Mesozoic, followed by the Deccan Traps and finally a complete sequence of the Cenozoic sediments. The Cenozoic sediments of Kachchh basin are mainly shallow marine deposits characterised by five formations viz. Matanomadh, Naredi, Harudi, Fulra Limestone and Maniyara Fort Formation. The Maniyara Fort Formation belongs to the Oligocene age. The field and petrographic characteristics of the Oligocene limestones from the Golay river section were studied in order to understand the depositional environment. The petrographic investigation of the carbonate rocks of three members of the Maniyara Fort Formation, namely Lumpy Clay Member, Coral Limestone Member and Bermoti Member provides important information for understanding the depositional facies and diagenetic signatures. The Lumpy Clay Member has shale-siltstones with interbedded limestones, characteristically composed of a significant proportion of detrital grains of quartz and some lithic fragments. The lithic fragments are sub-angular to rounded, which indicates substantial transport. They are also worn down and broken, bear small cracks which are filled by micritic matrix or mud. The presence of stylolitic seams within the limestone (though not significant) along with mud filling is also noticed. The dissolution is not prominent, pointing towards shallow burial of the sediments. Paucity of marine fossils as well as the rarity of foraminifera in the Lumpy Clay Member indicate a restricted to semi-restricted shallow marine environment. The limestones of the Coral Limestone Member are petrographically classified as packstone, wackestone and mudstone. Thus, the environment of deposition seems to have varied from restricted lagoonal to shallow marine environment. The Bermoti Member is characterised by a lens of claystone, which consists of both greyish to yellow coloured claystones interbedded with limestones. The Bermoti limestones are petrographically classified as packstone, wackestone and mudstone assemblage. The limestones were observed to be highly micritised, which indicates open, shallow marine settings. The Maniyara Fort Formation, thus characterised by wackestone-packstone-mudstone facies of carbonates, is interpreted to be part of a carbonate ramp system. The limestones from Maniyara Fort Formation exhibit signatures of marine as well as meteoric diagenesis.

Transoceanic Interconnectivities Between India- Tanzania Coastal Communities from the Antiquity to Contemporaries: The Archaeologic Perspectives from the Ancient Maritime Trade Connections via the Indian Ocean

The currently available archaeological and historical records indicate that since the prehistoric times, India and Tanzania shared a very long antiquity in terms of human civilization through the Indian Ocean maritime trade especially during the Neolithic period in aspects such as maritime trade links, ancient technology transfer, and intermarriages, expressly in monumental built heritage assets along the coast of the Indian Ocean. Outstandingly, the East African coast and its offshore islands preserve a lot of ancient remnants of built heritage assets, religious and symbolic entities, and socio-cultural traditions. Archaeologically, Swahili culture, which is one of the most powerful African civilizations along the coastal towns and littoral regions in East Africa is to some extent predisposed and inspired by Indian elements of early civilizations. The prehistoric contacts between the Indian Ocean communities of East Africa and Indian subcontinent have left some legacies in terms of language, crop and animal domestication, trade, architecture, and intermarriage. Some of these cultural elements are clearly visible in the forms of a spectacular series of historic stone towns along the coast and littoral regions of Tanzania for instance, especially ones that contain ruins of houses, mosques, and tombs built of coral limestones are typically Indian heritage inspired, which significantly influenced coastal and littoral societal socio-cultural developments in Tanzania.

