Carbonate Shelf Research Articles

Stratigraphic and palaeoenvironmental framework of the Early Permian sequence in the Salt Range, Pakistan

The Early Permian Gondwana regime succession of the Nilawahan Group is exposed only in the Salt Range of Pakistan. After a prolonged episode of non-deposition that spanned much of the Palaeozoic, the 350 m thick predominantly clastic sequence of the Nilawahan Group records a late glacial and post-glacial episode in which a range of glacio-fluvial, marine and fluvial environments evolved and accumulated. The Early Permian succession of the Salt Range has been classified into four formations, which together indicates a changing climatic regime during the Early Permian in the Salt Range region. The lower-most, Tobra Formation unconformably overlies a Cambrian sequence and is composed of tillite, diamictite and fresh water facies, which contain a floral assemblage (Gangamopteris and Glossopteris) that confirms an Asselian age. The Tobra Formation is overlain by marginal marine deposits of the Dandot Formation (Sakmarian), which contain an abundant brachiopods assemblage (Eurydesma and Conularia). Accumulation of the Dandot Formation was terminated by a regional sea-level fall and a change to the deposition of the fluvial deposits of the Warchha Sandstone (Artinskian). The Warchha Sandstone was deposited by high sinuosity meandering, avulsion prone river with well developed floodplains. This episode of fluvial sedimentation was terminated by a widespread marine transgression, as represented by the abrupt upward transition to the overlying shallow marine Sardhai Formation (Kungurian). The Early Permian Gondwana sequence represented by the Nilawahan Group is capped by predominantly shallow shelf carbonate deposits of the Tethyan realm. The sedimentologic and stratigraphic relationship of these four lithostratigraphic units in the Salt Range reveals a complex stratigraphic history for the Early Permian, which is mainly controlled by eustatic sea-level change due to climatic variation associated with climatic amelioration at the end of the major Gondwana glacial episode, and the gradual regional northward drift to a lower latitude of the Indian plate.

The end-Ordovician chitinozoan zones of Anticosti Island, Québec: Definition and stratigraphic position

The Ellis Bay Formation cropping out in the central and western parts of the Island of Anticosti, is one of the thickest uppermost Ordovician carbonate shelf successions. Three new species of Hercochitina: Hercochitina florentini, Hercochitina changi and Hercochitina longi, are described from the lower part of the formation. These species are associated with Clathrochitina concinna, Belonechitina concava and Ancyrochitina longispina, and define the new H. florentini–C. concinna Biozone. This zone is present at the Anse aux Fraises section in the western part of the island and in the lower Lousy Cove and probably the Prinsta members of the Ellis Bay Formation in a section on the northeastern coast. The H. florentini–C. concinna Biozone follows the Hercochitina crickmayi Biozone of the Vauréal Formation and is overlain by the B. gamachiana Biozone, which ranges through most of the Ellis Bay Formation in western Anticosti. The B. gamachiana Biozone is succeeded by the Spinachitina taugourdeaui Biozone just below the reefal Laframboise Member. In eastern Anticosti the B. gamachiana Zone has only been recognized in the upper Lousy Cove Member of the Ellis Bay Formation.The presence of a Hirnantian shelly fauna, including the typical genus Hirnantia, the comparison of the Anticosti chitinozoan assemblages with those from other sections dated by graptolites and the available stable isotope geochemistry information suggest that the Ellis Bay Formation is of Hirnantian age.

Iranella inopinata Gollestaneh 1965, a puzzling dasycladalean alga from the Lower Cretaceous shallow carbonate shelf deposits of the Zagros fold-thrust belt, SW Iran

Iranella inopinata gen. and sp. nov. was first described in the unpublished thesis of Gollestaneh (1965), as an incertae sedis from the Lower Cretaceous carbonate rocks of the Zagros fold-thrust belt. More recently, the taxon was formally, although provisionally described by Hosseini and Conrad (Geol Croat 61:215–237, 2008), as a dasycladalean alga named Salpingoporella? inopinata. Here, based on the interpretation of quite-abundant although scattered fragments, it is assigned to Iranella, a large-sized, stalked, and capitulum-shaped new genus of Dasycladales. The lower, stalked part of the thallus is cylindrical, strongly calcified, with first-order laterals only, while the large capitulum is only partly calcified, showing one or two orders of laterals. Traces of cysts (reproductive organs) are present in the basal stalk, either in the stipe or the laterals. Iranella inopinata looks to be endemic to the southwestern part of the Tethyan realm, in the Zagros area and also south of the Persian Gulf. In the Zagros Mts., it extends from the Berriasian to the Aptian, with an Acme Zone in the Valanginian. Sequential interpretation proves the presence of this species in the late transgressive and early highstand stages of system tracts, and reveals a low-energy, restricted, lagoonal or back-reef depositional environment, in an inner-platform setting.

