Early Pliocene Sediments Research Articles

Evolution of hydrocarbon deposits in the South Caspian Basin

Studies of the South Caspian Basin display that the Early Pliocene sediments define mainly the structural characteristic of the section in this area. The Productive Series consists of deposits accumulated during the Pliocene epoch. It is known that within the basin, the major commercial hydrocarbon accumulations are attributed to the Productive Series of the Early Pliocene and concentrated mainly in the Absheron oil and gas province, Baku archipelago and Low Kur oil and gas provinces. Studies of fluid generation are required for correct planning of geological exploration for oil and gas in these areas.
 This research work aimed to study the fluid generation processes in the South Caspian Basin by use of 3D modeling.
 The history of hydrocarbon formation was reconstructed. Fluid generation focuses were studied and the distribution areas of these focuses was clarified. The maturity of the Middle Jurassic and Low Cretaceous sediments and Maikop and Diatom deposits were assessed, the temperature regime of the Maikop and Diatom deposits were analyzed. We also evaluated the hydrocarbon fields’ and mud volcanoes’ relations to the focal areas of small-focused earthquakes.
 In the South Caspian Basin, the Middle Jurassic, Low Cretaceous, Maykop, and Diatom focuses of fluid generation were outlined and their allocation and time-spatial evolution history were researched.
 Evaluation of the maturity of Middle Jurassic and Low Cretaceous sediments, Maykop, and Diatom showed neither oil formed at the peak of oil-gas generation with maturity values Ro=0.8ff0.9 %, nor low-maturity gases of the transition zone even within the fluids of gas-condensate fields, while some oil fields had gases of abnormally high maturity of Ro=2.4ff3.09 %.
 3D modeling of paleogeotemperatures in Maykop and Diatom suites found that a) both in the western and the eastern part of the South Caspian Basin the temperature in the bottom of Maykop increases by 20 ◦C in comparison to the top of the suite; b) in the west of the trough in the middle portion of Diatom at a depth of 8000 m and in the east of the trough at 9000 m, the temperature reaches 120 ◦C.
 In the case of small-focused seismicity caused by fluid-generation processes, the latter at the phase conversions are accompanied by high energy output, decompaction, pressing-out of fluids and matters in pseudo-liquefied state into the permeable areas of the media, thus assisting the development of diapiric structures and mud volcanoes.

Palynostratigraphy and paleoenvironmental analysis of late Miocene–early Pliocene sediments from ML‑1 well, Offshore Eastern Niger Delta, Nigeria

Palynostratigraphy and paleoenvironmental analysis of late Miocene–early Pliocene sediments from ML‑1 well, Offshore Eastern Niger Delta, Nigeria

Magnetic properties of early Pliocene sediments from IODP Site U1467 (Maldives platform) reveal changes in the monsoon system

We report a study of the magnetic stratigraphy and the anisotropy of isothermal remanent magnetization of Pliocene sediments from International Ocean Discovery Program (IODP) Site U1467 drilled in the Maldives platform (Indian Ocean) during Exp. 359. Magnetic stratigraphy gives a precise record of geomagnetic reversals of the early Pliocene from approximately 5.3 Ma to 3.1 Ma providing a detailed age model in an interval where the biostratigraphic record is scarce. We use the anisotropy of isothermal remanent magnetization (AIRM) to investigate the statistical orientation of fine magnetic particles and provide data on the strength and direction of bottom currents during the early Pliocene. The strength of bottom currents recorded by the AIRM, shows a prominent increase at the top of Chron C3n.1n (about 4.2 Ma), and the current direction (NE - SW) is consistent with that of modern instrumental measurements. Since bottom currents in the Maldives are driven by the monsoon, we speculate that the 4.2 Ma increase of bottom currents could mark the onset of the present-day setting, probably related to the coeval uplift phase of the Himalayan plateau.

