Chalk Deposits Research Articles

The end of the Cretaceous: depositional palaeogeographical reconstruction of the Gulf of Mexico and adjacent areas just prior to the Chicxulub impact

Abstract Until recently, information about the end of the Cretaceous was based upon investigation of global outcrop sections. New subsurface drilling and characterization from well cores and logs in the Gulf of Mexico Basin have greatly illuminated the end Cretaceous event. However, the palaeogeography of the late Maastrichtian just prior to bolide impact is less well understood and is of great importance in terms of modelling the resulting distribution and composition of the Chicxulub impact material, as well as tsunami and seiche wave height. Here, we examine the Maastrichtian strata in the basin, synthesizing lithostratigraphy and chronostratigraphy, tectonic plate reconstructions, global and local sea level history, palaeoclimate and depositional systems. Our new Maastrichtian palaeogeographical reconstruction shows the basin prior to the Chicxulub impact at a time of globally high sea level, with widespread deposition of deepwater chalks and shallow marine carbonates and local siliciclastic shorelines fed by the nascent Cordilleran belt. Stratigraphic correlations of wells and outcrops illustrate the range of palaeoenvironments from coastal plain to deep marine. As much as 610 m (2000 ft) of Maastrichtian and Campanian section is mapped around the basin, reflecting accommodation provided by basin subsidence, salt deflation and palaeophysiography. A large thickness of carbonates accumulated in the basin centre, with steep shoreline to basin gradients particularly in Mexico. At the end of the Cretaceous, carbonate palaeoenvironments probably covered 96% of the Gulf of Mexico Basin, with less than 4% of the area likely occupied by siliciclastic systems, a distribution that evolved from the Early Cretaceous. Our maps thus explain dominance of carbonate breccia and chalks in K–Pg boundary units deposited over the basin sites proximal or distal to the Chicxulub impact crater. This also elucidates the large impedance contrast and high amplitude seismic response of the K–Pg boundary horizon, mappable over vast portions of the basin.

The interplay between siliciclastic and carbonate depositional systems: Maastrichtian to Danian basin‐floor sediments of the mid‐Norwegian Møre Basin

AbstractSource‐to‐sink sedimentary systems associated with volcanic rifted margins serve as important archives for basin development by recording lithospheric changes affecting the depositional systems. Distinguishing between sediment transport processes and their sediment source(s) can guide the interpretation of a basin's history, and thereby inform regional paleogeographic reconstructions. In this contribution, we integrate and utilize wireline geophysical logs, detailed petrographic observations from side‐wall cores, and seismic analysis to describe and decipher a Maastrichtian to Danian‐aged basin‐floor depositional system in the deep outer Møre Basin, mid‐Norwegian margin. Well 6302/6‐1 (Tulipan) is a spatially isolated borehole drilled in 2001 that penetrates Maastrichtian and younger strata. A succession of hitherto undescribed carbonates and sandstones in the outer Møre Basin was discovered. It is investigated for sediment transport, provenance, and depositional processes on the basin floor surrounded by structural highs and ridges. The strata from the lower parts form a basin‐floor apron consisting of redeposited carbonate sourced from a westerly sub‐aerial high. The apron transitions vertically from mixed siliciclastic and carbonate into a purely siliciclastic fan with intercalated sandstone and mudstone, providing a rare high‐resolution record of how depositional environments experience a complete shift in dominant processes. The development coincides with similar latest Cretaceous‐earliest Palaeocene sequences recorded south of this region (e.g., well 219/20‐1) and may have been influenced by regional uplift associated with the onset of magmatism in the Northeast Atlantic. This study improves our understanding of a late, pre‐breakup source‐to‐sink sedimentary system developed near the breakup axis of an infant ocean, and documents what is possibly the northernmost chalk deposit in the Chalk Group.

Geology of the Chiltern Chalk aquifer, southern England

The unique geological history which resulted in the evolution of the Chiltern Hills to the north of London, The United Kingdom, created the underlying foundations for everything that we see there on the surface today. The roots of the Chiltern Hills lie in their Chalk foundations. To understand the details of the way the chalk acts as an aquifer it is important to understand first the origins of the chalk sediment and how the subsequent geological history of the region has impacted on the rocks preserved today.

