Middle Miocene Sediments Research Articles

Bryozoan nodules as a frame-builder of bryozoan-microreef, Middle Miocene sediments, Egypt

Bryozoan nodules, coralline algae, scleractinian corals and oysters form an important or- ganic buildup, 1.2-4.5 m thick in the Langhian-Serravaliann sediments of Egypt. Based on type, shape and size of the substrate, bryozoan nodules take tree-like and globular morphologies. Tree-like speci- mens reach 10 cm in maximum height and 3 cm in diameter, while Globular ones attain 9 cm in maxi- mum diameter. Most tree-like nodules are perforated with wide or narrow pores, few are non-perforated. Globulars and few tree-like forms are with mamelon-like structures. Perforations on the outer surfaces may indicate a symbiotic relationship between bryozoans and a live plant substrate. Nod- ules from Homiera and Gharra areas of the Cairo-Suez District with wider perforations may indicate growth in slightly lighter or turbid areas of the continental shelf than those of North Western Desert of narrower perforations. Non-perforated nodules may assume an incrustation on ephemeral substrate.

Geochemical indicators of paleoclimatic changes in the Cenozoic deposits of the Lower Aldan Basin

Major and trace element composition of the Upper Cenozoic deposits of the Chuya section (the lower reaches of the Aldan River, Central Yakutia) made up of the Middle Miocene and Neopleistocene sediments was studied as indicator of paleoclimatic conditions. It was established that primary sediments were precipitated under moderately humid conditions in the Middle Miocene and under subarid climatic conditions at relatively high sedimentation rates in the Neopleistocene. Close contents of trace elements in all lithologies suggest that the source area remained constant. Variation trends of ICV index indicate an increasing role of fluvioglacial accumulation during formation of Pleistocene beds. It was determined that the Neopleistocene is marked by a sharp change in sedimentation conditions.

Fluvial weathering environment of the Middle Miocene sediments based on the paleosols in the Tokiguchi Porcelain Clay Formation in Gifu Prefecture, central Japan

Fluvial weathering environment of the Middle Miocene sediments based on the paleosols in the Tokiguchi Porcelain Clay Formation in Gifu Prefecture, central Japan

The Steinheim Basin impact crater (SW-Germany) – Where are the ejecta?

The ∼24km Nördlinger Ries and the ∼3.8km Steinheim Basin in southern Germany are thought to represent a ∼14.8Ma old impact crater doublet. The complex craters of the Steinheim Basin with its crater fill deposits and the Nördlinger Ries and its voluminous impact ejecta blanket are still widely preserved. Although located in an environmental setting that presumably underwent the same erosional history as the Ries crater, field geologic studies suggest that no proximal or distal ejecta of the Steinheim impact event are presently preserved. Generally, the lack of the ejecta blanket around the crater could be explained either by intense erosion, the scarcity of outcrops, or it never formed. In contrast to the lack of ejecta, fluvial and lacustrine Middle Miocene sediments deposited prior to, synchronous with, and shortly after the impact are preserved in many places in the surroundings of to the Steinheim Basin.On low-density asteroids or planets with highly porous target rocks (⩾30–40% effective porosity), impact structures can form without significant ejecta outside the craters due to the compaction of porosity and a concordant drastic reduction of the ejecta velocity. In the Steinheim area, the target rocks comprised loose, porous Miocene sands, Upper Jurassic limestones and Middle Jurassic porous sand- and claystones. The average porosity of the entire sedimentary target suite may have reached 20–30% or even higher values assuming the existence of open karst cavities in the Upper Jurassic carbonates. Compaction of the porous target rocks, resulting in the reduction of ejected material, in combination with erosion could explain the apparent lack of impact ejecta in the wider periphery of the Steinheim impact structure. The Steinheim Basin represents the first proposed terrestrial example of an impact crater characterized by porosity-related ejecta suppression, and it is suggested that other sediment-hosted impact structures on Earth might exhibit analogous excavation-process characteristics.