Decline and recovery of the Aptian carbonate factory in the southern Apennine carbonate shelves (southern Italy): Climatic/oceanographic vs. local tectonic controls

In interpreting the inception and demise of different carbonate depositional systems, climatic-oceanographic variations together with sea-level oscillations are commonly considered key elements. However, local tectonic controls cannot be ruled out. In attempts to discriminate among the main factors controlling the evolution of the southern Apennine mid-Cretaceous carbonate system, detailed facies analyses have been performed on Aptian–Albian carbonate successions in the Matese Group (southern Apennines). Since the mid Aptian, the analysed successions testify to a tectonically-driven topography, replacing the previous large tropical shallow-water domain with subdomains characterised by diversified sedimentological trends. Nevertheless, around the middle part of the Aptian, the studied successions register palaeoecological signals that cannot be linked exclusively with tectonic disturbance because of the coeval appearance of analogous signals at a global scale, including a significant change in biological assemblages and an outbreak of organisms indicative of stressful conditions in the water mass.Upper Bedoulian strata clearly record open marine settings characterised by a significant richness of the benthic communities. The biota included rudists, gastropods and echinoids plus many different benthic foraminifers and green algae. Rudists considered to be typically “tropical” forms (the caprinid Offneria nicolinae (Mainelli) and Offneria murgensis Masse, the requieniid Lovetchenia Masse and the monopleurid Agriopleura Kühn) characterise thick subtidally deposited strata in which large coral colonies and mollusc shells contributed to occasional storm-related skeletal concentrations.The analysed Gargasian strata show impoverished biota: caprinids totally disappear, both as in situ and storm-related layer components, and hermatypic corals are drastically reduced. Muddy lithofacies prevail in intertidal metric cycles in which cyanobacterial consortia, both in the form of dense laminae and coalescent oncoids, orbitolinids and small gastropods (cerithiids) suggest restricted, nutrient-rich water. Large oncoids of Bacinella irregularis/Lithocodium aggregatum and mollusc (mostly chondrodontids and gastropods) shell fragments significantly contribute to storm-related coarse skeletal intercalations, in which oligotrophic condition-adapted forms (e.g., hermatypic corals) are reduced or absent. This pattern suggests generalised conditions of stress in the water mass and in more marginal open areas.During the mid-Aptian interval, characterised by the flourishing of assemblages adapted to mesotrophic–eutrophic conditions, the southern Apennines shallow-water domain shows a progressive reduction of the previous mainly aragonite-dominated chlorozoan assemblages and an increase of calcite-dominated skeletal components, including rudists with thickened calcitic outer shell layers. Cyanobacteria and polychaetes characteristically marked the first phases of recovery in the shallow-water domains, rapidly evolving into more complex and differentiated assemblages. The outbreak of nerineid and acteonid gastropods seems to be related to a flourishing of cyanobacterial mats and related microphytae and also to the presence of polychaetes tubes (Thartarella cocumeriformis (Wahlman)). Moreover, the grazing activity of the nerineids favoured the flourishing of oyster-like bivalves. Among the rudists, the persistence and radiation of species adapted to a wide range of temperatures, such as Requieniidae and Monopleuridae as well as the first elevator Radiolitidae suggests some kind of oceanographic change (e.g., seawater chemistry and/or temperature).On the basis of the features described above, we propose the existence of a complex environmental scenario in which cooler conditions, presumably coupled with meso/eutrophic and locally oligophotic conditions, related to climatic/oceanographic global changes, cooperated in modifying the carbonate factory characterisation in a tectonically controlled setting.

New Cenomanian florule and a leaf mine from southeastern Morocco: Palaeoecological and climatological inferences

The recently found Gara Sbaa florule of southeastern Morocco comes from distinctive carbonate lamellites with abundant fish fauna above the terrestrial/paralic Kem Kem sequence and correlated with the basal horizon of the open shelf carbonate Akrabou Formation. It is a “mixed” assemblage of ferns and gymnosperms of “Wealden aspect” associated with relatively advanced angiosperms, suggesting floristic exchanges between the insular land masses of northern Africa and southern Europe. The climatic conditions are inferred to have been similar to the mildly dry subtropical climate of the western Canary Islands. New taxa of aquatic angiosperms Garasbahia fexuosa Krassilov et Bacchia gen. et sp nov. and a leaf mine Troponoma constricta Krassilov, sp. nov. are described.