Influence of carbonate rocks on soil hydromorphism in mining activity zone

Operation of mining and processing plants violates the hydrogeological conditions of the land, which can contribute to the hydrogenous transformation of landscapes and soils. The geological feature of the Belgorod Region is the presence of chalk eluvium as soil-forming rocks on hill slopes (3.6% of the territory). Soils are often underlain by chalk deposits which are characterized by significant microporosity and microfracturing. Five soil profiles were studied using the profile-genetic and morphological methods. The morphological indicators of the process of gleying are the color of the soil and the presence of glandular neoplasms. The catena included soils: gray forest soil-contact-gley on mantle loam underlain by chalk eluvium; soddy underdeveloped on eluvium chalk; soddy-carbonate medium washed out on the eluvium of chalk; soddy-reclaimed thin humus soil-gley on deluvial deposit. The appearance of gray forest gley soils nearby groundwater occurrence in flat areas in the upper parts of the slopes is due to the fact that the soils are underlain by carbonate rocks, which can contribute to moisture stagnation. The main cause of formation of hydromorphic soils on the upland slope is the occurrence and weathering of carbonates in combination with their water-lifting capacity. This leads to a violation of the law of similar topographic series. Thus, Cretaceous rocks make significant adjustments to the formation of soils and their distribution over the relief. When anomalous soil properties are detected, even in the industrial zones of mining plants, a detailed consideration of all possible causes of the observed phenomena, not only anthropogenic, but also natural, is necessary.

Animal–substrate interactions preserved in ancient lagoonal chalk

Trace-fossil assemblages reflect the response of the benthos to sets of paleoenvironmental conditions during and immediately after sedimentation. Trace fossils have been widely studied in pelagic shelf and deep-sea chalk deposits from around the globe but never documented from ancient lagoonal chalk successions. Here we report the first detailed ichnologic analysis of a lagoonal chalk unit, using as an example the Upper Cretaceous Buda Formation from the Texas Gulf Coast Basin. In this unit, variable interconnection with the open ocean, accompanied by marked fluctuations in physicochemical parameters inherent to lagoonal circulation (e.g., salinity, hydrodynamic energy, bottom-water oxygenation), highly influenced the resultant trace-fossil content of the chalk. These lagoonal chalk deposits contain twenty ichnotaxa, displaying a clear dominance of Thalassinoides isp. and Chondrites isp., which are present in most of the bioturbated strata. The dominance of Thalassinoides isp., both in softgrounds as an element of the Cruziana Ichnofacies and in firmgrounds as a component of the Glossifungites Ichnofacies, highlights similarities with trace-fossil assemblages from shallow-water shelf-sea chalks. In contrast to both (open) shallow-water shelf-sea chalks and deep-sea chalks, the Buda Formation chalk exhibits more diverse assemblages and sharp fluctuations in ichnodiversity and ichnodisparity during relatively short periods of time. The increased ichnodiversity and ichnodisparity in this lagoonal chalk (in comparison with its open ocean counterparts) may reflect a complex interplay of taphonomic (i.e., incomplete bioturbation allowing preservation of shallow-tier trace fossils and ecologic (i.e., increased spatial environmental heterogeneity in the carbonate lagoonal setting) factors.

