Tectono-sedimentary evolution of the External Liguride units (Northern Apennines,Italy): insights in the pre-collisional history of a fossil ocean-continent transition zone

In the Northern Apennines, the External Liguride (EL) units are interpreted as derived from the domain that joined the Ligure–Piemontese oceanic basin to the Adriatic plate continental margin. The EL units can be divided into two different groups according to the lithostratigraphic features of the basal complexes underlying the Upper Cretaceous–Lower Tertiary carbonate flysch (e.g. Helminthoid flysch). The first group includes the western successions characterized by Santonian–Campanian sedimentary melanges where slide blocks of lherzolitic mantle, gabbros, basalts, granulites, continental granitoids are represented. The second group is represented by the eastern successions where the Cenomanian–Campanian basal complexes mainly consist of sandstones and conglomerates where the mafic and ultramafic rocks are scarce or completely lacking. Their original substrate is represented by the Middle Triassic to Lower Cretaceous, mainly platform carbonate deposits, found as slices at the base of the eastern successions.The stratigraphic features shown by the basal complexes allow the reconstruction of their source area that is assumed to be also representative for the pre-Upper Cretaceous setting. The proposed reconstruction suggests the occurrence in the EL domain of two distinct domains. The eastern domain was characterized by a thinned and faulted continental crust belonging to the Adriatic continental margin. The western domain was instead floored by subcontinental mantle associated with lower and upper continental crust, representing the ocean–continent transition. This setting is interpreted as the result of the opening of the Ligure–Piemontese oceanic basin by passive rifting, mainly developed by simple shear, asymmetric extension of the continental crust.     

Tectono-sedimentary evolution of the External Liguride units (Northern Apennines,Italy): insights in the pre-collisional history of a fossil ocean-continent transition zone

Abstract

In the Northern Apennines, the External Liguride (EL) units are interpreted as derived from the domain that joined the Ligure–Piemontese oceanic basin to the Adriatic plate continental margin. The EL units can be divided into two different groups according to the lithostratigraphic features of the basal complexes underlying the Upper Cretaceous–Lower Tertiary carbonate flysch (e.g. Helminthoid flysch). The first group includes the western successions characterized by Santonian–Campanian sedimentary melanges where slide blocks of lherzolitic mantle, gabbros, basalts, granulites, continental granitoids are represented. The second group is represented by the eastern successions where the Cenomanian–Campanian basal complexes mainly consist of sandstones and conglomerates where the mafic and ultramafic rocks are scarce or completely lacking. Their original substrate is represented by the Middle Triassic to Lower Cretaceous, mainly platform carbonate deposits, found as slices at the base of the eastern successions.

The stratigraphic features shown by the basal complexes allow the reconstruction of their source area that is assumed to be also representative for the pre-Upper Cretaceous setting. The proposed reconstruction suggests the occurrence in the EL domain of two distinct domains. The eastern domain was characterized by a thinned and faulted continental crust belonging to the Adriatic continental margin. The western domain was instead floored by subcontinental mantle associated with lower and upper continental crust, representing the ocean–continent transition. This setting is interpreted as the result of the opening of the Ligure–Piemontese oceanic basin by passive rifting, mainly developed by simple shear, asymmetric extension of the continental crust. © 2001 Éditions scientifiques et médicales Elsevier SAS     

Late Oligocene-Miocene syn-/-late-orogenic successions in Western and Central Mediterranean Chains from the Betic Cordillera to the Southern Apennines*