Middle Miocene–Pliocene siliciclastic influx across a carbonate shelf and influence of deltaic sedimentation on shelf construction, Northern Carnarvon Basin, Northwest Shelf of Australia

AbstractMiddle Miocene to Pliocene siliciclastics of the Bare Formation represent a long‐lived (ca. 11 Myr) break in the otherwise carbonate‐dominated shelf of the Northern Carnarvon Basin, Northwest Shelf of Australia. The quartz‐sandstone interval is correlated with the appearance of spectacular clinoform sets mapped on 3D and dense 2D seismic data. Twenty‐seven clinoform sets are interpreted as delta lobes primarily based on their plan‐view morphology (strike‐elongate to lobate features) and their 40–100‐m‐high clinoform amplitudes. The delta lobes were deposited on outer‐shelf to shelf‐edge positions, and the older deltas show evidence of a higher degree wave reworking than the younger deltas. Measurements of the along‐strike (migration) and down‐dip (progradation) movement of these deltas are compared with relative sea‐level behaviour inferred from shelf‐edge trajectory analysis. Delta lobes exhibit greater lateral shifting during relative sea‐level rise, whereas delta lobes are more restricted to dip‐oriented fairways during sea‐level fall, although no major incised valleys have been identified. Long‐term (cumulative) progradation of this delta system and subsequent backstepping correlates with long‐term sea‐level fall and rise during the late middle and late Miocene. In addition, a long‐term northeastward migration trend for these delta lobes was likely a result of localized uplift of an inversion anticline in the Rosemary–Legendre Trend; the growth of this anticline probably steered the fluvial source for the delta system towards the northeast. The Bare Formation siliciclastic influx correlates with other middle Miocene increases in siliciclastic sediment supply worldwide. Global cooling and a shift to more arid conditions, negatively influencing vegetation cover, may have combined with more seasonally variable rainfall to generate the high sediment supply that built the deltas. Retreat of the siliciclastics could correlate with ice‐sheet growth in the Northern Hemisphere and/or increase in the Indonesian Throughflow and Leeuwin Current (ca. 1.6 Ma), which might have modified climate regionally.

OBSERVATIONS ON THE LIFE CYCLE OF THE SYMBIONT-BEARING FORAMINIFER AMPHISTEGINA LOBIFERA LARSEN, AN INVASIVE SPECIES IN COASTAL ECOSYSTEMS OF THE AEGEAN SEA (GREECE, E. MEDITERRANEAN)

Research Article| April 01, 2012 OBSERVATIONS ON THE LIFE CYCLE OF THE SYMBIONT-BEARING FORAMINIFER AMPHISTEGINA LOBIFERA LARSEN, AN INVASIVE SPECIES IN COASTAL ECOSYSTEMS OF THE AEGEAN SEA (GREECE, E. MEDITERRANEAN) Maria V. Triantaphyllou; Maria V. Triantaphyllou 3 1Department of Historical Geology and Paleontology, Faculty of Geology and Geoenvironment, University of Athens, Panepistimiopolis 15784, Athens, Greece 3Correspondence author. E-mail: mtriant@geol.uoa.gr Search for other works by this author on: GSW Google Scholar Margarita D. Dimiza; Margarita D. Dimiza 1Department of Historical Geology and Paleontology, Faculty of Geology and Geoenvironment, University of Athens, Panepistimiopolis 15784, Athens, Greece Search for other works by this author on: GSW Google Scholar Olga Koukousioura; Olga Koukousioura 1Department of Historical Geology and Paleontology, Faculty of Geology and Geoenvironment, University of Athens, Panepistimiopolis 15784, Athens, Greece Search for other works by this author on: GSW Google Scholar Pamela Hallock Pamela Hallock 2College of Marine Science, University of South Florida, 140 7thAve. S., St. Petersburg, FL 33701 USA Search for other works by this author on: GSW Google Scholar Author and Article Information Maria V. Triantaphyllou 3 1Department of Historical Geology and Paleontology, Faculty of Geology and Geoenvironment, University of Athens, Panepistimiopolis 15784, Athens, Greece Margarita D. Dimiza 1Department of Historical Geology and Paleontology, Faculty of Geology and Geoenvironment, University of Athens, Panepistimiopolis 15784, Athens, Greece Olga Koukousioura 1Department of Historical Geology and Paleontology, Faculty of Geology and Geoenvironment, University of Athens, Panepistimiopolis 15784, Athens, Greece Pamela Hallock 2College of Marine Science, University of South Florida, 140 7thAve. S., St. Petersburg, FL 33701 USA 3Correspondence author. E-mail: mtriant@geol.uoa.gr Publisher: Cushman Foundation for Foraminiferal Research Received: 05 Jul 2011 Accepted: 21 Jan 2012 First Online: 13 Jul 2017 Online ISSN: 1943-264X Print ISSN: 0096-1191 © 2012 Cushman Foundation for Foraminiferal Research Journal of Foraminiferal Research (2012) 42 (2): 143–150. https://doi.org/10.2113/gsjfr.42.2.143 Article history Received: 05 Jul 2011 Accepted: 21 Jan 2012 First Online: 13 Jul 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Maria V. Triantaphyllou, Margarita D. Dimiza, Olga Koukousioura, Pamela Hallock; OBSERVATIONS ON THE LIFE CYCLE OF THE SYMBIONT-BEARING FORAMINIFER AMPHISTEGINA LOBIFERA LARSEN, AN INVASIVE SPECIES IN COASTAL ECOSYSTEMS OF THE AEGEAN SEA (GREECE, E. MEDITERRANEAN). Journal of Foraminiferal Research 2012;; 42 (2): 143–150. doi: https://doi.org/10.2113/gsjfr.42.2.143 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyJournal of Foraminiferal Research Search Advanced Search Abstract Members of the family Amphisteginidae have been nearly ubiquitous contributors to shelf carbonate facies through most of the Cenozoic. The most prolific carbonate producer of modern representatives is Amphistegina lobifera Larsen, which is the largest and shallowest dwelling of the Indo-Pacific taxa. This epiphytic, symbiont-bearing foraminifer is also a remarkably successful invasive species in coastal ecosystems of the eastern Mediterranean, where its shell production is altering the composition of shoreline sediment.This paper reports a temporal study of an A. lobifera population collected monthly between June 2008–May 2009 in the Vravron/Attica coastal ecosystem of the south Evoikos Gulf (Aegean Sea), where winter temperatures can drop below previously reported minima for the species. Monthly variations in size, frequency distribution, and abundance indicate that this population reproduced primarily during the summer (July–September), when both asexual and sexual reproduction occurred simultaneously, suggesting a predominantly coeval, one-year life span for each generation. However, a modest increase in juveniles in January indicates some winter reproduction.Comparison of these findings with previous studies shows that a) tolerance of low winter temperatures, b) adaptation of the life cycle to strong seasonality, and c) the mixotrophic feeding strategy have allowed A. lobifera to proliferate in the exceptionally clear, low nutrient, coastal waters of the Mediterranean Sea. These attributes elucidate how previous Cenozoic populations of Amphistegina were able to rapidly expand their latitudinal ranges and invade shallow epeiric seas during episodes of climatic warming. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Lutetian magnetostratigraphic calibration of larger foraminifera zonation (SBZ) in the Southern Pyrenees: The Isuela section