Osady paleogenu i neogenu w wielkoskalowych strukturach glacitektonicznych Wzgórz Dylewskich

PALEOGENE AND NEOGENE SEDIMENTS IN MEGA-SCALE GLACIOTECTONIC STRUCTURES OF THE DYLEWSKIE HILLS Abstract. The Wysoka Wieś borehole located in the center of Dylewskie Hills (NE Poland) reached a depth of almost 490 metres, with more than 400 metres of the Paleogene and the Neogene deposits. Palynological studies were designed to determine whether this huge Paleogene and Neogene sedimentary complex is located in situ or it has been glacitectonically redeposited. Forty-seven samples were analysed for all palynological matter components, i.e. palynomorphs (sporomorphs, phytoplankton, zoomorphs), palynoclasts (phytoclasts) and inorganic debris. Among the palynomorphs, 13 assemblages have been distinguished. Describing these assemblages from the bottom to the top of the section, dual or triple repetition of the same palynomorph zones indicates a strong glacitectonic deformation of the sediments. Palynological data evidence several disengagement zones and displacement of rock packages. The lowest sedimentary complex occurs in the primary position and it contains the pollen and phytoplankton assemblage D3–D4 of the Middle Paleocene to the Upper Paleocene (terrestrial facies), and the Lower Eocene assemblage D8. At a depth of ca . 455m there is the first discontinuity zone, along which the over 100-metres thick package of Middle Miocene sediments, containing pollen zones V, VI, VIII, IX and XI, became intruded/ pressed into the Paleogene deposits. The next disengagement zone occurs at a depth of ca . 339 m, where the Miocene sediments are overlain by a about 60-metres thick package of Paleogene deposits dated with the stratigraphically younger pollen and phytoplankton zones D12 of the Upper Eocene and Lower Oligocene (terrestrial facies). These Paleogene deposits were intruded by the Miocene series, a few metres thick, representing pollen zone IX. Then, at a depth of 240 m, occurs the Middle Miocene sedimentary complex, ca . 150m thick, with pollen zones V, VII and IX. The complicated glacitectonic processes caused such mosaic succession, reflecting the slice structure of glaciotectonic thrust moraines. Palynological studies provided unique data to define the glaciotectonic disengagement zones. The absence of Quaternary deposits in the internal moraine structure indicates the Early Pleistocene age of deformation.

Clay Mineralogy and its Paleoclimatic Significance of the Oligocene-Miocene Sediments in the Gerze Basin, Tibet

This study collected the early Oligocene to middle Miocene sediments from the Gerze Basin of Tibet, and used X-Ray diffraction (XRD) and Scanning Electron Microscope (SEM) to discuss their clay mineralolgy, clay indices, better understand the clay mineralogy and its paleoclimatic significance. The results show that clay minerals of the Gerze Basin sediments are mainly composed of illite and chlorite, with minor amounts of smectite and kaolinite, and their relative content varies along the section. Variations of relative contents and clay indices suggest that the Gerze Basin has experienced three-stage evolution of paleoclimate: I) high illite and chlorite contents, with fluctuant smectite and low (I+Ch)/(K+S) ratio, indicative of a dominant seasonal arid climate from the early Oligocene to late Oligocene; II) higher illite and chlorite contents and larger (I+Ch)/(K+S) ratio but absence of kaolinite, indicating a colder and drier climate from the late Oligocene to early Miocene; III) high illite and chlorite contents with fluctuant (I+Ch)/(K+S) ratios and occasional occurrence of kaolinite, suggesting that the climate became warmer and more humid compared with that of stage II in the mid-Miocene. These conclusions were also reinforced by the clay morphology, which suggests that physical weathering dominated in stage II, while relatively strong chemical weathering was dominant in stages I and III. Clay minerals of the sediments mainly consist of illite and chlorite, indicating that the source rock played a significant role in clay origin. It is inferred that global cooling and the enhancement of denudation and obstruction of northward moisture due to the uplift of the Qinghai-Tibet Plateau were responsible for the provenance of illite and chlorite under weak chemical weathering. Though the Qinghai-Tibet Plateau reached a certain elevation by the mid-Miocene, yet the mid-Miocene widespread warming might have largely impacted the Gerze climate.