Other coiling changes in Globoratalia Acostaensis unknown till now in Mediterranean area

In this study, all samples from Tortonian to Early Pliocene sediments of Zvernec-Vlora and Kavaja-Durres regions within Peri-Adriatic Foredeep (PAF) of Albania containing Globorotalia acostaensis were studied qualitatively and quantitatively. Based on these analyses resulted that G. acostaensis have changed coiling ratio direction during G. acostaensis and G. obliquus extremus Zone of Tortonian, differently from that known in Mediterranean area up to now. This is not a short time interval, which more exactly is from the first appearance of G. acostaensis to first appearance of G. suterae, at the upper part of G. extremus Zone. Another documented and explaining unconformity here is related with beginning of Pliocene sediments. There are at least four alienating sinistral and dextral coiling changes in G.acostaensis populations. Also in this work is given the history of the study of G acostaensis and which maybe causes that this species in Mediterranean province and especially in our country is used relatively late as zonal marker species. The main object of stratigraphers and paleontologists has been finding a successive section, with uninterrupted sedimentation, possibly for the longest geological time. Regarding to this phenomenon could be explained resulting unconformity between coiling ratio changes in Globorotalia acostaensis of the present study and other studies carried out in Mediterranean area on this occasion up to now. It is difficult to understand here the resulting unconformity during the main part of Tortonian age, which prolonged more than 2 m.y. Another resulting unconformity discovered at the Miocene/Pliocene boundary of the Kavaja-Durres regions is very significant. In these regions was discovered an earlier Pliocene sedimentation than known up to now according to resulting alternations of coiling direction of Globorotalia acostaensis prior to Pliocene Sphaeroidinellopsis Acme zone. These data are in favour of those based on the isotopie stratigraphy, which give a new definition at 5.32 M.Y. Miocene/Pliocene boundary instead of 5.1 or 5.2 M.Y. given previously based on absolute age. Coiling changes, in our case that of G. acostaensis are in response to changing climates or alternation of different cold and warm water populations resulting from changes in the boundaries between water masses as at the beginning of the Pliocene when the water masses of the Atlantic Ocean overflowed the Mediterranean area. Here is also proposed to correct the Neogene paleoclimatic curve referring, for the interval of G. acostaensis range distribution.

Two new Pliocene hamsters (Cricetidae, Rodentia) from southwestern Tibet (China), and their implications for rodent dispersal ‘into Tibet’

ABSTRACTTwo new species of fossil hamsters (Cricetinae, Cricetidae) collected from early Pliocene sediments (∼4.4 Ma) in the Zanda Basin, southwestern Tibet (China), demonstrate greater past diversity among cricetines in the hinterland of the Tibetan Plateau within the Himalayan Range (beyond the previously known ‘Plesiodipus’ thibetensis from the late Miocene of the Gyirong Basin). The occurrence of Nannocricetus qiui, sp. nov., in the Zanda Basin indicates a dispersal of Nannocricetus from its center of origin in northern and northwestern China and the Mongolian Plateau, into the hinterland of the high-elevation Tibetan Plateau and subsequently into the Himalayan Range. The new taxon Aepyocricetus liuae, gen. et sp. nov., possibly represents a specialized (and endemic) Neogene hamster from the Tibetan Plateau. The dispersal of these hamsters into the high-elevation portions of Tibet during the early Pliocene contrasts with the hypothesized biogeographic shift of several large mammal lineages out of Tibet. The absence of Aepyocricetus and Nannocricetus from adjacent portions of the south slope of the Himalayans (and the Siwalik Hills in India and Pakistan) further implies that the Himalayan range functioned as a dispersal barrier for these small mammals by the early Pliocene.http://zoobank.org/urn:lsid:zoobank.org:pub:9EE286AA-0C00-4041-8F0C-877B35283181.SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Li, Q., T. A. Stidham, X. Ni, and L. Li. 2018. Two new Pliocene hamsters (Cricetidae, Rodentia) from southwestern Tibet (China), and their implications for rodent dispersal ‘into Tibet’. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1403443.

Early Pliocene gastropod assemblages from the eastern Mediterranean (SW Peloponnese, Greece) and their palaeobiogeographic implications

We here report on the systematics, paleoecology and biostratigraphy of a rare, but diversified gastropod fauna found in the early Pliocene sediments of the Agia Triada section in the Falanthi Basin (Peloponnese, Greece). Sixty-one species belonging to forty-eight genera are identified, allowing biostratigraphic assignment to the Mediterranean Plio-Pleistocene Molluscan Unit 1 (MPPMU1). Planktonic foraminiferal biostratigraphic analyses indicate that the Agia Triada section correlates with Zones MPL2 and MPL3, corresponding to the latest Zanclean. A comparison is further carried out between the studied assemblages and those previously documented from the Atlantic coasts of Europe and the Mediterranean region. New information on the palaeobiogeography of early Pliocene gastropod fauna is given, as seven species from the Mediterranean, thirty-nine species from the eastern Mediterranean and forty-four species from Greece, are documented here for the first time.