In this paper, we present a chronostratigraphic calibration of the shallow benthic zones (SBZs) of larger foraminifera during Lutetian times based on new magnetostratigraphic data (Isuela section) and two new densely sampled biostratigraphic sections (Isuela and Gabardiella). These sections are located in the External Sierras (Southern Pyrenees) and represent an ideal location to avoid previous chronostratigraphic problems. 1) They belong to a shallow carbonate shelf environment with abundant larger foraminifera, which ensure the reliability of SBZ data. 2) The time span covers almost the entire Lutetian interval. 3) The profiles are sufficiently long to establish trustworthy local scales, both the SBZs (520m and 760m in Isuela and Gabardiella respectively) and the paleomagnetic local polarity sequence (LPS) (520m). 4) The excellent outcropping conditions also permit a detailed paleomagnetic and biostratigraphic sampling to be performed.The LPS at the Isuela section was built after sampling every 2.6m. In total, more than 359 samples were thermal (244) and alternating field (115) demagnetized. Characteristic remanent magnetization (ChRM) usually dropped at 560°C. Only 43% the samples (359 demagnetizations) gave reliable directions (high quality) for the LPS. A further short section (Gas line) was also cored (38 samples in 90m) to obtain more detailed data for the upper part of the section. At the Isuela section, the results allow three pairs of trustable magnetozones to be assembled within the Lutetian. A further 255 samples were taken for biostratigraphic purposes, 55 sites at the Isuela and 52 at the Gabardiella sections being determinant. This density enabled a thorough study of changes in fossil associations to be performed. Assuming a constant accumulation rate within the chron boundaries, absolute ages have been estimated for the biostratigraphic boundaries. Combining all these data allows the previous calibration of SBZ during Lutetian times in the geological time scale to be refined. In particular, with this new data, we identify the SBZ 13/SBZ 14 boundary at 44.46Ma reaching C20r; a boundary interval spanning from SBZ 14 to SBZ 15 (41.36 and 42.45Ma) is found within C20n and C19n; and, finally, the top of SBZ 15 can be accurately located at 41.12Ma (C19r).

Depositional environment and constraining factors on the facies architecture of the Qom Formation, Central Basin, Iran

In the Central Iran Basin, the mixed carbonate–siliciclastic deposits of the C member of the Qom Formation were deposited on a carbonate platform which is dominated by rhodalgal associations occurring in tropical–subtropical environment. The biogenic rhodalgal association is dominated by bryozoa, coralline red algae, bivalves and echinoids together with smaller amounts of photo-dependent biota including large benthic foraminifera and corals. The abundance of heterozoan association and the bloom of suspension-feeding organisms are the result of an increase in nutrient availability which has profound controlling effect on the biotic system. The low occurrence of symbiont-bearing benthic foraminifera and coral, typical of stable, oligotrophic condition, represents their low tolerance to unstable, nutrient-rich environment. In the investigated Oligocene–Miocene shallow marine carbonate succession, 10 different microfacies were distinguished through depositional texture and biotic components. The rock sequences investigated are referred to an open shelf carbonate platform in which the depositional environments range from outer shelf to inner shelf conditions.

