An analysis of beach profile changes subsequent to the Colombo Harbor Expansion Project,Sri Lanka

Man-made coastal structures directly affect sediment balance and sediment dynamics on the surrounding beaches. The Colombo Harbor Expansion Project has created about 5-km-long breakwater nearly perpendicular to the beach. The present study is focused on quantitatively and qualitatively analyzing the effect of the Colombo Harbor Expansion Project on economically important beaches in and around Colombo city area. In this study, the authors measured monthly variations of beach width, beach profile and the mean grain-size of the sediments at mean sea level for complete annual monsoon cycle. Data were analyzed to establish site-specific erosion vulnerability. Monitoring results show that cumulative beach erosion has increased after the construction of the breakwater (rate = 0.7 m/year from May 2000 to April 2011 and rate = 28.2 m/year from April 2011 to June 2012). In addition, the cumulative and site-specific sand accretion and erosion patterns have a clear relationship with the monsoon seasonality. Beaches were narrower during the stormy southwestern monsoon, whereas beaches were wider during fair weather of northeast monsoon and inter-monsoon periods. In contrast, the constructed breakwater obstructs natural longshore sediment dynamics. For example, a significant amount of sediments from the Kelani-Ganga River were buried in the Colombo Harbor due to alteration of prominent longshore sediments transportation on the western coast of Sri Lanka. Therefore, this study shows enhancement of coastal erosion in the studied southern beaches due to a lack of sediment deposition.     

广东达濠半岛近代高海滩岩的研究

广东达濠半岛现已发现距今三千多年的3个时期的海滩岩残留体,对它的认识有海滩岩与风成砂丘岩两种观点,笔者确定是海滩岩。本文从层面构造的流水线理、障碍物痕迹、波痕、鸟类足迹,岩层的韵律,胶结物的文石,微体古生物动物群,以及氧碳同位素的测定等多方面研究,认为该地海滩岩为热带、广盐度、与外海相通的滨海沉积物。 达濠海滩岩不是高海面的遗迹,而是海岸地壳抬升的证据。在构造格架上,位于北西西向强（震）隆起带上,上地幔隆起达2km。     

AMS 14C ages and petrological features for solidified fractures with carbonates at coastal outcrops of Yakushima Island, Japan

This paper describes the petrological features and the ages of rock fractures filled mainly with carbonates at coastal outcrops of Yakushima Island, Japan. Microscopic observation and geochemical analysis were used to investigate the petrological features and the compositions of the fracture fillings. In addition, AMS ¹⁴C dating was also performed to estimate the ages of them. Microscopic study indicated that the fracture fillings contain not only cementing materials but also lithic fragments from host rock and bioclasts. SEM observation showed that the cements exhibit the characteristic textures of beachrocks. The cements were identified as Mg-calcite from XRD analysis. It was also observed from geochemical analysis that there were at least two stages of precipitation within the fractures. In addition, AMS ¹⁴C dating for seventeen samples of fracture fillings showed that the ages range from 2,460 to 5,130 years BP which is found to be younger than that of the uplifted coral at Yakushima Island (approximately 5,300–5,600 years BP). The results suggest that the fractures were solidified after the coral was uplifted.     

Coastal geology and revised stratigraphy of the Brega area,northeastern Libya

While describing the geology of the Brega area, NE Libya, the Brega Sandstone Bed of Pliocene age was established as a new stratigraphic unit in this part of Libya (Kumar, 2014). New field data from the western regions of Brega especially along the Brega Area One beach provides some new significant geological information. New outcrops of the Brega Sandstone Bed and Ajdabiya Formation are described. A new hitherto unknown outcrop of beachrocks is also described. Based on these outcrops and their stratigraphic relationships, a new stratigraphy for the Brega area is proposed. The new outcrop of the Brega Sandstone Bed is much larger and is exposed along the sea coast. It is of grayish yellow to brown color and intensely bioturbated, and unlike the outcrops of this stratigraphic unit in the Brega Area Two, this outcrop shows distinct bedding planes that dip 15° to 20°E to ESE. A new outcrop of Pleistocene Ajdabiya Formation was observed in close vicinity of the newly observed outcrop of the Brega Sandstone Bed. There is an unconformable contact between the Ajdabiya Formation and underlying Brega Sandstone Bed. A new outcrop of beachrocks was observed on the southwestern end of the Brega Area One beach. These rocks are very hard, of gray to dark gray color, and are characterized by numerous circular to sub-circular holes of various diameter and depth; these are filled by floating crude oil that is derived from leakages and spills of crude oil pumped into ships for export from the Brega Port. These rocks are mostly unfossiliferous but at places, fossil corals and gastropods were noted. Presence of corals is problematic because there are no coral reefs offshore Braga or in the nearby waters of the Mediterranean Sea. It is possible that the fossil corals from Libya could have been eroded and transported by wind and water during the past and transported to the beaches of Brega. Ultimately, these corals along with calcareous beach sand were lithified by calcium carbonate and became parts of beachrocks. The gastropods found in the beachrocks are local shallow marine inhabitants, and they can be observed on the surface of the Brega Sandstone Bed as well as in the recent sediments.     