Oligocene to Lower Pliocene deposits of the Norwegian continental shelf, Norwegian Sea, Svalbard, Denmark and their relation to the uplift of Fennoscandia: A synthesis

This study provides the results of the first integrated study of Oligocene–Pliocene basins around Norway.Within the study area, three main depocentres have been identified where sandy sediments accumulated throughout the Oligocene to Early Pliocene period. The depocentre in the Norwegian–Danish Basin received sediments from the southern Scandes Mountains, with a general progradation from north to south during the studied period. The depocentre in the basinal areas of the UK and Norwegian sectors of the North Sea north of 58°N received sediments from the Scotland–Shetland area. Because of the sedimentary infilling there was a gradual shallowing of the northern North Sea basin in the Oligocene and Miocene. A smaller depocentre is identified offshore northern Nordland between Ranafjorden (approximately 66°N) and Vesterålen (approximately 68°N) where the northern Scandes Mountains were the source of the Oligocene to Early Pliocene sediments. In other local depocentres along the west coast of Norway, sandy sedimentation occurred in only parts of the period. Shifts in local depocentres are indicative of changes in the paleogeography in the source areas.In the Barents Sea and south to approximately 68°N, the Oligocene to Early Pliocene section is eroded except for distal fine-grained and biogenic deposits along the western margin and on the oceanic crust. This margin was undergoing deformation in a strike-slip regime until the Eocene–Oligocene transition. The Early Oligocene sediments dated in the Vestbakken Volcanic Province and the Forlandssundet Basin represent the termination of this strike-slip regime.The change in the plate tectonic regime at the Eocene–Oligocene transition affected mainly the northern part of the study area, and was followed by a quiet tectonic period until the Middle Miocene, when large compressional dome and basin structures were formed in the Norwegian Sea. The Middle Miocene event is correlated with a relative fall in sea level in the main depocentres in the North Sea, formation of a large delta in the Viking Graben (Frigg area) and uplift of the North and South Scandes domes. In the Norwegian–Danish Basin, the Sorgenfrei-Tornquist Zone was reactivated in the Early Miocene, possibly causing a shift in the deltaic progradation towards the east. A Late Pliocene relative rise in sea level resulted in low sedimentation rates in the main depositional areas until the onset of glaciations at about 2.7 Ma when the Scandes Mountains were strongly eroded and became a major source of sediments for the Norwegian shelf, whilst the Frigg delta prograded farther to the northeast.

Analysis of well log and pressure data of the gas-bearing sand reservoirs of Kafr El-Sheikh formation: Case study from the off-shore Nile Delta-Egypt

The off-shore Nile Delta is one of the most promising areas for gas exploration and production in Egypt and the Middle East. The present study deals with evaluation of the gas-bearing sand anomalies at the off-shore Nile Delta of Egypt using the available well logging and the pressure datasets. The early to middle Pliocene sediments (Kafr El Sheikh Formation) of eleven wells scattered in the Darfeel and Port Fouad Concessions are analyzed and studied for determining the different petrophysical parameters necessary for reservoir evaluation. This study reveals the presence of three gas-bearing sand zones (anomalies-1, -2 and -3), with good hydrocarbon potential, encountered at different depth levels at the Early Pliocene sediments of Kafr El Sheikh Formation. The detailed petrophysical analysis of these zones shows that anomalies-1 and 2 attain good reservoir parameters, while anomaly-3 is not penetrated in majority of wells in the study area. However, anomaly-2 exhibits unique characteristics; in terms of the good porosity (27 to 33%), low shale volume (Vsh<10%) and high gas potentiality (42 to 93%), which it attains. The constructed petrophysical property maps of gas anomalies-1 and -2, reveal an observed diminish of gas saturation towards the eastern flank of the study area. The potential accumulations with the best reservoir cut-off parameters, are recognized in the central and western parts of Darfeel Concession. The analysis of pressure data is concerned mainly with locating the different fluid contacts and determining the pressure gradients of the gas-bearing zones. Very close pressure regimes are detected for most of the investigated gas anomalies through out the study area. Pressure gradient ranges of 0.331 to 0.345 psi/ft and 0.314 to 0.444 psi/ft are indicated for anomalies-1 and 2, respectively. Key words: Well logs, pressure data, gas-bearing sand anomalies, off-shore Nile Delta, Egypt.

