Uppermost Miocene Research Articles

Architecture and evolution of shelf‐margin clinoforms developed in a back‐arc tectonic setting: Insights from quantitative analysis on the south‐west shelf margin of the Ulleung Basin

AbstractGeophysical and geological research in the Ulleung Basin has been ongoing since the 1970s, involving continuous seismic acquisition and multiple well‐drilling projects. This study utilized an integrated quantitative approach with conventional seismic interpretation based on recent trends to understand the history of the shelf‐margin development and individual controls that may have influenced each period in the Ulleung Basin. Quantitative analysis was conducted by measuring the progradation (Pse), aggradation (Ase) and sediment influx (Fc) of individual shelf margins in seven dip‐oriented seismic profiles, and calculating the shelf‐edge gradient (αse) and the P/A ratio. Based on these data and the ratio of accommodation to sediment supply (A/S ratio), which was interpreted from the stratal stacking pattern, five shelf‐edge trajectory types were defined and assigned to each shelf margin. By considering individual controls (eustatic fluctuations, sediment supply and tectonic events), we defined the three evolution intervals of the Ulleung Basin during the Middle Miocene to Late Miocene (15 to 6.5 Ma): (1) the upper Middle Miocene (15 to 11.63 Ma) characterized by a moderate sediment supply and high aggradation margin induced by rapid subsidence, (2) the lower Upper Miocene (10.8 to 10 Ma) as a high sediment supply and low aggradation margin associated with reworked sediments from the uplifted Dolgorae Thrust and (3) the uppermost Miocene (9.2 to 6.5 Ma) characterized by a low sediment supply and low aggradation margin experiencing sediment starvation. A comparison with worldwide continental margins indicated that the Ulleung Basin formed under a relatively low rate of progradation (low sediment supply; 4.79 km/Myr) and a high rate of aggradation (high shelf accommodation; 361.04 m/Myr) condition. The SW margin of the Ulleung Basin provides a unique example of understanding stratigraphic architecture variations under changing stress regimes of back‐arc setting (extensional to compressional) and understanding of individual controls that influence margin development.

Northeastward expansion of the Tibetan Plateau: Topographic evidence from the North Qinling Mts.–Weihe Graben Coupling system, Central China

Mountain-Basin Coupling systems form during late stages of the collisional orogeny when mountains rise compared to the adjacent sedimentary basins. In this study, we focus on the spatial and temporal pattern of uplift, subsidence and related topographic features of the transtensional Weihe Graben–North Qinling Mountain Coupling system, at the northeastern extension of the Tibetan Plateau. The opening of the Weihe Graben and the ongoing high seismicity in the Weihe Graben result from the lateral extrusion of the Qinling Block away from the Tibetan Plateau. We quantify the influence of uplift gradients on topography and drainage divides by (a) carrying out field surveys, (b) conducting a digital elevation model-based analysis of topographic properties, and (c) compiling and integrating data on exhumation, uplift, subsidence, and denudation of numerous previous studies. Together, these morphological analyses show that the influence of the uplift of the Tibetan Plateau on the study area gradually decreases from the westernmost Taibai Mts. to the easternmost Huashan Mts. We found large χ gradients across the drainage divide of the Huashan Mts. and river piracy implying a southward migration of the drainage divide in the Huashan Mts. We conclude that the initial exhumation of the North Qinling Mts. occurred during the Lower Eocene to Oligocene (cycle 1). As peneplanation surfaces formed, this implies discontinuous exhumation and surface uplift. A second stage of uplift occurred in the Oligocene to Middle Miocene (cycle 2), followed by the third stage from Middle to Upper Miocene (cycle 3). The final period of uplift occurred from latest Miocene to Holocene times (cycle 4). The uppermost Miocene to Holocene geomorphological features imply surface uplift within the westernmost North Qinling Mts. and are controlled by the inflation of a mid-crustal magma layer, prograding from the eastern Tibetan Plateau towards the Taibai Mts., associated with lateral extrusion of the Qinling Block away from the rising Tibetan Plateau. The high seismicity of the Weihe Graben implies ongoing tectonic activity influenced by deep-seated lithospheric motion.