Middle and Upper Jurassic Ostracods from Western Kachchh, Gujarat, India: Biostratigraphy and paleobiogeography

This paper presents a study of the Middle and Upper Jurassic Ostracods from Western Kachchh, India. The first part discusses the biochronological importance of the Ostracod assemblages, while the second part reports the paleobiogeographical results.Benthic foraminiferal biozones are used to calibrate the biostratigraphical distribution of ostracod species and genera from sections in the Aalenian–Tithonian interval located in Western Kachchh (or Kutch) (Mundham Anticline, Jumara Dome, Jhurio Dome and Habo Dome) and on Pachchham Island (Khavda Nala), Gujarat, India. A total of 71 species are listed, including 32 previously published species and 38 species in open nomenclature, belonging to 23 genera. The ostracod assemblages indicate that faunal communication was first established during the Bathonian and Callovian (Middle Jurassic) and continued until the early Cretaceous. These faunal exchanges occurred between Laurasia (USA, Europe, Russia and Siberia) and the Indo-East African Province, extending along the Western Tethyan carbonate shelves (bordering West and East Gondwana) through to the Pacific Ocean margin of West Gondwana.

Encrustation and bioerosion on late Sheinwoodian (Wenlock, Silurian) stromatoporoids from Saaremaa, Estonia

A shallow shelf carbonate platform (pelletal limestone facies) stromatoporoid association from the late Sheinwoodian of Saaremaa (Baltica) contains a diverse assemblage of sclerobionts (both epi-and endobionts). The studied stromatoporoids vary from low domical to extended domical shapes. Cornulites sp. aff. C. stromatoporoides, Conchicolites sp., Anticalyptraea calyptrata, microconchids, tabulate (Aulopora sp., Catenipora sp. and favositids) and rugose corals, sheet-like trepostome bryozoans, and discoidal crinoid holdfasts encrust the stromatoporoids. The dominant sclerozoans were tabulate and rugose corals, which is significantly different from several analogous Silurian sclerobiont communities. There may have been taxonomic polarity between an upper surface and a cryptic sclerozoan community. Bioerosion occurs as macroborings in 45.5 % of studied (N=22) stromatoporoids. Endobionts were represented by Trypanites and Palaeosabella borings, as well as embedded symbiotic rugose corals and Cornulites stromatoporoides.

Přídolí carbon isotope trend and upper Silurian to lowermost Devonian chemostratigraphy based on sections in Podolia (Ukraine) and the East Baltic area

Insufficient knowledge of carbon isotope cycling in the latest Silurian initiated the study of two regions at the western and southwestern margins of Baltica in order to obtain a more complete picture about the carbon isotope trend through the Přidoli. Shallow and open shelf carbonate rocks of the Dniester River outcrops and Kotuzhiny core in Podolia and deep shelf rocks of the East Baltic area, especially the Lithuanian cores, were studied for bulk-rock isotope analysis. The data sets of both regions begin with the mid-Ludfordian excursion and include also some part of the lowermost Devonian. The data show a new minor twin positive δ 13 C excursion (peak values 0.8-1.7‰) in the upper Ludfordian. The Přidoli carbon isotope trend begins with a low of negative δ 13 C values, succeeded by the lower to middle Přidoli 'stability' interval (variable values below or close to 0‰ with a slight rising trend). The upper Přidoli begins with a medium to major excursion (peak values 2.3-4.5‰), which reflects the pattern of the carbon isotope trend on the west of the Baltica palaeocontinent. Its wider significance awaits confirmation from observations elsewhere. The carbon isotope excursion at the Silurian-Devonian boundary, named here the SIDE excursion (its δ 13 C values range from 1.6‰ in deep shelf settings to 3.8‰ in shallower ones and 4.5‰ in brachiopod shells), has been traced on several continents, and now also in Baltica. This excursion can serve as a well-dated global chemostratigraphic correlation tool. The shape of the excursion indicates the completeness of the studied section. We conclude that carbon isotope chemostratigraphy may contribute to subdividing the Přidoli Series into stages and that Baltica sensu lato seems to be the right place for such a development.

Microfacies of Mesozoic Carbonate

Carbonate rocks of Mesozoic age are widespread in Slovenia where they consitute about 40 % of its territory, and attaining total thickness of more than 5000 metres . With respect to microfacies almost all structure types can be recognized, the limestones and dolomites being formed in various sedimentary environments, such as in open and in restricted parts of carbonate shelf, in lagoons and on coastal plains, in different types of reefs, on slopes and in the basin. Carbonate sedimentation was often accompanied also by the supply of terrigenous material and products of volcanic activity. Among diagenetic processes in investigated carbonate rocks the most extensive are dolomitization and silicification. In the present text 250 microscopic photographs of characteristic limestones and dolomites from Slovenian territory are assembled. In the introductory part, to which for orientation schematic stratigraphic columns are added, the geologic development od these carbonate rocks is briefly outlined. For the sake of completeness in presenting the »carbonate era« in the overview, Upper Permian limestones and dolomites are also described next to Mesozoic beds.

