Maastrichtian Section Research Articles

Scaphitid ammonites from the lower Maastrichtian of Nahoryany (western Ukraine) and discussion on the origin of Hoploscaphites constrictus

Abstract The lower Maastrichtian (Upper Cretaceous) section at Nahoryany, south of Lviv (western Ukraine), has been known as a rich source of fossils since 1843. However, the section is not available since a long time ago and fossils collected from it can only be studied in museum collections. In the present paper, ammonites of the scaphitid genus Hoploscaphites are studied based on Nahoryany material, comprising Hoploscaphites pumilus, H. constrictus and H. sp. Specimens from Nahoryany in museum collections lack data on their provenance level within the section so it cannot be determined whether or not they occurred together or formed a succession; data on inoceramid bivalves indicate the presence of two successive zones at Nahoryany. Some specimens from Nahoryany here referred to as H. pumilus are similar to the controversial H. constrictus anterior from the lower Maastrichtian of Poland. This morphology suggests an ancestor–descendant relationship between H. pumilus and H. constrictus, a common species once considered as an informal index for the Boreal Maastrichtian in Europe. The inferred evolutionary transition from H. pumilus to H. constrictus was towards a less robust, recoiled shell, which would have enhanced the horizontal swimming ability and manoeuvrability of these cephalopods. Recoiling trends occurred in several lineages of Late Cretaceous scaphitids.

New Radiolarian Species of the Genus Patellula Kozlova from the Turonian–Maastrichtian Sections of Cyprus and Crimea

New Radiolarian Species of the Genus Patellula Kozlova from the Turonian–Maastrichtian Sections of Cyprus and Crimea

Characterization of channelized turbiditic reservoirs using elastic properties modeling: An application in the Sergipe-Alagoas basin, Brazil

Sandy channelized reservoirs in deep water environments are significant for oil exploration and production. The 3D nature of the outcrops described in the literature and the local limitation of the information acquired through drilled wells are limiting factors for the reliable subsurface characterization of this type of sedimentary environment and its related heterogeneities. Aiming to overcome the information absence between the sampled well points in hydrocarbon reservoir studies, the 3D seismic data is a conventional approach adopted. However, due to the intrinsically low seismic resolution aspect, the usage of inverted seismic volumes enhances the confidence rock properties spatial distribution into the geological models, even though the uncertainties are not eliminated. This study presents a methodology of synthetic elastic properties modeling in association with measured physical properties, velocity, density and thickness to assess and optimize the geostatistical built model using real turbiditic reservoirs data of a Maastrichtian section of Calumbi Formation, in the Sergipe sub-basin, Brazil. It was successively tested geomorphological and geological features, as described in the previous work as well as similar Alagoas Sub-basin outcrops, associating their responses in terms of compressional and shear velocities, densities, and thicknesses, reducing uncertainties in the spatial distribution of them, which are present in high vertical-resolution well data. The obtained results show that compressional and shear waves variations are the main influences for the seismic signal and the related attributes rather than the intrinsically geometrical features. It was built a specific equation intending to model the effects of these attributes over the measured seismic data to identify paths to implement needed corrections in the geometric and faciological characteristics of the evaluated reservoir-rocks. They confirm the importance for better understanding of subsurface geological characterization using the seismic data as conditioning, even below the intrinsically data resolution, especially when dealing with seismic inversion. Additionally, the 1D synthetic model acts to do deal with tuning effect and to control the elastic property distribution avoiding misinterpretations that may suggest unfavorable portions for new well locations, enhancing the hydrocarbon production because it provides feasible elements for project decision-making.

