Organogenic Limestones Research Articles

Arsenopyrite from the Low-sulphidation Sedefche Au-Ag deposit, Eastern Rhodopes: Mineral Association and Gold Potential

The Sedefche Au-Ag deposit is located in the eastern Rhodopes, Bulgaria and is part of the Zvezdel-Pcheloyad ore field. The deposit is of low-sulphidation epithermal type, hosted in Oligocene highly silicificated intermediate volcanic tuffs, which lie above shallow marine sediments of organogenic limestones. The orebody has stratiform shape partly outcroping onto the surface. The ore mineralization is represented by small crystals and fine grained aggregates of sulphides (mainly pyrite, arsenopyrite, marcasite, chalcopyrite, galena, sphalerite) and associated sulphosalts (tetrahedrite, pyrargyrite, freibergite, and miargyrite) within matrix of quartz, formed in several stages of deposition. Gold in the deposit is detected in significant amounts in bulk ore samples, while native gold (a single < 1 μm gold nugget) and gold-bearing phases were sporadically discovered. The form of gold presence in the deposit is nevertheless debatable. Using combined SEM-EDS, EPMA and LA-ICP-MS approach, the highest concentrations of gold have been established in the arsenopyrite – the gold content there is up to hundredfold higher than in other ore minerals being potential concentrators of gold such as pyrite, marcasite and chalcopyrite. The presence of gold in arsenopyrite predominantly as nanoparticles, irregularly disseminated in the crystals as clusters of inclusions is suggested.

Living in the shadow of Vesuvius: Analysis of the wall paintings of Pollena Trocchia’s Roman buildings across historical eruptions

Through a multi-analytical approach the research focused on the evolution of wall painting technology used for two decorated buildings in Pollena Trocchia buried by volcanic deposits of Vesuvius. The study highlighted a different stratigraphy (with two or three layers) of mortar-based supports. Volcanic aggregate was added to lime binder for rinzaffo and arriccio, whereas calcite and marble dust first, then organogenic limestones were used for intonachino. Pictorial layers, applied using fresco and mezzo-fresco techniques, were obtained combining common (e.g., ochre) and expensive pigments (e.g., cinnabar, aragonite, Egyptian blue), showing diachronic changes in raw materials selection and the refinement of decoration.