BASALT FIBER AS A COMPONENT OF CEMENT CONCRETE

In the article we consider. The analysis of the main fibers currently used in theproduction of building materials as a microreinforcing component is presented. A comparativeanalysis of fibers on a set of indicators: geometry, chemical composition, physical and mechanicalcharacteristics.Recently, there has been a steady trend towards finding ways to reduce the cost of roadconstruction caused by higher prices for materials and energy. That is why modern road constructionconditions dictate the widespread use of industrial waste - slag, burnt shale dumps of coal mines, flyash, as well as virtually inexhaustible resources - chalk deposits and igneous rocks (basalts).Properties of basalt fibers open wide prospects for their use for reinforcement of concretestructures in the construction of bridges, tunnels, dams, floor structures, runways and otherstructures, where exposure to moisture, salt solutions and alkaline concrete media leads to corrosionof metal reinforcement.Based on the properties, basalt fibers have an extremely broad prospect of application invarious industries and construction: as structural building elements: bridges, tunnels, railwaysleepers and subways; as facing materials: facing mixes and reinforcing grids; as reinforcingmaterials: in the production of cement and asphalt pavements, building blocks and foam concretematerials; as a reinforcing material for the construction of dams, materials for land irrigation andother hydraulic structures.Thus, basalt fiber is a promising material with which it is possible to obtain a new class ofbuilding materialsAnalysis of the main fibers currently used in the production of building materials as amicroreinforcing component, according to a number of variable criteria, allowed to identify basaltfiber as the most rational in terms of its use in obtaining fine-grained microreinforced cement,including for road construction. The comparative analysis of fibers of 4 manufacturers on set of indicators: geometry, chemical composition, physical and mechanical characteristics, allowed toallocate fibers of LLC Armbud which most corresponds to the shown requirements.It is established that the basalt fiber in the process of keeping in an aggressive and alkalineenvironment with a pH corresponding to the hydration of cement stone, is subject to significantdissolution. After 28 days of exposure in an alkali solution, the weight loss is about 30%. Prolongedstorage of fiber (72 days) in solution leads to weight loss of up to 59%. It becomes obvious the needto develop a method of increasing the alkali resistance of basalt fiber to increase its durability.

Inversion tectonics in the Sorgenfrei–Tornquist Zone: insight from new marine seismic data at the Bornholm Gat, SW Baltic Sea

ABSTRACT New seismic profiles located within the Bornholm Gat in the SW Baltic Sea area image Late Cretaceous-Paleogene inversion and exhumation of a previously poorly characterized narrow crustal zone in the southern end of the Sorgenfrei–Tornquist Zone (STZ), a long pre-Alpine tectonic lineament in Europe. Thrusts and pop-up structures developed along the inversion axis accompanied by subsidence troughs on its sides. Stratigraphic analysis of chalk deposits indicates that structural shortening and inversion resulted from compressional deformation. Marginal troughs formed synchronously to inversion and adjacent to the tectonically active slope, where sediment redeposition was focused. Deposition of chalk units, composed predominantly of contourites and gravity-driven sedimentation were largely controlled by inversion tectonics and influenced by intensification of bottom currents. We find that allochthonous chalk has been buried in horizontally deposited autochthonous (pelagic) chalk. An erosional unconformity represents the base of the Maastrichtian and marks the onset of along slope deposition due to a more hydrodynamic environment. The revealed asymmetric inversion across the STZ with fold tightening and superposition of NE-NW folds attest to more than one pulse during the Late Cretaceous-Cenozoic inversion. The STZ may belong to the end-member mode of intraplate foreland basins resulting from a far-field NE-SW compression transmitted from the Africa-Iberia-Europe convergence. The intraplate stress associated with the following Maastrichtian enhanced collisional coupling between the Alpine-Carpathian orogen and its foreland, which is widely recognized (e.g., the Mid-Polish Trough, the Bohemian Massif and the Central Graben), may also have had its maximum extent to the northeast in southern Sweden.

Hydrogeohazards in post-mining areas – the phenomenon of uncontrolled groundwater outflows in wetlands

Aquifers formed in the wetland area around the closed lacustrine chalk mine at Mierzyno (northern Poland) are distinguished by a specific groundwater flow system, the main component of which is lateral flow and ascent seepage from the deep aquifer to the ground surface. In investigating the origin of the uncontrolled groundwater outflows and the phenomenon of progressing spring pools, field and laboratory work, as well as model studies of groundwater flow, allowed assessment of damage to the soil and aqueous environment. These occurred due to defective reclamation of post-mining areas, as a result of which the natural hydrodynamic balance in the groundwater was disturbed. Artesian pressure in the deep aquifer caused layer interruption at the boundary of the lacustrine chalk deposit. In consequence, strong uncontrolled outflow of groundwater occurred, and the accompanying spring pools are changing their position as a result of headward erosion. So far, the amount of washed-out carbonate sediment exceeds 5,600 m 3 .