New Radiolarian Species of the Genus <i>Patellula</i> Kozlova from the Turonian–Maastrichtian Sections of Cyprus and Crimea

Numerous representatives of the Genus Patellula Kozlova, 1972 were studied from the Upper Cretaceous deposits of Perapedhi, Kannaviou and Lefkara formations (Cyprus). Two new species were described: Patellula mangaleniensis sp. nov. and P. solaris sp. nov. The species P. mangaleniensis was found in the Crimea within Afens perapediensis Zone (upper part of upper Santonian). The earliest representatives of Patellula euessceei Empson-Morin, 1981 were for the first time found in the Upper Cretaceous of the Crimea, within Actinomma (?) belbekense Zone (upper part of middle Turonian–upper Turonian), while the latest representatives of P. euessceei were for the first time detected in the Maastrichtian of Cyprus. The stratigraphic ranges of Patellila euessceei and Genus Patellula are expanded.

The Maastrichtian Section of Mount Kyz-Kermen (Crimean Mountains): Biostratigraphy, Sedimentation Conditions, and Paleogeography

The Maastrichtian Section of Mount Kyz-Kermen (Crimean Mountains): Biostratigraphy, Sedimentation Conditions, and Paleogeography

New genus of Cupressaceae from the Upper Cretaceous of Patagonia (Argentina) fills a gap in the evolution of the ovuliferous complex in the family

AbstractThe conifer family Cupressaceae encompasses seven subfamilies. Five of them were once considered to constitute the family Taxodiaceae, later eliminated because of its paraphyletic nature but remaining as an informal category for early‐diverging Cupressaceae lineages. Among the taxodiaceous subfamilies, Athrotaxoideae shows a unique morphology in its ovuliferous complexes (OCs) and a phylogenetically unexplored fossil record. We describe the new genus and species Patagotaxodia lefipanensis, based on OC adpressions associated with leafy branches collected at the Maastrichtian section of the Lefipán Formation (Patagonia, Argentina), and we refer it to Athrotaxoideae. We include Patagotaxodia in total evidence phylogenetic analysis to test its affinity, and we recover it within the subfamilies Athrotaxoideae or Cunninghamioideae. However, we argue that the characters supporting the athrotaxoid affinity are more meaningful in a taxodiaceous systematic context. This placement is also supported by taxon inclusion‐exclusion experiments. We discuss the position of other Cretaceous athrotaxoid records. With basis on the morphological insights provided by the OC morphology of extant and extinct Athrotaxoideae, we study the evolution of the OC morphology in the family in a phylogenetic context and discuss the results in the light of the fossil record of the family. We discuss how and when the different morphologies appeared in the family. Based on phylogenetic, temporal, morphological, and ontogenetic evidence, we conclude that the OC morphology shown by the subfamily Athrotaxoideae is intermediate between two of the most common morphologies within extant and extinct Cupressaceae species, one of which would show adaptative advantages over basal morphologies.

The δ13C record of Maastrichtian-Paleocene oil shales from Jordan – Stratigraphic and environmental implications for an epicontinental setting

Organic matter (OM) rich marls were deposited in several intrashelf basins in Jordan (e.g. Yarmouk Basin, Lajjun Basin, Azraq-Hamza Basin, Jafr Basin, Eshidiyya Basin) on the southeastern Tethyan margin during the Maastrichtian to middle Eocene. Factors like surface water productivity fueled by upwelling and sea level changes affected their deposition. Potential effects of climatic changes have not been determined yet.We present the first stable carbon and oxygen isotope records of Maastrichtian-Danian oil shales from the Azraq-Hamza and Jafr Basins in south- and central-east Jordan. The δ13Ccarb curves were time-calibrated based on calcareous nannofossil biostratigraphy. Eight notable excursions were identified in the Jordanian Maastrichtian sections. These were correlated with the documented Maastrichtian δ13Ccarb events in the (sub) tropical sections of Italy and the western Pacific: the Campanian-Maastrichtian boundary Events 4 and 5 (CMBE-4, CMBE-5), the Middle Maastrichtian Events 1 to 3 (MME-1 to MME-3) and the Cretaceous-Paleogene boundary Events 1 to 3 (KPgE-1 to KPgE-3). Signs of the Latest Danian Event (LDE) were recognized as well. Total organic carbon (TOC) data exhibit a complex relationship with the δ13Ccarb proxy record. The δ13Ccarb signals are repeatedly dampened due to the OM oxidation and subsequent 12C release. The effect of short term climate changes is observed, but is not always straight forward. Long term climate changes had indirect effects on bottom water oxygenation and OM preservation via sea level changes. The δ18Ocarb data from both sections reveal minor temperature changes in the Maastrichtian. Slight warming is observed in the MME interval. A potential increase of the paleotemperature is reported from the Azraq-Hamza section occurring in the latest Maastrichtian to earliest Danian.