Літогенез верхньоюрських відкладів Зовнішньої зони Передкарпатського прогину

Geological- and biological-paleogeographical conditions of sedimentogenesis within the Carpathian segment of Tethys ocean during Tithonian were considered. The rock-forming organisms with calcic function (flora and fauna), which compose main lithological types of carbonate rocks were identified. On the base of biological-paleoceanographical and lithological investigation of different genetic types of Upper Jurassic carbonate rocks of the Outer zone of the Carpathian Foredeep and analysis of literature data on modern carbonate sediments, the structural classification of Late Jurassis epipelagic sediments of the Carpathian segment of the Meso-Tethys was made. In that classification pelitic, aleuritic, psammitic and ruditic fractions of sediments were distingnished. Geological-paleogeographical model of occurrence of the Tithonian sediments within the Carpathian segment of the Meso-Tethys (the Outer zone of the Carpathian Foredeep) was built by the author. That model presents areals of biogenic and abiogenic epipelagic sediments and depicts their facial variations. Geological-paleogeographical study of Upper Jurassic sediment complexes of epipelagic part of the Meso-Tethys has shown that they were formed within widespread interior shelf, probably, with small inclination of the sea bottom. In Upper Jurassic there was abundant growth of the benthos with calcic function and avalanchecal sedimentation of their skeletal remains took place with forming of biogenic carbonate sediments. The coral-algae biocoenosis there were biological indicators of considered parts of Tethys region. In modern basins of the World ocean analogous processes take place at the depths of about 50 m, in temperature conditions about 23–25 °C and the salinity of the sea waters about 2.7–3.8 ‰. The manifestations of diagenetic and katagenetic processes in the Upper Jurassic carbonate rocks of Outer zone of the Carpathian Foredeep have been investigated and their influence of the formation of the reservoir properties of rocks has been found out. During the diagenesis, the rocks were recrystallized, micritizated and cemented. From the mineralogical point of view, the changes consisted in the transformation of primary aragonite and magnesium-calcite skeletal remains of organisms into calcite, as well as processes of dolomitization, ferruginization and silicification. At the stage of diagenesis, Fe-containing minerals ̶ glauconite and pyrite ̶ has been formed. The dolomitization of Jurassic organogenic limestones of Outer zone of the Carpathian Foredeep has been caused by the mixing of the fresh meteoric waters with buried marine pore waters in the underground phreatic zone adjacent to the ancient coastline. Silicification is a consequence of the metasomatic substitution of the carbonate substance by silicate, which has been caused by decrease of the pH occurred after dolomitization. Katagenetic transformation of the rocks are manifested in the dissolution of the remains of organisms, grains of carbonate cement and the late cementation of pores and microfractures. Changes of carbonate rocks are associated with the bringing of certain substances in the sediment (sulphatization, celestinization) or their removal (dedolomitization, decementation). Neoplasm minerals of the katagenesis stages are represented by anhydrite and celestine. The proceses of recrystallization of carbonate rocks at different stages of katagenesis contributed to the selective leaching of limestones and dolomites and led to formation of secondary cavities and caverns, different in shape and size. The predominance of cavities of certain types determines the type of reservoir, among which are distinguished pores, pore-caverns and joint caverns. The processes of diagenesis and katagenesis are associated with the dissolution of carbonate material, which differently affects the reservoir properties of sediments. Authigenous mineral formation, with the exception of dolomitization, impairs the reservoir properties of the Upper Jurassic carbonate rocks, and recrystallization improves. Burial of carbonate rocks at depth contributes to the preservation and even improvement of their reservoir properties both due to dissolution and textural heterogeneity (jointing develops at the boundary of the elements of textural heterogeneity). Observations show that the most favourable in this respect are organogenic and detrital varieties of carbonate rocks. The presence of clay minerals in the composition of their cement increases the textural heterogeneity and, as a consequence, the ability to formation of joints.

Archaemineralogical study of plasters and paints from the Thracian tomb Maglizh (4th–3rd century BC), Bulgaria

Fragments of plasters and paints from the decoration of the chamber and the grave of the Thracian tomb Muglizh (4th–3rd century BC) were studied. It was established that the plasters are two or three-layered and consist of coarse plaster, pink colored plaster and white putty (stucco). The binder in all three layers is a lime prepared from organogenic limestone. Crushed materials from rocks and minerals were used as fillers in the coarse and pink plasters, and only white-colored minerals such as quartz, calcite, albite were used in the stucco. A mixture of red earth ocher and cinnabar was used as pigment in the red paint and pink plaster. For the black paint, a mixture of crushed charcoal and Egyptian blue was used. The binder in the red and black paints is lime. In pink paint, the binding material is gypsum, and the pigment is cinnabar.

ANALYSIS OF THE TAXONOMIC COMPOSI TION OF THE LLANDOVERIAN AND WENLOCKIAN FOSSILS OF MOLDAVIAN PRIDNESTROVYE ENTERED IN THE ELECTRONIC DATABASE “THE PALAEONTOLOGY OF PRIDNESTROVYE”