The identification of syn- and late-orogenic flysch deposits, extending from the Betic Cordillera to the Southern Apennines, assists in the reconstruction of the tectonic-sedimentary evolution of the perimediterranean chains. A microplate was located between the European and African Plates during the Late Jurassic–Early Cretaceous, bordered northwards by the Piemontese Ocean and southwards by another (North Africa ‘Flysch’ Basin or Maghrebian) Ocean. The Piemontese Ocean and the northern margin of the microplate were structured from the Late Cretaceous to the Eocene to create an Eo-alpine Chain. The southern margin of the microplate was deformed in the Aquitanian, when the internal areas of the Maghrebian Ocean were characterized by syn-orogenic flysch deposits. This episode culminated with metamorphism (25–22 Ma) and nappe emplacement, which destroyed the former palaeogeography and created an orogenic belt (AlKaPeCa). Afterwards, a lower Burdigalian late-orogenic cycle started in the deformed area, which as a result of the opening of the Algero-Provençal Basin, caused the fragmentation of the AlKaPeCa, its thrusting on the ‘Flysch’ Basin and the collision with the North Africa and South Iberia Margins. These latter were folded and thrusted, the ‘Flysch’ Units pushed over the External Domain and also back-thrusted. Langhian late-orogenic deposits suture the new tectonic features. Finally, the whole orogen was thrust onto the foredeep during the Middle–Late Miocene.     

The Ligurian Units of Western Tuscany (Northern Apennines): insight on the influence of pre-existing weakness zones during ocean closure

Most of the tectonic units cropping out in Western Tuscany are fragments of the Jurassic oceanic crust, ophiolitic successions, overlaid diachronously by Upper Cretaceous-middle Eocene carbonate and siliciclastic flysch successions with their Cenomanian-lower Eocene shalycalcareous basal complexes. These units, so called Ligurian, have been emplaced during the closure of the Ligurian-Piedmont Ocean. Ophiolite bearing debris flows are common in the flysch basins and their relationship with ophiolitic tectonic slices points to a strong relation between tectonics and sedimentation from the early compressive events of the Late Cretaceous. The tectonic activity reflects in a rough morphology of the ocean floor. It progressively influences the distribution and sedimentology of the turbidites. During middle Eocene this relationship begun very important and a paleogeographic reconstruction with prominent linear ophiolitic reliefs that bounded some turbiditic basins can be done. In our reconstruction the sedimentary and structural evolution can be framed in the context of strain partitioning, developed during the ocean closure, between subduction processes and ancient weakness zones crosscutting both the ocean and the Adria continental margin and reactivated in compressive regime. These weakness zones can be interpreted as transform faults of the Ligurian-Piedmont Ocean with prolongations in the Adria passive margin.

The weakness zones crosscut the oceanic lithosphere and the Adria continental margin and interfered with the subduction processes. The activity of the weakness zones is reflected in the Ligurian Units architecture where two main structural strike trends of thrusts and folds axial planes occur. The first trend is WSW-ENE oriented and it is connected with the reactivation of the weaknesses zones. This first orientation developed progressively from Late Cretaceous to Pliocene, from oceanic to ensialic convergence (D1, D2, and D4 deformation phases). The second trend is NNE-SSW oriented and is related to the late Eocene continental collision and the subsequent translation to the NE of the oceanic units onto the Adria continental margin (D3 deformation phase).     

The Northern Carpathians plate tectonic evolutionary stages and origin of olistoliths and olistostromes

The olistostromes formed in Northern Carpathians during the different stages of the development of flysch basins, from rift trough post-rift, orogenic to postorogenic stage. They are known from the Cretaceous, Paleocene, Eocene, Oligocene and Early Miocene flysch deposits of main tectonic units. Those units are the Skole, Subsilesian, Silesian, Dukla and Magura nappes as well as the Pieniny Klippen Belt suture zone. The oldest olistoliths in the Northern Carpathians represent the Late Jurassic-Early Cretaceous rifting and post-rifting stage of the Northern Carpathians and origin of the proto-Silesian basin. They are known from the Upper Jurassic as well as Upper Jurassic-Lower Cretaceous formations. In the southern part of the Polish Northern Carpathians as well as in the adjacent part of Slovakia, the olistoliths are known in the Cretaceous- Paleocene flysch deposits of the Pieniny Klippen Belt Zlatne Unit and in Magura Nappe marking the second stage of the plate tectonic evolution - an early stage of the development of the accretionary prism. The most spectacular olistostromes have been found in the vicinity of Haligovce village in the Pieniny Klippen Belt and in Jaworki village in the border zone between the Magura Nappe and the Pieniny Klippen Belt. Olistoliths that originated during the second stage of the plate tectonic evolution occur also in the northern part of the Polish Carpathians, in the various Upper Cretaceous-Early Miocene flysch deposits within the Magura, Fore-Magura, Dukla, Silesian and Subsilesian nappes. The Fore-Magura and Silesian ridges were destroyed totally and are only interpreted from olistoliths and exotic pebbles in the Outer Carpathian flysch. Their destruction is related to the advance of the accretionary prism. This prism has obliquely overridden the ridges leading to the origin of the Menilite-Krosno basin.