Implications for carbonate mass-wasting complexes induced by volcanism from Upper Cretaceous Austin Chalk strata in the Maverick Basin and San Marcos Arch areas of south-central Texas, USA

The upper part of the Austin Chalk (AC-B1 subunit), as seen in a series of cores in areas of the Maverick Basin and San Marcos Arch in south-central Texas, contains a stratigraphic section of mass-wasting complexes resulting from penecontemporaneous volcanic-induced gravity-flow deposition. The types of gravity flows are variable in composition depending on sources of volcanic or carbonate sediments available and position of initiation of the flow on the volcanic mounds.The gravity flows occurred in a deeper-water drowned-shelf setting where argillaceous chalk-rich sediments were being deposited. The mafic volcanoes are part of the Balcones Igneous Province that was active during very Late Santonian to Early Campanian time. Some of the volcanoes formed mounds that created elevated areas in the photic zone or above sea level. In the shallow-water photic zones, carbonate factories formed as atolls and shoals. These carbonate factories were a source for shallow-water allochems, and along with the volcanic debris, constituted gravity flows that were likely triggered by volcanic-associated earthquakes. As gravity flows moved downslope, they eroded deeper-water, bottom sediments, which were incorporated into the flows. The two major transport mechanisms were debris flows and hyperconcentrated-density flows.The debrites appear as two types: those dominated by mud clasts and those dominated by cm-scale skeletal fragments such as inoceramid or disarticulated oyster shells. The clasts in the mud-clast-dominant debrites range in rigidity from very soft (i.e., easily deformed) to firm (i.e., resist deformation and preserved burrows). Since the mud clasts are composed of planktic foraminifers and calcispheres in a coccolith-hash matrix, they are assumed to have originated from the deeper flanks of the volcanic mounds. The rigidity of the mud clasts are likely related to initial (i.e., early) depth of burial of the unlithified mud.The skeletal-dominated debrites with disarticulated oyster shells appear to have been sourced from the upper slopes of the volcanic mounds and underwent little abrasion during debris-flow transportation. The inoceramid-fragment-dominated debrites may have been initiated lower on the volcanic mounds where these low-oxygen-tolerating bivalves would dominate the macrofauna.The hyperconcentrated-density-flow deposits are grain-rich in skeletal fragments with a mixture of shallow- and deep-water biota, suggesting some direct sourcing from shallow-water shoals and later incorporation of deeper-water sediments from the flanks of the volcanic mounds. These hyperconcentrated-density-flow deposits are positioned close to the base of the mounds.This distinct stratigraphic interval varies greatly from the rest of the Austin Chalk section in the Maverick Basin and San Marcos Arch areas. Deeper-water chalk deposition was the general background environmental setting, but it was disrupted by this period of volcanism that initiated numerous mass-wasting complexes punctuating the deeper-water chalk deposits. Within the gravity-flow deposits, volcanic components such as lapilli, ash, and glauconite-altered volcanic grains occurred along with both shallow- and deep-water carbonate allochems. Investigation of this stratigraphic unit within the Austin Chalk provides an analog for mass-wasting complexes associated with active volcanism and explains the variations in composition of the gravity-flow deposits.

Ichnofabric analysis of bathyal chalks: the Miocene Inglis Formation of the Andaman and Nicobar Islands, India

In the Bay of Bengal, the Andaman and Nicobar Islands represent part of the Burma–Sunda–Java subduction complex. The Islands are composed of sediments ranging in age from Jurassic to Recent, represented by ophiolites, flysch sediments, along with deep marine sediments scraped off from the subducting plate. The stratigraphic succession that overlies meta-sedimentary and ophiolite suites consists of turbidite and non-turbidite sequences, along with thick-bedded nannofossil chalks. The present study describes ichnofabrics of chalks from the Inglis Formation (Early to Middle Miocene). These chalks are highly to moderately bioturbated and comprise several levels of ferruginised layers as weak discontinuity surfaces. The studied section shows the recurring occurrence of ichnotaxa belonging to Asterosoma, Chondrites, Cladichnus, Ophiomorpha, Palaeophycus, Planolites, Taenidium, Thalassinoides, and Zoophycus. Sediments are represented by Bioturbation indices varying between BI-2 to BI-5, represented by (a) light coloured trace fossils in dark sediment (LID ichnofabric) and (b) dark coloured trace fossils in light sediment (DIL ichnofabric). Ichnofabric analysis suggests multiple colonization, complex tiering, and multilayer tiering. The LID ichnofabric exposed at Kalapathar reveals three tiers, a diverse shallow tier and a moderately low diverse middle and deep tiers. At the Lacam Point Section, in contrast, the LID ichnofabric is represented by condensation of the tiers and the absence of shallow tiers. The DIL ichnofabric at the Kalapathar Section seems to be more expanded and is represented by four tiers with extensive bioturbation. Ichnofabric analysis supports deposition of the chalk sediments in a lower bathyal paleoenvironment and suggests that organic matter, pore water, and bottom-water oxygenation were the main controlling factors. Thus, the ichnofabric analysis of the Early-Middle Miocene Inglis Formation gives first-hand information regarding the poorly known chalk facies of the Andaman and Nicobar Islands pre-Bengal fan stage of the Indian plate.

