Abstract The Nishikubiki Mountains, which are located on the northwestern margin of the northern Fossa Magna region, central Japan, and the area offshore to the north of the mountains are underlain by folded and faulted Neogene and Quaternary sequences. The folds are composed of open, symmetric anticlines or tight, asymmetric anticlines trending north 20–70° east. On the basis of the geometry of the anticlines and growth strata, the symmetric and asymmetric anticlines are interpreted as fault-bend folds and fault-propagation folds, respectively. The formation of the anticlines is attributed to the growth of an imbricate thrust system composed of three thrust sheets that developed, from southeast to northwest, mainly in the late Pliocene, early Pleistocene, and middle Pleistocene–Holocene. The horizontal component of the northwestern-most sheet was estimated to be approximately 1.2 km on the basis of the width of the growth triangle, and the thickness of the sheet at its southeast margin was estimated to be 8.5 km on the basis of area balancing along one of the seismic profiles. The thrust is inferred to extend to a depth of more than 10 km toward the southwest. The three thrust sheets are probably connected by a detachment zone along the boundary between the upper and lower crusts. The anticlines are bounded by the Itoigawa–Shizuoka Tectonic Line (ISTL) to the west and by lateral ramps or tip lines to the northeast. The ISTL possibly continues northward offshore into the Toyama Trough. The structural model proposed in this paper suggests that similar thrust systems are wide spread in the northern Fossa Magna region and that active deformation zones have migrated and switched during the past 2–3 million years along the fold belt. 相似文献
In Greece, several occurrences of phosphates have been located in Mesozoic and Cenozoic sedimentary rocks. The aim of the present paper is to describe the mineralogy, geochemistry and the origin of the phosphates deposited in marine and lacustrine basins of Neogene age in Greece. Phosphates of marine origin formed in an outer shelf-upper slope environment (Palliki Peninsula, Kefalonia Island) as well as in a hemipelagic environment (Heraklion, Crete Island). In both the deposits, the phosphate minerals belong to the apatite group. In Kefalonia Island, phosphatic material accumulations occur in the field as scattered or accumulated vertebrate bones, fish teeth and other biogenic components, hosted in a sandy limestone of Upper Tortonian age. On a microscopic scale, in the groundmass of the limestone, phosphate minerals are present as fillings and secondarily as replacements of foraminiferal and other calcareous microfossil tests. In Crete Island, burrowed cobbles and phosphatic concretions up to 10 cm in diameter have been detected east of Heraklion town. The phosphatic material is hosted in a sandy marlstone that is interbedded with diatomaceous rocks of Middle Pliocene age. Phosphates of lacustrine origin have been formed in the NW–SE-oriented Upper Miocene basins of Florina–Ptolemais and Elassona–Sarantaporo, located, respectively, in western Macedonia and Thessaly, Greece. The phosphate minerals are mainly represented by Ca/Fe phosphates such as anapaite and mitridatite and secondarily by Ca phosphates of the apatite group that are hosted in a thick succession of clayey diatomite rock. They usually form lenticular layers, asymmetric lenses, nodular and botryoidal aggregates, and faecal pellet replacements.
The major and trace element content of a representative set of rocks was studied. Their geochemistry was found to be controlled by the presence of detrital minerals, the host rock mineralogies, and the types of phosphate minerals present. The relatively high amounts of uranium, arsenic and barium detected in some of the phosphate rocks studied are mainly related with organic matter and are comparable to those detected in other phosphate deposits worldwide.
In the deposits studied, phosphogenesis was mainly promoted by the decay of organic substances derived from diatoms, fishes and other vertebrates, leaves and trunks, and faecal pellets in a highly reducing environment on or just below the sea or lake bottom, and secondarily by the feeding of the basin with phosphate-bearing nutrients that originated in the land. 相似文献
Summary A previously unknown, very large barn owl,Basityto rummeli is described from the early Miocene of Grafenmühle 21 in Bavaria, Germany. This raises the number of tytonine genera known from the early Miocene to three.Necrobyas is known only from France,Prosybris from France and Austria, andBasityto so far only from Germany.Further taxonomic conclusions are as follows:Palaeotyto cadurcensis Mourer-Chauviré,Palaeobyas cracrafti Mourer-Chauviré, andTyto edwardsi (Gaillard) are excluded from the Tytoninae. Six species are synonymized:Necrobyas rossignoli Milne-Edwards withNecrobyas harpax Milne-Edwards,Necrobyas edwardsi Gaillard withNecrobyas arvernensis (Milne-Edwards),Necrobyas minimus Mourer-Chauviré withProsybris antiqua (Milne-Edwards),Tyto campiterrae Jánossy withTyto sanctialbani (Lydekker),Tyto robusta Ballmann withTyto gigantea Ballmann, andTyto melitensis (Lydekker) withTyto alba (Scopoli).Necrobyas medius Mourer-Chauviré was transferred to the genusProsybris. In addition,Strix ignota Milne-Edwards andStrix ignota Paris emerge as not available for nomenclatural purposes.
