Structure and tectonic evolution of the Pirin-Pangaion Structural Zone (Rhodope Massif,southern Bulgaria and northern Greece)

The Pirin-Pangaion Structural Zone occupies the south-western part of the Rhodope Massif. It consists of Proterozoic amphibolite facies metamorphic rocks of the Rhodopian Supergroup, and granitoids of Hercynian, Late Cretaceous and Palaeogene age. The pre-Hercynian structure of the zone is dominated by an interference pattern of three superimposed fold generations of NE-SW and NW-SE trends. These structures are cut by Hercynian granitoids, and the entire complex is affected by late Hercynian or early Alpine conical folds. The zone was overthrusted by the Ogražden and Kroussia Units (Serbo-Macedonian ‘Massif’) along the north-east vergent Mid-Cretaceous Strimon overthrust, and by the Central Rhodope Zone of the Rhodope Massif, along the south-west vergent Meso-Rhodopean Overthrust. With this thrusting event, the Pirin-Pangaion Structural Zone was brought together with the Serbo-Macedonian ‘Massif’ and the Central Rhodope Zone to form the Late Cretaceous Morava-Rhodope Zone, which acted as a ‘plateau’ along the southern edge of the Eurasian plate. Late Cretaceous granitoid magma of crustal origin intruded this zone, whereas north of it the Srednogorie volcanic island arc was the site of igneous activity with magmas originating in the upper mantle. The West Thrace Zone developed as a Palaeocene to Oligocene depression superimposed over the older basement obliquely to the southern periphery of the Rhodope Massif. In the Late Eocene and Early Oligocene, this depression represented a volcanic island arc with mantle-derived basic to intermediate magmas; contemporaneous granitoid magmas formed through crustal melting in the thickened crust of the Rhodope Massif (Pirin and Pangaion Units included). Early Miocene thrusting was most intense in the Pangaion Unit, and was followed by Late Miocene to Quaternary extension.     

ANALYSIS OF FOLDS SOUTH OF MALAKAND AND ADJOINING AREAS, NORTH PAKISTAN

ANALYSIS OF FOLDS SOUTH OF MALAKAND AND ADJOINING AREAS, NORTH PAKISTAN1　Can啨ｒｏｔＪ,QuG .CuadernosdeGeologiaiberica ,1998,2 4:311～ 331. 2　DebelmasJ,MascleG .EnsSciencesdelaTerre[M ].Masson ,ed .1991.2 99.3　GaetaniM ,GarzantiE .AAPGBull ,1991,75 (9) :142 7～ 144 6 . 4　HendrixMS ,GrahamSA ,CarrollAR ,etal.GeolSocAmBull,1992 ,10 4:5 3～ 79.. 5　Jia ,Coll.PetroleumIndustryPress,Beijing .1997,2 95 . 6　JiaD ,LuHCaiD ,etal.AAPGBull ,8…     

The Monte Orfano Conglomerate revisited: stratigraphic constraints on Cenozoic tectonic uplift of the Southern Alps (Lombardy, northern Italy)

The Monte Orfano Conglomerate (MOC), exposed in the foothills of the Southern Alps (northern Italy), is one of the few outcrops of sediments documenting the Cenozoic tectonic evolution of the Alpine retrowedge. Calcareous nannofossil biostratigraphy allowed us to constrain the upper part of the MOC, formerly attributed to the Early-Middle Miocene in the type-locality, to the earliest Miocene (Neogene part of the NN1 nannofossil zone). A likely latest Oligocene age is therefore suggested for the bulk of the underlying conglomerates, whose base is not exposed. Deposition of the MOC can be placed within the post-collisional tectonic uplift of the Alps, documented in the Lake Como area by the Como Conglomerate (CC) at the base of the Gonfolite Lombarda Group, and supports the correlation with Upper Oligocene clastic sediments cropping out further to the East, in the Lake Garda and in the Veneto-Friuli areas (“molassa”). The remarkable difference in petrographic composition between the western (CC) and eastern (MOC) clastics deposited in the Alpine retro-foreland basin highlights the synchronous tectonic activity of two structural domains involving different crustal levels. Whilst the bulk of the CC, that straddles the Oligocene/Miocene boundary, records largely the tectonic exhumation of the Alpine axial chain crystalline complexes, the coeval MOC consists of detritus derived from the superficial crustal section (Triassic to Paleogene sedimentary rocks) of the Alpine retrowedge and constrains the onset of the post-collisional deformation phase of the Southern Alps as not younger than the Late Oligocene.     