In the final, postcollisional stage of the Northern Carpathian plate tectonic development, some olistoliths were deposited within the late Early Miocene molasse. These are known mainly from the subsurface sequences reached by numerous bore-holes in the western part of the Polish Carpathians as well as from outcrops in Poland and the Czech Republic.

The largest olistoliths (kilometers in size bodies of shallow-water rocks of Late Jurassic-Early Cretaceous age) are known from the Moravia region. The largest olistoliths in Poland were found in the vicinity of Andrychów and are known as Andrychów Klippen. The olistostromes bear witness to the processes of the destruction of the Northern Carpathian ridges. The ridge basement rocks, their Mesozoic platform cover, Paleogene deposits of the slope as well as older Cretaceous flysch deposits partly folded and thrust within the prism slid northward toward the basin, forming the olistostromes.     

The Ligurian Helminthoid flysch units of the Emilian Apennines: stratigraphic and petrographic features,paleogeographic restoration and structural evolution

Abstract

This work deals with the Cretaceous-Tertiary Helminthoid flysch successions of the Emilian Apennines and related basal complexes (Mt. Caio, Val Baganza, Solignano, Mt. Venere-Monghidoro and Mt. Cassio Units): it is based on an integrated approach which included stratigraphic, petrographic and structural observations. Detailed stratigraphic sections measured in the various successions evidenced the specific features of the different flysch formations. The main framework composition analysis of the arenites pointed out a partly ‘oceanic’ alimentation for the Mt. Caio Flysch Fm; the Mt. Venere-Monghidoro, and Mt. Cassio Flysch Fms have been alimented exclusively by a terrigenous detritus mainly derived from continental basement source areas. The heavy mineral assemblage of the Mt. Caio Flysch Fm is characterized by picotite, that of the Mt. Venere-Monghidoro, Solignano and Mt. Cassio Flysch Fms commonly contains straurolite, garnet and chloritoid, generally considered to be typical products of the Adriatic continental margin. The calcareous nannofossils biostratigraphy indicated that the flysch sedimentation started during the Late Campanian and ended between the Paleocene (Mt. Cassio Flysch Fm and Mt. Venere-Monghidoro Fms) and the Middle Eocene (Mt. Caio Flysch Fm). We propose a schematic paleogeographic restoration for the External Ligurian Domain which implies a more internal position for the Mt. Caio succession and a more external one for the Mt. Venere-Monghidoro and Mt. Cassio successions. The Helminthoid flyschs sedimented after and during deformation and subduction phases in perched and fore-arc basins partly overlying the marginal part of the Adriatic plate. The External Ligurian nappes’ stacking consists, in the study area, from the bottom, of the following units: Caio Unit, Val Baganza Ophiolitic Unit, Monghidoro Unit, Cassio Unit. This pile of thrust-nappes, sealed by the Epiligurian succession, has been already realized before Late Eocene. In our opinion it was generated by a frontal west-verging frontal accretion process (offscraping), which let the flysch successions remain, in this phase, quite undeformed. This westverging thrusting phase, starting from the Middle-Late Eocene, has been followed by an important folding event which generated striking hectometric and kilometric ‘Apenninic’ reverse folds, sometimes associated with NE-verging thrust surfaces. The Oligocene and post-Oligocene evolution is characterized by a block-translation of the Ligurian staking over the Subligurian, Tuscan and Umbrian Domains, associated with a new generation of minor thrusts and thrust related Apenninic folds. © 2000 Éditions scientifiques et médicales Elsevier SAS     