Lithological models of reservoir rocks for upper cretaceous deposits in East Caucasian Region

The article describes the results of lithological and petrophysical investigations that would be a base for characterization of reservoir rocks in Upper Cretaceous deposits. These investigations include thin sections description, SEM and NMR analysis. As found that three main factors have constrained final quality of reservoir rocks: 1) depositional settings favorable for coccoliths and chalk sedimentation; 2) late diagenesis changes – compaction and recrystallization degree; 3) fracture intensity.

Redox conditions, glacio-eustasy, and the status of the Cenomanian–Turonian Anoxic Event: new evidence from the Upper Cretaceous Chalk of England

The nature of the Cenomanian–Turonian Oceanic Anoxic Event (CTOAE) and its δ13 C Excursion is considered in the light of (1) the stratigraphical framework in which the CTOAE developed in the European shelf seas, (2) conclusions that can be drawn from new detailed investigations of the Chalk succession at three locations in England, at Melton Ross and Flixton in the Northern Province where organic-rich ‘black bands’ are present, and at Dover in the Southern Province (part of the Anglo-Paris Basin) where they are absent, and (3) how these conclusion fit in with the present understanding of the CTOAE. The application of the cerium anomaly method (German and Elderfield 1990) at Dover, Melton Ross and Flixton has allowed the varying palaeoredox conditions in the Chalk Sea and its sediments to be related to the acid insoluble residues, organic carbon, δ18O (calcite), δ13C (calcite), δ13C (organic matter), Fe 2+ and Mn2+ (calcite), and P/TiO2 (acid insoluble residue). This has provided evidence that the initial stages of the δ13C Excursion in England were related to (1) a drop of sea level estimated at between 45 and 85 metres, (2) influxes of terrestrial silicate and organic detritus from adjacent continental sources and the reworking of exposed marine sediments, and (3) the presence of three cold water phases (named the Wood, Jefferies and Black) associated with the appearance of the cold-water pulse fauna during the Plenus Cold Event. Conditions in the water column and in the chalk sediment were different in the two areas. In the Northern Province, cerium-enriched waters and anoxic conditions were widespread; the δ13C pattern reflects the interplay between the development of anoxia in the water column and the preservation of terrestrial and marine organic matter in the black bands; here the CTOAE was short-lived (~0.25 Ma) lasting only the length of the Upper Cenomanian Metoicoceras geslinianum Zone. In the Southern Province, water conditions were oxic and the δ13C Excursion lasted to the top of the Lower Turonian Watinoceras devonense Zone, much longer (~1.05 Ma) than in the Northern Province. These differences are discussed with respect to (1) the Cenomanian–Turonian Anoxic Event (CTAE) hypothesis when the ocean-continent-atmosphere systems were linked, (2) limitations of chemostratigraphic global correlation, and (3) the Cenomanian–Turonian Anoxic Event Recovery (CTOAER), a new term to define the varying lengths of time it took different oceans and seas to recover once the linked ocean-continent-atmosphere system was over. The possibility is considered that glacio- eustasy (the glacial control hypothesis of Jeans et al. 1991) with the waxing and waning of polar ice sheets, in association with the degassing of large igneous provinces, may have set the scene for the development of the Cenomanian–Turonian Anoxic Event (CTAE).