南沙东北部海域礼乐盆地含油气组合静态地质要素分析

针对礼乐盆地含油气组合静态地质要素的分析表明，盆地内主要发育中生界、古新统一中始新统和下渐新统3套烃源岩，并以中、下两套源岩生烃潜力最好；砂岩、碳酸盐岩和生物礁是盆地的主要储层类型，砂岩储层在中、新生界内广泛发育，而碳酸盐岩和生物礁储层则主要发育于上渐新统一第四系；盆地总体上缺少广泛发育、封盖性能良好的区域性盖层，但局部性盖层发育，且封闭性能良好。盆地主要存在3套含油气组合：中生界含油气组合，这是盆地内较有远景的一套含油气组合；古近系含油气组合，这是盆地最主要的勘探目的层系；新近系含油气组合，该套组合在盆地中部隆起难以形成良好的油气组合关系，而在盆地坳陷区，尤其是南部坳陷则可形成良好的油气组合关系。     

U-Pb zircon geochronology of rocks from west Central Sulawesi,Indonesia: Extension-related metamorphism and magmatism during the early stages of mountain building

Sulawesi has generally been interpreted as the product of convergence in the Cretaceous and Cenozoic, and high mountains in west Central Sulawesi have been considered the product of magmatism and metamorphism related to Neogene collision. New SHRIMP and LA-ICP-MS U-Pb zircon dating of metamorphic and granitoid rocks has identified protoliths and sources of melts, and indicates an important role for extension. Schists, gneisses and granitoids have inherited Proterozoic, Paleozoic, Mesozoic and Paleogene zircons. Mesoproterozoic and Triassic age populations are similar to those from the Bird’s Head region. Their protoliths included sediments and granitoids interpreted as part of an Australian-origin block. We suggest this rifted from the Australian margin of Gondwana in the Jurassic and accreted to Sundaland to form NW Sulawesi in the Late Cretaceous. Some metamorphic rocks have Cretaceous and/or Late Eocene magmatic zircons indicating metamorphism cannot be older than Late Eocene, and were not Australian-origin basement. Instead, they were metamorphosed in the Neogene after Sula Spur collision and subsequent major extension. Associated magmatism in west Central Sulawesi produced a K-rich shoshonitic (HK) suite in the Middle Miocene to Early Pliocene. A later episode of magmatism in the Late Miocene to Pliocene formed mainly shoshonitic to high-K calc-alkaline (CAK) rocks. I-type and silica-rich I-type granitoids and diorites of the CAK suite record a widespread short interval of magmatism between 8.5 and 4 Ma. Inherited zircon ages indicate the I-type CAK rocks were the product of partial melting of the HK suite. S-type CAK magmatism between c. 5 and 2.5 Ma and zircon rim ages from gneisses record contemporaneous metamorphism that accompanied extension. Despite its position in a convergent setting in Indonesia, NW Sulawesi illustrates the importance of melting and metamorphism in an extensional setting during the early stages of mountain building.     

TECTONICS OF THE JUNCTION ZONE BETWEEN THE CENTRAL PAMIRS TROUGH AND NORTH PAMIRS UPLIFT

The Central Pamirs trough, trending E - W, lies between the North Pamir uplift and the Pamir- Hindukush uplift. The North Pamir uplift Was a positive Area during the Mesozoic, while continuous deposition took place in the trough. Within the trough the structures are Alpine. The North Pamir uplift is divisible into three zones. Adjacent to the trough and separated from it by a major northdipping thrust is a zone of highly contorted Ordovician strata. To the north, the central zone, also bounded by thrusts, has gently folded Paleozoic strata in the west, passing eastward into complex structures where the zone is narrowest. The Paleozoics of the northernmost zone lie in broad open folds, thrust southward over the central zone and northward over Permian volcanics and sediments. The northern part of the Central Pamirs trough is an area of broad open folds in Mesozoic and Paleozoic sediments, bounded on the north by a belt of generally north-dipping thrust slices of Paleozoic rocks, paralleling the fold trends. Thrust synclines have been thrust both northward and southward over the intervening anticlines, in some cases with superposition of younger beds over older. The structures described can only be the result' of tangential compression. They do not support the current (Russian) theory that the tectonics Of the area are due to gravitational movement of rock masses from uplifts to troughs. -- P. B. Jones.     