Stages of development in the Polish Carpathian Foredeep basin

In southern Poland, Miocene deposits have been recognised both in the Outer Carpathians and the Carpathian Foredeep (PCF). In the Outer Carpathians, the Early Miocene deposits represent the youngest part of the flysch sequence, while in the Polish Carpathian Foredeep they are developed on the basement platform. The inner foredeep (beneath the Carpathians) is composed of Early to Middle Miocene deposits, while the outer foredeep is filled up with the Middle Miocene (Badenian and Sarmatian) strata, up to 3,000mthick. The Early Miocene strata are mainly terrestrial in origin, whereas the Badenian and Sarmatian strata are marine. The Carpathian Foredeep developed as a peripheral foreland basin related to the moving Carpathian front. The main episodes of intensive subsidence in the PCF correspond to the period of progressive emplacement of the Western Carpathians onto the foreland plate. The important driving force of tectonic subsidence was the emplacement of the nappe load related to subduction roll-back. During that time the loading effect of the thickening of the Carpathian accretionary wedge on the foreland plate increased and was followed by progressive acceleration of total subsidence. The mean rate of the Carpathian overthrusting, and north to north-east migration of the axes of depocentres reached 12 mm/yr at that time. During the Late Badenian-Sarmatian, the rate of advance of the Carpathian accretionary wedge was lower than that of pinch-out migration and, as a result, the basin widened. The Miocene convergence of the Carpathian wedge resulted in the migration of depocentres and onlap of successively younger deposits onto the foreland plate.     

Void-filling deposits in karst terrains of isolated oceanic islands: a case study from Tertiary carbonates of the Cayman Islands

Caves, fossil mouldic cavities, sinkholes and solution-widened joints are common in the Cayman and Pedro Castle members of the Bluff Formation (Oligocene-Miocene) on Grand Cayman and Cayman Brac because they have been subjected to repeated periods of karst development over the last 30 million years. Many voids contain a diverse array of sediments and/or precipitates derived from marine or terrestrial environs, mineral aerosols, and groundwater. Exogenic sediment was transported to the cavities by oceanic storm waves, transgressive seas, runoff following tropical rain storms and/or in groundwater. At least three periods of deposition were responsible for the occlusion of voids in the Cayman and Pedro Castle members. Voids in the Cayman Member were initially filled or partly filled during the Late Oligocene and Early Miocene. This was terminated with the deposition of the Pedro Castle Member in the Middle Miocene. Subsequent exposure led to further karst development and void-filling sedimentation in both the Cayman and Pedro Castle members. Speleothems are notably absent. The void-filling deposits formed during these two periods, which were predominantly marine in origin, were pervasively dolomitized along with the host rock 2–5 million years ago. The third period of void-filling deposition, after dolomitization of the Bluff Formation, produced limestone, various types of breccia, terra rossa, speleothemic calcite and terrestrial oncoids. Most of these deposits formed since the Sangamon highstand 125 000 years ago. Voids in the present day karst are commonly filled or partly filled with unconsolidated sediments. Study of the Bluff Formation of Grand Cayman and Cayman Brac shows that karst terrains on isolated oceanic islands are characterized by complex successions of void-filling deposits that include speleothems and a variety of sediment types. The heterogenetic nature of these void-filling deposits is related to changes in sea level and climatic conditions through time.     

Geology of the northern side of the Gulf of Edremit and its tectonic significance for the development of the Aegean grabens

This paper describes the Neogene evolution of northwestern Anatolia based on geological data collected in the course of a new mapping program. The geological history of the region, as recorded by the Neogene sedimentary and magmatic rocks that overlie the Paleozoic–Triassic basement, began after a lake invasion during the Early Miocene period with the deposition of shale-dominated successions. They were accompanied by calc-alkaline intermediate lavas and pyroclastic rocks ejected through NNE trending fractures and faults. The Lower–Middle Miocene successions were deformed under a compressional regime at the end of the Middle Miocene. The deposition of the overlying Upper Miocene–Lower Pliocene successions was restricted to within NE–SW trending graben basins. The graben bounding faults are oblique with a major strike-slip displacement, formed under approximately the N–S extension. The morphological irregularities formed during the Miocene graben formations were obliterated during a severe erosional phase to the end of the deposition of this lacustrine succession. The present E–W graben system as exemplified from the well-developed Edremit graben, postdates the erosional phase, which has formed during the Plio-Quaternary period.     