Campanian–Maastrichtian foraminiferal stratigraphy and palaeoenvironment of the Lower Tar Member in the Wadi Tar section, Western Sirte Basin (Libya)

Upper Campanian–Maastrichtian sections on the western flank of the Hun Graben in the Western Sirte Basin (WSB) are displaying two major type facies based on the foraminiferal assemblages. The first one indicates open-marine to outer-shelf conditions, and is represented by numerous bathy-pelagic planktonic foraminiferal species referable to the Radotruncana calcarata, Globotruncana aegyptiaca and the lower part of the Gansserina gansseri Zone (all late Campanian).The second type facies indicates an inner-shelf environment and is represented in the middle-upper part of the Gansserina gansseri Zone (early Maastrichtian) and Racemiguembelina fructicosa (late Maastrichtian) dominated by epi-pelagic planktonic and large benthic foraminifers. Large benthic foraminiferal index species Siderolites calcitrapoides Lamarck and Omphalocyclus macroporus (Lamarck) occur in abundance by the middle–late Maastrichtian. Correlation between planktonic foraminiferal zonation and large benthic foraminiferal zonation is given. An open-marine to outer-shelf environment passed into shallower marine conditions during the late Campanian–early Maastrichtian to late Maastrichtian, then a slight deepening and again shallowing is noticed.

New bio- and magnetostratigraphic data on Campanian‒Maastrichtian deposits of the classical Nizhnyaya Bannovka section (Volga river right bank, southern Saratov region)

The integral investigation of the upper Campanian‒Maastrichtian section near the settlement of Nizhnyaya Bannovka (Krasnoarmeiskii district, Saratov oblast) included its detailed lithological description and the study of different organic remains (belemnites, benthic and planktonic foraminifers, radiolarian, calcareous nannofossils, dinocysts) with the analysis of their taxonomic composition and stratigraphic distribution and magnetostratigraphic (magnetic polarity and petromagnetic) properties. The belemnite findings indicate the presence of the upper Campanian Belemnitella langei Zone in the section, which comprises sediments previously attributed to the lower Maastrichtian Belemnitella lanceolata Zone. The analogs of magnetic polarity chrons 33n, 32r, and 31n (probably superposed chrons 31n and 30) are established. It is assumed that radiolarians offer the opportunity to define the middle Campanian substage by analogy with the standard (international) stratigraphic scale. On the basis of benthic foraminifers, calcareous dinocysts, and paleomagnetic data, the late Maastrichtian age of sediments previously dated back to the early Maastrichtian is substantiated. A large hiatus corresponding to the terminal Campanian‒early Maastrichtian is revealed in the section. The succession of sedimentological, biotic, and paleogeographic events is outlined for the late Campanian‒Maastrichtian interval. The obtained data make it possible to disclose paleobiogeographic connections between microfaunal communities of the Campanian and late Maastrichtian seas on the East European and West Siberian plates. It is established that the uppermost Maastrichtian sediments are enriched in extraterrestrial matter.

