Middle Tortonian Research Articles

New data on the palynostratigraphy and paleoenvironments of the late Miocene (Tortonian) Quifangondo Formation in the Cabo Ledo section, Kwanza Basin, Angola

A detailed palynostratigraphic and palynofacies analysis, associated with a lithological control, was carried out on eleven outcrop samples from the Quifangondo Formation in the Cabo Ledo (Petrofina) section, Kwanza Basin, Angola. The samples yield relatively diverse and well-preserved terrestrial and marine palynomorphs. A systematic analysis of the samples enables the identification of nine spore genera and 3 species, 20 pollen genera and 13 species, and 32 dinoflagellate cyst genera and 34 species. In addition, 10 genera of other aquatic palynomorphs, such as Chlorophyceae green algae, are identified. Dinoflagellate cysts and other aquatic palynomorphs typically dominate throughout the assemblages. In this section, a combined pollen - dinoflagellate cyst zonation is used to define two palynoassociations. The first palynoassociation is middle Tortonian in age and is characterized by the presence of the pollen grain Fenestrites spinosus and the first occurrence of the dinoflagellate cyst species Selenopemphix armageddonensis. Additionally, diverse Chlorophyceae green algae dominate most of this interval samples. The second palynoassociation is assigned to the late Tortonian and is characterized by a drastic decrease in Chlorophyceae green algae, as opposed to the gonyaulacales dinoflagellate cysts. The first occurrence of the pollen grain Fenestrites longispinosus marks the transition between the palynoassociations. Lithologically, the Cabo Ledo (Petrofina) section is dominated by a claystone with an increase in the silt and carbonate components towards the upper section. The lithological data, integrated with palynostratigraphy and palynofacies, suggests that the upper part of the Quifangondo Formation was mainly deposited in an inner to middle neritic environment characterized by dysoxic conditions punctuated by periods of terrestrial inflows. Such conditions typically result from seasonal fluctuations. The age and depositional environment of the upper Quifangondo Formation inferred from this new data allows a correlation with the other Quifangondo sequences previously studied by the authors. This multi-proxy approach is important for further stratigraphic analysis with other age-controlled lithostratigraphic units in the basin. Furthermore, the improvement of paleoenvironmental and depositional models for this unit is of great importance for cross-basin correlation and future petroleum exploration plays.

Preliminary late Miocene palynomorph assemblages from the Quifangondo and Luanda formations, Onshore Kwanza Basin, Angola

A Miocene succession exposed at the Cabo Ledo and Miradouro da Lua sections in the Onshore Kwanza Basin, Angola, was examined for palynology. Palynomorphs of preliminary late Miocene age identified are presented herein. The upper part of the Quifangondo Formation is dated as middle Tortonian in age based on the co-occurrence of the pollen grain Fenestrites spinosus and the dinoflagellate species Selenopemphix armageddonensis. The palynomorph signature indicates a middle neritic marine environment dominated by dinoflagellate cyst taxa.A late Miocene (late Tortonian to Messinian) age is also documented for the first time at the base of the Luanda Formation based on the co-occurrence of the pollen taxa Echitricolporites spinosus, Fenestrites spinosus, Fenestrites longispinosus, Monoporopollenites annulatus, and Retistephanocolpites gracilis. The palynomorph signature of this unit reflects an inner neritic marine (coastal/lagoon transitional) environment dominated by terrestrial palynomorphs and very rare dinoflagellate cyst taxa.The present research contributes data for improving the stratigraphical framework of the Quifangondo and Luanda formations, both of which are recognized as the main potential source rocks and reservoirs of the Post-Salt Paleogene/Neogene Petroleum System of the Kwanza Basin. This significant contribution provides important biostratigraphic and palaeoenvironmental data for defining the vital temporal horizons of these settings in a basin where petroleum exploration is of interest.

Three (middle to) late Miocene plant macroremain assemblages (Pitsidia, Kassanoi and Metochia) from the Messara–Gavdos region, southern Crete

Based on macroremains, we describe three fossil plant assemblages from the Miocene of the Messara Basin (southern Crete) and the adjacent Gavdos Island. The palaeoflora of Kassanoi, which is the oldest (Messara Basin, Viannos Fm, Serravallian/early Tortonian), is documented mainly by leaf imprints, including a fern, a conifer (Tetraclinis cf. salicornioides) and 23 angiosperms. The assemblage is dominated by Daphnogene polymorpha, Podocarpium podocarpum and Myrica lignitum. The plant record from Pitsidia (Messara Basin, Ambelouzos Fm, early Tortonian) comprises thousands of specimens. The plant fossils are preserved as imprints often covered by an inorganic encrustation (replica). One alga, 2 ferns, at least 5 conifers and more than 45 woody angiosperms were identified. Dominant taxa are Myrica and Pinus pitsidiensis, documented by numerous vegetative and reproductive organs (Zidianakis et al., 2015, 2016). Leaves of oaks (Q. pseudocastanea, Q. kubinyii) and Daphogene polymorpha as well as twigs of Taxodium dubium are also fairly common. From the palaeoflora of Metochia, which is the youngest (Gavdos Island, Metochia Fm, middle Tortonian), (Mantzouka et al., 2015), we report further taxa, including Quercus mediterranea, Ziziphus paradisiaca and a palm (Sabalites sp.). The vegetation is assessed both empirically (phytosociologically) and by Integrated Plant Record (IPR) Vegetation Analysis. The reconstructed vegetation models are presented in detail and discussed in the context of the geological and palaeontological settings of the area. The climate is assessed based on the Coexistence Approach (CA) and the Climate Leaf Analysis Multivariate Program (CLAMP). The palaeoclimatic datasets reveal a warm temperate to subtropical climate, probably with a weak seasonal drought.