Eine neue Schleiereule (Aves: Strigidae) aus dem Untermiozän in Deutschland: mit Anmerkungen zur fossilen Geschichte der Tytoninae
Zusammenfassung Eine neue, sehr große Schleiereule,Basityto rummeli, wird aus dem Untermiozän von Grafenmühle 21 in Bayern beschrieben. Damit ist die Anzahl der aus dem Untermiozän bekannten Schleiereulengattungen auf drei gestiegen.Necrobyas ist bisher nur aus Frankreich,Prosybris aus Frankreich und Österreich, undBasityto aus Bayern bekannt. Weitere taxonomische Ergebnisse sind wie folgt:Palaeotyto cadurcensis Mourer-Chauviré,Palaeobyas cracrafti Mourer-Chauviré undTyto edwardsi (Gaillard) wurden aus den Tytoninae entfernt. Sechs Arten wurden synonymisiert:Necrobyas rossignoli Milne-Edwards mitNecrobyas harpax Milne-Edwards,Necrobyas edwardsi Gaillard mitNecrobyas arvernensis (Milne-Edwards),Necrobyas minimus Mourer-Chauviré mitProsybris antiqua (Milne-Edwards),Tyto campiterrae Jánossy mitTyto sanctialbani (Lydekker),Tyto robusta Ballmann mitTyto gigantea Ballmann undTyto melitensis (Lydekker) mitTyto alba (Scopoli).Necrobyas medius Mourer-Chauviré wurde in die GattungProsybris überführt. Die NamenStrix ignota Milne-Edwards undStrix ignota Paris sind für nomenklatorische Zwecke nicht verfügbar.
During the Neogene, the sedimentary succession changed from marine shallow water formations during the Early and Middle Miocene to lagoonal and continental formations during the Late Miocene and the Pliocene. This succession is subdivided into three sedimentary major cycles that are mainly due to compressional tectonic events. Propagating folds above a detachment within the evaporitic Triassic strata caused the formation of the tectonics. To cite this article: M. Chikhaoui, C. R. Geoscience 336 (2004).相似文献
Abstract Shipboard and shore‐based investigation on siliceous and calcareous microfossil biostratigraphy, magneto‐stratigraphy and tephrostratigraphy identified numerous datum events from the sedimentary sequences of Sites 1150 and 1151 drilled on the forearc basin of northern Japan by the Ocean Drilling Program Leg 186. Some 83 datum events were selected to construct new age–depth models for the sites. Based on the reliable magneto‐stratigraphy from the Pleistocene to the Upper Miocene, which were correlated to the standard geomagnetic polarity timescale, and on excellent records of diatom and radiolarian biostratigraphy throughout the sequences, the shipboard age model was revised. Major revisions referred to stratigraphic position of the Miocene–Pliocene boundary that has been shifted more than 200 m downward in each sequence. The age–depth relations of the forearc sites represent drastic changes in the sedimentation rate—extremely high (40 cm/k.y. on average) in the Early Pliocene and low (less than 2 cm/k.y. on average) in the Middle Miocene—and several hiatuses exist throughout the sequence. The drastic changes can be related mostly to changes in diatom sedimentation and the tectonics of the Japanese Island Arc. Local ages for some foraminiferal, calcareous nannofossil and radiolarian bioevents are estimated from the age–depth models at each site. These newly calibrated bioevents and biozones as well as established diatom biostratigraphy are incorporated into the updated magneto‐biochronologic timescale, which will contribute to an improvement in biochronologic accuracy of Neogene sediments in northern Japan and adjacent areas. 相似文献
Chinese Neogene Rhinocerotidae has quite a complete record and its temporal range is the Early Miocene to Late Pliocene. The samples include 25 species in 4 tribes of 2 subfamilies. They are used as a foundation for the study of the evolution of the family and its relation to climatic changes. Taxonomic diversity, new records and extinctions are estimated for each Chinese Neogene mammal faunal unit (NMU). The diversity of Chinese Rhinocerotidae varies noticeably throughout the Neogene and is recognized within five stages: the Middle Miocene and Late Miocene are stages of high diversity and the Early Miocene, early Late Miocene and Pliocene are stages of low diversity. Rhinocerotid diversity and morphology are closely related to environmental factors and particularly sensitive to changes in ambient temperature and humidity. The interpretation of climatic variation reflected in the evolution of Rhinocerotidae corresponds precisely with the conclusions drawn from other workers and provides new evidence fen 相似文献