Heterogeneity of hydrological connectivity in coral limestone groundwater pool from vertical, spatial and temporal tracing of groundwater chemicals and isotopes

Carbonate aquifers are critical for the health and well-being of human communities. Despite considerable efforts on the structure of karst aquifers, the variable and invisible flow paths or the vertical and spatial heterogeneity of karst systems remain too complex to be fully understood. An artificially constructed small limestone aquifer with an extensive network of observation wells in the Miyako Island, Japan, provides a unique opportunity to illustrate the vertical and spatial hydrological connectivity for water movement and storage. Water chemical data at two different depths over six years, including electrical conductivity (EC), dissolved oxygen (DO), oxidation–reduction potential (ORP), major ions (Na+, K+, Ca2+, Mg2+, SO42−, and HCO3−), δ18O and δ2H capture water mixing processes during groundwater recharge in the aquifer influenced by irrigation pumping and recharge by precipitations throughout drying and wetting cycles. Results suggest that the intensive weathering of coral limestone under the impact of agricultural fertilization, as indicated by high EC values and high concentrations of Ca2+ and HCO3−. The high DO and low ORP values imply a lack of organic decomposition activity, which is typical in the karst groundwater condition. More importantly, groundwater recharge in the small aquifer was found to be influenced by following three processes. Spatially, both Cl− and NO3−−N indicate the large heterogeneity of water mixing as rainfall or drainage water percolates differently to various parts of the aquifer. Vertically, there are apparent differences in the concentration of Cl− and NO3−−N between the top and bottom layers in several wells, suggesting that, even within a single well, the vertical profile can be weakly connected between the top and the bottom layers. The bottom layer should have been recharged by lateral water inflow from fractures or conduits. And thirdly, the even distribution of Cl− over the long precipitation season from October 2016 and March 2021 and another nearly even distribution of NO3−−N in the low fertilization season in March 2021, demonstrate that the aquifer system is basically connected and porous. In summary, the insights gained from our study reveal that: 1) coral limestone can be treated as a well-developed porous aquifer and 2) the hydrological connectivity is highly heterogeneous and influenced by rock properties, including formation structure, degree of weathering, and clay content. Such findings are essential for understanding the hydrogeological properties of coral limestone aquifers globally.

The Bolognano Fm in the south-eastern sectors of Majella and correlation with the north-western domain

This work investigated the evolution of the Bolognano Fm in the southern portion of the Majella Mountain and correlated it with the northwestern sector. Here the Bolognano Fm overlies unconformably the Eocene deposits of the S. Spirito Fm. The first unit is the Burdigalian Bryozoan Calcarenite, overlain by the Hemipelagic limestone to calcareous marls Burdigalian to Langhian in age. Lastly, the Tortonian to early Messinian interval is represented by different units. The first unit, which unconformably overlies the hemipelagic limestone to calcareous marls, is the Bioclastic calcarenites unit, which is fed by sediments produced within a euphotic inner ramp and accumulated in a deep environment. Upwards, the Marly limestones and laminated calcareous marls unit shows a mixing of deep water and shallow skeletal components deposited in an outer ramp. Moving southward, the Coralline algal limestone crops out, identifying a productive middle ramp environment. Lastly, a coral limestone unit was identified, where coral bioconstructions interfinger with seagrass meadows and ooidal shoals, in the euphotic zone. The Marly limestone and laminated calcareous marls testify for a deterioration of environmental conditions due to both global climate change as well as the approaching of the Apennines accretionary wedge, which triggered an increase of terrigenous runoff.

Experimental Study on Damage Behavior of Porous Coral Limestone from the Zhongsha Islands, South China Sea

Experimental Study on Damage Behavior of Porous Coral Limestone from the Zhongsha Islands, South China Sea

Potential Geotourism Attractions on Nusa Penida Island, Klungkung Regency, Bali

Nusa Penida Island is one of the leading tourist destinations in Bali Province. Tourist destinations on the Island consist of various types of beaches, hills, caves to unique landscapes formed due to the karstification process. Nusa Penida Island is geologically composed of limestones (the Selatan Formation) with various types such as clastic limestones and coral limestones(Hadiwidjojo et al, 1998). In addition to the unique geology of Nusa Penida Island, it also has archaeological uniqueness. The Gede Cave shows that Nusa Penida was once inhabited by prehistoric humans (Abdillah, 2011). During the COVID-19 pandemic, tourism seems to be forced to accelerate and requires new tourist attraction innovations that support sustainable tourism. This research discusses geotourism-based tourist attractions that can be developed and explored in Nusa Penida. The approach used is geological diversity inventory method (Geological Agency, 2017). Primary data was obtained through survey activities. From the research carried out, it can be concluded that 10 geological site locations in the Nusa Penida area have the potential to be developed as areas with geotourism attractions, which offer unique geology, especially regarding karts landscape processes and one of the key geological history on the island of Bali. In addition, Nusa Penida Island has the potential to be developed as a geopark as an effort to develop sustainable tourism in Klungkung Regency.