Petrology of Bengal Fan turbidites (IODP Expeditions 353 and 354): provenance versus diagenetic control

ABSTRACT High-resolution petrographic and heavy-mineral analyses of Bengal Fan turbidites from six cores drilled during IODP Expeditions 353 and 354 elucidate factors controlling their intersample compositional variability as a key to understanding sedimentary processes and erosional evolution of the Himalayan belt since the Miocene. Bengal Fan turbidites are feldspatho-quartzose to litho-feldspatho-quartzose with plagioclase > K-feldspar; slow-settling micas increase in abundance in very fine sand and coarse silt. The feldspar/quartz ratio and higher-rank metamorphic rock fragments notably increase from uppermost Miocene to Pleistocene deposits, which is ascribed to the onset of rapid exhumation of the Eastern Himalayan syntaxis since ∼ 5 Ma. The same trends are documented in Nicobar Fan turbidites, confirming that they belong to the same sedimentary system. Both Bengal and Nicobar fans record a pulse in mass accumulation rate at Tortonian times, when supply of sedimentary and very-low-grade metasedimentary detritus reflected accelerated exhumation of the Lesser Himalaya. In contrast to foreland-basin sediments, where ferromagnesian minerals have been completely dissolved in strata as young as Pliocene–Pleistocene, in both Bengal–Nicobar and Indus fans amphibole invariably represents about half of the moderately rich to rich transparent-heavy-mineral suite, demonstrating that amphibolite-facies Greater Himalaya metamorphic rocks were widely exposed in the Himalayan range well before the late Miocene and possibly since the late Oligocene, as indicated by a few sillimanite and kyanite grains in Bengal Fan sediments as old as 23 Ma and 28 Ma, respectively. Diagenetic dissolution strongly affected olivine and pyroxene in strata older than the middle and early Pleistocene, respectively, whereas amphibole decreases markedly through progressively older Miocene strata. Ferromagnesian minerals and sillimanite are almost completely dissolved in lower Miocene strata, where durable zircon, tourmaline, rutile, and apatite make up half of the strongly depleted heavy-mineral assemblage. Quaternary turbidites from the six studied cores have virtually the same compositional signatures, testifying to efficient homogenization by turbidite transport and reworking across the fan. Turbidites in western cores closer to peninsular India (U1444A and U1454B) are not different from those in eastern cores, indicating very minor supply from the subcontinent. Forward-mixing calculations based on integrated petrographic and heavy-mineral data indicate that sand supply from the Brahmaputra River to Quaternary turbidites was four times larger than supply from the Ganga River, indicating up to six times higher sediment yields and erosion rates in the Brahmaputra than in the Ganga catchment, largely reflecting superfast erosion of the Eastern Himalayan syntaxis.

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Corrigendum

Evolution of organic matter quantity and quality in a warm, hypersaline, alkaline lake: The example of the Miocene Nördlinger Ries impact crater, Germany

The Nördlinger Ries (NR) impact crater in southern Germany contains Miocene lacustrine fine-grained post-impact sediments, which were deposited under saline, alkaline, and hydrologically closed aquatic conditions. To obtain information on the organic matter quantity, quality and environmental evolution, samples from one central (NR 1973) and one more marginal (Enkingen SUBO-18) well were analyzed by pyrolytic, organic geochemical and micro-petrographic techniques. Deposits of the marginal drilling can be linked to the thicker stratigraphic units of the well from the lake center based on total organic carbon (TOC), hydrogen index (HI) and lithology. Central deposits contain mainly hydrogen-rich type I kerogen with a mean HI of 447 mg HC/g TOC, whereas the marginal sequence contains type II-III kerogen with an average HI of 206 mg HC/g TOC. In the center, high total sulfur (TS) over TOC ratios of 1.5 on average, and δ13C values of biomarkers in combination with low α-/total MTTC (α-/total methyl-trimethyltridecyl chromans ∼ <0.6) and Pr/Ph ratios <0.2 suggest the prevalence of hypersaline water. Salinity only decreased during deposition of the uppermost Miocene units, when the then shallow alkaline lake turned, at least temporarily, into acidic-neutral conditions during the time of peat deposition. A similar trend, but at overall lower salinities is recorded for the marginal site. Water stratification in the center is stronger than in the marginal domain based on salinity variation. Anoxic bottom water prevailed in the whole lake, as recorded by exceptionally low Pr/Ph ratios (∼<0.2), the occurrence of des-A-lupane and small pyrite framboids (<5 µm) except for the youngest layers of the Miocene lake. Autochthonous, halophilic red algae/plankton prevailed as reflected by abundant C27steranes, while terrestrial material and aerobic bacteria significantly contributed to the OM only in the latest stages of lake as evident from abundant vitrinite/inertinite particles, high values of diterpenes/C27sterane (up to 255) as well as low values of C27-29regular steranes/C29-32hopanes (<0.5). The same trend, but less well resolved, can be seen at the margin of the paleo-lake.