Tectono-Sedimentary Evolution of the Cenozoic Basins in the Eastern External Betic Zone (SE Spain)

Four main unconformities (1–4) were recognized in the sedimentary record of the Cenozoic basins of the eastern External Betic Zone (SE, Spain). They are located at different stratigraphic levels, as follows: (1) Cretaceous-Paleogene boundary, even if this unconformity was also recorded at the early Paleocene (Murcia sector) and early Eocene (Alicante sector), (2) Eocene-Oligocene boundary, quite synchronous, in the whole considered area, (3) early Burdigalian, quite synchronous (recognized in the Murcia sector) and (4) Middle Tortonian (recognized in Murcia and Alicante sectors). These unconformities correspond to stratigraphic gaps of different temporal extensions and with different controls (tectonic or eustatic), which allowed recognizing minor sedimentary cycles in the Paleocene–Miocene time span. The Cenozoic marine sedimentation started over the oldest unconformity (i.e., the principal one), above the Mesozoic marine deposits. Paleocene-Eocene sedimentation shows numerous tectofacies (such as: turbidites, slumps, olistostromes, mega-olistostromes and pillow-beds) interpreted as related to an early, blind and deep-seated tectonic activity, acting in the more internal subdomains of the External Betic Zone as a result of the geodynamic processes related to the evolution of the westernmost branch of the Tethys. The second unconformity resulted from an Oligocene to Aquitanian sedimentary evolution in the Murcia Sector from marine realms to continental environments. This last time interval is characterized as the previous one by a gentle tectonic activity. On the other hand, the Miocene sedimentation was totally controlled by the development of superficial thrusts and/or strike-slip faults zones, both related to the regional geodynamic evolutionary framework linked to the Mediterranean opening. These strike-slip faults zones created subsidence areas (pull-apart basin-type) and affected the sedimentation lying above the third unconformity. By contrast, the subsidence areas were bounded by structural highs affected by thrusts and folds. After the third unconformity, the Burdigalian-Serravallian sedimentation occurred mainly in shallow- to deep-water marine environments (Tap Fm). During the Late Miocene, after the fourth unconformity, the activation of the strike-slip faults zones caused a shallow marine environment sedimentation in the Murcia sector and a continental (lacustrine and fluvial) deposition in the Alicante sector represented the latter, resulting in alluvial fan deposits. Furthermore, the location of these fans changed over time according to the activation of faults responsible for the tectonic rising of Triassic salt deposits, which fed the fan themselves.

The myth of the Messinian Dardanelles: Late Miocene stratigraphy and palaeogeography of the ancient Aegean-Black Sea gateway

The Dardanelles region has formed a key gateway connecting the Eastern Paratethys and the Aegean/Mediterranean since the late Miocene. Its sedimentary sequences contain crucial information about connectivity and tectonics but so far lack unambiguous age constraints. Only a few Miocene marine episodes have been documented and fossil assemblages are predominantly composed of Paratethyan fauna (mollusks and ostracods). Here, we apply an integrated stratigraphic approach and use the recently established chronostratigraphy for the Eastern Paratethys to re-evaluate the faunal assemblages and palaeoenvironments of the Seddülbahir and İntepe sections that allegedly played a crucial role in the geodynamic evolution of the Dardanelles during the Messinian-Zanclean. The Paratethyan ostracods and mollusks, however, clearly indicate that these sections correspond to the middle Tortonian (~9 Ma; Bessarabian–Khersonian in Eastern Paratethys terminology). Nannofossil assemblages are dominated by a mixing of reworked taxa from the late Eocene and Oligocene and no age-diagnostic taxa have been observed. Dinoflagellate analyses are also hampered by reworking and mainly reveal non-marine (fresh to oligohaline) aquatic conditions. Fossil mammal remains in the Seddülbahir section and other localities in the region confirm the late Miocene age. Strontium (87Sr/86Sr) isotope ratios of the anomalohaline (brackish) ostracods are significantly below open ocean values and similar to values obtained from Khersonian ostracods of Bulgaria. Fresh water assemblages reveal much higher 87Sr/86Sr values, which are interpreted to reflect the composition of local rivers. We conclude that in late Miocene times the Dardanelles region was a fresh to anomalohaline embayment, ephemerally connected to the Eastern Paratethys. We found no evidence for a major Messinian erosional surface nor for marine Mediterranean fossils indicative of the early Zanclean. Our results furthermore indicate that the proposed Messinian age for the propagation of the North Anatolian Fault into the Dardanelles region must be revised.