Stability Assessment of the Slopes of an Oceanside Coral Limestone Quarry under Drawdown Condition of Semidiurnal Ocean Tides

Vipingo quarry in Kilifi county, Kenya, is one of the quarries supplying coral limestone for limestone manufacturing in the coastal region. Due to its close proximity to the Indian ocean, the semidiurnal ocean tides tend to have an influence on the stability of the quarry slopes adjacent to the shoreline. Finite element numerical analysis using the generalized Hoek–Brown criterion is conducted to assess the stability condition of the slopes followed by slope-angle optimization to determine the safest overall slope angle as well as analyzing the stability of the slopes due to action of varying ocean tides. The optimum overall slope angles for various excavation depths are found to be 52° for 20 m, 46° for 30 m, 42° for 40 m, and 39° for 50 m, which are the same even with varying distance of the slope face from the shoreline. A parametric analysis shows that there is no significant effect of the tides on slope stability for excavations above the water table, but as the quarry gets deeper, the slope stability is affected. A sensitivity factor (ζ) is introduced, being a measure of how much the slope safety factor is reduced as a result of the semidiurnal tidal action.

Autochthonous nutrient recycling driven by soil microbiota could be sustaining high coconut productivity in Lakshadweep Islands sans external fertilizer application

The soils of Lakshadweep Islands are formed as a result of the fragmentation of coral limestone, that iscarbonate-rich, with neutral pH, but poor in plant nutrients. Coconut palm (Cocos nucifera L.) isthe main crop cultivated, supporting the life and livelihood of the islanders. No external fertilizer application or major plant protection measures are adopted for their cultivation as the Islands were declared to go organic decades back. Yet, Lakshadweep has one of the highest productivity of coconut compared with other coconut growing areas in India. Therefore, a question arises: how is such a high coconut productivity sustained? We try to answer by estimating in three main islands (i) thenutrients added to the soil via the litter generated by coconutpalms and (ii) the role of soil microbiota, including arbuscular mycorrhizae, for the high productivity. Our results indicatedthat, besides adding a substantial quantum of organic carbon,twice the needed amount of nitrogen, extra 20% phosphorus to the already P-rich soils, 43-45% of potassium required by palms could be easilymet by the total coconut biomass residues returned to the soil.Principal Component Analysis showed thatsoil organic carbon %, potassium, and organic carbon added via the palm litter and AM spore load scored >± 0.95 in PC1, whereas, available K in the soil, bacteria, actinomycetes, phosphate solubilizers and fluorescent pseudomonads scored above >± 0.95 in PC2. Based on our analysis, we suggest that the autochthonous nutrients added via the coconut biomass residues, recycled by the soil microbial communities, could be one of the main reasons for sustaining a high productivity of the coconut palms in Lakshadweep Islands, in the absence of any external fertilizer application, mimicking a semi-closed-loop forest ecosystem.