Problem statement and purpose. In geological surveys of the territory of the Moldavian SSR from the 1960th to the 1990th, deep horizons of Palaeozoic sedimentary rocks were discovered, the leading place among which belongs to the Silurian deposits. At that time, several dozen species and genera of fossils were identified in the Silurian of Moldavian Pridnestrovye. In 2020, as part of the work financed from the state budget on the theme of the creation of GIS “The Geology of Pridnestrovye”, the laboratory “The Geological Resources” developed an electronic database called “The Palaeontology of Pridnestrovye”. The fauna included in the database of palaeontology was divided into groups corresponding to their palaeontological classes and stratigraphic horizons: “Ordovician brachiopods”, “Silurian tabulates”, “Palaeogene foraminifers”, “Neogene bivalves”, etc. Species and genera of the fauna were linked to specific formations and locations, which provides good opportunity for palaeontological analysis of individual formations, horizons, cores of drilling and outcrops. The purpose of this article is to compile lists of fauna from the Llandoverian and Wenlockian formations of Moldavian Pridnestrovye and to compare their chronology with fossil fauna data on the sameage rocks of Podillia, Estonia and Lithuania. Material and methods. Four survey reports deal that on sheets L‑35-V and L‑35-XII were used as the material. The goal was concerning the sedimentary rocks of Llandovery and Wenlock Series. In the local scheme it corresponds to the Marasesti, Step-Soci, Cioc-Maidan (all in Llandovery), Balti formations and Lower Puhoi subformation (Wenlock). The intervals of the formations in boreholes are composed of organogenic limestones, silty, argillaceous stones, argillites and dolomites. The species and genera of the fauna from these intervals are compared with the biostratigraphic data from Podillia, Estonia and Lithuania. Results. In the stratigraphic sequences of Llandovery and Wenlock of the Moldavian Pridnestrovye, (in most cases) species and genera unique to those divisions of brachiopods, tabulates, stromatoporoids, ostracods, rugosans, and trilobites were identified by specialists; a smaller part of the taxa pass between the lowest formations of the Silurian and the overlying Balti formation. Most taxa have correspondences in the Podillian and Baltic basins; however, in these regions, the species and genera identified in Llandovery or Wenlock of Moldavian Pridnestrovye are mostly transitive between Silurian divisions, up to the Ludlow and Pridoli Series. There is practically no identified fauna in the Lower Puhoi sub-formation of Moldavian Pridnestrovye because of its facial specifics. The species Acidolites lateseptatus (Lindstroem), Altha modesta Neckaja, Longiscula caudalis (Jones) in Llandovery and Pentamerus oblongus Sowerby, Halysites catenularius Linnaeus = Halysites priscus Klaamann in Llandovery and Wenlock Series were the only guideing fauna for the first two Silurian series of Moldavian Pridnestrovye. Due to the attribution of the Muksha sub-formation of Podillia to Ludlow Series, no guiding species of the Wenlock stage was identified in the Balti formation of Moldavian Pridnestrovye.

Carbonate-Quartz Cement Composites

The technology of obtaining multicomponent high-quality concrete using limestone powders as fillers is considered. In order to select fillers for powder-activated concrete, a study was made of the water absorption of limestone gravel of various kinds. According to the water absorption index, eight categories of limestone species have been identified. It was revealed that organogenic limestone is one of the materials that is preferred as a filler for high-quality concrete. The experimental results were obtained and graphical dependences of changes in the tensile strength under bending and compression, the dynamic modulus of elasticity and water demand of organogenic cement composites filled with limestone from granulometric composition and filler content were constructed. It has been established that the best strength properties are manifested in materials with optimal indicators of the content and size of limestone and silica powder.

Residual Sediments of the Vema Fracture Zone, Central Atlantic

The Vema Fracture Zone orthogonally intersecting the Mid-Atlantic Ridge along 11° N is a complex tectono-sedimentary system, through which bottom water is transferred from the western to the eastern Atlantic. The southern surrounding of the fault valley is an extended (about 320 km) transverse ridge. At the early stages of the Vema System evolution, the ridge was located at shallow depths in the photosynthesis zone, which led to the formation of extensive biogenic carbonate buildups on its surface. Spreading, general sinking of the system, and associated movements along faults caused disintegration of ultramafic basement and bioherms with subsequent fractionation of colluvial–pelagic sediments and their eastward transport by bottom currents. The formation of coarse-grained residual sands completely devoid of pelitic material is associated with the high flow rates of Antarctic bottom waters. The presence of rounded pebbles of organogenic limestones and ultramafic rocks with traces of bioproductivity indicates that clastic material was transferred over a few hundred kilometers.