Depositional and tectonic constraints for hydrocarbon targets of the Lutetian–Langhian sequences from the Gulf of Gabes — Tunisia

The sequence stratigraphy of the Lutetian–Langhian series in the Gulf of Gabes basin was defined using cuttings from 50 wells, wireline logs, biostratigraphic data and seismic data. The seismic profiles display a shallow inner shelf passing northeastward to an outer shelf break. Our study helps constrain the depositional and tectonic constraints for hydrocarbon targets. Indeed, syndepositional tectonics and related subsidence and eustatism as well, were found to exert remarkable control on the source-rock and oil-reservoir formations and spatiotemporal repartitions. Detrital facies in the inner shelf pass seaward into a broad carbonate shelf and then into storm-influenced turbidites; whereas marls in the deep shelf and outer basin extend onto the inner-shelf during major highstands. Three major supersequences were identified and each of these comprised multiple third order sequences. The lower supersequence (Lutetian–Priabonian) contains marls interceded with inner-shelf skeletal carbonates which reflect shelf flooding due to rise in sea level. The second supersequence (Rupelian–Burdigalian) bears clays and sands admixed with foraminifered carbonates at the base. Rapid flooding and progradation of shelf carbonate sediments (Vascus Horizon and Ketatna Fm) reflect eustatic lowering. These deposits grew basinward into pelagic marls enriched in organic matter and interceded with limestones (Salammbô Fm). A variety of seismic patterns of the Ypresian–Langhian sequences, notably the concave/lens-shaped ones are associated with transparent seismic facies and are thought to be accounted for by tectonically subsiding depositional settings. Faulting and associated subsidence have caused uplapping seismic reflection patterns of sequences dating the Lutetian to Middle Langhian times. The tectonic pulses and flower faults striking to the NW, with antithetic branches continuously reactivating in the study time interval, caused subsidence and basin margin steepening toward the northeast. In contrast, the west and southwest parts of the basin, tectonically expulsed in the form of a broad paleohigh, were the sites for platform carbonates interfingering with episodes of pelagic sedimentation. A major gap of the Upper Eocene is due to a compressive tectonic period. The Ketatna Fm shows concordant and rather transparent seismic facies, thus contrasting with coeval pelagic intervals with dipping of internal seismic reflections due to intervening normal faulting. A broad transgression during the Middle Langhian deposited the third supersequence due to global warming and subsequent rise in sea level. The carbonate sequences in the Reineche Member, the Ketatna and the Aïn Ghrab formations are notably thick and are proven gas and oil reservoirs.

Tectonics and geodynamics of the western Central Asian Fold Belt ( Kazakhstan Paleozoides)

On the basis of stratigraphical and geological data, paleogeographical and palinspastic reconstructions of the Kazakhstan Paleozoides were done; their multistage geodynamic evolution was considered; their tectonic zoning was proposed. The main stages are described: the initiation of the Cambrian and Ordovician island arcs; the development of the Kazakhstan accretionary–collisional composite continent in the Late Ordovician as a result of continental subduction and the amalgamation of Gondwana blocks with the island arcs (a long granitoid collisional belt also formed in this period); the development of the Devonian and Carboniferous–Permian active margins of the composite continent and its tectonic destruction in the Late Paleozoic. In the Late Ordovician, compensated terrigenous and volcanosedimentary complexes formed within Kazakhstania and developed in the Silurian. The Sakmarian, Tagil, Eastern Urals, and Stepnyak volcanic arcs formed at the boundaries with the Ural, Turkestan, and Junggar–Balkhash Oceans. In the late Silurian, Kazakhstania collided with the island arcs of the Turkestan and Ob'–Zaisan Oceans, with the formation of molasse and granite belts in the northern Tien Shan and Chingiz. This was followed by the development of the Devonian and Carboniferous–Permian active margins of the composite continent and the inland formation of the Early Devonian rift-related volcanosedimentary rocks, Middle–Late Devonian volcanic molasse, Late Devonian–Early Carboniferous rift-related volcanosedimentary rocks, terrigenous–carbonate shelf sediments, and carbonaceous lake–bog sediments, and the Middle–Late Carboniferous clastic rocks of closed basins. In the Permian, plume magmatism took place on the southern margin of the Kazakhstan composite continent. It was simultaneous with the formation of red-colored molasse and the tectonic destruction of the Kazakhstan Paleozoides as a result of a collision between the East European and Kazakhstan–Baikal continents.