Assessment of Aquifer Systems for The Sustainable Development of Groundwater Use in The Batutua Groundwater Basin

Groundwater exploration is an alternative to meet raw water needs because of the increasing water demand and the dwindling surface water availability. Water use continues to increase along with the rate of population growth in the Rote Ndao Regency. Therefore, an initial assessment of the presence of groundwater can be carried out by identifying the groundwater basin area. Batutua is one of the groundwater basin areas occupied by the most population because it is the capital of Rote Ndao Regency. This study aims to identify aquifer systems and flow patterns as the basis for groundwater exploration in the Batutua groundwater basin area. The method used in this groundwater aquifer system study is the Vertical Electrical Sounding (VES) method. The VES method is a geoelectrical method used to investigate the layers of an aquifer by interpreting the current that penetrates the soil using two electrodes and the potential response. Geoelectrical investigations were carried out at 8 points in the Batutua groundwater basin area. The aquifer is found in water-containing coral limestone areas where water flows through fractures as secondary permeability. The groundwater flow direction was obtained by measuring the groundwater levels in 14 dug wells and 24 springs. The research’s area aquifer system is formed by upper shallow aquifer as an unconfined aquifer with a thickness less than 20 m and lower shallow aquifer as a semi-confined aquifer that has clay or marls on upper layer and limestone in below with the flow direction from the East to the West and the North part of the study area.

Rocky coastal cliffs reinforced by vegetation roots and potential collapse risk caused by sea-level rise

Evaluation of the effect of vegetation roots on the stability of rocky coastal cliffs is necessary to understand geomorphological, environmental and ecological changes in coastlines caused by sea-level rise (SLR). To better understand these topics, coastal cliffs with and without vegetation were investigated. Study cliffs were selected on Taketomi-jima Island and Kuro-shima Island, both in Okinawa, southwestern Japan, because their environmental settings are similar except for the vegetation cover: the islands are only 10 km away from each other and comprise uplifted coral limestone, with an elevation below 5 m. Pandanus odoratissimus (PO) covers the seaward edge of the top surface of the coastal cliffs in Taketomi-jima but is absent in Kuro-shima. Field investigations were conducted on both islands to map the distribution of blocks with the dimension of one side exceeding 1 m to obtain the parameters required for stability analysis. The results indicate that the actual coastal cliff elevation is higher in Taketomi-jima than that in Kuro-shima by approximately 1 m, which results in the presence of PO on the seaward edge of the coastal cliffs in Taketomi-jima and its absence in Kuro-shima. The PO root system likely reinforces the cliffs in Taketomi-jima because the stability analysis results revealed that these cliffs are unstable in terms of their dimensions. Therefore, the possible disappearance of PO in Taketomi-jima caused by an SLR of 1 m in the following several decades or hundred years can increase the apparent frequency of cliff collapses by approximately tenfold.

Laboratory Investigation of the Physico-Mechanical Properties of Coral Limestone of Vipingo Area in Kenya’s Coastal Region

Laboratory Investigation of the Physico-Mechanical Properties of Coral Limestone of Vipingo Area in Kenya’s Coastal Region

Evaluating Rock Mass Properties of Vipingo Coral Limestone Quarry Based on a Modified Geological Strength Index (GSI) and State of Karstification

The process of evaluating rock mass strength requires that major structural features such as joints that influence rock strength are considered. In carbonate rock masses, however, the strength of the rock mass is largely dependent on intact rock strength and structural features play a secondary role. Laboratory experiments on porous rock have shown that intact rock strength reduces with increasing porosity, which has a direct effect on the rock mass strength. Rock porosity has however not been well accounted for in rock mass characterization methods currently in use. This research applies the modified GSI method for carbonate rock masses which is based on a combination of GSI and total porosity. The main aim is to quantify the GSI with respect to rock porosity which is a direct indicator of the state of karstification, as an inherent feature that affects rock mass strength. An empirical equation is proposed whereby the GSI as observed in the field is modified by a natural log of the value of porosity, giving rise to a modified GSI (GSIm). The GSIm together with laboratory properties of rock is used to determine the properties of Vipingo coral limestone from RocLab software. A deterministic parametric slope stability analysis is done using the finite element software Phase 2 with the rock mass properties as input parameters. The analysis results point to a direct dependence of the slope stability on slope angle, slope height and rock mass strength of the lithological unit. The graphs make a useful design guide for slopes engineered in this type of rock mass.