Mineralogical and Geochemical Characteristics and Genesis of the Sepiolite Deposits at Polatli Basin (Ankara, Turkey)

AbstractThe Middle—Upper Miocene—Pliocene sediments near Polatlı contain commercial sepiolitic clay deposits. The sepiolite-rich Polatlı basin sediments were studied to describe the sepiolitic clay deposits of the area and to assess the environments of formation using X-ray diffraction, optical and scanning electron microscopy, and chemical analysis. The Polatlı basin is an elongated, rift-related graben trending NE—SW in central Turkey, filled with continental Late Miocene to Early Pliocene sediments. The sediments which comprise claystone, marl and limestone, dolostone, and evaporites are characteristic deposits of low-salinity, playa-lake depositional environments. These sepiolite-rich deposits include sepiolite, dolomite, and calcite, with minor amounts of palygorskite, quartz, moganite, amorphous silica (opal-CT), and feldspar.The sepiolite shows all the characteristic X-ray diffraction reflections of that mineral, whereas amorphous silica containing sepiolite shows some of the characteristic reflections of sepiolite, but with somewhat broader and less intense basal reflections. In the siliceous deposits, the long, fibrous, and filamentous aggregates of the sepiolite were converted to thick, short fibers, low in Mg, and showing transition to amorphous silica.Major and trace elements (e.g. Si, Al, Fe, Mg, Sr, Ba, etc.) were found almost exclusively in Mg-rich smectitic claystone and detrital silicate-rich rocks, whereas Mg, Ca, and some Si were concentrated in the neoformed minerals in the basin. The rare-earth elements (REE) and some of the high-field strength elements (HFSE), large ion lithophile elements (LILE), and transition elements (TRE) patterns were similar for detrital silicate-rich rocks and formed from neoformed mineral lithologies. The REE, TRE, LILE, and some of the HFSE contents of limestone, dolostone, and sepiolitic claystone were similar while those of detrital silicate-rich rocks and Mg-rich smectitic claystones were similar to each other. PAAS-normalized REE and other trace-element patterns were typically subparallel and depleted in neoformed minerals. All sample groups had positive Eu* anomalies, except Mg-rich smectite (0.80). Limestone, dolostone, and amorphous silica compounds showed slightly negative Ce* anomalies, whereas sepiolitic claystones, Mg-rich smectitic claystones, and detrital silicate-rich rocks had a slightly positive Ce* anomaly.

TAPHONOMIC AND PALEOECOLOGICAL ANALYSES (MOLLUSKS AND FISHES) OF THE SUA MEMBER CONDENSED SHELLBED, UPPER ONZOLE FORMATION (EARLY PLIOCENE, ECUADOR)

Abstract The early Pliocene sediments of the Sua Member (Onzole Formation) are spectacularly exposed along coastal cliffs in the surroundings of Sua (northwestern Ecuador). The shellbed at the base of these strata contains rich mollusk and fish assemblages and provides a rare opportunity to document the virtually unknown Pliocene shallow-water faunas of Ecuador. Stratigraphic context, faunal composition (both mollusks and fishes), biofabric trend, ichnological signatures, and taphonomic features presented here, all indicate that the shellbed is a stratigraphically condensed (hiatal) skeletal concentration generated primarily by low rates of net background sedimentation. Shellbeds of this type, immediately overlying a Glossifungites-demarcated ravinement surface, are regarded as onlap shellbeds and record landward stratal convergence and attenuation during the earliest phases of marine transgression. Although composed of largely autochthonous-parautochthonous specimens, the fossil assemblage contains mollu...