From biologically to hydrodynamically controlled carbonate production by tectonically induced paleogeographic rearrangement (Middle Miocene, Pannonian Basin)

The Leitha Mountains in Austria are a chain of hills separating the southern Vienna Basin and the Danube Basin. The Lower East Alpine basement of the Leitha Mts. is covered by Middle Miocene sediments of the Badenian and Sarmatian regional stages. Close to the northeastern margin of these hills, upper Badenian successions are exposed, which are part of a coralline algal-dominated carbonate platform with hydrodynamically influenced sediments. Six sections have been logged and subjected to detailed investigation and sampling. They are characterized by inclined beds (foresets), which have been formed by unidirectional transport of sediments. Large-scale asymmetrical ripples indicate strong currents affecting shallow topset deposits. Generally, this hydrodynamically controlled sedimentation, documented by seven facies types, is reflected in a strongly reduced diversity of facies and biota, contrary to the older facies-rich middle Badenian sediments. This change from biologically to hydrodynamically controlled sedimentation led to a reduction in diversity of facies and biota. Sediment transport, however, caused secondary mass occurrences of echinoids or foraminifers derived from seagrass meadows. This study unravels the distribution and differences of middle and upper Badenian deposits of the Leitha Mountains and the influence of tectonic activity. Changes in hydrodynamics on the Leitha Platform are linked to the formation of the Danube Basin starting in the middle Badenian when a new seaway to the southeast has started to form.

Structural complexities in a foreland thrust belt inherited from the shelf-slope transition: Insights from the Alishan area of Taiwan

The Alishan area of Taiwan spans the transition from the platform with full thickness of the Eurasian continental margin in the north to the thinning crust of its slope in the south. This part of the foreland thrust and fold belt includes important along-strike changes in structure, stratigraphy, and seismic velocities. In this paper we present the results of new geological mapping from which we build geological cross sections both across and along the regional structural trend. Fault contour, stratigraphic cutoff, and branch line maps provide 3-D consistency between the cross sections. Minimum shortening is estimated to be ~15 km with displacement overall to the northwest. A P wave velocity model helps constrain the structure at depth by providing insight into the possible rock units that are present there. P wave velocities of ≥ 5.2 km/s point toward the presence of basement rocks in the shallow subsurface throughout much of the southeastern part of the area, forming a basement culmination. The changes in strike of thrusts and fold axial traces, the changing elevation of thrusts and stratigraphic contacts, and the growing importance of Middle Miocene sediments that take place from north to south are interpreted to be associated with a roughly northeast striking lateral structure coincident with the northern flank of this basement culmination. These transverse structures appear to be associated with the inversion of Eocene- and Miocene-age extensional faults along what was the shelf-slope transition in the Early Oligocene, uplifting the margin sediments and their higher P wave velocity basement during Pliocene-Pleistocene thrusting.

Discovery of the most distal Ries tektites found in Lower Silesia, southwestern Poland

AbstractWe report the first occurrence of moldavites in Poland. This discovery confirms the hypothesis that moldavites could have been distributed up to 500 km from the Ries crater in Germany. The tektites were reworked from Middle Miocene sediments and redeposited in Late Miocene (Pannonian) fluvial deposits of the Gozdnicka Formation in Lower Silesia. The Polish moldavites are represented by nine (<8 mm) fragments with a total of 0.471 g. The lack of the autochthonous tektites indicates that tektites investigated here had to be redeposited in a fluvial environment, probably from the Lusatian area. The chemical composition of the Polish moldavites plots in the same area with those from other localities.