Diagenesis of Holocene beachrocks: a comparative study between the Arabian Gulf and the Gulf of Aqaba,Saudi Arabia

Beachrocks occur in present-day intertidal zones of the Arabian Gulf and the Gulf of Aqaba, on the eastern and northwestern coasts, respectively, of Saudi Arabia. The beachrocks occur as linear patches within beach deposits, which have variable grain size and detrital compositions. The Arabian Gulf beachrocks are composed of sand-sized bioclasts and siliciclastic grains, whereas the Gulf of Aqaba beachrocks are composed of sand- to pebble-size grains, which are dominated by igneous rock fragments and small amounts of skeletal carbonate grains. The cement includes micritic high-magnesian calcite and isopachous acicular/bladed aragonite. In addition to cements, intergranular pores are locally filled by a lime–mud matrix. Radiocarbon dating of beachrock samples from the Arabian Gulf yielded ages from ca. 655 to 2185 year bp, whereas the Gulf of Aqaba samples range in age between 2745 and 5075 year bp.     

浙江沿海全新世海滩岩基本特征及其古地理意义

浙江沿海全新世海滩岩是正处于中亚热带的海滩岩,迄今已发现有13处,主要出露于两侧为基岩岬角的小海湾潮间带中部的沙滩上,14C年龄主要为2 705 a±160 a BP～6 485 a±210 a BP。通过多学科手段的综合研究,初步探讨了其基本特征及古地理意义。研究结果表明,受海水作用影响产生的颗粒(如生活于潮间带-潮下带的贝类壳体及其碎片、近岸底栖的有孔虫和介形虫等生物碎屑、花岗岩岩屑等)、颗粒支撑结构及文石针胶结物是其最重要特征。在其形成过程中,适宜的地貌如处于有砂砾滩的小海湾中,充足的经海蚀搬运来的陆源岩屑、石英、长石,大量的海洋生物碎屑作为物源,合适的颗粒粒径,适中的水动力,基本稳定或缓慢下降的海面及较高的气温等,都是有利的条件。在海滩岩形成时期,浙江中、北部地区沿岸线基本稳定,或略微缓慢向海推进。东海沿岸流不是如今这种低温水团,其水温应比现今高5～6^oC,最少应高2^oC,而其低盐度性质则古今基本一致。同时,热带扩展到浙江中、北部地区,或者当时的气候分带性不如现今这么明显。     

Early Carboniferous volcanic rocks of West Junggar in the western Central Asian Orogenic Belt: implications for a supra-subduction system