Consortial Associations of Phytophagous Beetles (Coleoptera: Chrysomeloidea, Curculionoidea) with Plants on the Unique Sterlitamak Shikhans

This paper summarizes the available data on the host plant associations of beetles of the superfamilies Chrysomeloidea and Curculionoidea on three unique natural objects, relict mountains (shikhans) composed of organogenic limestones and located near Sterlitamak in Bashkortostan. A total of 427 species from 9 families have been recorded on these mountains, this number comprising 35.5% of the total fauna of phytophagous beetles in the foreststeppe of the eastern Russian Plain and the Cis-Urals. In particular, 341 species of phytophagous beetles have been found on Tratau, 281 species on Kushtau, and 276 species on Yuraktau. Trophically specialized beetles (368 species, or 87% of the fauna) were found on 232 plant species from 40 families; of these, 213 monophagous or narrowly oligophagous species were found on 141 plant species from 35 families. Only polyphagous (generalist) herbivores were found on plants of 5 more families. The vast majority (75%) of the oligo- and monophagous beetle species are associated with host plants from 8 families, and half of them (49.7%) are associated with those from 3 families: Asteraceae, Fabaceae, and Brassicaceae. The beetle complexes associated with some plants on the shikhans are described in detail. The consortia of many rare and relict plants include not only common polyphagous beetles but also specialized herbivores (regional monophages or narrow oligophages), some of them living there in isolated parts of their disjunctive ranges or on the periphery of their distribution. The reviewed data indicate high specificity of the biotic complexes of the shikhans, emphasizing the uniqueness of these natural objects and the need for their preservation.

The definition of force parameters when grinding materials with anisotropic texture pressure in the press roller unit

The article deals with the issues of improving the efficiency of grinding materials with an anisotropic texture. The main specific features and conditions of the organization of the grinding process, including the conditions of loading materials with an anisotropic texture, the creating conditions of their directed motion and application of force load. The article explains the design of the press-roll unit (PRU) with a device for the directed supply of anisotropic materials is given, description its scheme and the process of work. The conditions of destruction of an anisotropic material between eccentrically mounted rolls are considered and an equation for the calculation of the specific force required for the destruction of anisotropic materials in eccentric rolls of PRU is obtained. The comparative data of values of specific values of crushing pressure at grinding of organogenic limestone obtained experimentally in PRU and by calculation are presented.

Famennian carbonate microfacies from the Preslavtsi-2 well (Moesian Platform, north-eastern Bulgaria)

The most representative subsurface section of the Famennian carbonate succession from the Moesian Platform in Bulgaria occurs in the R-2 Preslavtsi well. Nine microfacies types (MFTs 1–9) have been distinguished and described in the intraclastic and peloidal limestone unit and the organogenic limestone unit. They are grouped in four microfacies associations: 1) protected shallow subtidal (lagoon) (MFT 1, bioclastic-peloidal packstone/grainstone; and MFT 2, oncoidal wackestone); 2) wave-dominated shallow subtidal (MFT 3, intraclastic-peloidal grainstone and rudstone; MFT 4, oncoidal rudstone; MFT 5, peloidal-bioclastic packstone and grainstone); 3) reef (MFT 6, solenoporacean-calcimicrobial-stromatoporoid boundstone; MFT 7, crinoid-stromatoporoid floatstone); and 4) open-marine (MFT 8, bioclastic wackestone/packstone with intraclasts and peloids; and MFT 9, bioclastic wackestone and packstone). The carbonate deposits are interpreted as formed in various shallow- to open-marine environments at or above the fair-weather wave base (MFTs 1–7) and below it (MFTs 8 and 9). Most of the described microfacies are comparable with Wilson’s (1975) Standard Microfacies Types.

An interdisciplinary approach to a knowledge-based restoration: The dark alteration on Matera Cathedral (Italy)

An interdisciplinary analytical campaign was carried out on the exterior walls of the Santa Maria della Bruna and Sant’Eustachio Cathedral in Matera. Large areas of these walls have become darkened and the main objective was to evaluate the state of conservation of the stone material (a very porous, organogenic limestone called “Pietra di Matera”), and to suggest the best strategy for the current restoration. Several techniques were used in situ and ex situ-in laboratory analyses: X-ray diffraction, infrared spectroscopy, ion chromatography, pyrolysis/gas chromatography coupled with mass spectrometry, colour change measurements, laser-induced fluorescence together with biological techniques. Ex-situ and in situ cleaning tests were also carried out on the stone surface.The results showed the presence of chlorophyll and bacteria on the surface, together with sulfation and calcium oxalate films as the main decay phenomena. In addition, the determination of saccharide and egg residues suggest both biological activity and past conservative treatments as the cause of oxalate films. Data obtained from the analyses proved to be very useful for the conservation work; a complex plan of restoration was adopted, including both traditional and innovative techniques (such as biocleaning, bacterial-gel and a laser system) together with a final evaluation of several protective methods.