Geology of the northern side of the Gulf of Edremit and its tectonic significance for the development of the Aegean grabens

Abstract

This paper describes the Neogene evolution of north-Western Anatolia based on geological data collected in the course of a new mapping program. The geological history of the region, as recorded by the Neogene sedimentary and magmatic rocks that overlie the Paleozoic-Triassic basement, began after a lake invasion during the Early Miocene period with the deposition of shale-dominated successions. They were accompanied by calc-alkaline intermediate lavas and pyroclastic rocks ejected through NNE trending fractures and faults. The Lower-Middle Miocene successions were deformed under a compressional regime at the end of the Middle Miocene. The deposition of the overlying Upper Miocene-Lower Pliocene successions was restricted to within NE-SW trending graben basins. The graben bounding faults are oblique with a major strike-slip displacement, formed under approximately the N-S extension. The morphological irregularities formed during the Miocene graben formations were obliterated during a severe erosional phase to the end of the deposition of this lacustrine succession. The present E–W graben system as exemplified from the well-developed Edremit graben, postdates the erosional phase, which has formed during the Plio-Quaternary period. © 2001 Éditions Scientifiques et médicates Elsevier SAS     

Integrated biostratigraphy and carbon isotope stratigraphy of the Lower Cretaceous (Barremian to Albian) Adriatic-Dinaridic carbonate platform deposits in Istria, Croatia

The Adriatic-Dinaridic carbonate platform (ADCP) was one of the largest and relatively well preserved Mesozoic platforms in the Mediterranean region (central Tethys). The peninsula Istria, in the northwestern part of the ADCP, is built up predominantly of shallow-water carbonates of the Middle Jurassic (Dogger) to Eocene age and, to a lesser extent, of Paleogene clastic deposits (flysch and calcareous breccia). This study focuses on a Lower Cretaceous (Barremian to Albian) succession of strata at five localities in western Istria. Stratigraphic determinations are based on identification of nine microfossil assemblages (benthic foraminifera and calcareous algae Dasycladales) and on using their taxa as index fossils. The age of strata with these microfossil assemblages, however, is questionable. Most of the age uncertainties are associated with a regional emersion, which occurred on the ADCP during the Aptian or close to the Aptian-Albian transition. It is unclear what portions of the Upper Aptian and/or Lower Albian are missing along this unconformity. A stable isotope study was conducted on homogenous micritic matrix samples in an attempt to resolve some of these uncertainties. Variations in carbon isotope compositions proved useful for stratigraphic correlation between the examined successions of strata, for improving their age determination, and for relating them to other coeval successions that span an important time interval of major oceanographic changes and carbon-cycle perturbations associated with the Early Aptian oceanic anoxic event (OAE 1a).     

Tracking Paleozoic evolution of the South Korean Peninsula from detrital zircon records: Implications for the tectonic history of East Asia

The southern part of the Korean Peninsula preserves important records of the Paleozoic evolutionary history of East Asia. Here we present SHRIMP U–Pb ages of detrital zircon grains from Paleozoic metasedimentary successions (Okcheon and Joseon Supergroups, Yeoncheon Group, Taean Formation, and Pyeongan Supergroup) that are incorporated into the major Phanerozoic mountain belts (Okcheon and Hongseong-Imjingang Belts) in South Korea, providing new insights for provenances and paleotectonic evolution of the South Korean Peninsula during Paleozoic time. The zircon ages from our samples display two distinct spectra patterns in their presence/absence of Neoproterozoic and/or Paleozoic populations. Our results, together with the available data from the Korean Peninsula, suggest that: (1) the Early to Middle Paleozoic successions in the Okcheon Belt were deposited in continental margin setting(s) formed by Neoproterozoic intracratonic rifting, (2) the Middle Paleozoic metasedimentary rocks in the Imjingang belt can be interpreted as molasse and flysch sediments along an active continental margin, (3) the Late Paleozoic to Early Triassic Taean Formation along the western Gyeonggi Massif represents a syn- to post-collision deltaic complex of a remnant oceanic basin, and (4) the Late Paleozoic to possibly Early Triassic Pyeongan Supergroup in the Okcheon Belt might represent a wedge-top and/or foreland basin. The spatial and temporal discrepancy between the South Korean Peninsula and the Central China Orogenic Belt during Paleozoic might reflect lateral variations in crustal evolution history along the East Asian continental margin during the Paleo-Tethyan Ocean closure.     