The paper presents new U–Pb zircon ages and geochemical data from early Carboniferous volcanic rocks of the Wuerkashier Mountains in the northern West Junggar region, NW China, and of the Char suture–shear zone in East Kazakhstan. The study included analysis of geological setting, major and trace elements, and rock petrogenesis. Both localities host early Carboniferous volcanic units dominated by plagioclase-porphyry andesites and dacites. A West Junggar dacite yielded a ²⁰⁶Pb/²³⁸U age of 331 ± 3 Ma. The Junggar volcanic rocks are tholeiitic, and the Char samples are intermediate between tholeiitic and calc-alkaline. Both the Junggar and Char volcanic units are characterized by LREE enriched rare-earth spectra (La/Sm_n = 1.1–2.4) with Eu negative anomalies (Eu/Eu* = 0.12–1.0) and Nb-Ta minimums (Nb/Th_pm = 0.15–0.35; Nb/La_pm = 0.3–0.7) on multi-element spectra. The Junggar andesites and dacites have higher REE and HFSE (Ti, Nb, Zr, Y, and Th) compared with the Char rocks, suggesting their derivation from a different mantle source. The melting modelling in the Nb-Yb system showed that the Junggar volcanic rocks formed by low- to medium- (2–5%) degree melting of depleted mantle harzburgite and spinel lherzolite. The Char volcanic rocks formed by high-degree melting (15–20%) of spinel lherzolite and garnet-bearing peridotite. The regional geology of West Junggar and East Kazakhstan and the geochemical features of the rocks under study (i.e. depletion in Nb, Ta, and Ti and enrichment in Th, and combination of LREE enrichment and HFSE depletion) all suggest a subduction-related origin of both Junggar and Char volcanic rocks. The early Carboniferous volcanic rocks of West Junggar possibly formed by subduction of the Junggar-Balkhash ocean beneath an active margin of the Kazakhstan continent, whereas those of East Kazakhstan formed by subduction of the Irtysh-Zaisan Ocean beneath an intra-oceanic arc at the active margin of the Siberian continent.     

Provenance analyses of the heavy-mineral beach sands of the Annaba coast,northeast Algeria,and their consequences for the evaluation of fossil placer deposit

The paper presents the first study of heavy-mineral sand beaches from the Mediterranean coast of Annaba/Algeria. The studied beaches run along the basement outcrops of the Edough massif, which are mainly composed by micaschists, tourmaline-rich quartzo-feldspathic veins, gneisses, skarns and marbles. Sand samples were taken from three localities (Ain Achir, Plage-Militaire and El Nasr). The heavy-mineral fraction comprises between 74 and 91 vol%. The garnets of the beaches are almandine rich and tourmalines vary with respect to their location from schorl to dravite. Tourmaline at Ain Achir and the Plage-Militaire is schorlits, while at El Nasr beach dravite is ubiquitous. The World Shale Average normalised REE of the sands and the basement outcrops reveal: (i) Ain Achir beach: REE pattern of sand and the coastal rocks from the studied beaches reflects a multiple sources; (ii) Plage-Militaire: the sand and the coastal outcrops show similar LREE and a strong enrichment in HREE, suggesting the presence HREE-rich phases found as inclusions in staurolite; (iii) El Nasr: two types of sand patterns are found: one with flat REE pattern similar to the proximal rocks and other one enriched in HREE suggesting a mixed source.     

Evaluation of the impact of pyrite oxidation on rock characteristics and environment by laboratory tests

Pyrite is a common and abundant sulfidic mineral subject to oxidation. The weathering characteristics of rock-bearing pyrite sometimes impose serious influences on the surrounding environment as the oxidation of pyrite (FeS₂) generates acid drainage that results in the acceleration of rock weathering and the discharge of heavy metals into the environment. Such an accelerated weathering of rocks can reduce its mechanical properties and therefore menace the stability of rock structures, such as excavated slopes and tunnels. The evolution of physical properties of rocks and the chemical composition of drainage were evaluated in this study by a weathering test using a double Soxhlet extractor for 1 month in a laboratory setting. Three groups of biotite gneiss classified according to their pyrite content were used for the Soxhlet extraction experiment (group A with less than 0.1 wt% of pyrite; group B with about 3.3 wt% of disseminated pyrite; group C with about 5.65 wt% of vein type pyrite). The massive groups A and B had limited weathering on the surface; however, group C with the pyrite vein experienced weathering on the surface as well as along the pyrite vein. The weathering type regulated by the occurrence of pyrite apparently controlled the mechanical properties of the rock samples and the chemistry of the drainage. Groups A and B showed no significant quick absorption ratio after the 1-month experiment; however, group C had about 10 % increase in value. The uniaxial compressive strength of the three groups decreased about 20, 10 and 45 % for groups A, B and C, respectively. The mechanical properties of the samples and the chemical compositions of the drainage indicate that the oxidation of pyrite contained in the samples accelerated weathering, resulting in deterioration of mechanical properties of the rocks, and could result in the discharge of heavy metals and acid into the environment with the drainage.     