The Diest Formation: a review of insights from the last decades

Research conducted since the 1960s on the upper Miocene Diest Formation in NE Belgium is reviewed and integrated. Their lithology unites the deposits of the glauconiferous Diest Sand in one formation, though biozones and internal sedimentary structures strongly suggest the formation may agglomerate the deposits of two separate, successive sedimentary cycles. The lowermost cycle is thought to have deposited the "Hageland Diest sand" during the early or middle Tortonian. It contains the Diest Sand in the main outcrop area in Hageland, Zuiderkempen and central Limburg, and probably also the Deurne Member near the city of Antwerpen. It furthermore includes the lower part of the Dessel Member in the central Kempen and in the Belgian part of the Roer Valley Graben (RVG). The Hageland Diest cycle represents the infill of a large tidal inlet tributary to the southern North Sea bight, then situated over the southern Netherlands and the Lower Rhine embayment. The Hageland Diest sand has the composition of a marine deposit, yet the confined area of occurrence and the presence of tens of metres deep incisions at the base, set it apart. The confinement of the embayment, strong tides and a steady supply of coastal‐marine sand are invoked as the main driving forces that resulted in the distinctive geometry and internal architecture of the unit. The upper cycle is associated with the "Kempen Diest sand", which is found in the subsurface of the RVG and the Noorderkempen. It has a late Tortonian to earliest Messinian age with progressively younger ages occurring to the NW. It encompasses the upper part of the Dessel Member and the overlying, coarser Diest Sand, and correlates to most or all of the thickly developed Diessen Formation in The Netherlands. It is the deposit of a prograding marine delta, containing both marine components and continental components fed by the palaeo‐Meuse/Rhine river mouths. Accommodation space kept increasing during deposition, due to subsidence of the deposition area, especially inside the RVG but also in the Noorderkempen. Although there is a fair consensus on the above, many concrete points about the geometry and depositional history of the Diest Formation and even a definitive decision on its single or dual character remain to be sorted out. In addition, this review excludes the Flemish Hills sand and the Gruitrode Member from the Diest Formation.

Miocene tectono-sedimentary evolution of the eastern external Betic Cordillera (Spain)

ABSTRACTAn interdisciplinary study of Miocene successions in the eastern External Betic Zone (South Iberian Margin) was carried out. Evidences of syn-sedimentary tectonic activity were recognized. The results enabled a better reconstruction of the stratigraphic architecture (with an improved chronostratigraphic resolution) in the framework of the Miocene foredeep evolution of the eastern EBZ. Two main depositional sequences were dated as uppermost Burdigalian-upper Serravallian p.p. and middle-upper Tortonian. p.p., respectively. The vertical and lateral diversification of lithofacies associations and thicknesses resulted from the syn-depositional tectonic complexity of the area. A great variety of sedimentary depositional realms is due to different subsidence rates, and the growing of anticlines and synclines during the Langhian p.p.-Serravallian. After a regression with an early Tortonian erosional gap, platform to hemipelagic realms developed during the middle Tortonian. The end of the sedimentation coincided with the emplacement of an important olisthostrome-like mass consisting of Triassic material related to either the development of thrust systems or diapirs emerged in the middle-late Tortonian, during the nappe emplacement. Correlations with other external sectors of the Betic Chain, and the external domains of the Rif, Tell, and northern Apennine Chains highlighted a similar Miocene foredeep evolution during the building of these orogens.

MIOCENE SCLERACTINIAN CORALS OF GAVDOS ISLAND, SOUTHERN GREECE: IMPLICATIONS FOR TECTONIC CONTROL AND SEA-LEVEL CHANGES

Low-diversity scleractinian patch reefs that have been developed, during Early to Middle Tortonian, in Gavdos island are studied, aiming in a better understanding of the time and space relationships of the reef development and the associated basin fill evolution. Gavdos island consists part of a tectonically active setting constituting the southernmost extension of the Hellenic arc (Eastern Mediterranean). A representative Tortonian section (Bo section), located in the northwest part of the island, which hosts a mass occurrence of hermatypic corals, is studied. Scleractinian samples were collected from the upper 12 m of the section, which is characterized by interchanges of marly limestone and compact marls. The reefs are represented by the coral species Heliastraea oligophylla, Porites maicientensis, Thegioastraea roasendai and Porites collegniana. The microfacies analysis showed that the mediumto-thin-bedded carbonates of the limestone-marl alternations comprise patch reefs (boundstones-framestones, SMF 16, sensu Wilson, 1975, FZ 7-8, sensu Flügel 1982) consisted of screractinian corals. Corals are associated with corallinacean algae. Patch reefs are associated by bioclastic packstones-floatstones, characterized by benthic foraminifera, calcareous algae, spines of echinoids, gastropods and molluscs. Reefs are laterally associated by a bioclastic limestone rich in planktonic forams, associated by detrital material (fragments of quartz, feldspars, quartzites and cherts). The studied reef facies have been dolomitized and cemented in the meteoric realm. In places pseudomorphs after evaporites have been observed, tending to occlude cavities resulted after dissolution. The depositional environment corresponds to a moderate to high-energy inner platform setting, experiencing open-ocean influences. The pattern of coralgal reef development during Miocene, in the tectonically controlled Gavdos island, represents a complex interaction of tectonic activity and global sea-level changes.