Extreme aridity prior to lake expansion deciphered from facies evolution in the Miocene Ili Basin,south‐east Kazakhstan

Central Asia witnessed progressive aridification during the Miocene, commonly related to mountain uplift, the Paratethys retreat and global climate cooling. However, the formation of Miocene lakes in Central Asia seems to oppose drier conditions, suggesting that the precise timing, extent and forcing of the aridification is still not well constrained. This study presents a facies model for the alluvial–lacustrine part of the Middle to Late Miocene of the Ili Basin, obtained from two successions. The model enables the semi‐quantitative assessment of regional water level and salinity, and characterizes the control of water level on evaporite formation and diagenesis. Both the proximal Kendyrlisai and the distal Aktau successions show an overall increase in water availability from dry mudflat deposits to lacustrine sedimentation with a transitional playa phase. Increasing evaporation rates outpaced the water supply and caused groundwater salinization. Subsequent lake expansion coincided with a basin‐wide desalinization and required a shift to a positive water budget. A climatic control of the hydrological evolution is inferred due to abrupt salinization and a minor tectonic influence. The long‐term water accumulation is probably related to the hydrological closure of the basin in the early Middle Miocene (15·3 Ma). Starting at 14·3 Ma, the step‐wise salinization occurred simultaneously with the global cooling of the Miocene Climate Transition. The Miocene Climate Transition led to extreme aridity in the Ili Basin, highlighted by the early diagenetic formation of displacive anhydrite in the basin centre. The expansion of the freshwater lake (12·7 to 11·5 Ma) was possibly promoted by lower evaporation rates due to decreasing air temperatures in the Ili Basin after the Miocene Climate Transition. The extreme aridity in the Ili Basin is interpreted as a continental counterpart to the Badenian Salinity Crisis in the Central Paratethys. This emphasizes the role of atmospheric forcing on evaporite sedimentation across Eurasia during the Middle Miocene.     

遗迹相及其古环境的意义

遗迹相是指一组具有特征的遗迹化石组合,在一段相当长的地质时期中不断的重视以及它们的环境意义。本文结合中国实例指出7个常见和通用的遗迹相及其沉积环境。浊积岩或复理石沉积中含有Nereites遗迹相,文内列举了目前已知的中国10个复理石产地,证明它们主要分布在两个板块构造单元的对接（消减）带。     

Postglacial stratigraphic evolution of a current-influenced sandy shelf: offshore Kujukuri strandplain,central Japan

Sandy shelf sediments are important elements of clastic sedimentary systems because of their wide distribution in the geological record and their significance as hydrocarbon reservoirs. Although many studies have investigated shelf sediments influenced by waves or tidal currents, little is known about shelf sediments influenced by oceanic currents, particularly their lithofacies characteristics and stratigraphic evolution. This study investigated the stratigraphic evolution of shelf sediments off the Kujukuri strandplain facing the Pacific Ocean, which is influenced by the strong Kuroshio Current. Sediment cores were obtained from six locations on the Kujukuri shelf (34 to 124 m water depth) using a vibrocorer. The dominant lithofacies is mud-free sand with low-angle cross-lamination associated with alternating beds of finer and coarser sand with cross-lamination. These display depositional processes influenced by storm waves and the Kuroshio Current, respectively. This finding is consistent with the previously presented modern and historical observations of the Kuroshio Current and estimates of the storm-wave base. Radiocarbon dates show that the sediment succession formed during the last transgressive and highstand stages after 13·1 ka. The depositional processes during the stages represent a transition from storm waves with abundant sediment supply to both storm waves and the Kuroshio Current with sediment starvation mainly due to its trapping in the strandplain. Comparison to other Holocene–Modern shelf systems suggests that the sandy shelf successions are strongly influenced by oceanic currents under conditions of limited riverine input and open coastal geometry. The resultant sand-dominated succession is characterized by reversal of the proximal to distal grain-size trend compared to the fining for most other recognized wave/storm-dominated shelf successions. This is because of seaward increase in the influence of the Kuroshio Current. Thus, shelf deposits are naturally complex, and these may be further complicated by the additional influence of oceanic currents above the usual wave-dominated and tide-dominated end members.     