On the Middle Miocene avifauna of Maboko Island, Kenya

The Middle Miocene sediments of Maboko Island (Lake Victoria) in western Kenya yielded numerous avian bones, which remained, however, little studied. The significance of this material is shown by the recent identification of an opisthocomiform bird. In the present study, further avian remains from Maboko Island are described. Most of the specimens belong to aquatic or semi-aquatic groups, of which some are closely related to taxa known from Early and Middle Miocene European avifaunas, that is, Nectornis cormorants (N. africanus nov. sp.) and Laricola-like Laromorphae. The fossil material also includes Ciconiidae (cf. Ciconia), Pelecanidae, Phoenicopteridae (Leakeyornis aethiopicus), Musophagidae, and a species of Ardeidae, which closely resembles the taxon Pikaihao from the Early Miocene of New Zealand. Some avian remains from Maboko Island belong to higher-level taxa unknown from the Middle Miocene of Europe. The occurrence of a giant Jacanidae (?Nupharanassa mabokoensis nov. sp.) is of particular interest, because these are globally absent in extant avifaunas and were previously only known from the Late Eocene/Early Oligocene of Egypt. Further unknown from contemporaneous European sites are small representatives of Jacanidae, Bucerotidae, and Alcedinidae, with the fossils of the latter two taxa being among the earliest published records of their respective groups. Several of the taxa that are common in contemporaneous European avifaunas have not been found in Maboko, and in spite of less pronounced climatic differences, Middle Miocene Afrotropical avifaunas already appear to have been distinct from contemporaneous European ones.

An integrated magnetic susceptibility anisotropy (AMS) and structural geological study on Cenozoic clay-rich sediments from the Transdanubian Range

Systematic structural and anisotropy of magnetic susceptibility (AMS) measurements were carried out on Cenozoic clay-rich deposits from the Transdanubian Range, central part of the Alcapa Unit. The aim was to improve the knowledge of the Neogene tectonic evolution of the area and of the connection of the stress field and the magnetic fabric of the sediments. The measurements of AMS revealed dominant foliation with weak lineation for Middle Eocene-Lower Miocene sediments. The directions of AMS lineation are aligned either with the direction of NNE-SSW extension of a strike slip phase (30–19 Ma) or with the direction of NE-SW extension of the main rifting phase of the Pannonian Basin (19–14 Ma).The studied Late Miocene sediments have foliated AMS fabric, maximum and intermediate AMS directions are intermixed, and the AMS fabrics do not show any sign of tectonic deformation. In contrast, joints and faults were observed in the same rocks. Detailed structural analysis shows two extensional phases between ca. 1...

Tetracyclus chankaicus, a new species from Miocene sediments of the Khanka Lake, Primorye, Russia

A new species Tetracyclus chankaicus Dubrovina, Usoltseva, Pushkar & Likhacheva is described from Middle Miocene sediments of the Novokachalinskaya formation on the western coast of Khanka Lake in Primorye, Russian Far East. This species differs from T. clypeus (Ehrenberg) Li by the irregular stria density on the valve face, the absence of secondary ribs at the poles, different girdle band structure and the number of rimoportulae.

The Miocene coastal vegetation of southwestern India and its climatic significance

The late early to middle Miocene sediments at Varkala cliff section (SW India) offer a great potential to study paleoenvironmental and paleoclimatic conditions. The succession consists of coastal marine sands alternating with fine grained, organic-rich siliciclastics. Based on several palyno-samples, a mangrove flora could be reconstructed, composed of Rhizophoraceae, Avicennia, Xylocarpus, and Sonneratia. These grew in front of backswamps, followed by evergreen forests in hinterland with many rainforest elements.Despite these similarities between the Miocene and the modern vegetation, differences can be documented, e.g., the abundance of Nypa and the absence of gymnosperm in the Miocene vegetation. Based on the Coexistence Approach, a temperature is reconstructed, which is similar to today's (mean annual temperature 22.2–27.5°C; coldest month temperature 20.6–23.6°C; warmest month temperature 27.5–28.1°C). However, in comparison to today, significantly lower values for the mean annual precipitation are reconstructed (1748–1958mm), although a seasonality pattern was established (wettest month mean precipitation 225–358mm; driest month mean precipitation 18–83mm).Comparison with other localities along the west coast of southern India hints at a similar vegetation and climate throughout the early and middle Miocene. Furthermore, the same results were obtained for SE India. This is in contrast to the strong west-east gradient in rainfall caused by the Indian Monsoon nowadays. Therefore, the paleovegetation of the early and middle Miocene of southern India appears to be more uniform than today. This outlines the complexity of describing the paleoclimatic evolution in the tropics based on plant fossils, but emphasizes the need for further study of this area to understand the early history of the Indian Monsoon.