Microbialites and global environmental change across the Permian–Triassic boundary: a synthesis

Permian-Triassic boundary microbialites (PTBMs) are thin (0.05-15 m) carbonates formed after the end-Permian mass extinction. They comprise Renalcis-group calcimicrobes, microbially mediated micrite, presumed inorganic micrite, calcite cement (some may be microbially influenced) and shelly faunas. PTBMs are abundant in low-latitude shallow-marine carbonate shelves in central Tethyan continents but are rare in higher latitudes, likely inhibited by clastic supply on Pangaea margins. PTBMs occupied broadly similar environments to Late Permian reefs in Tethys, but extended into deeper waters. Late Permian reefs are also rich in microbes (and cements), so post-extinction seawater carbonate saturation was likely similar to the Late Permian. However, PTBMs lack widespread abundant inorganic carbonate cement fans, so a previous interpretation that anoxic bicarbonate-rich water upwelled to rapidly increase carbonate saturation of shallow seawater, post-extinction, is problematic. Preliminary pyrite framboid evidence shows anoxia in PTBM facies, but interbedded shelly faunas indicate oxygenated water, perhaps there was short-term pulsing of normally saturated anoxic water from the oxygen-minimum zone to surface waters. In Tethys, PTBMs show geographic variations: (i) in south China, PTBMs are mostly thrombolites in open shelf settings, largely recrystallised, with remnant structure of Renalcis-group calcimicrobes; (ii) in south Turkey, in shallow waters, stromatolites and thrombolites, lacking calcimicrobes, are interbedded, likely depth-controlled; and (iii) in the Middle East, especially Iran, stromatolites and thrombolites (calcimicrobes uncommon) occur in different sites on open shelves, where controls are unclear. Thus, PTBMs were under more complex control than previously portrayed, with local facies control playing a significant role in their structure and composition.

Decay and recovery of the mid-Aptian carbonate factory in the Southern Apennine Carbonate Shelf (southern Italy)

Decay and recovery of the mid-Aptian carbonate factory in the Southern Apennine Carbonate Shelf (southern Italy)

The Madotz Urgonian platform (Aralar, northern Spain): Paleoecological changes in response to Early Aptian global environmental events

Sudden addition of carbon dioxide to the atmosphere can reduce the CaCO3 saturation and weaken the biocalcification potential of marine organisms in shallow water and in open marine settings. In this study, the response of an Aptian neritic carbonate environment to sudden addition of carbon dioxide at the beginning of Oceanic Anoxic Event 1a is investigated. The beginning of the OAE1a was coupled with a major perturbation on the carbon cycle as indicated by a negative carbon isotope excursion in the sedimentary record. This isotope anomaly is regarded as a proxy for massive addition of volcanic or methane-derived CO2 to the atmosphere within only a few 104years. The impact of a rapid change in atmospheric pCO2 on biocalcifiers in low latitude shallow-water settings can be studied in a well preserved Aptian carbonate shelf succession cropping out today in the Aralar mountains (NE Spain). The Madotz section (N Spain) preserves a continuous shallow water record that was deposited on a mid-latitude, Atlantic-oriented mixed siliciclastic–carbonate ramp. Lower Aptian sediments consist of two neritic limestone successions separated by orbitolinid-rich marlstone enriched in organic matter. The lower neritic limestone succession ends with a submarine hardground and the transition from the lower neritic limestone to the orbitolinid marlstone coincides with a negative spike in the organic carbon isotope record. This negative spike can be correlated with the negative carbon isotope anomaly marking the base of OAE1a. The paleoecological change coinciding with the base of OAE1a occurred at a time of sea level rise and it coincided with a demise of heavily calcified nannoconids in the Tethys and Pacific Oceans. The paleoecological change observed in the Madotz section corresponds to a comparable change seen in the more distal and more expanded carbonate ramp section (Igaratza) at the Aralar Mountains. Ocean acidification caused by sudden increase in pCO2 may explain reduced calcification potential of some shallow water calcifiers. Calcification crisis was amplified by rising sea level, increasing temperatures and increased flux of detrital material and nutrients from continents into coastal seas.

Evolution of Cretaceous to Eocene alluvial and carbonate platform sequences in central and south Jordan