Latest Miocene ostracods from the Bookpurnong Formation in the Murray Basin of southeastern Australia: shallow marine migrants into an epicontinental sea

The uppermost Miocene Bookpurnong Formation within the Murray Basin of southeastern Australia overlies a regionally extensive subaerial unconformity formed by relatively low late Miocene eustatic sea levels, and the initial phase of the Kosciuszko Uplift tectonic event. A diverse marine fossil ostracod fauna has been recovered from the Bookpurnong Formation, and is associated with a marine transgression that flooded inland regions of southeastern Australia to form a shallow epicontinental sea. Many of the Bookpurnong Formation ostracods represent immigrant taxa, with species such as Puriana lubbockiana, evidencing a subtropical range expansion of thermophilic warm water forms into southern mid-latitudes. We attribute this to warm plumes from the East Australian Current, which would have impacted southeastern Australia at that time. In general, the Bookpurnong Formation ostracod assemblages indicate low to moderate energy shallow offshore palaeoenvironments subject to warm-temperate and subtropical conditions. One new genus and five new species are described: Fortistriginglymus gen. nov., Bradyleberis praecristatella sp. nov., Callistocythere bookpurnongensis sp. nov., Callistocythere mchenryi sp. nov., Callistocythere zigzaga sp. nov., and Parakeijia notoreticularis sp. nov.

Structural and chemical variability and provenance of lacustrine organic matter in the Miocene Nördlinger Ries post-impact sediments

The Nördlinger Ries in southern Germany contains a sequence of Miocene post-impact lacustrine sediments. To gain knowledge on the chemical composition and provenance of the organic matter (OM) through the up to 250 m thick sediment profiles, pyrolytic, organic geochemical and infrared spectroscopy measurements were performed on both sediments and concentrated OM. Type I kerogen prevails through the examined samples with high atomic H/C ratios (1.6 on average), hydrogen index (HI mostly >600 mg HC/g TOC), and spectral A- and C-factor values (mostly >0.8), but low oxygen index values (OI mostly <25 mg CO2/g TOC) for the concentrated OM. Exceptions occur in the uppermost Miocene sediments at the central site (Nördlingen-1973) and some marginal (SUBO-18) sediments containing hydrogen-lean type III kerogen having low H/C ratios (<1), HI (<300 mg HC/g TOC), spectral A- and C-factor values (<0.6), but high OI values (>40 mg CO2/g TOC). Mineral matrix effects induced by abundant clay minerals and zeolites significantly reduce the HI of bulk sediments as compared to concentrated OM. Organic sulfur-rich kerogen occurs in the basal units in the NR-1973 and occasionally in the SUBO-18 boreholes with high atomic Sorg/Corg ratios >0.04 and pyrolytic thiophenes/toluene ratio > 13. Abundant pyrolytic alkanes/alkenes, high spectral A-factor and CH2/CH3 values suggest prominent algal input to the OM for most of the samples. The aliphatic chain length of the kerogen decreases and the branching degree increases from the older, deeper to the younger, shallower deposits. While oxygen-bearing organic constituents are common, nitrogen-bearing moieties are rare. A general structural model is established for the type I sulfur-rich, Miocene kerogen of the Nördlinger Ries paleo-lake.

Tectonostratigraphic record of late Miocene–early Pliocene transtensional faulting in the Eastern California shear zone, southwestern USA