Геоморфология «Протопоповского» оползня в долине реки Оки (на территории города Коломны Московской области)

This article is devoted to the development of the slope processes in the Oka river valley in the city of Kolomna. There are considered the modern ecological and engineering-geological condition of floodplain terraces in the city quarter of Kolychevo. The aim of the work was to study the geomorphology of landslide processes. There is considered the identification of the causes of landslides in the Oka river valley. The is considered the identification of representatives of fossil fauna of organogenic limestones of the left Bank of the Oka river to. In this paper, for the first time the «Protopopovskiy» landslide is described in the scientific literature.

Some results of petrographic studies of ceramics from the settlement Toksanbay

The research is devoted to the studies of raw materials and molding masses of ceramic products from the settlement Toksanbay. The purpose of the research was to study the technological aspects taking place in the course of ceramic vessels production, as well as in-depth study of the raw materials and molding masses of pottery ceramics of the settlement. During the research of samples, in addition to petrographic analysis, fragments of ceramics were studied using the binocular microscopy method, chemical experiments were carried out (using a micromethod) with the use of ammonium molybdenum, hydrochloric acid, and microenacts were checked for iron in the composition of the crock. The received result revealed that as the raw material ferruginous clay was used, and the chemical reaction to Fe of all fragments turned out to be positive. The original clay contains sand, besides this, sand feldspars, fragments of sandstones, silicified schists and epidote are noted in the sand composition. Three recipes of molding masses were revealed. The organics is stated in the form of silicified voids. The composition of organic matter showed carbonate-siliceous or carbonate-phosphate. The microreaction analysis using ammonium molybdenum (МоН4)2АmО4 determined the presence of a phosphate type in organic samples. From the organic fillers, a part of the studied samples revealed hollows of round and oval shape from the burnt organics. The study of the pottery of the settlement will be continued but it can be argued that the Toksanbay potters used local clay, and the most common impurity was organogenic limestone.

Development of aragonite crystals in the Neoproterozoic Nikol’skoe formation of the Ura uplift (East Siberia)

It is established that organogenic limestones of the Neoproterozoic (Upper Riphean) Nikol’skoe Formation contain aragonite crystals surrounding filamentous calcified algae, which take part in the formation of stromatolites. They indicate the possibility of the development of fine-fibrous, acicular, and prismatic aragonite crystals in the calcareous mud during the calcification of red algal thalluses (for example, genus Chaptchaica Kolosov) enveloped by a common thick gelatinous (during the organism life) sheath. The group of red algae, which concentrate lime in the form of aragonite crusts appeared not later than the Neoproterozoic (Late Riphean). A high-quality image of the cell nucleus was obtained for the first time from the Neoproterozoic red algae Chaptchaica viva Kolosov, 1975.

Geology of the Magura Nappe in the Osielec area with emphasis on an Eocene olistostrome with metabasite olistoliths (Outer Carpathians, Poland)

The Magura Nappe in the Polish sector of the Outer Carpathians consists of four tectonic subunits characterized by differing development of facies. From the south to the north, they include the Siary, Raca, Bystrica and Krynica subunits. The sedimentary succession in the Raca Subunit in the vicinity of the village of Osielec is composed of Campanian–Palaeogene flysch deposited in the Magura Basin. In this succession, the Middle Eocene Pasierbiec Sandstone Fm consists of thick-bedded sandstones and conglomerates with occasional intercalations of thin-bedded shale-sandstone flysch. Within the Pasierbiec Sandstone Fm at Osielec there is an olistostrome, rich in pebbles and cobbles of exotic rocks. In addition, large blocks of Neoproterozoic metabasites and boulders of Palaeogene organogenic limestones were found. The discovery of metabasites raised the possibility that the rocks in question could be evidence of supposed oceanic crust in the basement of the Magura sedimentary basin, because of the suggestion that they represent the Alpine orogenic cycle. This concept was abandoned when investigations of the absolute age of the metabasites gave a date of ca. 600 Ma. In the Osielec area, there are two tectonic thrust sheets in the Raca Subunit, namely the Osielczyk Thrust Sheet in the north and the Bystra Thrust Sheet in the south; they are folded and cut by a transverse system of strike-slip and oblique faults. The Osielczyk Thrust Sheet was overthrust northwards on to the Siary Subunit.