Paleobotanical study of a section of the Oligocene–Lower Miocene Maikop Group along the Belaya River above the city of Maikop,Ciscaucasia

A stratotypical section of the Oligocene–Lower Miocene Maikop Group in the valley of the Belaya River above the city of Maikop was studied using a complex paleobotanical method. The hydrological regime of marine basin was specified, especially for the second half of the Early Oligocene, when the basin was brackish. Its desalination began prior to accumulation of the ostracod layers and continued until the beginning of the Late Oligocene. It was once interrupted by short-term ingression of seawater into the Paratethys in the Early Morozkina Balka time. The Karadzhalga and Septarian formations were formed at the end of the Oligocene and in the Early Miocene under frequent oscillations of climate and hydrological regime with accumulation of sediments within the Laba delta front. The complexes of plant microfossils, along with dominant recent marine organic-walled freshwater phytoplankton, contain algae, spores, pollen, and a huge amount of redeposited palynomorphs. They originated from areas of erosion and included Paleogene, Mesozoic, and, locally, Paleozoic taxa.     

帕米尔高原沙克达拉穹窿变质作用及新生代下地壳演化

帕米尔高原从西到东展布的8个新生代变质穹窿构成帕米尔高原变质地壳的主体,沙克达拉穹窿是其中最大的一个。沙克达拉穹窿变质杂岩中石榴矽线石片麻岩峰期组合(Grt+Ky+Bi+Rt+Pl+Qz)变质作用温压条件为T约810 ℃/P约10 kbar, 石榴石单斜辉石基性麻粒岩峰期组合(Grt+Cpx+Rt+Pl+Qz)变质作用温压条件为T约824 ℃/P约16.3 kbar, 榴闪岩退变较强,其残留峰期组合(Grt+Pl+Hbl+ilm+Qz)变质作用温压条件为T约683 ℃～873 ℃/P约8.6～11.7 kbar。基性麻粒岩变质锆石的U-Pb年龄为19～35 Ma,反映了从晚始新世到早中新世帕米尔高原下地壳加热加厚过程。帕米尔穹窿的变质作用可以与高喜马拉雅结晶岩系类比,在新生代印度亚洲大陆碰撞过程中,帕米尔陆内各地体沿前新生代缝合带的陆内俯冲可能是帕米尔下地壳加厚的主要动因。     

CENOZOIC BASIN EVOLUTION, STRUCTURAL STYLES OF THE QAIDAM AND AN ESTIMATE OF DENUDATION IN ADJACENT MOUNTAIN SYSTEMS, NORTHEAST QINGHAI—TIBETAN PLATEAU

CENOZOIC BASIN EVOLUTION, STRUCTURAL STYLES OF THE QAIDAM AND AN ESTIMATE OF DENUDATION IN ADJACENT MOUNTAIN SYSTEMS, NORTHEAST QINGHAI—TIBETAN PLATEAU     

Tertiary evolution of the central Menderes Massif based on structural investigations of metamorphics and sedimentary cover rocks between Salihli and Kiraz (western Turkey)

Augen gneisses, mica schists, and marbles of the Menderes Massif and its sedimentary cover rocks are exposed south of the Gediz graben. The augen gneisses form the structurally lowest part of the studied lithological sequence, and are overlain by a schist complex. The structurally highest part is formed by a series of marbles. The ages of this lithological sequence range from Precambrian to Early Paleocene. Furthermore, this sequence records the tectonic evolution since the Precambrian. The sedimentary cover of the Menderes Massif consists of two groups of sediments from Early Miocene to Quaternary. The lower group, the Alayehir group, consists of Early- to mid-Miocene-aged fluvial and limnic sediments which form the lower and the upper parts, respectively. The Alayehir group is overlain by mainly fluvial sediments of the Gediz group. Both the Alayehir and the Gediz groups are separated by an angular unconformity. Six deformational phases could be distinguished within the metamorphic rocks of the Menderes Massif and its Tertiary cover. The structures which were interpreted to belong to deformational events predating the Paleocene are summarized as deformational phase D1. D1 structures were nearly completely overprinted by the subsequent deformation events. The second deformational phase D2 occurred between Early Eocene and Early Oligocene. D2 occurred contemporaneously with a Barrovian-type regional metamorphism. The third deformational phase D3 is characterized by folding of the axial planes which formed at the end of Early Oligocene. The deformational event D4 occurred during the Late Oligocene and is related to an extensional period. The deposition of the sedimentary rocks which belong to the Tertiary cover of the Menderes Massif that started in the Early Miocene was interrupted by a compressional phase (D5) during the Late Miocene. Sediments which were deposited since the Early Pliocene record structures which were related to a young extensional phase (D6). This extensional phase has continued to the Present.