AbstractThe Eastern California shear zone (ECSZ; southwestern USA) accommodates ~20%–25% of Pacific–North America relative plate motion east of the San Andreas fault, yet little is known about its early tectonic evolution. This paper presents a detailed stratigraphic and structural analysis of the uppermost Miocene to lower Pliocene Bouse Formation in the southern Blythe Basin, lower Colorado River valley, where gently dipping and faulted strata provide a record of deformation in the paleo-ECSZ. In the western Trigo Mountains, splaying strands of the Lost Trigo fault zone include a west-dipping normal fault that cuts the Bouse Formation and a steeply NE-dipping oblique dextral-normal fault where an anomalously thick (~140 m) section of Bouse Formation siliciclastic deposits filled a local fault-controlled depocenter. Systematic basinward thickening and stratal wedge geometries in the western Trigo and southeastern Palo Verde Mountains, on opposite sides of the Colorado River valley, record basinward tilting during deposition of the Bouse Formation. We conclude that the southern Blythe Basin formed as a broad transtensional sag basin in a diffuse releasing stepover between the dextral Laguna fault system in the south and the Cibola and Big Maria fault zones in the north. A palinspastic reconstruction at 5 Ma shows that the southern Blythe Basin was part of a diffuse regional network of linked right-stepping dextral, normal, and oblique-slip faults related to Pacific–North America plate boundary dextral shear. Diffuse transtensional strain linked northward to the Stateline fault system, eastern Garlock fault, and Walker Lane, and southward to the Gulf of California shear zone, which initiated ca. 7–9 Ma, implying a similar age of inception for the paleo-ECSZ.

Os carcharhiniformes (cCondrichthyes, Neoselachii) da Bacia de Alvalade (Portugal)

The uppermost Miocene, Esbarrondadoiro Formation (Alvalade basin, Portugal) yielded more than 10 thousandSelachian teeth at Santa Margarida, Esbarrondadoiro and Vale de Zebro outcrops. Forty-five taxa were identifiedbelonging to the orders Hexanchiformes, Squaliformes, Lamniformes, Carcharhiniformes, Torpediniformes and Myliobatiformes. The Carcharhiniformes make up about 40% of the selachian fauna that has been identified in the studiedarea. The different distribution of the Carcharhiniformes (as well as that of the other orders) by the three sitespoints out to distinct environments in the corresponding areas: Esbarrondadoiro indicates relatively deeper, ratherstill waters; Santa Margarida represents a very littoral area and rough waters; while Vale de Zebro was a (probablyinner) part of a gulf with muddy bottoms. At the Alvalade Basin localities there are several “temperate” elements that still are present in Portuguese waters. However the high frequence of Carcharhinus, a genus that is scarce at present off Portugal, indicates waters somewhatwarmer than today’s but less warm than during Tortonian times. This is corroborated by the large number of Dasyatisspecies and the rarity of Raja. We may conclude that moderately warm (less warm than during Tortonian, but warmerthan today’s) waters predominated in the Alvalade Basin close by the end of Miocene. The scarcity of pelagic forms and especially of the larger pelagic predators points out to a quite narrow gulf and not to an open Atlantic front. The faunal differences between the Tortonian near Lisbon and the Messinian of the Alvalade Basin also indicate a rather confined gulf.

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The whole collection of Suidae from Kanapoi is revised in the context of the systematics and evolution of Nyanzachoerus in the Pliocene of Eastern Africa. It contains only two species, Nyanzachoerus kanamensis and Notochoerus jaegeri. The size and morphology of their premolars overlap, but not those of their m3s. No transitional form between them is known in Kenya, but some populations from Uganda and Ethiopia display intermediate characters, suggesting that No. jaegeri could be descended from a kanamensis-like ancestor. However, the cranial remains of No. jaegeri from Kanapoi are insufficient to formally establish the affinities of the species. On the basis of the dentition, Notochoerus euilus could be descended from No. jaegeri. The noticeable absence of Kolpochoerus at Kanapoi (and in the whole Turkana Basin at that time) remains unexplained. The presence of a species with affinity to Nyanzachoerus tulotos at Ekora raises the possibility that uppermost Miocene sediments occur there.

Shark fossil diversity (Squalomorphii, Squatinomorphii, and Galeomorphii) from the Langhian of Brielas (Lower Tagus Basin, Portugal)

The fossiliferous marine Miocene sediments of the Lower Tagus Basin (Portugal) present a great diversity of Chondrichthyes forms. The current study focuses on the fossil sharks from the Langhian Vc unit of the Brielas section, located in the Setúbal Peninsula. A total of 384 isolated fossil teeth were analysed and ascribed to 17 species from the Orders Hexanchiformes, Squaliformes, Squatiniformes, Lamniformes, and Carcharhiniformes.Centrophorus granulosusandIago angustidensare described for the first time in Portuguese sediments, whereasPachyscyllium dachiardiiandRhizoprionodon ficheurirepresent only their second reported occurrence.Galeorhinus goncalvesiwas already known from the Portuguese uppermost Miocene (Alvalade Basin), but it is now recognized in older sediments. Furthermore, the new material seems to include the first reported occurrence ofHexanchuscf.agassiziin Miocene sediments. As a whole, these new findings support the previous palaeoenvironment characterization of a warm infralittoral setting gradually deepening to a circalittoral one, where seasonal upwelling phenomena could have occurred.