Histoire plio-pléistocène des écosystèmes végétaux de Méditerranée sud-occidentale : apport de l’analyse pollinique de deux sondages en mer d’Alboran

The pollen analysis of sediments of two boreholes located in the northeastern Morocco (Nador 1) and in the southeastern Spain (Andalucia G1) has allowed shedding a new light on the vegetation and climate of the North African littoral plains, the Rif Massif and the Betic Range during the Pliocene. The vegetation around the Alboran Sea was open and xeric during the Zanclean, dominated by herbs including subdesertic elements as Calligonum, Lygeum, Nitraria and Neurada. This type of vegetation indicates a dry and hot climate. The southwestern Mediterranean steppes have therefore a climatic character; they existed before the presence and the heavy pressure of Man on the environment. From the Piacenzian, the development, at Andalucia as well as at Nador, of Artemisia and the appearance of some altitude trees such as Cedrus and Cathaya indicate a vegetation change linked to a climatic change. Modifications in the vegetation observed during the same period in northwestern Mediterranean seem to indicate that the vegetation changes observed at Andalucia and Nador are controlled by the appearance of the first arctic glacial-interglacial cycles. The cedar tree appears at Nador only at the end of the Piacenzian, at time of the first cooling, while it has been found punctually in Messinian and early Pliocene sediments of Habibas in Algeria and in Messinian sediments of the Bou Regreg section at Salé in Morocco. The regular presence of Cedar at Bou Regreg during the Messinian, allows supposing that it was present in the Middle Atlas Mountains and that its development was favoured by colder conditions.

La microflore de diatomées au passage mio-pliocène en Corse

The “Aleria formation”, described in northeastern Corsica, consists of siliciclastic deposits referred to a deltaic environment and comprises diatomitic lenses exposed at Casabianda. The Aleria formation fills a depression of the Messinian erosional surface and is overlain by Early Pliocene sediments in several places. This suggests a late Messinian-earliest Pliocene age. Diatom microflora is well-preserved and contains 59 species. Pennates indicate a very large diversity with 54 species, while Centrics are represented only by five species. Diatom assemblages show a relative constant composition along the studied interval. The species Aulacoseira granulata is the dominant taxon with about 90% in all samples. Taxa are of different salinity classes and different modes of life (planktic, tychoplanktic, benthic, epiphytic…), suggesting multiple environmental factor interactions. The environmental model suggested by sedimentological and biological data led as to assume a pond-like coastal receptacle common in deltaic system. This receptacle was slightly influenced by the close marine waters and was supplied by permanent freshwaters from continental run-off and alluvial sheet. This model based on diatom assemblages provides new data for palaeoenvironmental and chronological interpretations of the so-called Messinian Lago-Mare deposits.

Carbonate preservation patterns at the Ceará Rise – Evidence for the Pliocene super conveyor

Enhanced Atlantic overturning during the Pliocene was first proposed almost 10 yrs ago. Evidence for this Pliocene super conveyor scenario has been collected using a number of proxies (e.g., benthic δ 13C, Nd isotopic composition of manganese crusts). The present study contributes to the existing evidences by using carbonate dissolution and current vigour history of early Pliocene sediments from the Ceará Rise (ODP Sites 927 and 929). In order to reveal carbonate dissolution history, a number of commonly used and newly established proxies were applied, i.e., sand and carbonate contents, foraminifer fragmentation index, Bulloides Dissolution Index and carbonate silt grain-size distributions. Terrigenous silt grain-size distributions were used to unravel variations in relative current strength and sediment input to the two sites. Overall good carbonate preservation at the shallow Site 927 (3314 m water depth) shows that this level was bathed in North Atlantic Deep Water throughout the early Pliocene. The contrastingly poor carbonate preservation record of the deeper Site 929 (4358 m water depth, at present exposed to Antarctic Bottom Water) is frequently interrupted by phases of good carbonate preservation. These results indicate that the depth of the calcite lysocline was mainly tied to present level (∼ 4200 m water depth), and sometimes even dropped to water depths greater than 4360 m due to even more enhanced circulation. Surprisingly the expansion of NADW is not clearly reflected by an increase in current speed as shown by continuously fine terrigenous grain size.

Late Miocene and early Pliocene environments in the southwestern Black Sea region from high-resolution palynology of DSDP Site 380A (Leg 42B)

A high-resolution palynological study has been performed on late Miocene (Messinian) and early Pliocene (Zanclean) sediments cored at DSDP Site 380A (Leg 42B). A late Miocene coastal vegetation has been identified in association with a delta environment. The Pliocene is characterised by competition between the two most important vegetation components, namely humid thermophilous forests and dry steppes, with changes driven by large amplitude climatic variations. These variations are linked to other European reference pollen records and to the global temperature evolution for the early Pliocene, and result in climatostratigraphic relationships at large geographic scale. An orbital tuning is proposed with respect to new data clarifying time control on the section. The Black Sea appears to have dried up in response to the Messinian salinity crisis in the Mediterranean with which it might have been connected during periods of high sea level.