SYSTEMATIC TAXONOMY OF EARLY-MIDDLE MIOCENE PLANKTONIC FORAMINIFERA FROM THE EQUATORIAL PACIFIC OCEAN: INTEGRATED OCEAN DRILLING PROGRAM, SITE U1338

Integrated Ocean Drilling Program Expedition 320/321 at Site U1338 (equatorial Pacific Ocean) recovered lower–middle Miocene (17–13.5 Myr) sediments containing unusually well-preserved and diverse planktonic foraminifera. Previous taxonomic study of planktonic foraminifera from this interval in the eastern Pacific Ocean has been hindered by the absence of biogenic carbonate. Here we present a taxonomic analysis of these foraminifera, including wall textures and species variability, supported by scanning electron micrographs. Specimens exhibit open pore spaces, little evidence of calcitic overgrowth on the wall surface, and in many cases spines. Fifty-five species are recorded, including Dentoglobigerina juxtabinaiensis n. sp. Dominant genera include Paragloborotalia and Globigerinoides with common Dentoglobigerina .

The first fossil Microsoroid fern (Palaeosorum ellipticum gen. et sp. nov.) from the middle Miocene of Yunnan, SW China

AbstractThe microsoroid ferns make up a large group in the family Polypodiaceae, easily characterized by the combination of at least partly clathrate rhizome scales and anastomosing reticulate venation. The diversification of this clade is poorly known, both because of unresolved generic delimitations and the lack of fossil records. In this work, we describe the first microsoroid macrofossil: Palaeosorum ellipticum sp. nov. F. M. B. Jacques & Z. K. Zhou. The fossil specimen, represented by part and counterpart, was found in the middle Miocene sediment of the Dajie Formation in Ailsohan, central Yunnan, southwest China. Epiphytic ferns belonging to Drynaria are found in different locations in Yunnan during the Pliocene. The fossil described in this study deepens the occurrence of epiphytic ferns in Yunnan back to the middle Miocene. It demonstrates that forests with complex ecological relationships have existed in southwest China for more than 10 million years.