GEOLOGICAL AND MAGNETIC SUSCEPTIBILITY MAPPING OF MOUNT GIOUCHTA (CENTRAL CRETE)

Giouchta Mt. is located south of Heraklion city, in Crete. It is an N-S trending morphological asymmetric ridge, with steep western slope whilst the eastern slope represents a smoother relief, composed of Mesozoic limestone and Eocene- lower Oligocene flysch sediments of the Gavrovo -Tripolis zone. The present study focuses on the geological structure of Mt. Giouchta. Field mapping and tectonic analysis is performed for this purpose. The dominant structures are contractional in nature, deformed by normal faulting related to the extensional episodes initiated in Serravallian times. The strain pattern in the area is revealed from strain analysis. It is inferred that the orientation of the stress field in the area has changed several times: the N-S, stress field which was dominant during Late Serravallian times changed to NE-SW (in Late Serravallian? - Early Tortonian) and subsequently to WNW-ESE (Early to Middle Tortonian) to become NW-SE in Late Tortonian. This orientation changed also during the Quaternary times trending from NW-SE (Early Pleistocene) to ENE-WSW (Middle Pleistocene-Holocene). In addition to the above, surface soil samples were collected in the wider area of mount Giouchta and they were analyzed in order to determine the magnetic susceptibility. GIS techniques were used for mapping the spatial distribution of the geological features and the magnetic measurements on the topographic relief of the area. Statistical analysis techniques were also applied in order to investigate the relation of faulting and magnetic susceptibility. Maps representing the spatial distribution of the above measurements were created by using appropriate interpolation algorithms.

Arc‐parallel strain in a short rollback‐subduction system: The structural evolution of the Crotone basin (northeastern Calabria, southern Italy)

Calabria, located in southern Italy, is the exposed part of the forearc in the Ionian/Tyrrhenian subduction‐rollback boundary. We present a tectonic model for the evolution of Calabria during the last 12 Ma that incorporates the structure and stratigraphy of the Crotone basin. At the re‐initiation of rollback, we document listric normal faults that accommodated a deep‐rooted extensional regime. Extension ceased in the Tortonian and did not continue throughout rollback. The middle Tortonian to early Messinian is characterized by distal sedimentation despite rapid rollback. Westward verging thrusts in Tortonian sediments and olistrostrome deposits within the Messinian section can be explained by instabilities in the accretionary wedge during the Messinian salinity crisis. Tectonic quiescence returned to the basin after the crisis and continued until a north‐south shortening event in the middle Pliocene. Our kinematic data and new evidence of two basin inversions suggest arc‐parallel shortening of the forearc. We propose that this shortening correlates with the passage of the forearc through the Apulia‐Nubia narrow. This data also dispute previous interpretations of the Crotone basin as a pull‐apart or transtensional basin. The identification of the main structures in the Crotone basin suggest a shift from quiescence to upheaval, beginning with Pliocene arc‐parallel shortening associated with the passage of the forearc through the Apulia‐Nubia narrow and continuing until today.

Reconstruction of the last marine connectivity of the Zagros basin, based on fossil evidences of the clastic-dominated Bakhtiari Formation

In this study, new paleontology and lithology foundations on the Bakhtiari Formation were obtained from Shalamzar area in Zagros basin. A depositional mollasic cycle was divided into Bk1, Bk2 and Bk3 units from the base to the top of the Formation. Bk2, with limestone- and mudstone-dominated deposits, was found to alternate with conglomerates and form a marine succession between the two limestone clast-supported conglomeratic continental units. A diverse fossil association has been described for the first time and consists of foraminifera (Oolina spp., Oolina hexagona, Textularia spp., Spiroloculina spp., Peneroplis spp., Elphidium spp., Planulina sp., Amphistegina spp., Lagena spp. Globigerina spp., Globigerinoides spp., Uvigerina spp., Triloculina spp., Quinqueloculina spp., Spiroloculina spp. Nodosariid., Orbitina spp., Borelis melo, Bolivina spp. and Miogypsina spp.), a gastropod community of Strombus spp., Potamides spp., Turitella spp., Cyprea cf. persica and Pleurotomaria sp. and a higher energy colony of scleractinian corals comprising Porites branching, Porites-encrusting massive Favites spp., Favia spp., Tarbellastrea spp. and Acropora spp. The early–middle Miocene marine level of the Bakhtiari Formation, confirms a nearshore accommodation through a middle shelf and an open coastal lagoon (inner shelf) within a fluvial-dominated delta or open estuary during the last presence of a marine trough in the Zagros basin. This saline to hypersaline shallow marine regime was probably dominated in tropical to subtropical conditions. Palaeobiogeography analysis reflects a last seaway faunal exchange between the area and early–middle Miocene basins of Pakistan, India, Australia, Turkey, Greece, Romania Algeria, Egypt, Italy, France, Portugal and Austrian/Hungarian border, which reconstructs a shallow junction between Zagros basin and Mediterranean Tethys and Indo-pacific Ocean during Burdigalian–Langhian (Badenian) before the terminal Tethyan event in late middle Miocene and Tortonian.