ABSTRACT The Cretaceous to Eocene succession in central and south Jordan is characterised by passive continental margin depositional sequences, which pass upward from alluvial/paralic to carbonate shelf and pelagic ramp settings. Detailed section logging and outcrop mapping have produced robust lithostratigraphic and lithofacies schemes that can be correlated throughout the region and in the subsurface. These schemes are set in a sequence-stratigraphic context in relation to the evolution sedimentation on the Arabian and Levant plates. Three major megasequences are described (Kurnub, Ajlun and Belqa), and these are further subdivided into large-scale depositional sequences separated by regional sequence boundaries that represent maximum flooding surfaces. There is close correspondence between maximum flooding surfaces recording major sea-level rise with those derived for the Arabian and Levant plates, although there are some discrepancies with the precise timing of global sea-level fluctuations. An upward change from braided to meandering stream fluvial environments in central and south Jordan during the Early Cretaceous, reflects a decreasing geomorphological gradient of the alluvial plain, declining siliciclastic sediment flux, and increased floodplain accommodation, associated with a regional Late Albian (second-order) rise in relative sea-level. The Late Albian to Early Cenomanian marine transgression across the coastal alluvial plain marks a major sequence boundary. During Cenomanian to Turonian times a rimmed carbonate-shelf was established, characterised by skeletal carbonates showing small-scale, upward-shallowing cycles (fourth- to fifth-order parasequences) ranging from subtidal to intertidal facies, arranged into parasequence sets. Rimmed carbonate shelf sequences pass laterally to coeval coastal/alluvial plain facies to the south and east. Eustatic (third-order) fluctuations in relative sea level during the Cenomanian and Early Turonian resulted in deposition of ammonite-rich wackestones and organic-rich marls, during high sea-level stands (maximum flooding surfaces). Progradational sabkha/salina facies passing landwards to fluvial siliciclastics were deposited during an Early Turonian sea-level low stand, marks a regional sequence boundary, above which a highstand carbonate platform was established. A second-order, regional rise in sea level and marine transgression during the Early Coniacian marks a Type 2 sequence boundary, and subsequent drowning of the rimmed carbonate shelf by Late Coniacian times. Sedimentation during the Santonian to Maastrichtian was characterised by a hemi-pelagic chalk-chert-phosphorite lithofacies association, deposited in shallow to moderate water depths on a homoclinal ramp setting, although thicker coeval sequences were deposited in extensional rifts. The marked change in sedimentation from rimmed carbonate shelf to pelagic ramp is attributed to Neo-Tethyan mid-oceanic rifting, tilting, intracratonic deformation and subsidence of the platform; this is reflected in changes in biogenic productivity and ocean currents. Oceanic upwelling and high organic productivity resulted in the deposition of phosphorite together with giant oyster banks, the latter developing within oxygenated wave-base on the inner ramp. Chalk hardgrounds, sub-marine erosion surfaces, and gravitational slump folds indicate depositional hiatus and tectonic instability on the ramp. In the Early Maastrichtian, deeper-water chalk-marl, locally organic-rich, was deposited in density-stratified, anoxic basins, that were partly fault controlled. Pulsatory marine onlap (highstand sequences) during the Eocene is manifested in pelagic chalk and chert with a paucity of benthic macro-fauna, indicating a highly stressed, possibly hypersaline, and density-stratified water column. Comparison with global and regional relative sea-level curves enable regionally induced tectonic factors (hinterland uplift and ocean spreading) to be deduced, against a background of global sea-level rise, changing oceanic chemistry/productivity and climatic change.

Southwest Mallorca Island: A cool-water carbonate margin dominated by drift deposition associated with giant mass wasting

By means of new high-resolution Parasound, multi-channel reflection seismic and multibeam swath bathymetry data, we provide new insight into the sedimentation processes at the margin of a cool-water carbonate ramp system off southwestern Mallorca Island, western Mediterranean Sea. Here, we mapped 7 depositional units which we tied to the Messinian unconformity. The oldest units (1–3) are deposited from late Messinian to late Pliocene during phases of extreme sea-level fluctuations. 2.4Ma ago with the global climate cooling, when the estuarine water mass circulation switched into an anti-estuarine pattern in the Mediterranean Sea and sea-level highstands reached the today level, bottom currents started to shape the distal deposits of the cool-water carbonate system off southwestern Mallorca, represented by depositional units 4–7. Although, sediment supply from the carbonate shelf to the slope is low due to the insignificant input of terrigenous clastics and slow reef growth, slope sediments reach thicknesses >140m. Our study displays that the accumulation of sediments at the southwestern insular margin was mainly controlled by long-lived bottom currents and giant submarine landslides. The bottom currents formed elongated mounded drifts that contemporaneously developed in alongslope and upslope direction. They are probably controlled by an isobath-parallel bottom current in a present water depth of 350–550m which we associate with the Levantine Intermediate Water (LIW); and an upslope current acting in 250–600m associated with the Algerian mesoscale gyres that enter the Balearic straits from SE. Several scarps at the present sea-floor indicate the predominance of slope failures in the study area. Additionally, mass transport deposits occur basinwards in almost all depositional units. Accordingly, giant mass wasting events took place from the Pliocene into recent times.Locally, above the alongslope drift a field of sediment waves occurs in a water depth of 170–310m. They are oriented slightly oblique to the contour lines with their steep flank facing upslope, showing wavelengths of 400–800m and heights of 10–15m. We suggest that the waves migrate in upslope direction perpendicular to the main isobath-parallel flow.Furthermore, the results of this study indicate that sea-level fluctuations have only a minor influence on drift deposition; instead submarine landslides caused the creation of new drift units. They significantly altered the relief of the sea-floor and thereby initiate the realignment of the prevailing current pattern. The fault scarps and detachment surfaces left behind were the nucleolus for the development of new drift units.