Oxygen isotopes from the teeth of Cretaceous marine lizards reveal their migration and consumption of freshwater in the Western Interior Seaway, North America

Mosasaurs were widespread predators of the vast Cretaceous seas, and it is debated whether these extinct marine reptiles migrated to coastal environments to feed or reproduce. Here we investigate the potential for migration of mosasaurs through novel high-resolution sclerochronology that samples incremental growth lines in fossil mosasaur teeth and extracts oxygen isotopes from pristine enamel. Oxygen isotope trends of consecutive teeth are spliced to reconstruct one to seven month-long life histories of Platecarpus tympaniticus and Clidastes propython mosasaurs, respectively, collected from time-equivalent chalk deposits of the Western Interior Seaway and Mississippi Embayment of North America. The records of all individuals—two adults and one juvenile—are characterized by semi-regular depletions in oxygen isotope values, indicating travel from marine to freshwater coastal environments. Weekly to bi-weekly consumption of freshwater by two genera at diverse life stages implies that mosasaur osmoregulatory function was similar to their living sea snake relatives that drink freshwater periodically.

Population health risk assessment associated with air pollution in the area of natural chalk industrial processing complex influence

Increased air pollution in the areas where large mining complexes are located poses a risk to public health. The article examines harmful substances atmosphere emissions’ impact on the population health living near an industrial mining enterprise of the Kopanishchensky natural chalk deposit in the Ostrogozhsky district of the Voronezh region. Environmental risks calculations showed that out of 36 chemical substances that pollute the atmosphere, 5 substances have a carcinogenic effect. The maximum values of the total carcinogenic risk do not exceed the dangerous threshold, however, they need to be carefully monitored. The main contributor to the total risk is carbon soot – 99.9%. Calculations results of non-carcinogenic risks due to inhalation exposure showed that the respiratory organs which are negatively affected by 8 out of 10 priority chemicals, are most potentially affected.

Coccolithophores: an environmentally significant and understudied phytoplankton group in the Indian Ocean

Coccolithophores are unique primary producers in the ocean with the ability to calcify. They are known to produce calcareous scales, which form the significant part of calcite oozes or chalk deposits on the seafloor. Coccolithophores are very noteworthy and they are explored to a great extent as nannofossils to reconstruct the past climate. Calcite plates in coccolithophores make them a vital tool in global climate change studies specifically with ocean acidification. These microscopic plants are the major contributor of the carbonate rain that controls the inorganic carbon pump in the ocean, which in turn influences both carbon and carbonate cycles. The emergence of advanced techniques enables us to study the biological aspects of this pelagic calcifier with improved precision. But still, they are understudied world over compared to any other phytoplankton groups. The northern Indian Ocean, being landlocked in three sides and vulnerable to climate change and ocean acidification, severely lacks focused studies on coccolithophores, though the US JGOFS in the 1990s have outlined the ecological significance of coccolithophores in the Arabian Sea. This paper reviews and outlines our understanding of coccolithophores as well as the nix in the northern Indian Ocean.

Differences in the development of the Szczecin Lagoon area in the Late Glacial and Holocene based on the geochemical analysis of carbonate sediments from Lake Nowowarpieńskie (NW Poland)

This paper presents the results of geochemical analysis performed for the more-than-10-m-long core of sediments derived from Lake Nowowarpieńskie. Contrary to what its geographical name would suggest, it is in fact a peripheral bay  of the Szczecin Lagoon (NW Poland). A characteristic feature of the sedimentary cover of this water body is the several-metre-thick layer of lacustrine chalk, which is unique in the lithology of the sediments of today's Szczecin Lagoon. This sediment has been analysed using atomic absorption spectrometry (AAS), energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) imaging. The chalk sediment from Lake Nowowarpieńskie is of chemical origin, bearing no fragments of vascular plants, but only traces of C-org in the form of small plant remains. The analysis of individual crystals using the EDS method also show Ca contents of over 99%. SEM images reveal that the sediment is characterised by a loose, disordered pack-ing of individual crystals, often combined to form aggregates with a tabular structure. The individual calcite grains are usually a few micrometres in size, while developed ones are mostly hypidiomorphic and show signs of corrosion. The sedimentation of the lacustrine chalk indicates that the post-glacial natural development of this part of what today constitutes Szczecin Lagoon differed from that of the rest of the lagoon. This sediment was deposited in a shallow but fertile isolated lake. The full profile of sediments from Lake Nowowarpieńskie reveals its distinct bipartite character, indicating two main stages of its evolution: carbonate and post-carbonate. In the first, the water body showed similarities to the neighbouring lakes of the Wkrzańska Plain. Its evolution was driven by climatic factors. The second stage was initiated by a palaeohydrological factor – Littorina transgression, which resulted in the lake being included into the hydrological system of the Szczecin Lagoon.