Upper Devonian depositional system of Bel’kov Island (New Siberian Islands): An intracontinental rift or a continental margin?

The archipelago of New Siberian Islands situated on the northeastern continental shelf of Eurasia is considered a part of an exotic terrane that collided with Siberia in the Early Cretaceous. Bel’kov Island is located close to the inferred western boundary of this terrane and thus should demonstrate attributes of its localization at the margin of the Paleozoic oceanic basin. The Upper Devonian section on Bel’kov Island is a continuous sequence of deepwater terrigenous rocks, which indicates a tendency toward deepening of the basin previously revealed on adjacent Kotel’ny Island. The lowermost Upper Devonian unit on Bel’kov Island is represented by thin Domanik-like strata resting on the Middle Devonian carbonate platform. The main body of the Upper Devonian sequence, more than 4 km in total thickness, is made up of gravity-flow sediments including turbidites, clay and block diamictites, and olistostromes in the upper part of the section, which accumulated at the slope of the basin or its rise. At many levels, these sediments have been redeposited by along-slope currents. The uppermost unit of organogenic limestone is evidence for compensation of the trough. According to conodont assemblages, the deepwater terrigenous rocks were deposited from the early Frasnian to the early Tournaisian. This time is known for extensive rifting in the eastern Siberian Platform. The data obtained allowed us to reconstruct a NNW-trending Late Devonian rift basin on the Laptev Sea shelf similar to other rifts at the eastern margin of the Siberian Platform.

Using geophysical methods to define the attitude and extension of water-bearing strata in the Miocene sediments of the Pannonian Basin

Abstract In the area near the village of Jazak (southern part of Fruska Gora mountain, Serbia), hydrogeological investigations were carried out for the purpose of finding a water supply source to provide an adequate volume of water for a mineral water bottling plant. The first exploratory borehole (IBJf-1) penetrated a water-bearing layer of Miocene organogenic limestones. This aquifer has a thickness of about 30 m and a yield of only 2.2 l/s, which falls short of the required water volume (5 l/s). The objective of further exploration was to define the attitude and extension of the aquifer and thus select a more favourable site for a new exploratory borehole that would secure the required volume of water. For this purpose, geophysical exploration was carried out in 2003 through vertical electrical sounding (VES) and high-resolution 3D reflection seismic methods. The VES measurements enabled determination of aquifer depth and indicated that the water-bearing strata extend over the entire area studied. However, because of the equivalence problem, it was not possible to determine the thickness of the water-bearing stratum based solely on the VES data. Thus, the 3D seismic method was used in the second stage of investigation. A low-cost 3D seismic survey was carried out with fixed receiver lines, using a vibrator as the source of the seismic waves. From the 3D seismic data it was possible to determine the aquifer thickness. The depth of the aquifer determined by interpretation of the 3D seismic data was in accordance with the depth determined by the VES method. Based on the assumption that the hydraulic conductivity of this formation is identical or similar over the entire area, as well as the fact that the first well showed the presence of a subartesian aquifer, we proposed drilling another borehole (IBJf-2) in the zone where the data indicated that the water-bearing stratum was much thicker. The data obtained by drilling and coring were in agreement with the predicted aquifer thickness. Pumping tests showed that the water discharge in borehole IBJf-2 was 6 l/s. The results show that the objective of delineating the groundwater body by combined application of two geophysical methods (VES and 3D seismic) was successfully performed.