Assessments of Strength Anisotropy and Deformation Behavior of Banded Amphibolite Rocks

Assessment of strength anisotropy in transversely isotropic rocks has been one of the most challenging subjects in rock engineering. However, far too little attention has been paid to banded amphibolite rocks. This study aim to evaluate strength and deformation anisotropy behavior of banded amphibolite rocks. The dynamic mechanical tests including ultrasonic pulse test, uniaxial compressive strength, Brazilian test and deformability test were performed on drilled rock samples as a function of foliation plane angle (β = 0°, 30°, 60° and 90°). The results obtained have shown that the dynamic mechanical properties of amphibolite rocks have different values concerning banding plane. Compression and shear waves taken parallel to the foliation plane show highest values than those obtained in the other directions. Under uniaxial test, the banded amphibolite has a U-shaped anisotropy with maximum strength at β = 90° and minimum strength is obtained when β = 30°. Strength anisotropic index ranges between 0.96 and 1.47. It seems that the high range value of anisotropic index is mainly due to slight undulation of foliation planes, that being not perfectly straight. The results of elastic deformation test show that there is no clear dependence on microstructures characteristics of subtype-amphibolite rocks that controlling modulus “shape-anisotropy”. However, in this study, Young modulus values of amphibolite rocks with β follow both types of shape-anisotropy, “U-shape” and “decreased order-shaped”. Thus, this study recommended that further research be undertaken regarding the role of modulus “shape-anisotropy” within the same lithotype.     

Timing the tectonic mingling of ultramafic rocks and metasediments in the southern section of the coastal accretionary complex of central Chile

Uranium-lead ages are reported for zircons from ultramafic bodies and metamorphic host rocks of the Western Series that outcrop at La Cabaña, in the southern section of the coastal accretionary complex of central Chile. Metasedimentary mica schists hosting the ultramafic bodies contain a main detrital zircon population of Devonian age (365–380 Ma) clustering around ~368 Ma, differing significantly from neighbouring areas where Devonian zircons are scarce. Zircons from the metasomatic reaction zones (albitites and chloritites), formed during the emplacement and alteration of the ultramafic bodies, are mainly Ordovician (~478 Ma) and lack Devonian zircons, resembling a typical detrital zircon pattern from other locations in the Western Series. Zircons from the chloritite reaction zone of the Lavanderos serpentinite, the easternmost ultramafic body in La Cabaña, are in textural equilibrium with metamorphic ilmenite. Some of these zircons yield an average age of 283.4 ± 7 Ma (n = 6) which is identical, within error, to a previously reported K-Ar fuchsite cooling age of 282 ± 6 Ma from the reaction zone. Most zircons extracted from chromitite boulders have euhedral oscillatory-zoned growth patterns with a similar range of ages than those reported for the Western Series (324–1090 Ma; n = 12), except for two zircons with cloudy appearance and high U/Th ratios which yielded an average age of 285.5 ± 7 Ma. The presence of Early Permian zircons (~280–290 Ma) in all studied rocks suggests remobilization of Zr, possibly triggered by metasomatic fluids released during the disequilibrium reaction associated with the tectonic emplacement of the ultramafic rocks into the metasedimentary rock. Simultaneously with the formation of metasomatic zircons, Palaeozoic and Mesoproterozoic zircons from the metasedimentary rocks were mechanically incorporated into the ultramafic rocks, thus providing a record of the timing of crustal emplacement of the ultramafic rocks into the accretionary complex.     

矾山碱性岩体磷铁矿床金的地球化学

河北矾山钾质碱性岩体,由３期侵入岩和脉岩正长岩组成。第１期岩石为层状超镁铁质岩系,具韵律层结构。层状岩系中赋存巨大磁铁磷灰石矿床。碱性岩体全岩２２５个样品平均含金为７．８×１０－９。矾山岩体金的丰度为６．１×１０－９,是地壳金丰度（３．５×１０－９）的１．７４倍。第１期岩石平均金含量为８．８×１０－９,第２期岩石为５．１×１０－９,第３期岩石为７．４×１０－９,正长岩为４．２×１０－９。第１期侵入岩中辉石岩平均金含量为９．３１×１０－９,黑云辉石岩平均为７．７８×１０－９,伟晶正长黑云辉石岩为７．４０×１０－９,间隙状正长辉石岩为８．００×１０－９,磁铁磷灰石岩为１３．７８×１０－９,磷灰石岩和黑云磷灰石岩为１１．８０×１０－９,黑云母岩为１８．６３×１０－９。在垂直层状岩系的剖面上,岩石金含量呈韵律性变化。在东矿区,岩石金含量由西向东趋于降低。在岩浆液相分离过程中,金倾向富集在含铁、镁、钙和磷的熔体相中,而在岩浆结晶分异过程中,金可能富集在流体相中。     