The fauna of a Danian fossil Conservation Lagerstätten from the cold-water coral mound complex at Faxe, Denmark

Fossil cold-water coral mound ecosystems are rare in geological history. One of the best known examples are the Danian coral mounds of Faxe comprising a complex interplay between corals, bryozoans, and a diverse associated fauna. The Baunekule facies is a special type of weakly consolidated coral rudstone to floatstone found in the Faxe Formation. The facies has a rich fauna of 220 species that are extremely well-preserved due to an early diagenetic recrystallization of aragonite to calcite prior to dissolution and is regarded as a fossil conservation Lagerstätten. The fauna lived between dead and living coral fragments on the flank of a growing Dendrophyllia coral mound. The fauna is authocthonous and dominated by small gastropods, polychaete tubeworms, bivalves and brachiopods. The fauna from Baunekule facies are compared to other parts of the Faxe Formation which have experienced a significantly different diagenesis. More than 57% of the fauna are not described from others parts of the Faxe Fm. More than 80% of the studied species from the coral limestone are unknown from other parts of Danian localities worldwide. The study of the Baunekule facies compares well with data from modern living coral mounds of Lophelia with a low species richness of framebuilding corals and a high species richness of the associated highly specialised fauna that show a dominance of attached suspension feeders, mobile carnivores, and grazers. The small gastropods are apparently lacking on the modern mounds, probably related to the sampling methods in the deep ocean. In general, there is agreements between the ecology of the fossil and the modern cold-water coral ecosystems with evidence for similar environments from Danian to modern time. The fossil cold-water coral mounds probably acted as diversity hotspots in the outer shelf – slope settings in the Danian epicontinental sea. • Palaeoecological studies of 21,000 specimens from rare fossil cold-water coral mounds • Identifying a rich fauna of 220 well-preserved small species (mainly gastropods) • Preservation is due to an early diagenetic recrystallization of aragonite to calcite. • The ecology of the fossil and the modern cold-water coral ecosystems are comparable. • The fossil cold-water coral mounds acted as diversity hotspots on the Danian shelves.

Lithostratigraphy, facies, mineralogy and diagenesis of the syntectonic late Oligocene and Neogene Barzaman Formation (Al-Khod, Sultanate of Oman)

This is the first comprehensive study of the >170-m-thick late Oligocene to Pliocene(?) Barzaman Formation from the northern side of the Oman Mountains. Our work closes a major gap in the understanding of a complex geological interval and region which was affected by regional doming, syndepositional thrusting, changing eustatic sea level and changing climate. The dynamic, and diverse setting is reflected by the formationʼs varied lithologies. Based on seven measured sections we subdivided the Barzaman Formation into five lithostratigraphic units which we correlated over a distance of 1.3 km. The lower three units are shallow marine, the remaining two units are terrestrial. The marine development was at first siliciclastic (near-shore; Unit 1), followed by coral limestone deposition with some associated siliciclastics (Unit 2) and then siliciclastic again (Unit 3). The limestones include a coral-bearing limestone debrite. Associated (or at least contemporary) with the debris flow, are coral limestone boulders which rolled downslope beyond the area of limestone deposition. The lower terrestrial unit (Unit 4) is marked by isolated lenticular claystone beds within weathered conglomerates. The claystone beds, which may be cellular, consist of palygorskite and commonly also of saponite. Their clay mineralogy, limited areal extend and association with conglomerates indicate their origin from evaporation of small ponds/pools between wadi gravel. Within the claystones and conglomerates, two slides were identified. These slides and the limestone debrite indicate slope instability which we attribute to syndepositional thrusting. Thrust deformation may explain the thickness variations of units 2–4. The uppermost Unit 5 is characterized by highly altered conglomerates whose primary features are largely obliterated by diagenesis such as (1) alteration and replacement of igneous ophiolite clasts, (2) local basal silica cementation and (3) mainly dolomite cement with some calcite cement. Based on the general geological setting (doming, falling eustatic sea level) and the involved near-surface diagenetic processes we interpret these conglomerates as terrestrial. Diagenesis of Unit 5 indicates an increasingly wet climate. Considering the foraminifer-constrained age of Unit 2, paleostress constraints and dated climatic change data, we conclude that the Barzaman Formation dates as late Oligocene to at least the mid-Miocene.