Upper Campanian-lower Maastrichtian sections of northern Rostov oblast: Article 2. Depositional environments and paleogeography

The study present the results of the integrated study on the Belgorod and Pavlovka formations (upper Campanian), Sukhodol Formation (Campanian-Maastrichtian), and Efremovo-Stepanovka Formation (Maastrichtian). Variations in lithological indicators and associated changes in the biotic assemblages were used to distinguish three stages in the basin evolution separated by hiatuses (Belgorod-Pavlovka, Sukhodol, and Efremovo-Stepanovka). This basin occupied the upland area in the north of the Paleozoic Donets Basin during late Campanian-early Maastrichtian times. Each stage was characterized by a specific depositional environment accompanied either by a decrease or by an increase in the terrigenous sediment supply from the Donets Basin and, possibly, Ukrainian Shield and sea-level and temperature fluctuations, as well as specific paleobiogeographic relations. During the Belgorod-Pavlovka stage, the basin was characterized by relatively deep-water environments, with warm waters and normal salinity, and predominantly carbonate sedimentation. The Sukhodol stage was marked by terrigenous sedimentation, a predominance of the agglutinated foraminiferal forms, and abundant radiolarians, which occurred during a marine regression and overall cooling. This stage corresponds to the global “Campanian-Maastrichtian boundary event.” The first half of the Efremovo-Stepanovka stage was marked by resumed carbonate sedimentation, warming, transgression, and deepening of the basin, which were replaced by a renewed regression at the end of this time interval.

Upper Campanian-lower Maastrichtian sections of the northwestern Rostov region. Article 1. Description, paleontological assemblages, and lithobiostratigraphy

Four upper Campanian-lower Maastrichtian reference sections are described in the Glubokaya and Kalitva river basins and in the Znamenka 1-A Borehole located in the northwestern Rostov region. The sections are composed of the upper Campanian Kagal’nik, Belgorod, Pavlovka, Sukhodol and lower Maastrichtian Efremovo-Stepanovka formations. They are characterized by successive stratigraphically significant macro- and microfossil assemblages: belemnites, calcareous nannoplankton, benthic foraminifers, and radiolarians. The Pavlovka and, particularly, Sukhodol formations contain a specific assemblage of coarsely-agglutinated benthic foraminifers. The first data obtained on radiolarians in upper Campanian-lower Maastrichtian sections of the northwestern Rostov region revealed four assemblages, two of which were previously unknown from Upper Cretaceous sediments of the East European Platform. Most sections enclose a hiatus at the base of the Sukhodol Formation, which comprises two upper Campanian benthic foraminiferal zones. The problem of recognition of the lower Maastrichtian boundary on the East European Platform is considered in accordance with international GSSP requirements.

Stratigraphy and palaeoceanography of upper Maastrichtian chalks, southern Danish Central Graben

Upper Maastrichtian chalks form important hydrocarbon reservoirs in the Danish sector of the North Sea and have been intensively studied, yet their lithological uniformity can frustrate attempts to develop a high-resolution stratigraphic subdivision and a genetic understanding of the factors controlling production and sedimentation of the pelagic carbonate ooze. Recent research into these topics, supported by the Danish Energy Authority, was carried out by the Geological Survey of Denmark and Greenland (GEUS) in collaboration with the Geological Institute, University of Copenhagen by means of a multidisciplinary study involvingquantitative/semiquantitative palynology, micropalaeontology (nannofossils, foraminifers) and isotope geochemistry, integrated with detailed sedimentology. Two key wells were selected, the M-10X well from the Dan Field and the E-5X well from the Tyra SE Field (Fig. 1), based on the extensive core coverage in these wells and on their position in the southern part of the Danish Central Graben where evidence of large-scale resedimentation (and consequent stratigraphic complexity) is uncommon within the Maastrichtian section. In focusing on such a pelagic carbonate system, the ultimate aim is a holistic understanding of the marine system including temperature variation, nutrient supply and distribution, salinity, watermass layering, circulation and oxygen distribution. All these factors influence organic productivity and thus the accumulation of biogenic sediment. This study concentrated on a number of palaeoceanographic signals that can be derived from the sedimentary record, summarised in Fig. 2. Planktonic organisms, both phytoplankton (e.g. coccolithophores, some dinoflagellates) and zooplankton (e.g. foraminifers) provide a record of conditions in the upper water masses, largely within the photic zone, while bottom conditions are indicated by epifaunal/infaunal organisms (e.g. benthic foraminifers) and bioturbation, and by the sedimentological evidence of depositional processes at the sea floor. On a larger scale, the input of terrestrial organic material relative to the marine component can provide an indirect measure of shoreline migration and thus relative sea-level change, a factor that is also reflected in the δ13C isotopic composition of the seawater, as recorded by the biogenic carbonate ooze.