Prediction of Unconfined Compressive Strength for Jointed Rocks Using Point Load Index Based on Joint Asperity Angle

This research paper is aimed to briefly highlight the correlation between unconfined compressive strength and point load index for jointed rocks based on joint asperity & orientation. In this observe, specimens were tested to obtain their unconfined compression strength and point load index for a different joint condition. The different joint conditions considered for this study were clean joint and joint filled condition. For both clean joint and joint filled specimens were prepared by various asperity angles of 30°, 45°, 60° and 90° with different orientation angles such as 0°, 30°, 45°, 60°, 90°. Plaster of Paris was used as model material to simulate weak rock mass in the field. By testing intact model specimens for unconfined compressive strength leads to revealing of optimum moisture content for further testing. The curing period for the model specimens is 3 days at room temperature. To simulate jointed rocks, various moulds of different orientation of joint with respect to major principal stress are prepared separately. The inner diameter of the mould is 50 mm and height is 100 mm. After casting, a rough joint was created by cutting the prepared sample using the cutter. The specimens are tested for both clean joint and joint filled condition to determine the favorable joint orientation and asperity angle. After curing, the specimens are tested for unconfined compressive strength and Point load index. The new multi-linear correlation for determining unconfined compressive strength with the help of point load index is developed and cross checked with equations formed for actual rock. On comparing both results it is found that the new equation can suitable for assessing the unconfined compressive strength of limestone and serpentinite rocks through point load index value.     

Rapid and Intense Phosphate Desorption Kinetics When Saltwater Intrudes into Carbonate Rock

It is important to understand how phosphate sorption dynamics of coastal carbonate aquifers are affected by seawater intrusion, because many coastal aquifers are composed of carbonate rocks and subject to an increase in saltwater intrusion during relative sea-level rise. Twelve carbonate rock and unconsolidated sediment specimens were acquired from a test corehole spanning the full thickness of the Biscayne aquifer in southeastern Florida. All 12 samples exhibit low phosphorus content but variable contents of iron. Column leaching experiments were conducted with two carbonate aquifer samples, alternating between freshwater and saltwater flow. With the first influx of saltwater, phosphate concentration in leachate increased rapidly from a freshwater value of approximately 0.2 μM to peaks of between 0.8 and 1.6 μM. The phosphate concentration began to diminish as saltwater continued to flow, but sustained desorption continued for over 2 h. Overall, seawater drove sorption behavior much more than chemical composition for the aquifer rocks and sediment from the seven rock samples for which we did isotherm sorption experiments. Our results indicate that an immediate and intense pulse of phosphate desorption from carbonate rock and sediment with low phosphorus content occurs in response to an influx of seawater and that the duration of desorption will vary by layer within a single aquifer.     

Meso–Neoarchaean crustal evolution of the Bundelkhand Craton,Indian Shield: new data from greenstone belts

ABSTRACT

The Mauranipur and Babina greenstone belts of the Bundelkhand Craton are formed of the Central Bundelkhand greenstone complex (CBGC). This complex represents tectonic collage which has not been previously studied in depth. The purpose of this study is to contribute to the understanding of the main features of the Archaean crustal evolution of the Bundelkhand Craton. The CBGC consists of two assemblages: (1) the early assemblage, which is composed of basic-ultramafic, rhyolitic–dacitic, and banded iron formation units, and (2) the late assemblage, which is a felsic volcanic unit. The units and assemblages are tectonically unified with epidote–quartz–plagioclase metasomatic rocks formed locally in these tectonic zones.