ПЕРСПЕКТИВЫ НЕФТЕГАЗОНОСНОСТИ И ИЗУЧЕНИЕ КОЛЛЕКТОРСКИХ СВОЙСТВ МЕЛОВЫХ ОТЛОЖЕНИЙ ЕВЛАХ-АГДЖАБЕДИНСКОГО ПРОГИБА

The aim of the study is to substantiate the prospects for the oil and gas content of the Upper Cretaceous effusive and carbonate deposits by studying their reservoir parameters. Previous studies have established that a sedimentary complex, present in the geological structure of the Muradkhanly field, is lithologically represented by clays, siltstones, sands and sandstones, dolomites, limestones, tuffs, Upper Cretaceous porphyrites. Since this lithofacies composition of the section is of great importance as a reservoir rock, volcanic sandy tuffs, mudstones and dense sandstones of the Upper Cretaceous age have been comprehensively investigated throughout the territory. We studied carbonates of this age and found that they have compaction of varying extent and are divided into 3 groups: weakly, moderately and strongly compacted and this, in turn, has considerable effect upon the rock porosity. At the beginning of the study, the reservoir features of Meso-Cenozoic sediments in the Yevlakh-Agdjabedi depression [YAD] were studied mainly on the basis of terrigenous rocks that refer to the Cenozoic. In our studies, Cretaceous deposits were studied, which are represented by effusive, carbonate rocks with secondary reservoir properties. The reservoir properties of chalk deposits in the YAD areas were investigated on the basis of studies of core samples in laboratories. It was found that the reservoir rocks of the area under investigation are volcanic, volcanic-sedimentary and carbonate, that is, they mainly consist of fractured limestones, marls and dolomites. Studies have shown that the oil and gas content of the depression is associated mainly with carbonate and effusive reservoirs. To assess the prospects for the oil-bearing capacity of the YAD, geological sections were studied in terms of the reservoir properties of a number of structures, and on the basis of the obtained core samples data. Trend maps were compiled using the "Surfer" software. Analysis of the maps allows identifying the corresponding zones of carbonate content, permeability, porosity, characterized by high, medium and low values. According to the carbonate readings, the studied territory does not have a strict distribution pattern and, according to the permeability distribution data, it is divided into two zones: the northern zone with average and the southern one with low values. There is, to a certain extent, pattern for variation of the values of carbonate content and permeability, and this can be explained by the secondary transformation of the reservoir properties of carbonate rocks, as a result of which permeability and porosity changed. Porosity distribution, to some extent, is aligned with permeability. Inverse relationship between the values of porosity and permeability can be explained with the filling of voids with cement material in the rock formation environment. Currently, in order to continue exploration and drilling works, comprehensive geological and geophysical studies are being carried out, as a result of which comparison of data obtained will make it possible to assess the prospects of each structure in more detail.