Late Campanian–Maastrichtian foraminifera from the Simsima Formation on the western side of the Northern Oman Mountains

A precise correlation of Upper Campanian–Maastrichtian (Upper Cretaceous) sections on the western side of the Northern Oman Mountains (Jabals Qarn El Barr, El Aqabah and Malaqet in the United Arab Emirates and Jabal El Rawdah in the Sultanate of Oman), reveals two distinct facies based on microfaunal assemblages. The first indicates open marine conditions, and is represented by the Qarn El Barr section. This yields numerous planktonic foraminiferal species referable to the Globotruncana aegyptiaca (Upper Campanian), Gansserina gansseri (Upper Campanian–Middle Maastrichtian) and Abathomphalus mayaroensis (Upper Maastrichtian) planktonic foraminiferal zones. During the Campanian–Maastrichtian, this open marine environment passed laterally into shallower marine conditions that were characterized by larger foraminiferal species including Loftusia morgani, Orbitoides media, O. apiculata, Omphalocyclus macropora, Lepidorbitoides minor, Sulcoperculina dickersoni, and Siderolites calcitrapoides. This facies is well developed in the Jabal El Aqabah, Jabal El Rawdah and Jabal Malaqet sections.

87Sr/86Sr test of the degree of impact-induced slope failure in the Maastrichtian of the western North Atlantic

Analyses of 8 7 Sr/ 8 6 Sr in foraminifera and sedimentological observations suggest that the Chicxulub impact was not the trigger for slumps or a hiatus within the Maastrichtian section recovered at Ocean Drilling ProgramSites 1049, 1050, and 1052 (subtropical western North Atlantic). The slumps and hiatus occur within a sequence dominated by pelagic chalk. The 8 7 Sr/ 8 6 Sr measurements show a general increase through the Maastrichtian at each site, but suggest chronostratigraphic gaps on the order of 10 6 yr across the slumps. Some of the slumps have burrowed upper surfaces and are composed of material that is older and coarser grained than the bounding chalks. Pelagic deposition punctuated by gravity flows easily explains the Maastrichtian record on Blake Nose, whereas an impact-based explanation for slumping is difficult to reconcile with sedimentological and geochemical observations.

Trends in late Maastrichtian calcareous nannofossil distribution patterns, western North Atlantic margin