Paleoenvironmental implications of molecular and carbon isotopic distributions of n-alkanes in the hominoid-bearing upper Miocene sediments from the Zhaotong Basin, southwestern China

It is crucial to understand the relationship between hominoid primates and their living environment. Located at the southeastern margin of the Tibetan Plateau, the Shuitangba (STB) outcrop from the Zhaotong Basin is famous for bearing the remains of the youngest known ape fossil in the terminal Miocene (~6.2 Ma). In this study, the molecular and carbon isotope compositions of n-alkanes, together with the loss on ignition and the bulk carbon isotope composition of total organic matter, were investigated in the STB outcrop to infer the paleoenvironmental conditions in this uppermost Miocene sedimentary sequence, with the emphasis on the habitat of the STB hominoid. In the hominoid-bearing peaty clay layer and the surrounding lignite layers, the n-alkane molecular and carbon isotope compositions support a primary contribution from terrestrial higher plants. In contrast, n-alkanes in the upper shallow lake sediments are derived from multiple origins, mainly from aquatic plants and bacteria. Both carbon preference index (CPI) and average chain length (ACL) vary closely with the lithology, but the CPI record shows the larger amplitude of change than the ACL and varies sharply during the lithological boundary. It is notable that the changes of the molecular and carbon isotope compositions of long-chain n-alkanes do not parallel with the abrupt increase of Poaceae pollen percentage during the STB hominoid appearing stage. Such an inconsistency between herb pollen percentage and n-alkane ratios may result from the different sources. Our results clearly support that these organic matter-based ratios have the potential to record the paleoenvironmental changes in ancient lacustrine sediments.

Castor-like postcranial adaptation in an uppermost Miocene beaver from the Staniantsi Basin (NW Bulgaria)

The Staniantsi-Mazgoš Basin is one of several Neogene intramontane basins in NW Bulgaria. Recent fieldwork in the open pit coal mine yielded material of an exceptional diversity of vertebrates from the uppermost Miocene. In particular, skeletal remains of a large Castorinae are very numerous and well-preserved. Here we perform a comparative morphological description of the postcranium of the Staniantsi-beaver and compare it with the extant Castor fiber and closely related fossil taxa, noting an overall high degree of similarity in many cases. Analyses of the functional anatomy confirm similar locomotor adaptations of the large Staniantsi-beaver and the extant Castor fiber. It is shown that the hindlimb exhibits typical adaptations for swimming and the forelimb is modified for a primary fossorial movement. Further, the caudal vertebrae indicate a flattened tail. Minor osteological differences can be used in a future clarification of the taxonomic status of this fossil castorine. In conclusion, the large Staniantsi-beaver seems to be equivalent to the extant Castor fiber and several fossil castorids in his locomotor adaptations and fits perfectly into the assumed swampy to lacustrine palaeoenvironment of the Staniantsi-Mazgoš Basin. Our results highlight the importance of the postcranium for reconstructing the palaeobiology and elucidating the taxonomy of fossil rodents.

Biochronology, paleoenvironments, and stratigraphic sequences of the late Albian–middle Eocene fore-arc Vizcaino basin, western Baja California, Mexico