Miocene precipitation in Europe: Temporal trends and spatial gradients

It is known from present-day climates that both temporal and spatial variations in precipitation can be more pronounced than those in temperature and thus influence ecosystems and human society in more substantial way. However, very little is known about such variations in the past. Here we present an analysis of 206 palaeoprecipitation data from two twelve million year long proxy records of precipitation for Southwest (Calatayud-Teruel basin) and Central Europe (Western and Central Paratethys), spanning the late Early and Middle to Late Miocene (17.8–5.3 Ma) at a temporal resolution of about 80 kyr and 200 kyr, respectively. The estimates of precipitation are based on the ecophysiological structure of herpetological assemblages. The results show that precipitation variations in both regions have large amplitudes during the Miocene with comparable temporal trends at longer time scales. With locally 300 mm up to more than 1000 mm more rainfall per year than present, the early Langhian and the Tortonian were relatively wet periods, whereas the late Langhian and late Serravallian were relatively dry, with up to 300 to 500 mm less precipitation than present. The most humid time intervals were the early and middle Tortonian washhouse climate periods. Overall, our data suggest that the latitudinal precipitation gradient in Europe from the Middle to Late Miocene were highly variable, with a general tendency towards a reduced gradient relative to present day values. The gradient decreases during cooling periods and increases during warming periods, similar to results from simulations of future climate change. Interestingly, the precipitation gradient was reversed during the second washhouse climate period and the Early Messinian, which may have causes a negative hydrologic balance in the Eastern Paratethys during the latter time. Yet, our reconstructed gradient curve shows no direct correlation with the global temperature signal from oxygen isotopes, which implies a non-linear regional response. Our results further suggest that major fluctuations in the precipitation gradient can be responsible for shifts in ecosystem distribution, and particularly, for faunal turnover in South Western Europe.

Precipitation gradients during the Miocene in Western and Central Turkey as quantified from pollen data

In the present paper, we have analyzed thirty-five palynofloras covering the time span from the Early Miocene (Aquitanian) to the Late Miocene (middle Tortonian) in Turkey. The results obtained are presented in tables and maps showing temporal palaeoprecipitation values. The mean annual precipitation (MAP) exceeds 1200 mm during the Aquitanian and early-middle Serravallian. It is suggested to have been between 1000 and 1300 mm in the latest Serravallian–earliest Tortonian in Western and Central Turkey. In the early-middle Tortonian, the lower boundary of MAP decreases to below 1000 mm in Central and Eastern Turkey. Today, MAPs are represented by lower values around 600–1000 mm in Western and 400–600 mm in Central Turkey. For the driest month (LMP), the rainfall was not distributed homogeneously. In the Aquitanian, the calculations are between 36 and 48 mm with humid conditions in Western and Eastern Turkey. During the Burdigalian and Middle Miocene, the driest month precipitation varied with respect to locations. However, it is clear that there was a reduction in precipitation during the early-middle Tortonian, with values around 26–27 mm in Central and Eastern Turkey. The same pattern is observed for the wettest month precipitation (HMP), with estimates higher than 200 mm during the Aquitanian and earliest Tortonian, although some areas received low rainfall. HMP was reduced between 130 and 140 mm in the early-middle Tortonian. The warmest month precipitation (WMP) varied from 96 to 140 mm except for Konya–Ilgın, Kırşehir–Hacıbektaş and Manisa–Soma that received 88 mm during the Early-Middle Miocene. In the early-middle Tortonian, the amount of summer rainfall lay between 58 and 88 mm. The reason of the decrease in all rainfall parameters during the early-middle Tortonian could be related to several factors such as climatic cooling, altitude, aridification, palaeotopograhy or continentality. However, it is necessary to indicate that the Tortonian cooling had previously been proposed by Akgün et al. (2007) as the explanation, using a large number of palynological assemblages in Turkey. We also observe a decrease in precipitation parameters during the Middle Miocene. This could be related to fact that either low species diversity can result in wide coexistence intervals or the Monterey cooling event was related to a cooling during the Langhian and Serravallian.