Stratigraphy and petrophysical characteristics of Lower Paleocene cool-water carbonates, Faxe quarry, Denmark

The Faxe limestone quarry in eastern Denmark exposes Danian (Lower Paleocene) cool-water carbonate deposits. They constitute remnants of an apparent build-up that covers about 12 km2 today. The Danian deposits at Faxe are conspicuous due to their pronounced thickness of coral limestone relative to the regional carbonate system. In the Faxe quarry, scleractinian corals are uniquely exposed in up to 30 m high mounds. The rapid accumulation of scleractinians combined with induration of the mounds may locally have protected the limestone from Quaternary glacial erosion and created a Danian thickness anomaly at Faxe. The position of Faxe above a local fault-bounded basement high and the extent of coral limestone has been better defined by new mapping. A mapped lithostratigraphic surface in the quarry reveals the large-scale organisation of nested bryozoan mounds on three elongated ridges striking NW–SE. The main scleractinian coral mounds are located above this horizon. Data for reservoir characterisation, mainly of the bryozoan mounds, were collected as photographs of the outcrop, petrophysical and petrographical data from cored boreholes, and as ground-penetrating radar sections. Old boreholes and measured sections were used to reconstruct the build-up, and new nannofossil data allow a discussion of stratigraphy and accumulation rate. The petrophysical data show that common mound-building bryozoan packstone has higher permeability and lower capillary entry pressure than chalk, whereas less commonly occurring grain-dominated packstone and grainstone deposits from local higher-energy sites of the mound complex were found to have reduced amounts of coccolith mud, significantly higher permeability and a higher degree of lithification. Based on biostratigraphic age constraints, correlation of flint – limestone couplets and recog-nised hierarchical patterns, we develop a cyclostratigraphy for the middle Danian and suggest that cyclicity in lithology and petrophysical characteristics of bryozoan limestone are controlled by precession and eccentricity of the orbit of the Earth.

The role of bacterial community in the formation of a stalactite in coral limestone areas of Taiwan by 16S rRNA gene amplicon surveys

The role of bacterial community in the formation of a stalactite in coral limestone areas of Taiwan by 16S rRNA gene amplicon surveys

Karst-Induced Geoharzards in Kenya’s Coastal Region: A Case Study of Vipingo Coral Limestone Quarry

As the human population grows, the demand for space to settle and infrastructure development puts a strain on land resources hence people move to occupy areas of difficult terrain such as mountainous regions and karst environments. The trends in anthropogenic activities mean that there will be increased human interaction with the perilous terrain and consequently geohazards associated with them. Studies on geohazards in Kenya have focused mostly on landslides in mountainous regions but not much has been reported on geohazards that are common in areas of carbonate rocks such as coral limestone. Vipingo coral limestone quarry, a coastal quarry, is taken as a case study as a number of hazardous situations have been encountered during mining. This paper outlines the karst features, their formation processes in the coralline limestone rock mass, and the resultant geohazards. Field visits made to the quarry complemented with previous exploration reports enabled the collection of field data on rock mass characteristics, karst features, and potential hazardous sites were mapped out. Karstification is evident in traces of pores and fissures filled with soil in the upper layers of the rock. Cavities, voids, and caves occur randomly in the rock mass and are the genesis of incidents such as bench collapse, sagging of overlying rock slaps leading to sinkholes. The rock mass is weak and prone to slope failures. Suggestions have been fronted for geohazard mitigation and further research work for the scientific community. Thus, this work constitutes an important knowledge base for infrastructure development and any other quarries around the area, and for those who are settled around this karst environment in order to preempt geo-accidents.