한반도 남동부 경주시 양북면 마이오세 입천소분지의 형성과 발달사

입천소분지는 기반암과 단층으로 경계되며 북동 방향으로 길쭉한 형태의 비대칭 지구의 기하를 가지는 분지로 인근 와읍과 어일분지와는 기반암에 의해 격리되어 있는 독립된 소규모 마이오세 분지이다. 분지충전물의 층리는 대부분 북서 내지 서북서 방향으로 경사지며, 분지 북동부에는 데사이트질 화산물질을 다량 포함하는 전기 마이오세 퇴적물이 그리고 남서부에는 사암을 협재하는 비화산성 중기 마이오세 육성 역암이 분포한다. 또한 분지충전물 내 퇴적동시기 공액상 정단층들은 분지가 서북서-동남동 방향으로 확장하였음을 지시한다. 이러한 특징들은 인근 와읍 및 어일분지와 것들과 매우 유사한 것으로, 분지의 확장이 북서부 경계단층에 의해 주도되었으며 분지의 열개가 북서에서 남동으로 전파되었음을 지시한다. 한편, 입천소분지 내에는 어일분지에서 흔히 나타나는 현무암질 화산물질이 관찰되지 않는다. 슬랩과 경하관찰 결과, 입천소 분지의 데사이트질 응회암과 응회질 이암은 와읍분지의 용동리응회암과 매우 유사한 특징을 보인다. 중기 마이오세의 비화산성 퇴적층은 와읍과 어일분지 그리고 입천소분지에 공통적으로 분지의 남서부에 분포한다. 따라서 입천소분지의 확장은 22 Ma 경 와읍분지의 확장과 함께 시작되어 다량의 데사이트질 화산물질이 유입되었으며, 이후 어일분지의 주 확장시기인 20~18 Ma 사이에는 확장을 멈추었다가, 약 17 Ma에 이르러 연일 구조선의 운동과 함께 분지의 열개가 남서쪽으로 전파되면서 중기 마이오세 초의 연일층군에 해당하는 비화산성 역암이 분지의 남서부에 퇴적된 것으로 결론지어진다. The Ipcheon Subbasin is an isolated Miocene basin in SE Korea, which has the geometry of an asymmetric graben elongated in the NE-SW direction. It is in contact with basement rocks by faults and separated from adjacent Waup and Eoil basins by the basement. The strata of the basin fills have an overall homoclinal structure, dipping toward NW or WNW. The basin fills consist of Early Miocene sediments rich in dacitic volcanic and volcaniclastic deposits and Middle Miocene non-volcanic and nonmarine conglomerates intercalated with sand layers, which are distributed in the northeastern and southwestern parts of the basin, respectively. Kinematic analysis of syndepositional conjugate faults in the basin fills indicates WNW-ESE extension of the basin. These features are very similar to those of the adjacent Waup and Eoil basins, indicating that the basin extension was governed by the NE-trending northwestern border faults and that the basin experienced a propagating rifting from NE to SW. Basaltic materials, which occur abundantly in the Eoil Basin, are totally absent in the Ipcheon Subbasin. The observations of the dacitic tuff and tuffaceous mudstone in the subbasin, on slabs and under microscope, suggest that they have lithologies very similar to those of the Yondongri Tuff in the Waup Basin. The Middle Miocene non-volcanic sediments of the Waup and Eoil basins and the Ipcheon Subbasin are distributed consistently in the southwestern part of each basin. It is thus concluded that the extension of the Ipcheon Subbasin began at about 22 Ma together with the Waup Basin and was lulled during the main extension period of the Eoil Basin between 20-18 Ma. At about 17 Ma, the subbasin was re-extended due to the activation of the Yeonil Tectonic Line associated with the propagating rifting toward SW. This event is interpreted to have provided new sedimentation space for the Middle Miocene sediments in the southwestern parts of the Waup and Eoil basins and the Ipcheon Subbasin as well.

Foraminifera as environmental proxies of the Middle Miocene (Early Badenian) sediments of the Central Depression (Central Paratethys, Moravian part of the Carpathian Foredeep)

Foraminifera as environmental proxies of the Middle Miocene (Early Badenian) sediments of the Central Depression (Central Paratethys, Moravian part of the Carpathian Foredeep)

Paleoenvironmental reconstruction of the Early to Middle Miocene Central Paratethys using stable isotopes from bryozoan skeletons

Stable carbon and oxygen isotope values from single bryozoan colonies were used to reconstruct the paleoenvironments of the Early to Middle Miocene (Ottnangian to Badenian) sediments of the Central Paratethys. This approach utilizes a locally abundant allochem while avoiding matrix and multiple allochem contamination from bulk rock samples. Bryozoan colonies (and a few foraminifera and rock matrix samples) from 14 localities yielded 399 carbon and oxygen isotope values. Data from six of the localities (15 % of the total number of samples) were interpreted as having been diagenetically altered and were rejected. The remaining data indicate a primarily localized upwelling signal with lesser variation caused by global climatic and regional tectonic forcing of sea level, salinity, and temperature. Paleotemperatures were calculated to range from 12 to 21 °C. Despite potential taxonomic and diagenetic problems, bryozoan colonies are a powerful, underutilized source of paleoenvironmental carbon and oxygen isotope data.