Paleoenvironmental changes at the Messinian–Pliocene boundary in the eastern Mediterranean (southern Cyprus basins): significance of the Messinian Lago-Mare

The study of the late Messinian–Early Pliocene sediments in south Cyprus (Pissouri and Polemi basins) and the comparison with the offshore coeval deposits drilled in the ODP Leg 160 boreholes, provide new data illustrating the environmental changes which occurred in the eastern Mediterranean at the end of the salinity crisis. The Messinian–Pliocene transition is marked by a very rapid environmental change indicated by sharp variations in lithology, sedimentology, microfaunal assemblages and stable isotope composition. The latest Messinian interval is dominated by the ‘Lago-Mare’ oligo-mesohaline environments. The most striking feature in the Pissouri Basin is the intercalation between the uppermost gypsum bed and the base of the Zanclean deposits of four main horizons of paleosols interbedded with carbonates and conglomerates. Paleosols indicate periods of subaerial exposure long enough to permit pedogenesis to develop. Conglomerates indicate intense erosion of the Troodos Massif and its sedimentary cover as a result of the water level drop, tectonic activity and more humid climatic conditions. Thus, several subaerial exposure phases occurred in the marginal areas like the Pissouri Basin whereas shallow oligohaline conditions persisted in the deeper parts of the basin, as indicated at ODP Site 968. Both in the Pissouri Basin and on the flank of the Erathostenes Seamount the late Messinian paleosols are directly overlain by the lowermost Pliocene sediments deposited in well-oxygenated deep marine conditions. This drastic change of water depth shows that the water level of the late Messinian saline to brackish lakes dropped far below that of the world ocean, at least more than several hundred meters. Both these base level fluctuations and the oligohaline conditions caused intensive erosion–karstification of the upper gypsum beds as also reported from many other Mediterranean regions. Moreover, the study of the Polemi sections shows that oligohaline conditions had already started during the deposition of the upper gypsum sub-unit. Typical brackish and fresh water assemblages are present in the last two gypsum layers and intergypsum beds. This indicates that freshwater dilution, i.e. the Lago-Mare conditions, resulted from a progressive change of the hydrological budget which started during deposition of the upper evaporites and climaxed after the deposition of the uppermost gypsum layer (classical Lago-Mare facies). During this time, periods of increased evaporation over precipitation led to deposition of the uppermost gypsum layers. This evolution is interpreted as being due both to the severance from the open ocean and to the increasing contribution of the runoff–precipitation versus marine inputs in the hydrological budget of the Mediterranean.

Terrestrial Climate Evolution in Northwest Germany Over the Last 25 Million Years

Other| October 01, 2000 Terrestrial Climate Evolution in Northwest Germany Over the Last 25 Million Years TORSTEN UTESCHER; TORSTEN UTESCHER 1Institut für Geologie, Nussallee 8, 53115 Bonn, Germany Search for other works by this author on: GSW Google Scholar VOLKER MOSBRUGGER; VOLKER MOSBRUGGER 2Institut für Geologie und Paläontologie der Universität Tübingen, 72119 Tübingen, Germany Search for other works by this author on: GSW Google Scholar ABDUL R. ASHRAF ABDUL R. ASHRAF 2Institut für Geologie und Paläontologie der Universität Tübingen, 72119 Tübingen, Germany Search for other works by this author on: GSW Google Scholar PALAIOS (2000) 15 (5): 430–449. https://doi.org/10.1669/0883-1351(2000)015<0430:TCEING>2.0.CO;2 Article history accepted: 26 Jun 2000 first online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation TORSTEN UTESCHER, VOLKER MOSBRUGGER, ABDUL R. ASHRAF; Terrestrial Climate Evolution in Northwest Germany Over the Last 25 Million Years. PALAIOS 2000;; 15 (5): 430–449. doi: https://doi.org/10.1669/0883-1351(2000)015<0430:TCEING>2.0.CO;2 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 SocietyPALAIOS Search Advanced Search Abstract The first detailed reconstruction of the continental paleoclimate evolution of the Northwest German Tertiary (Late Oligocene to Pliocene) is presented. The paleoclimate data are derived from the paleobotanical record using the coexistence approach, a method recently introduced that employs climatic requirements of the Nearest Living Relatives of a fossil flora. Twenty six megafloras (fruits and seeds, leaves, woods) from the Tertiary succession of the Lower Rhine Basin and neighboring areas are analyzed with respect to ten meteorological parameters. Additionally, two sample sets from Late Miocene to Early Pliocene sediments comprising 396 palynofloras are analyzed by the same method providing a higher temporal resolution. The temperature curves show a comparatively cooler phase in the Late Oligocene, a warm interval the Middle Miocene, and a cooling starting at 14 Ma. The cooling trend persisted until Late Pliocene with a few higher frequency temperature variations observed. From the beginning of Late Miocene to the present, the seasonality increases and climate appears to have been less stable. As indicated by the precipitation data, a Cfa climate with wet summers persisted in NW Germany from Late Oligocene to Late Pliocene.The results obtained are well in accordance with regional and global isotope curves derived from the marine record, and allow for a refined correlation of the Tertiary succession in the Lower Rhine Basin with the international standard. It is shown that the reconstructed data are largely consistent with the continental climate record for the Northern Hemisphere, as reported by various authors. Discrepancies with previous reconstructions are discussed in detail. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Timing of rifting in the Alboran Sea basin — correlation of borehole (ODP Leg 161 and Andalucia A-1) to seismic reflection data: implications for basin formation