The Integrated Plant Record: An Essential Tool For Reconstructing Neogene Zonal Vegetation In Europe

A semi-quantitative evaluation method has been developed to map integrated fossil plant records (leaf, fruit, and pollen assemblages) in terms of zonal vegetation. It incorporates taxonomy, physiognomy, and autecological features of the fossil plants. To derive vegetation types, the final stage of this method involves a quantitative evaluation. The maps presented here are based on 198 organ assemblages from 173 localities and stratigraphic levels of the Miocene–early Pliocene across Europe. They cover three time intervals: (1) 4–7 Ma (Messinian–middle Zanclean; late Miocene–early Pliocene); (2) 8.5– 12 Ma (latest Serravallian–middle Tortonian); and (3) 14–17 Ma (late Burdigalian–late Langhian). We also look at the interval 13–14 Ma (late Langhian–early Serravallian). They not only show vegetation types but offer more detailed information on the composition of these associations (proportions of major components). The major zonal vegetation types recognized here are broad-leaved deciduous forests, mixed mesophytic forests, broad-leaved evergreen forests, subhumid sclerophyllous forests, open woodlands, and xeric grasslands. Between 14 Ma and 17 Ma, broad-leaved evergreen forests were widespread, and subhumid sclerophyllous forests were more strongly represented in western parts of Central Europe than in eastern parts. In the interval 8.5–12 Ma, broad-leaved deciduous forests largely replaced the evergreen forests, although these were still present in some refugia (e.g., the Lower Rhine embayment and northern Balkan peninsula), and first records of xeric grasslands are found along the northern margin of the Black Sea. The more discontinuous record available from 4 Ma to 7 Ma indicates that broad-leaved evergreen forests still occurred in northern parts of the Mediterranean (northern Italy, Balkan peninsula), while open woodlands increasingly appeared in central and southern parts of Italy and Greece.

Palaeoclimatic evolution and vegetational changes during the Late Oligocene–Miocene period in Western and Central Anatolia (Turkey)

Neogene basins are widespread in Turkey and contain important lignite deposits. In this study, we reconstruct quantitatively the Late Oligocene–Miocene climate evolution in western and central Anatolia by applying the Coexistence Approach to the palynofloras obtained from the published literatures and ongoing studies.The Coexistence Approach results show that sedimentation occurred mainly under warm subtropical climatic conditions during the Chattian and Aquitanian period in western Anatolia (16.5–21.3 °C mean annual temperature (MAT) and 5.5–13.3 °C mean temperature of coldest month (CMT)). Rare occurrences of dinoflagellate cysts in the Chattian and Aquitanian indicates a marine influence. After the regression of the sea during the Burdigalian period, climate becomes cooler due to a decrease of the Palaeotropical/Arctotertiary-ratio during the latest Burdigalian–Langhian. Vegetation developed under terrestrial conditions, which had started in the Burdigalian time in western and central Anatolia and continued to the early–middle Serravallian period. The climate was subtropical in western and central Anatolia during the early–late Serravalian (17.2 to 20.8 °C for MAT and 9.6 to 13.1 °C for CMT). Besides, increase of the CMT and MAT values in western and central Anatolia supports the latest Chattian–earliest Aquitanian warming and Middle Miocene climatic optimum being also globally observed. Warm temperate climatic conditions are observed in the Late Miocene. During the early–middle Tortonian, the values are 15.6 to 20.8 °C for the MAT, 5.5 to 13.3 °C for the CMT and 823 and 1520 mm for the mean annual precipitation (MAP). They had experienced dry seasons due to lower boundary of MAP lying at 823 mm during the middle–late Tortonian.The palaeotopography of central Anatolia was higher, compared to that of western Anatolia during the Middle–Late Miocene as indicated by a rich species diversification in mountain forests. This study provides the first quantitative model for Late Oligocene–Miocene palaeoclimatic evolution in western and central Anatolia.

Paleoecological constraints on reef-coral morphologies in the Tortonian–early Messinian of the Lorca Basin, SE Spain

Abstract Coral reefs represent one of the main carbonate factories that contributed to the control of the stratigraphic architecture of carbonate platforms, which had a widespread development during the late Miocene in the paleo-Mediterranean area. The late Miocene reef complexes of the Lorca Basin in southeastern Spain are composed of five mixed siliciclastic/carbonate units, middle Tortonian to early Messinian in age. The development of coral reefs probably ceased when the first evaporitic event occurred in the basin centre in the early Messinian. This study mainly focuses on the response of reef communities and the modifications of reef organisation to global and regional parameters. At the platform scale, the carbonates are intermixed with terrigenous deposits related to two main types of clastic systems: torrential fans and fluvial to deltaic systems. The amount of clastic input greatly affected reef growth and coral morphologies. Three different types of stratal geometries were delineated in the reef complex: sigmoids, bioherms, and patches and carpets. The reef frameworks are mainly constructed by a poorly diversified assemblage of corals composed of poritids, faviids, and mussids. Porites is the principal reef builder of the sigmoids and carpets where it is widely distributed. Tarbellastraea is common in bioherms and Acanthrastraea appears generally associated with Porites in patches. Five basic growth forms of Porites are observed: thin branching or “finger-shaped”, thick branching to columnar, domed to hemispheric, encrusting, and platy to dish. Differences in coral morphology are used to define a relative water depth zonation in monogeneric reefs. The distribution of these growth forms was principally controlled by water depth. The reef flat is dominated by small thin branching or finger-shaped corals that are replaced towards the reef front by domed to hemispheric corals commonly encrusted by coralline algae. Downslope, columnar morphologies grade into thin branching shapes. The reef morphologies are variable throughout the five mixed siliciclastic/carbonate units at the platform scale. The first and oldest unit is dominated by bioclasts, whereas units 2, 3, and 5 are Porites-dominated, sigmoid complexes. Unit 4 is a well-developed biohermal complex mainly composed of Tarbellastraea. These units started to develop as early as middle Tortonian and stopped as late as early Messinian, and show a progradational trend, where the two latest units are well developed. Thus, carbonate production changed from grain-producing biota in the basal unit to framework-producing biota in the overlying units, consistent with evolution from a distally steepened ramp to a reef-rimmed shelf. At the scale of individual reef units, the relative water depth zonation of the corals is controlled by ecological changes (substrate, nutrients, synecologic relations, and diversification of coral species). In the transects across the carbonate platform related to the different units, the coral zonation records changes in spatial distribution of corals in response to ecological stresses and changes in regional and global environments (tectonic, relative sea-level changes, and runoff).