The eastern part of the Tasman Orogenic Zone

The eastern part of the Tasman Orogenic Zone (or Fold Belt System) comprises the Hodgkinson—Broken River Orogen (or Fold Belt) in the north and the New England Orogen (or Fold Belt) in the centre and south. The two orogens are separated by the northern part of the Thomson Orogen.The Hodgkinson—Broken River Orogen contains Ordovician to Early Carboniferous sequences of volcaniclastic flysch with subordinate shelf carbonate facies sediments. Two provinces are recognized, the Hodgkinson Province in the north and the Broken River Province in the south. Unlike the New England Orogen where no Precambrian is known, rocks of the Hodgkinson—Broken River Orogen were deposited immediately east of and in part on, Precambrian crust.The evolution of the New England Orogen spans the time range Silurian to Triassic. The orogen is orientated at an acute angle to the mainly older Thomson and Lachlan Orogens to the west, but the relationships between all three orogens are obscured by the Permian—Triassic Bowen and Sydney Basins and younger Mesozoic cover. Three provinces are recognized, the Yarrol Province in the north, the Gympie Province in the east and the New England Province in the south.Both the Yarrol and New England Provinces are divisible into two zones, western and eastern, that are now separated by major Alpine-type ultramafic belts. The western zones developed at least in part on early Palaeozoic continental crust. They comprise Late Silurian to Early Permian volcanic-arc deposits (both island-arc and terrestrial Andean types) and volcaniclastic sediments laid down on unstable continental shelves. The eastern zones probably developed on oceanic crust and comprise pelagic sediments, thick flysch sequences and ophiolite suite rocks of Silurian (or older?) to Early Permian age. The Gympie Province comprises Permian to Early Triassic volcanics and shallow marine and minor paralic sediments which are now separated from the Yarrol Province by a discontinuous serpentinite belt.In morphotectonic terms, a Pacific-type continental margin with a three-part arrangement of calcalkaline volcanic arc in the west, unstable volcaniclastic continental shelf in the centre and continental slope and oceanic basin in the east, appears to have existed in the New England Orogen and probably in the Hodgkinson—Broken River Orogen as well, through much of mid- to late Palaeozoic time. However, the easternmost part of the New England Orogen, the Gympie Province, does not fit this pattern since it lies east of deepwater flysch deposits of the Yarrol Province.     

New geological framework for Western Amazonia (Brazil) and implications for biogeography and evolution

Although many of the current hypotheses to explain the origin and distribution of the Amazon biodiversity has been based directly or indirectly on geological data, the reconstruction of the geological history of the Amazon region is still inadequate to analyze its relationship with the biodiversity. This work has the main goal to characterize the sedimentary successions formed in the Brazilian Amazon in the Neogene-Quaternary discussing the evolution of the depositional systems through time and analyzing their main controlling mechanisms in order to fill up this gap. Radar image interpretation, sedimentological studies, and radiocarbon dating allowed the mapping of Plio-Pleistocene to Holocene units along the Solimões-Amazonas River, Brazil. This integrated work led to the characterization of five sedimentary successions overlying Miocene deposits of the Solimões/Pebas Formation, which include the following: Içá Formation (Plio-Pleistocene), deposits Q1 (37,400-43,700 ¹⁴C yr B.P.), deposits Q2 (27,200 ¹⁴C yr B.P.), deposits Q3 (6730-2480 ¹⁴C yr B.P.), and deposits Q4 (280-130 ¹⁴C yr B.P.). These deposits occur mostly to the west of Manaus, forming NW-SE elongated belts that are progressively younger from SW to NE, indicating a subsiding basin with a depocenter that migrated to the NE. The reconstruction of the depositional history is consistent with significant changes in the landscapes. Hence, the closure of a large lake system at the end of the Miocene gave rise to the development of a Plio-Pleistocene fluvial system. This was yet very distinct from the modern drainage, with shallow, energetic, highly migrating, braided to anastomosed channels having an overall northeast outlet. This fluvial system formed probably under climatic conditions relatively drier than today's. During the early Pleistocene, there was pronounced erosion, followed by a renewed depositional phase ca. 40,000 ¹⁴C yr B.P., with the development of prograding lobes and/or crevasse splays associated with a lake system (i.e., fan-delta) and/or fluvial flood plain areas. After a period of erosion, a fluvial system with eastward draining channels started to develop at around 27,000 ¹⁴C yr B.P. The fluvial channels were overflooded in mid-Holocene time. This flooding is attributed to an increased period of humidity, with a peak between 5000 and 2500 ¹⁴C yr B.P. The data presented herein support that, rather than being a monotonous area, the Amazonia was a place with frequent changes in landscape throughout the Neogene-Quaternary, probably as a result of climatic and tectonic factors. We hypothesize that these changes in the physical environment stressed the biota, resulting in speciation and thus had a great impact on modern biodiversity.     