To constrain the timing of rifting in the western, eastern, and northern parts of the Alboran Sea basin, seismic reflectors, corresponding to biostratigraphic boundaries and unconformities from the Miocene to Recent, are correlated using synthetic seismograms. Regions of adjacent coeval compression and extension are found in the Alboran Sea basin. Normal faulting continues in parts of the eastern Alboran Sea basin later than in the western Alboran Sea basin. Seismic reflection data in the vicinity of ODP Site 976 (western Alboran Sea basin) suggest that rifting ended in the Miocene. Near Site 976 (western Alboran Sea basin), no compressional features affect Miocene and younger sediments. In the eastern Alboran Sea basin north of Al-Mansour Seamount (ODP Site 977), normal faults are observed in Miocene and Early Pliocene sediments. Later folds affect Pleistocene-Recent sediments in the eastern Alboran Sea basin (Site 977). After the folding event, there is evidence for normal faulting in Pleistocene-Recent sediments close to Site 977. South of Al-Mansour Seamount (ODP Site 978), compressional features in the eastern Alboran Sea basin from Miocene to Recent are evidenced by reverse faulting followed by folding. In the northern Alboran Sea basin (Andalucia A-1 well), there is evidence for strike-slip faulting in the Late Miocene that can be related to the Serrata fault system. We envision the development of the Alboran Sea basin through a southeasterly migration of the delaminating continental lithosphere to explain younger extension in the eastern Alboran Sea basin. The rate of the migration of the delamination front is of the range of millimeters-centimeters/year. We see evidence for the migration of the delamination front from Miocene to Recent as tectonic inversion occurs near Site 977. In contradiction to an extensional collapse hypothesis for the formation of the Alboran Sea, rifting did not end in the Late Miocene in the entire Alboran Sea basin. We exclude retreating subduction in a westward direction or a westward continental delamination as a model for Alboran Sea basin development because it would predict younger extension in the western part of the basin.

No evidence for extreme, long term warming in early Pliocene sediments of the Southern Ocean

During the past ~ 10 years there has been considerable debate with respect to the response of the Antarctic ice sheets to early Pliocene warmth. Interpretations generally fall into one of three categories; (1) there was a major drawdown of the East Antarctic Ice Sheet (EAIS), (2) drawdown of EAIS was relatively small; (3) EAIS was largely unaffected by early Pliocene warmth. Here, this question is approached by using biogenic opal and carbonate in deep-sea sediments as proxy for paleoceanographic change. During the present day, these measures are largely dictated by the position of the Antarctic Polar Front (APF) with biogenic carbonate exhibiting an increase north of the APF and biogenic opal increasing to the south. That the carbonate/opal transition zone is a reliable feature in deep-sea sediments is evidenced by the fact that it is recorded north of its present position during the Last Glacial Maximum (LGM) and to the south of it during oxygen isotope stage 11, a warmer than present interglacial. When these proxies are applied to Southern Ocean sediments, high frequency glacial/interglacial changes are seen in the Pliocene and early Pleistocene. What appears to be a major glacial is recorded at about 4.5 Myrs B.P. Three, short duration carbonate highs (up to 18%), suggesting a southward movement of APF, occur at discrete intervals between about 4.6–4.8 Myrs B.P. However, these disappear or become reduced in amplitude toward the continent. Such data do not support any appreciable warming of surface waters near the Antarctic continent; neither does it support any claims of high (circa 20 °C) sea-level air temperatures over the EAIS. It is concluded that there is no evidence for significant drawdown of EAIS during early Pliocene warmth.