First and last occurrences of several Maastrichtian calcareous nannofossil species are shown to be diachronous across paleodepth and paleoenvironment using the graphic correlation method. Calcareous nannofossil assemblages examined from eleven cores from a deep- to shallow-water transect along the eastern United States Atlantic margin document that the first occurrence of Micula murus (Martini 1961) Bukry 1973 is diachronous, appearing 2.0 million years earlier in open ocean sites than in shallow marine sites. The first occurrence (FO) of Lithraphidites kennethii Perch-Nielsen 1984 is also nonsynchronous, appearing in the deep ocean before its FO in neritic waters. The last occurrence (LO) of L. praequadratus Roth 1978 is diachronous across paleodepth, going locally extinct first in deeper water. The LO of Watznaueria bybelliae Self-Trail 1999 is also diachronous, going locally extinct first in shallow-water settings. Ceratolithoides amplector Burnett 1997, C. pricei Burnett 1997, C. self-trailiae Burnett 1997, C. ultimus Burnett 1997, Cribrocorona gallica (Stradner 1963) Perch-Nielsen 1973, Micula praemurus (Bukry 1973) Stradner and Steinmetz 1984, Pseudomicula quadratus Perch-Nielsen et al. 1978, and Semihololithus spp. are present consistently in common to frequent abundances in ODP holes 1050C and 1052E on the Blake Nose, but they are rare or absent from neritic sections in Coastal Plain cores. It is apparent that these species flourished in an open ocean setting, suggesting that differences in assemblage abundance and diversity between deep ocean and nearshore areas were controlled by paleoceanographic factors. These species are not used for biostratigraphy, but may be useful indicators of open ocean conditions. The line of correlation (LOC) for nine Coastal Plain cores clearly defines the Cretaceous-Tertiary (K/T) boundary unconformity at the top of the Maastrichtian section (Peedee Formation) and the Campanian-Maastrichtian (C/M) unconformity at the base of the Maastrichtian section (Peedee/Donoho Creek formational contact). The K/T boundary unconformity is undulatory in nature; updip Maastrichtian sections have been stripped to a greater depth than the downdip sections. The uppermost Campanian, all of the lowermost Maastrichtian, and the basal upper Maastrichtian sediments are missing from the study area.

Trends in late Maastrichtian calcareous nannofossil distribution patterns, Western North Atlantic margin

First and last occurrences of several Maastrichtian calcareous nannofossil species are shown to be diachronous across paleodepth and paleoenvironment using the graphic correlation method. Calcareous nannofossil assemblages examined from eleven cores from a deep- to shallow-water transect along the eastern United States Atlantic margin document that the first occurrence of Micula murus (Martini 1961) Bukry 1973 is diachronous, appearing 2.0 million years earlier in open ocean sites than in shallow marine sites. The first occurrence (FO) of Lithraphidites kennethii Perch-Nielsen 1984 is also nonsynchronous, appearing in the deep ocean before its FO in neritic waters. The last occurrence (LO) of L. praequadratus Roth 1978 is diachronous across paleodepth, going locally extinct first in deeper water. The LO of Watznaueria bybelliae Self-Trail 1999 is also diachronous, going locally extinct first in shallow-water settings. Ceratolithoides amplector Burnett 1997, C. pricei Burnett 1997, C. self-trailiae Burnett 1997, C. ultimus Burnett 1997, Cribrocorona gallica (Stradner 1963) Perch-Nielsen 1973, Micula praemurus (Bukry 1973) Stradner and Steinmetz 1984, Pseudomicula quadratus Perch-Nielsen et al. 1978, and Semihololithus spp. are present consistently in common to frequent abundances in ODP holes 1050C and 1052E on the Blake Nose, but they are rare or absent from neritic sections in Coastal Plain cores. It is apparent that these species flourished in an open ocean setting, suggesting that differences in assemblage abundance and diversity between deep ocean and nearshore areas were controlled by paleoceanographic factors. These species are not used for biostratigraphy, but may be useful indicators of open ocean conditions. The line of correlation (LOC) for nine Coastal Plain cores clearly defines the Cretaceous-Tertiary (K/T) boundary unconformity at the top of the Maastrichtian section (Peedee Formation) and the Campanian-Maastrichtian (C/M) unconformity at the base of the Maastrichtian section (Peedee/Donoho Creek formational contact). The K/T boundary unconformity is undulatory in nature; updip Maastrichtian sections have been stripped to a greater depth than the downdip sections. The uppermost Campanian, all of the lowermost Maastrichtian, and the basal upper Maastrichtian sediments are missing from the study area.