Detrital blue amphiboles from the western Othrys Mountain and their relationship to the blueschist terrains of the Hellenides (Greece)

In contrast to blue amphiboles of the Ossa and Olympos tectonic windows in Thessaly, detrital blue amphiboles in Paleocene flysch deposits in the western Othrys Mountain (Pelagonian Zone s.l.) are chemically comparable with blue amphiboles from the Cyclades. For the detrital material, therefore, a source with "Cycladic" chemical affinities is assumed. The occurrence of these detrital minerals is in line with a Cretaceous onset of blueschist facies metamorphism in parts of the Hellenides, especially in the Cycladic belt. This was in response to Cretaceous subduction of the Pindos oceanic plate along the external margin of the Pelagonian micro-continent. Blueschist complexes were exhumed latest in the Paleocene when the terrigenous flysch sedimentation started in the Pelagonian and Pindos zones.     

班公湖-怒江缝合带洞错混杂岩物质组成、时代及其意义

班公湖-怒江缝合带中段洞错混杂岩保存了完整的与大洋演化相关的混杂岩系,包括蛇绿岩岩块、洋岛残片,以及复理石岩片、大陆边缘沉积等沉积岩块体,是恢复和反演班公湖-怒江洋演化的理想地区。在综述前人研究的基础上,结合近年来的研究成果,归纳和总结洞错混杂岩的物质组成和时代,初步阐述洞错混杂岩对班公湖-怒江洋演化的指示意义。结果表明,洞错混杂岩中无论是蛇绿岩残块、洋岛残片还是次深海-深海复理石岩片等,均是不同时代多期次构造混杂的混杂体。最早的年龄记录可追溯至晚二叠世末期,最晚可延至早白垩世中晚期,是班公湖-怒江洋晚二叠世末期—早白垩世中晚期连续演化的记录。洞错混杂岩早白垩世中晚期大陆边缘沉积与蛇绿岩等的不整合仅是弧前楔顶盆地沉积的产物,不能约束班公湖-怒江洋的最终消亡。     

藏北龙木错—双湖—澜沧江板块缝合带发现晚石炭世—早二叠世洋岛型岩石组合

天泉群岛出露于龙木错—双湖—澜沧江板块缝合带的中西段,也是目前该缝合带上所发现的第一套洋岛型岩石组合。通过野外踏勘、剖面测制等对天泉群岛进行了较为详细的研究,结果显示,天泉群岛由9个孤立、岩石组合不同的洋岛组成,其中独泉沟洋岛、屏风岭洋岛的洋岛组分齐全,见玄武岩、灰岩、砾岩、硅质岩等,其他洋岛的洋岛组分不全。天泉群岛与展金组复理石沉积为整合接触,表明其形成时代为晚石炭世—早二叠世。天泉群岛的厘定,说明龙木错—双湖—澜沧江大洋在晚石炭世—早二叠世仍具有成熟的洋壳。该项研究进一步丰富了龙木错—双湖—澜沧江板块缝合带的演化内容,为反演区域地质演化历史提供了依据。