Origin and deformation of the Neogene–Recent Maghrebian foredeep at the Gela Nappe, SE Sicily

SE Sicily contains one of the few exposures of orogenic foreland to the Maghrebian-Apennine orogenic system in the central Mediterranean. Here the African foreland is represented by the Hyblean plateau, adjacent to the frontal thrust structures of the Maghrebian chain. These structures include the disrupted foredeeps to earlier parts of the thrust system. One of these, the Gela nappe, is a major structure composed of late Oligocene to early Pliocene sediments emplaced onto Pliocene–Pleistocene rocks of the buried foreland. This paper presents a correlation of late Miocene stratigraphic units between the foreland and the foredeep basin. Abrupt lithological and thickness variations of these units suggest that the foredeep basin was limited towards the foreland by normal faults. In the hinterland these foredeep sediments lap back onto previously emplaced thrust sheets, including the far-travelled units of ‘Numidian flysch’. The precursor Oligocene–Serravallian foredeep may also have been controlled by normal faulting. Compressional tectonics are reflected in folding and thrusting which post-dates deposition of lower Pliocene chalks (Trubi Formation), although minor folding and erosion preceded this unit. Larger thrusts repeat the basin stratigraphy and carry it out onto the adjacent foreland. A minimum of 8 km shortening since Messinian times can be demonstrated although a more realistic figure is c. 25 km, at a time-averaged rate off. 0.5cm/a −1 . The stratigraphic relationships on the foredeep sedimentary sequences may provide analogues for offshore areas of the thrust belt.

Stratigraphy and palaeogeography of the Capo Milazzo area (NE Sicili, Italy): clues to the evolution of the southern margin of the Tyrrhenian Basin during the Neogene

The Neogene sedimentary sequence of Capo Milazzo (NE Sicily, Italy), with particular reference to the Niocene interval, is described in detail and a paleoenvironmental evolution for the Late Miocene/Pliocene time is proposed. The sequence represents a portion of the northern side of the Calabrian Arc and documents the response of the coastal environment to the complex events (salinity crisis, opening of the Tyrrhenian Basin) which affected the Mediterranean Basin during the Neogene. The beginning of rifting and increased subsidence of the northern sectors along NE-SW faults are recorded in the Late Tortonian, together with a southbound marine transgression, documented by clastic littoral facies. The transgressive trend continued during the Early Messinian, though the moderate subsidence maintained a neritic environment in which a small reef complex adjacent to a lagoon developed. Emersion, and karstic erosion of the Early Messinian limestones is recorded in the Late Messinian time equivalent of the Lower Evaporite. Reactivation of NE-SW faults at this time favoured the formation of large breccias, collapsed from the peripheral portions of the reef complex. Subsequent lowering of the NW sector allowed the area to ne reached by a limited marine episode during the Intra-Messinian Transgression. High-energy stream deposits, coeval with the deposition of the “Lago-Mare” facies in the Mediterranean, end the Messinian sequence. The Pliocene sequence fossilizes a complex palaeotopography with submerged highs and narrow depressions. A rapid marine transgression is recorded at the Miocene/Pliocene boundary, with the development of circalittoral/epibathyal environments. Tensional movements during the latest Messinian/earliest Pliocene and Late Pliocene are recorded by a system of fractures and respective fillings that affect the upper portion of the Early Messinian limestones. The erosion and reworking of most Early Pliocene sediments into Late Pliocene bathyal deposits, together with the local presence of clastic foreset deposits and large blocks of Messinian limestones collapsed into the lower part of Late Pliocene deep water sediments, document a Mid-Pliocene event, likely referable to the Middle-Pliocene Tectonic Phase.