The early assemblage of the Mauranipur greenstone belt is estimated at 2810 ± 13 Ma, from the U–Pb dating (SHRIMP, zircon) of the felsic volcanics. Also, there are inherited 3242 ± 65 Ma zircons in this rock. It is deduced that this assemblage is related to early felsic subduction volcanism during the Mesoarchaean that occurred in the Bundelkhand Craton.

Zircons extracted from metasomatic rocks in the early assemblage’s high-Mg basalts show a concordant age of 2687 ± 11 Ma. This age is interpreted as a time of metamorphism that occurred simultaneously with an early accretion stage in the evolution of the Mauranipur greenstone belt.

The felsic volcanism, appearing as subvolcanic bodies in the late assemblage of the Mauranipur greenstone belt, is estimated to be 2557 ± 33 Ma from the U–Pb dating (SHRIMP, zircon) of the felsic volcanic rocks. This rock also contains inherited 2864 ± 46 Ma zircons. The late assemblage of the Mauranipur greenstone belt corresponds with a geodynamic setting of active subduction along the continental margin during Neoarchaean.

The late assemblage Neoarchaean felsic volcanic rocks from the Mauranipur and Babina greenstone belts are comparable in age and geochemical characteristics. The Neoarchaean rocks are more enriched in Sr and Ba and are more depleted in Cr and Ni than the Mesoarchaean felsic volcanic rocks of the early assemblage.

Through isotopic dating and the geochemical analysis of the volcanic and metasomatic rocks of the CBGC, this study has revealed two subduction–accretion events, the Meso–Neoarchaean (2.81–2.7 Ga) and Neoarchaean (2.56–2.53 Ga), during the crustal evolution of the Bundelkhand Craton (Indian Shield).     

Geo-engineering evaluation of Harrat Irbid Basaltic Rocks,Irbid District—North Jordan

The basalt flow in Irbid district covers an area of about 300 km² and forms different shapes: elongated strips, sub-rounded spots, and arc-like outcrops. The basalt flow in the study area has thicknesses ranging from 1 to 30 m. This study is conducted to evaluate the basaltic rocks as a construction material in eight different places of Harrat Irbid. Thirty-six rock cores were prepared from the collected fresh basaltic rock samples to study the physical and mechanical properties. The basaltic rocks in the study area have desirable physical and mechanical properties; the rocks have high apparent specific gravity values (2.70–2.90), bulk specific gravity (2.60–2.84), absorption values (0.33–1.60 %) that indicates the texture is crystalline, porosity (0.22–2.15 %), void ratio (0.002–0.022), water content (0.35–1.08 %), degree of saturation (41–68 %), rebound number of Schmidt hammer hardness test (average 44.10), point load strength(average 11.35 MPa),uniaxial strength (average 106.83 MPa) which is classified as medium strength, basalt uniformity of wear (0.206), and very high durability which is equal to 99.52 % in average, recorded after the second cycle of the test. Based on field observations and physical and mechanical tests, this study confirms that the genesis of basalt in the study area is strongly related to Harrat Al-Shaam basalt. Therefore, this study adds a new area of about 300 km² to the Harrat Al-Shaam area. Additionally, this study strongly recommends the use of the basaltic rocks that have been tested in this study for some industrial applications (e.g., in construction).     

Geochemistry and petrology of rift-related mafic sills and arc-related Gabbro–Diorite bodies,Northern Bafq District,Central Iran

Two types of mafic intrusions have been recognized in the north of the Bafq district, Central Iran. A number of olivine-gabbroic to gabbroic sills intruded the Rizu Formation, comprised of alternating carbonate and volcanic rocks. Mineralogical data show that olivine + pyroxene + brown amphibole (kaersutite) + calcic plagioclase + opaque comprise the olivine-gabbroic rocks, and intermediate (or sodic) plagioclase + altered pyroxene and altered amphibole to biotite + opaque minerals the gabbroic rocks. Both rock types have shown within-plate and alkaline characters and have been presumed to be related to rift formation. The mafic-alkaline magma source of the sills is proposed to have been derived from enriched mantle. Regionally, two Gabbro–Diorite intrusions have been identified in the metamorphic complexes. Mineralogical data suggest that the pyroxene + amphibole (hornblende) + plagioclase + biotite + opaque minerals formed the gabbro to diorite intrusions. These rocks have shown characteristics of calc-alkaline and volcanic arc magmatism.     