The Antiquity of the Rhine River: Stratigraphic Coverage of the Dinotheriensande (Eppelsheim Formation) of the Mainz Basin (Germany)

BackgroundMammalian fossils from the Eppelsheim Formation (Dinotheriensande) have been a benchmark for Neogene vertebrate palaeontology since 200 years. Worldwide famous sites like Eppelsheim serve as key localities for biochronologic, palaeobiologic, environmental, and mammal community studies. So far the formation is considered to be of early Late Miocene age (∼9.5 Ma, Vallesian), representing the oldest sediments of the Rhine River. The stratigraphic unity of the formation and of its fossil content was disputed at times, but persists unresolved.Principal FindingsHere we investigate a new fossil sample from Sprendlingen, composed by over 300 mammalian specimens and silicified wood. The mammals comprise entirely Middle Miocene species, like cervids Dicrocerus elegans, Paradicrocerus elegantulus, and deinotheres Deinotherium bavaricum and D. levius. A stratigraphic evaluation of Miocene Central European deer and deinothere species proof the stratigraphic inhomogenity of the sample, and suggest late Middle Miocene (∼12.5 Ma) reworking of early Middle Miocene (∼15 Ma) sediments. This results agree with taxonomic and palaeoclimatic analysis of plant fossils from above and within the mammalian assemblage. Based on the new fossil sample and published data three biochronologic levels within the Dinotheriensand fauna can be differentiated, corresponding to early Middle Miocene (late Orleanian to early Astaracian), late Middle Miocene (late Astaracian), and early Late Miocene (Vallesian) ages.Conclusions/SignificanceThis study documents complex faunal mixing of classical Dinotheriensand fauna, covering at least six million years, during a time of low subsidence in the Mainz Basin and shifts back the origination of the Rhine River by some five million years. Our results have severe implications for biostratigraphy and palaeobiology of the Middle to Late Miocene. They suggest that turnover events may be obliterated and challenge the proposed ‘supersaturated’ biodiversity, caused by Middle Miocene superstites, of Vallesian ecosystems in Central Europe.

Palaeoflora and Climate of Lignite-bearing Lower−Middle Miocene Sediments in the Seyitömer and Tunçbilek Sub-basins, Kütahya Province, Northwest Turkey

Lower-Middle Miocene successions from Kütahya province (Seyitömer and Tunçbilek sub-basins) were analyzed to reconstruct the palaeoclimate and vegetation of the period. A rich coniferous forest formed the dominant components among sporomorphs and consisted mainly of undeterminable Pinaceae, Pinus haploxylon type, Pinus diploxylon type, Picea, Cedrus, Cathaya, Keteleeria and Podocarpus. Pollen data also indicate the presence of some fern taxa (Osmunda, Polypodiaceae, Schizeaceae) Selaginella and Lycopodium. Cupressaceae frequently occur in all samples from both sub-basins, and form part of the mixed forest assemblage. Two woody plants Castanea-Castanopsis and evergreen Quercus predominate in the assemblages as well. The reconstruction of palaeoclimate is based on the Coexistence Approach (CA) method and documents subtropical climate with cyclic variation in the sediment sequence. The vegetation does not show a clear change through the sequences studied. Small changes in the quantity of pollen taxa (e.g., thermophilous and arctotertiary) indicate small-scale cyclic temperature and precipitation oscillations during the deposition of the sediments. Using CA, seven palaeoclimate parameters were estimated. Quantitative palaeoclimate data indicate mean annual temperatures of 17-18°C, with winter temperatures of 8-10°C and summer temperatures of 27-28°C. Mean annual precipitation exceeded 1200 mm. The driest month precipitation was between 20 and 25 mm, the wettest month precipitation most frequently ranged between 200 and 250 mm and the summer precipitation was 100-150 mm. These values imply that the Kütahya area was warm and received more precipitation during the Early-Middle Miocene than in modern times.