Unique Cenozoic lithofacies in the northern part of the Darnó Fault Belt and its surroundings: an overview

In the area where the Darno Fault belt breaks up as a horsetail fault system in southern Slovakia and northwestern Hungary, beside the dominant lithologies such as calcareous siltstone and claystone several peculiar lithofacies generated in different paleoenvironments of the Buda (Hungarian) Paleogene and Fiľakovo/Petervasara Eggenburgian Basins occur. Laminated limestone and shale classified as oil shale from the village of Drienovec, the Szendro and the Batka vicinities (Eocene-Oligocene and Early Miocene in age) came to existence in coastal lagoons and/or subtidal lagoons under anaerobic conditions at the bottom and affected by seasonal weather changes. The Batka, Novaj, Budikovany, Bretka bioclastic and organogenic limestone units (Kiscellian and Egerian in age respectively) were deposited under shallow marine littoral conditions. The Drienovec and Szuhogy Conglomerate units originated under fluviatile conditions. Almost all mentioned lithologies were generated in genetic (conglomerate) or spatial (oi...

Clay mineralogy of the Tertiary sediments in the Internal Subbetic of Málaga Province, S Spain: implications for geodynamic evolution

AbstractThe clay mineralogy of a set of Tertiary marine sediments from the Internal Subbetic of the Betic External Zone was examined. Two types of sedimentary environment were distinguished: a platform environment consisting of limestones, marls, organogenic limestones, conglomerates and silexites distributed heterogeneously in time and space; and deep environments, where the sedimentation consisted of marls, marly limestones, marly clays and silexites, with no sedimentary gap. A third group of sediments studied belongs to the Águila Complex, with mineralogical and stratigraphic characteristics very similar to the platform sediments. This third type of sediment is found in the sediments of the Campo de Gibraltar Complex as large, disperse blocks resulting from tectonic activity. A very similar mineral association was observed in all three domains, consisting of smectite, illite, mixed-layer I-S, kaolinite and lesser amounts of palygorskite and chlorite. Materials mainly derive from the erosion of Mesozoic sediments, and sedimentation was controlled by the compressive tectonics of the region.

Литостратиграфия мезозойских пород в Восточных Родопах

Mesozoic slightly metamorphosed sedimentary and volcano- sedimentary rocks have been proven in the south-eastern part of the Eastern Rhodopes around the villages of Bregovec, Orešino, Mandrica and Dolno Lukovo. They are subdivided into two groups: Mandrica Group (new group) - with supposed Triassic or Triassic - Early Jurassic age, and Maglenica Group (new group) - with Early Jurassic and Late Cretaceous age. Mandrica Group is built up of sedimentary and sedimentary-volcanogenic rocks accompanied by basic and ultrabasic magmatic rocks, all subjected to greenschist facies to epidote-amphibolite facies regional metamorphism. Two formations are subdivided within this group: Orešinovo Formation (new formation) mainly metasedimentary, with intrusive basic igneous rocks, and Gorno-Lukovo Formation (new formation), predominantly volcanogenic. Maglenica Group is represented by two formations: Dolno-Lukovo Formation (new formation), and Meden-buk Formation (new formation). Dolno-Lukovo Formation is of sedimentaryvolcanogenic composition and Early Jurassic age. It contains olistostroms with Upper Permian and MiddleUpper Triassic silicites and organogenic limestones as well as boudinaged bodies of tholeiitic basalts - clastolavas. The degree of alteration is anchimetamorphic. Meden-buk Formation belongs to the Upper Senonian (Campanian). It is sedimenrary volcanogenic, non-metamorphic, with basaltoid andesites. It is intruded by diorite-granodioritic hypabyssal intrusions. The rocks of Mandrica Group and Dolno-Lukovo Formation from the Eastern Rhodopes on Bulgarian territory are correlated after their composition, metamorphism and age with the lithostratigraphic units Makri and Drimos-Melia, described on Greek territory in Western Thrace. The Mesozoic rocks in the Eastern Rhodopes build together with the high-grade Precambrian metamorphics an allochthonous sheet (East-Rhodope complex nappe) which has been thrust over paraautochthonous in tensely diaphthorized Precambrian ultrametamorphics. The presence of Precambrian, Paleozoic, Triassic, Jurassic and Upper Cretaceous rocks in complex allochthonous structures supports the idea about the existence of a complex collisional orogen.