BARMAKY SITE IN THE CONTEXT OF EPIGRAVETTIAN OF THE MIDDLE DNIEPER BASIN

The Upper Paleolithic site Barmaky, 2nd cultural layer from Volyhnia-Lublin upland is the most western manifestation of Epigravettian of the Mid Dnieper basin. During several field campaigns the 147 m2 of cultural deposits with three pits and one chalk / marl concentration were studied (fig. 1). The silty-loess deposits of Barmaky, 2 accumulated about 19 kyr cal BP (table 1) under the permafrost conditions. The fauna assemblage is represented by: mammoths, bison, reindeer, red deer, horse, bear, wolf, wolverine, polar fox, fox and hare. More than 100 thousand artifacts were recovered during the last two field campaigns. In essential account (without chips, chunks, unidentifiable debitage), the artifacts assemblage is represented by: cores and pre-cores — 0.87 %; flakes — 45.23; blades — 17.34; bladelets — 14.27; micro-blades — 7.34; burin spalls — 8.08; tools — 6.79 % (table 2). The reduction sequences are based on the flaking of uni-, bidirectional sub-cylindrical and narrow flaking surface unidirectional cores for blades and bladelets (table 3; fig. 2). There is no evidence of micro-blade technology implication. The structure of tool-kit is characterized by the dominance of burins — about 50 %; microliths — 25 %; and truncated pieces — about 18 % (table 4). The rest of tool classes are represented by a few percentages each. Among them are the end-scrapers on blades with truncated base (fig. 3). The most part of burins are represented by pieces made on obliquely truncated blades (table 5; fig. 4). Also, the obliquely truncated blades dominate the truncated pieces assemblage (table 6; fig. 5). The most representative type of microliths is the micro-points with abruptly retouched straight back and obliquely retouched base (table 7; fig. 6). The points, pendants, bracelet fragment made on tusk and perforated fossil marine shells from local chalk deposits are available. The composition of microliths, burins and end-scrapers in Barmaky, 2 tool-kit is characteristic to the cultural layers beyond the dwelling structures on such base-camps as Mezhyrich (fig. 7). Also, the presences of pits and fauna composition are close to what expected from Epigravettian base-camps. The artifacts assemblage of Barmaky, 2 belongs to the Mizyn industry. Also, Barmaky, 2 is the earliest manifestation of Epigravettian in the Mid Dnieper basin.

RESEARCH TO CREATE A BIODIVERSITY DATABASE IN THE AREA OF THE CEMENT PLANT «CASPIAN-CEMENT»

. The result of field studies the state of biological diversity, in order to create a database for monitoring the state of the animal world, on the territory of the existing cement plant. The following taxonomic groups were studied: birds (the largest numerous groups, easily identifiable), mammals (requiring special research methods), reptiles and amphibians. The identification of species that occurred in the study area of the chalk Deposit was carried out and the bio topic requirements for each of these species were studied. Along with the classical methods of environmental assessment and monitoring, a new method for studying biological diversity in the mining area is used. The method is based on geoinformation analysis and mapping data. All data on biodiversity were obtained using a map divided into grid squares (500×500 m), and were collected in a qualitative way (the number of representatives of animal species per grid square). The study area on the South Shetpe Cretaceous Deposit in the area of the plant "Caspian Cement" met with widespread desert species (mole lemming, tushkanchik). In the local fauna there are absolutely no true steppe species, and there are few semi-desert species (small gopher, korsak, saiga). A qualitative assessment of the importance of biodiversity was presented, taking into consideration the landscape-stabilizing factor, maps of "natural habitats". A map of the territory of the cement plant with the site of the chalk quarry with the indication of the natural habitats of biodiversity and their database was compiled.

Magnetic resonance sounding for the estimate of hydrogeologic characteristics of chalk aquifers (North of France)

The hydrogeological characteristics are required for investigating the modelling processes. The transmissivity and hydraulic conductivity values which are obtained from the inverse methods and pumping tests are not representative in the northern part of France where the major aquifer is composed of the chalk deposits. In addition, these methods are costly and time-consuming. In the north of the Paris Basin and by using the magnetic resonance sounding (MRS), the chalk aquifer reveals the vertical distribution of the porosity, the hydraulic conductivity, and the transmissivity. The decay constants of the MRS signal which have been identified from the MRS analysis are considered parameters which control the permeability and the transmissivity values. Five MRS surveys were realized and performed by the electrical resistivity tomography (ERT) aiming to characterize the lithology variation and the thickness of the hydrogeological units. This comparison shows the power of MRS methods of the chalk aquifer in the characterization of the hydrogeological system in the north of France. The water content which is deduced from the MRS highlights a heterogeneous distribution in the aquifer and the water content can reach 35%. Results which are deduced from the pumping test and the MRS are consistent. Indeed, the transmissivity values vary generally between 10−3 and 10−2 m2/s. This comparison shows the utility of the multidisciplinary approaches in the characterization of the chalk system in the north of France.