The effect of cubic specimen size on uniaxial compressive strength of carbonate rocks from Western Turkey

One of the most important quality and design parameters of natural rock materials is uniaxial compressive strength (UCS). UCS value of a building stone determines its application area such as cladding, roofing, facing, and coverings. In rock mechanics and engineering practice determination of UCS values of rock materials is suggested on core specimens whereas in construction and building stone sector, cubic specimens are suggested. In this experimental study, the effect of cubic specimen size on UCS values of some carbonate rocks which are being used as dimension stones are investigated. A total of 299 cubic specimens at five different edge sizes (3, 5, 7, 9, and 11 cm) from limestone, marble, and travertine are prepared. Chemical, petrographic analyses and physical properties of specimens are determined and after that UCS tests are carried out. It is observed that as the specimen sizes increase from 3 to 11 cm, average UCS values decrease about 7% for the tested carbonate rocks. In the light of this finding, results of UCS tests could be interpreted considering cubic specimen sizes for the same rock types in various fields.     

Coastal erosion in the south-eastern Mediterranean: case of beaches in North Tunisia

This research is conducted as part of a Spanish International Cooperation Agency project with the aim to investigate the sustainable protection of Tunisian coastal zones, as in the case of Beni Khiar and Dar Chaabane coasts (Hammamet Gulf) separated by Oued El Kebir river. The sedimentary dynamic of these beaches is studied in order to identify the main causes responsible for their erosion by the use of different approaches of in situ measurements and numerical methods. Geophysical surveys and sedimentary analyses have demonstrated that sediments are finer and less carbonated from Beni Khiar to Dar Chaabane. Then, the shoreline mapping of several missions of aerial photos has illustrated a mean shoreline retreat between 3 and 4 m/year. In terms of sand volume, a sediment loss more than 30,000 m³/year at Dar Chaabane has been observed since the hill lake structures were built within Oued El Kebir river in 1996. Finally, modelled hydrodynamic and sedimentary patterns have illustrated the refraction of waves in deep water close to shoals and a high-energy concentration along Dar Chaabane coast. The sediment transport direction is mainly of NE-SW induced by ESE-SE wave-driven alongshore current. Results provided by these approaches have shown the importance of Oued El Kebir sediment yield in supplying the neighbouring beaches. Changes in sedimentary dynamics are affected by the modification of hydrodynamic patters caused by the presence of hydrological dams and the implementations of hotels close to the shoreline. This finding underlines the key role of Oued El Kebir fluvial activity in controlling the equilibrium of beaches and their sensitivity to coastal managements induced by man activities, as in the case of the most Mediterranean beaches.     

Geochemical and mineralogical composition of black weathering crusts on limestones from seven different European countries

Twenty-seven samples of black weathering crust and host carbonates were studied from seven European countries (Germany, Hungary, Belgium, Czech Republic, France, Italy and Poland) representing 11 different sites. The samples were collected for sites for which long-term air pollution records are available. The mineralogical analyses (XRD, polarizing microscopy, SEM) have shown that despite decreasing SO₂ emissions crust samples are still very rich in gypsum. Further, in all host rock samples gypsum was also detected. Good correlations (R² > 0.9) were also found between water-soluble calcium and gypsum content and between sulphate and gypsum content both for black crusts and host rocks. The black gypsum crusts are four or five times richer in sulphate than the host rock. The conductivity of dissolved crust and host rock samples also shows a positive correlation with gypsum content of the samples. LA-ICP-MS analyses allowed the detection of high Pb-levels in black crusts and a negative shift in lead concentration at the crust/host rock transition. The lead content of the host rock is 2–5 mg/kg, while that of the crust is 3–25 mg/kg in the sample collected from Germany, while in the Belgian sample these values are 2–14 mg/kg and 80–870 mg/kg for the host rock and crust, respectively. The GC–MS technique allowed to detect the PAH content of black crusts and host rocks. The former one contains 0.6–15.6 (102.5) mg/kg, while in the host rock values between 0.2 and 2.4 mg/kg were found. The present study suggests that still large amounts of air pollution-related minerals and organic pollutants are found in the black weathering crusts of European carbonate buildings despite decreasing trends in air pollution.