Inoceramid extinction in the Gubbio basin (northeastern Apennines of Italy) and relations with mid-Maastrichtian environmental changes

Abstract A detailed study of five representative Maastrichtian sections of deep-water pelagic limestones in the Umbria-Marche Apennines of Italy shows that inoceramids became extinct synchronously throughout this region some 3.5 Ma before the Cretaceous/Tertiary boundary. The decline and disappearance of these bivalves are immediately preceded by two closely spaced peak abundance zones, and are linked with an important change in environmental conditions during the mid-Maastrichtian period, as is indicated by modifications in the δ13C composition of sea water and variations in planktonic foraminiferal assemblages. The restoration of stable environmental conditions after this biotic crisis took about half a million years in this region. Excursions of the δ13C signal contemporaneous to the extinction of inoceramids in other Maastrichtian basins throughout the world (i.e. Basque Country and southern oceans) indicate that these bivalves were extremely sensitive to environmental changes. However, accurate magneto- and biostratigraphic correlations between the Italian, Basque, and southern hemisphere sections unambiguously indicate that the extinction of inoceramids was widely diachronous throughout the world of as much as 4 Ma.

New species of the genus <i>Parkiella</i> (Foraminifera) from the Late Cretaceous Central Pacific Ocean: biostratigraphy, biogeography, and the Cretaceous–Palaeogene boundary

Abstract. Two new species, Parkiella angulocamerata sp. nov. and P. globocamerata sp. nov., are described from the Late Cretaceous (late Maastrichtian) Central Pacific Ocean, DSDP Sites 465 and 171. Examination under the SEM revealed apertural features that were not documented in the original description of Parkiella. An ‘L’-shaped aperture was originally considered as a diagnostic character of Parkiella; we suggest that this is a preservational artefact and question its diagnostic value. The existence of internal toothplates determine both Parkiella described here as members of the family Turrilinidae Cushman 1927. Both species were found to be endemic to the tropical Pacific Ocean. They occurred in sequence throughout the Maastrichtian section at Site 465 with a minimum (one sample) stratigraphic overlap. Parkiella globocamerata is one of the few deep-sea benthic foraminiferal species that indeed became extinct at the Cretaceous/Palaeogene (K/Pg) boundary. However, we document a decrease in both relative abundance and accumulation rate of the species already prior to the K/Pg transition. We propose that the interval between the LO (Last Occurrence) of P. angulocamerata and the LO of P. globocamerata is indicative of uppermost Cretaceous (Micula prinsii Zone) strata in the tropical Pacific.

New Nannofossil Biostratigraphy for Upper Cretaceous Organic-Rich Carbonates in Israel

New Nannofossil Biostratigraphy for Upper Cretaceous Organic-Rich Carbonates in Israel

Studies of Burial Metamorphism in the Cretaceous Sediments of the Southern Benue Trough and Anambra Basin, Nigeria: ABSTRACT

Organic matter reflectance, illite crystallinity and fluid inclusion techniques are applied to the evaluation of burial history of Cretaceous sediments in the southern Benue Trough and Anambra Basin. The successions are invaded by intrusives, volcanic rocks and intra-formational veins especially in the Albian sections of the Abakaliki anticline and sub-bituminous coals in the Lower Maastrichtian sections of the Anambra Basin. Vitrinite reflectance (Rm) data from exposed NW/SE sections from Enugu to Abakaliki are ca: .55% in the Lower Maastrichtian coals and shales, 0.67% in the Coniacian shales, 0.91 in the Turonian shales and 4.31% in the Albian shales. A corresponding decrease in illite crystallinity indices coupled with a decrease in the percentage of smectite from 30% to 0% (%S in I/S) was observed on the NW/SE section. Fluid inclusion temperatures from vein quartz in the Albian shales range from 170 to 250{degrees}C. Our data suggest that sediments in the study area were buried to ranks within and beyond the oil window at their present outcrop levels. Possibilities for Cretaceous targets should be sought in the deeper non emergent sections of the Benue Trough and the Anambra Basin.