The Vizcaino fore-arc basin accumulated approximately 4 km (∼13,000 ft) of upper Albian–middle Eocene siliciclastic marine sedimentary rocks derived from the Peninsular Ranges in Baja California. Data from eight exploratory wells document the micropaleontological content and lithological characteristics of these rocks. The strata studied represent mostly neritic–upper bathyal marine environments and overlie a basement composed of Cretaceous granitic rocks, or Aptian–Albian volcaniclastic sedimentary rocks correlative with the Alisitos Formation. We recognize four major depositional sequences within the basin that are related to the regional geology. The basal Albian–Turonian sequence 1 represents the initiation of fore-arc basin sedimentation, contains continental conglomerates that change to bathyal shales, and correlates with the lower part of the Valle Group of the Vizcaino Peninsula. Sequence 2 is Coniacian–Paleocene, includes basal conglomeratic sandstones grading into Maastrichtian bathyal shales, and usually overlies a Coniacian–Santonian unconformity. Sequence 2 is represented at the surface by the Rosario Group in northwestern Baja California and the upper part of the Valle Group in the Vizcaino Peninsula. Sequence 3 is Paleocene–middle Eocene, represents continuity of fore-arc sedimentation in neritic–upper bathyal conditions, is capped by a major unconformity, and correlates with the Sepultura and Bateque Formations to the north and south of the basin, respectively. The uppermost Miocene–Pliocene sequence 4 is composed of marine sandstone–siltstone unconformably overlying sequence 3 and is correlative with the Tortugas Formation that represents sedimentation after the end of subduction of the Farallon plate beneath the North America plate.

Some Reports of Paratethyan Ostracods from the Central Mediterranean Area

Uppermost Miocene stratigraphic sections have been sampled in Sicily and eastern Tunisia. Some of the stratigraphic levels contained in them are related to the continentalization phase (“Lago Mare”) of the Mediterranean Basin, which occurred at the end of the Messinian Salinity Crisis. Within these levels, ostracod associations reflecting fresh or brackish water environments are reported here for the first time. Species considered to be Paratethyan in affinity lived in these environments. The discovery, both in Sicily and Tunisia, of species such as C agrigentina, A propinqua, and M. punctate, suggests that the Sicilian Channel did not prevent the migration of the non-marine fauna from NW to SE in the Paleomediterranean area during the Post Evaporitic Phase

NEOTECTONIC BASIN EVOLUTION IN CENTRAL-EASTERN MAINLAND GREECE: AN OVERVIEW

The neotectonic evolution of central-eastern mainland Greece (Sterea Hellas) is documented in the result of local extensional tectonics within a regional transtensional field, which is related to the westward propagation of the North Anatolian Fault. The observed tectonic structures within the neotectonic basins and their margins (range-bounding faults and fault zones, rotation of tectonic blocL·) suggest a close relation to the Parnassos Detachment Fault (PDF), which is a reused alpine thrust surface. Lokris basin (LB) occupied a central position in this neotectonic configuration, having received its first sediments in the Uppermost Miocene and subsequently been greatly affected by tectonic episodes, which continue until nowadays. LB is considered to have been separated from the present-day North Gulf of Evia not earlier than the Lower Pleistocene. Voiotihos Kifissos Basin, on the other hand, is tightly related to the activation of PDF, occupying the position of a frontal basin and having developed along the main detachment front.

Facies and Sequence Stratigraphy Analyses of Klasaman Formation in the “X Well”, Northern Salawati Basin, Papua, Indonesia

The “X Well” is located in the Salawati Basin which is part of Western Papua. The interval of study is the Klasaman Formation that is characterized by thick sediment intercalated sandstones and shales. The movement of Sorong Fault strongly controlled the sedimentation of this formation. This study is very important to give a contribution for developing exploration prospect by predicting reservoir distribution since localized facies change may mark the distribution of sandstones. The current study aims: 1) to define the age of Klasaman Formation; 2) to define the vertical facies; 3) to define the sequence stratigraphy; and 4) to predict the lateral change of facies. Five nannofossil datum planes are found throughout the interval and cover the age Late Miocene to Early Pliocene. LO Sphenolithus abies points the age 3.65 Ma, LO Reticulofenestra pseudoumbilicus points the age 3.79 Ma, FO Pseudoemiliania lacunosa points the age 4 Ma, LO Discoaster quinqueramus and LO Discoaster berrgrenii point the age 5.59 Ma and Top of small Reticulofenestra Interval points the age 7.167 Ma. They define the NN11 up to NN16 Martini’s zonation. The age of Klasaman Formation is known as the uppermost Late Miocene to the Early Pliocene. Four facies can be identified, namely Upper Shoreface, Lower Shoreface, Offshore Transition and Offshore. The upper shoreface facies is characterized by thick and clean sandstones, about 2.41 - 20.64 meters thick, while the lower shoreface facies consists of predominantly very fine to fine-grained sandstones intercalated by siltstones and claystones. The offshore transition facies is marked by thick claystones and siltstones intercalated with thin sandstones, whilst the offshore facies is marked by thick laminated claystones. Nine Parasequences 4th order can be identified within study interval, namely Progradational Parasequence-1 to 2, Retrogradational Parasequence-3, Progradational Parasequence-4 to 6, Retrogradational Parasequence-7 to 9. They are bounded by Sequence Boundary-1 to 8. The upper shoreface sandstones of Parasequence-4 to 9 can be potential reservoir rocks in the Klasaman Formation since the sandstones are very thick and clean. The sediments of Klasaman Formation have been sourced from elevated highland in the northeast area, so the upper shoreface sandstones have changed become the offshore claystones from northeast to southwest. High sedimentation rate and rapid subsidence of the basin mark the deposition of Klasaman Formation especially during the deposition of Parasequence-6 to 9 as a result of Sorong Fault tectonics.