Paleoecological constraints on reef-coral morphologies in the Tortonian–early Messinian of the Lorca Basin, SE Spain

Coral reefs represent one of the main carbonate factories that contributed to the control of the stratigraphic architecture of carbonate platforms, which had a widespread development during the late Miocene in the paleo-Mediterranean area. The late Miocene reef complexes of the Lorca Basin in southeastern Spain are composed of five mixed siliciclastic/carbonate units, middle Tortonian to early Messinian in age. The development of coral reefs probably ceased when the first evaporitic event occurred in the basin centre in the early Messinian. This study mainly focuses on the response of reef communities and the modifications of reef organisation to global and regional parameters. At the platform scale, the carbonates are intermixed with terrigenous deposits related to two main types of clastic systems: torrential fans and fluvial to deltaic systems. The amount of clastic input greatly affected reef growth and coral morphologies. Three different types of stratal geometries were delineated in the reef complex: sigmoids, bioherms, and patches and carpets. The reef frameworks are mainly constructed by a poorly diversified assemblage of corals composed of poritids, faviids, and mussids. Porites is the principal reef builder of the sigmoids and carpets where it is widely distributed. Tarbellastraea is common in bioherms and Acanthrastraea appears generally associated with Porites in patches. Five basic growth forms of Porites are observed: thin branching or “finger-shaped”, thick branching to columnar, domed to hemispheric, encrusting, and platy to dish. Differences in coral morphology are used to define a relative water depth zonation in monogeneric reefs. The distribution of these growth forms was principally controlled by water depth. The reef flat is dominated by small thin branching or finger-shaped corals that are replaced towards the reef front by domed to hemispheric corals commonly encrusted by coralline algae. Downslope, columnar morphologies grade into thin branching shapes. The reef morphologies are variable throughout the five mixed siliciclastic/carbonate units at the platform scale. The first and oldest unit is dominated by bioclasts, whereas units 2, 3, and 5 are Porites-dominated, sigmoid complexes. Unit 4 is a well-developed biohermal complex mainly composed of Tarbellastraea. These units started to develop as early as middle Tortonian and stopped as late as early Messinian, and show a progradational trend, where the two latest units are well developed. Thus, carbonate production changed from grain-producing biota in the basal unit to framework-producing biota in the overlying units, consistent with evolution from a distally steepened ramp to a reef-rimmed shelf. At the scale of individual reef units, the relative water depth zonation of the corals is controlled by ecological changes (substrate, nutrients, synecologic relations, and diversification of coral species). In the transects across the carbonate platform related to the different units, the coral zonation records changes in spatial distribution of corals in response to ecological stresses and changes in regional and global environments (tectonic, relative sea-level changes, and runoff).

Rock fragments from mud volcanic deposits of the Gulf of Cadiz: an insight into the Eocene–Pliocene sedimentary succession of the basin

Two hundred clasts from the mud breccia extruded by the Yuma mud volcano in the Gulf of Cadiz are used to establish an offshore stratigraphy. The clasts are a very complex mixture of material from the sedimentary successions through which the mud volcano erupted and provide important information about the composition and genesis of deep-seated strata. We deal with fragments of rocks that were deposited millions of years ago, subsequently buried and later erupted on to the seafloor. Rock fragments from the mud breccia, studied in thin section under a polarizing microscope, provide genetic indications suggestive of deep-sea conditions during the accumulation of strata. A reconstruction of the sedimentary succession through which the Yuma mud volcano erupted and the depositional evolution of the Gulf of Cadiz was made on the basis of lithology and age determinations of the rock. Age and depositional environment documented by the clasts indicate that a marine basin existed in the Gulf of Cadiz area at least from the Eocene, and that in the Early and Middle Eocene a deep-sea fan depositional environment prevailed in the region, resulting in the accumulation of thick turbidites. The Late Eocene and Oligocene are not represented among rock fragments from the mud breccia, suggesting regional uplift and non-deposition in the area. Sedimentation was re-established in the Miocene with the accumulation of a clayey Aquitanian–Burdigalian succession. Pelagic carbonate sedimentation became predominant in the Langhian time. The Serravallian–Early Tortonian is characterized by a high supply of terrigenous material, resulting in the deposition of turbiditic clays and sands. Shallow water sedimentation with accumulation of carbonate rocks prevailed in the basin during the Middle Tortonian.