A Scansorial Passerine Bird (Passeriformes, Certhioidea) from the Uppermost Lower Miocene of Eastern Siberia

A new scansorial passerine bird, Kischinskinia scandens gen. et sp. nov., from the uppermost Lower Miocene of the Tagay locality (Olkhon Island, Lake Baikal) is described based on a distal tarsometatarsal fragment. This is the first Asian member of the clade Certhioidea. A tibiotarsal fragment is also tentatively assigned to this taxon. Both bones display adaptations for climbing on a vertical surface. The find of a scansorial passerine bird of the clade Certhioidea is evidence of ecological similarity of Early Miocene avifaunas of southern Eastern Siberia and Western Europe, since a representative of Certhioidea showing a similar level of specialization was described from the Lower Miocene (MN3) of Germany. In addition, Kischinskinia scandens is the earliest reliable member of oscine passerines (Oscines) from Asia.

Suidae from Kanapoi

The whole collection of Suidae from Kanapoi is revised in the context of the systematics and evolution of Nyanzachoerus in the Pliocene of Eastern Africa. It contains only two species, Nyanzachoerus kanamensis and Notochoerus jaegeri. The size and morphology of their premolars overlap, but not those of their m3s. No transitional form between them is known in Kenya, but some populations from Uganda and Ethiopia display intermediate characters, suggesting that No. jaegeri could be descended from a kanamensis-like ancestor. However, the cranial remains of No. jaegeri from Kanapoi are insufficient to formally establish the affinities of the species. On the basis of the dentition, Notochoerus euilus could be descended from No. jaegeri. The noticeable absence of Kolpochoerus at Kanapoi (and in the whole Turkana Basin at that time) remains unexplained. The presence of a species with affinity to Nyanzachoerus tulotos at Ekora raises the possibility that uppermost Miocene sediments occur there.

Geology and paleontology of Tresjuncos (Cuenca, Spain), a new diatomaceous deposit with Konservat-Lagerstätte characteristics from the European late Miocene

Purpose A new Iberian Konservat-Lagersta¨tte discovered in Tresjuncos (Cuenca, Spain) is described and interpreted based on geological and paleontological information. Methods The samples were studied using conventional mineralogical (powder X-ray diffraction), petrographic (optical and scanning electron microscopy) and geochemical (X-ray energy-dispersive spectrometry) techniques. Results Based upon geological context, stratigraphy, lithology, sedimentology and origin of the rocks, we describe and interpret the new fossil site as originated in a lacustrine environment. The micromammals found in the Tresjuncos 1 outcrop suggest that the main site is Turolian in age (uppermost Miocene), continental chronological unit MN13. The fossils are preserved in laminates comprising rhythmic, millimeterscale alternations of diatomites and calcareous diatomites. An analysis of the lake paleobiota includes amphibians, crustaceans, insects, plants, and diatoms. The diatoms are dominated by Cyclotella iris. The whole assemblage is indicative of a planktic community developed in somewhat alkaline waters. An extremely well preserved premetamorphic Pelobates (Pelobatidae) tadpole was discovered; it is remarkable because of its gigantic size. Its digestive tract predominantly contains the rare diatom Navicula halionata var directa, likely associated with the shore vegetation in which it presumably lived and fed. The arthropods form a typical lacustrine aquatic assemblage, lacking fish. This assemblage is made up of small filtering crustaceans and of both predator and nonpredator insects of diverse sizes. Conclusions The available evidence on Tresjuncos shows the extraordinary potential for paleontological information that can be expected from this new Konservat-Lagersta¨tte, which constitutes a significant finding that improves our understanding of continental late Miocene Mediterranean environments.