The Miocene tectono‐sedimentary evolution of the southern Tyrrhenian Sea: stratigraphy, structural and palaeomagnetic data from the on‐shore Amantea basin (Calabrian Arc, Italy)

AbstractWe report on new stratigraphic, palaeomagnetic and anisotropy of magnetic susceptibility (AMS) results from the Amantea basin, located on‐shore along the Tyrrhenian coast of the Calabrian Arc (Italy). The Miocene Amantea Basin formed on the top of a brittlely extended upper plate, separated from a blueschist lower plate by a low‐angle top‐to‐the‐west extensional detachment fault. The stratigraphic architecture of the basin is mainly controlled by the geometry of the detachment fault and is organized in several depositional sequences, separated by major unconformities. The first sequence (DS1) directly overlaps the basement units, and is constituted by Serravallian coarse‐grained conglomerates and sandstones. The upper boundary of this sequence is a major angular unconformity locally marked by a thick palaeosol (type 1 sequence boundary). The second depositional sequence DS2 (middle Tortonian‐early Messinian) is mainly formed by conglomerates, passing upwards to calcarenites, sandstones, claystones and diatomites. Finally, Messinian limestones and evaporites form the third depositional sequence (DS3). Our new biostratigraphic data on the Neogene deposits of the Amantea basin indicate a hiatus of 3 Ma separating sequences DS1 and DS2.The structural architecture of the basin is characterized by faulted homoclines, generally westward dipping, dissected by eastward dipping normal faults. Strike‐slip faults are also present along the margins of the intrabasinal structural highs. Several episodes of syn‐depositional tectonic activity are marked by well‐exposed progressive unconformities, folds and capped normal faults. Three main stages of extensional tectonics affected the area during Neogene‐Quaternary times: (1) Serravallian low‐angle normal faulting; (2) middle Tortonian high‐angle syn‐sedimentary normal faulting; (3) Messinian‐Quaternary high‐angle normal faulting.Extensional tectonics controlled the exhumation of high‐P/low‐T metamorphic rocks and later the foundering of the Amantea basin, with a constant WNW‐ESE stretching direction (present‐day coordinates), defined by means of structural analyses and by AMS data. Palaeomagnetic analyses performed mainly on the claystone deposits of DS1 show a post‐Serravallian clockwise rotation of the Amantea basin.The data presented in this paper constrain better the overall timing, structure and kinematics of the early stages of extensional tectonics of the southern Tyrrhenian Sea. In particular, extensional basins in the southern Tyrrhenian Sea opened during Serravallian and evolved during late Miocene. These data confirm that, at that time, the Amantea basin represented the conjugate extensional margin of the Sardinian border, and that it later drifted south‐eastward and rotated clockwise as a part of the Calabria‐Peloritani terrane.

Age, distribution and composition of Miocene diatom bearing sediments in the Guadalquivir Basin, Spain

The biostratigraphy and lithological composition of diatomaceous marls have been defined in 93 outcrops of the Guadalquivir Basin. They are included in different lithological formations affected by diachronous tectonic events. The diatom assemblages are dominated by the following upwelling and oceanic species: Thalassionema nitzschioides, Thalassiothrix longissima, Crucidenticula nicobarica, Crucidenticula punctata, Denticulopsis hustedtii and several taxa from Coscinodiscus and Thalassiosira genera. Benthic diatoms are scarce. Three diatom sedimentation episodes have been defined. The Lower Episode includes the Cestodiscus peplum and Coscinodiscus lewisianus Zones and is assigned to the middle Langhian-early Serravallian. After a period of no diatom occurrence (the Coscinodiscus gigas var. diorama Zone is missing), the Middle Episode is defined by the Craspedodiscus coscinodiscus and the Actinocyclus moronensis Zones and covers the late Serravallian-early Tortonian. The Upper Episode corresponds to the Thalassiosira yabei Zone and is assigned to the middle Tortonian. The diatomaceous marls are comprised of opal A (10–85%) (mainly diatoms), calcite (5–80%) (principally foraminifers and nannoplakton), clay minerals (5–40%) and terrigenous quartz (<15%). The proportions of dilutants in diatomaceous sediments (biogenic calcareous, terrigenous and clay minerals), vary among the three episodes, reflecting their genesis and paleogeographic context. The beds containing the highest amounts of biogenic silica (opal A) and the lowest of biogenic calcite, located in the Middle and Upper Episodes, are the diatomaceous sediments formed under the most vigorous upwelling. The Upper Episode, where the clay and terrigenous dilutants predominate over calcareous dilutants, is interpreted as having been formed in an environment closer to the shore than the other episodes. The narrowing of the North Betic Strait from the Langhian to the Tortonian could have given rise to the progressive intensification of the upwelling.