Sea‐level reconstructions from the Peri‐Vocontian Zone (South‐east France) point to Valanginian glacio‐eustasy

The Valanginian is a period of global environmental change as illustrated by sedimentary, palaeontological, geochemical and climatic perturbations. A production crisis in most of the carbonate platforms suggests important changes in palaeoenvironmental conditions. During the same time interval, a major positive excursion in δ¹³C, the Weissert Event, suggests perturbations of the carbon cycle from the latest Early Valanginian to the Early Hauterivian. In order to better understand the link between these changes, sea‐level fluctuations have been reconstructed in detail from the Middle Berriasian to the earliest Hauterivian. Sections from the Peri‐Vocontian Zone (South‐east France) have been investigated because of the good quality of outcrops on the carbonate platforms, their margins and in the Vocontian Basin. Sections ranging from the most proximal zone (Swiss Jura) to the basin were interpreted in terms of sequence stratigraphy and cyclostratigraphy, and correlated at high resolutions. Using the identified small, medium and large‐scale sequences as well as depositional geometries, sea‐level fluctuations were reconstructed. Two main trends are evidenced during the studied interval: (i) the peak amplitude (magnitude) of the sea‐level fluctuations increased gradually from the Middle Berriasian to the Early Valanginian, and reached a maximum (more than 50 m) from the middle Early Valanginian to the Valanginian/Hauterivian boundary; and (ii) sea‐level variations were quite symmetrical during the Late Berriasian, slightly asymmetrical during the Early Valanginian and strongly asymmetrical (fast sea‐level rise, slow fall) from the latest Early Valanginian to the earliest Hauterivian. Moreover, three orders of sea‐level fluctuations were recognized in the sedimentary rocks of the Peri‐Vocontian Zone. Platform‐basin correlations and cyclostratigraphic interpretations of the basinal sections evidence an astronomical control on the sea‐level variations, mainly by the two eccentricity cycles of 100 and 400 kyr. The increase in the amplitude of the sea‐level fluctuations and their change from symmetrical to asymmetrical can be related to the onset of a major cooling event in the Early Valanginian. Fast transgressions followed by slower regressions would correspond to waxing and waning of high‐latitudinal ice during most of the Valanginian, especially from the latest Early Valanginian to the latest Late Valanginian. Glacio‐eustatic sea‐level fluctuations in tune with the 100 and 400 kyr eccentricity cycles are in agreement with glaciations during the Valanginian.     

Sedimentary response to a tectonically induced sea-level fall in a shallow back-arc basin: the Mulichinco Formation (Lower Cretaceous), Neuquén Basin, Argentina

This study examines the sedimentary response to a tectonically driven relative sea‐level fall that occurred in the Neuquén Basin, west‐central Argentina, during the late Early Valanginian (Early Cretaceous). At this time the basin lay behind the emergent Andean magmatic arc to the west. Following the relative sea‐level fall, sedimentation was limited to the central part of the Neuquén Basin, with the deposition of a predominantly clastic, continental to shallow marine wedge on top of basinal black shales. This lowstand wedge is called the Mulichinco Formation and consists of a third‐order sequence that lasted about 2 Myr and contains high frequency lowstand, transgressive, and highstand deposits. Significant variations in facies, depositional architecture, and internal organization of the sequence occur along depositional strike. These variations are attributed mainly to tectonic and topographic controls upon sediment flux, basin gradient, fault tilting, and shifting of the depocentre through time. These controls were ultimately related to asymmetrically distributed tectonic activity that was greater towards the magmatic arc in the west. The superposition of fluvial deposits directly upon offshore facies provides unequivocal evidence for a sequence boundary at the base of the Mulichinco Formation. However, the Mulichinco sequence boundary is marked by shallow, low erosional relief and widespread fluvial deposition. The surface lacks prominent valleys traditionally associated with sequence boundaries. This non‐erosive sequence boundary geometry is attributed to the ramp‐type geometry of the basin and/or rapid uplift that limited stratigraphic adjustment to base‐level fall. Significant along‐strike facies changes and a low‐relief sequence boundary are attributes that may be common in tectonically active, semi‐enclosed basins (e.g. shallow back‐arc basins, foreland basins).     

The Triassic of the Thakkhola (Nepal). I: stratigraphy and paleoenvironment of a north-east Gondwanan rifted margin

The Mesozoic sediments of Thakkhola (central Nepal) were deposited on a broad eastern north Gondwanan passive margin at mid-latitudes (28–41 °S) facing the Southern Tethys ocean to the north. The facies is strikingly similar over a distance of several thousand kilometres from Ladakh in the west to Tibet and to the paleogeographically adjacent north-west Australian margin (Exmouth Plateau, ODP Legs 122/123) and Timor in the east. Late Paleozoic rifting led to the opening of the Neo-Tethys ocean in Early Triassic times. An almost uninterrupted about 2 km thick sequence of syn-rift sediments was deposited on a slowly subsiding shelf and slope from Early Triassic to late Valanginian times when break-up between Gondwana (north-west Australia) and Greater India formed the proto-Indian Ocean. The sedimentation is controlled by (1) global events (eustasy; climatic/oceanographic changes due to latitudinal drift; plate reorganization leading to rift-type block-faulting) and (2) local factors, such as varying fluvio-deltaic sediment input, especially during Permian and late Norian times. Sea level was extremely low in Permian, high in Carnian and low again during Rhaeto-Liassic times. Third-order sea-level cycles may have occurred in the Early Triassic and late Norian to Rhaeto-Liassic. During the Permian pure quartz sand and gravel were deposited as shallowing upward series of submarine channel or barrier island sands. The high compositional maturity is typical of a stable craton-type hinterland, uplifted during a major rifting episode. During the early Triassic a 20–30 m thick condensed sequence of nodular ‘ammonitico rosso’-type marlstone with a ‘pelagic’ fauna was deposited (Tamba Kurkur Formation). This indicates tectonic subsidence and sediment starvation during the transgression of the Neo-Tethys ocean. During Carnian times a 400 m thick sequence of fining upward, filament-rich wackestone/shale cycles was deposited in a bathyal environment (Mukut Formation). This is overlain by about 300 m of sandy shale and siltstone intercalated with quartz-rich bioclastic grain- to rudstone (Tarap Shale Formation, late Carnian-Norian). The upper Norian to (?lower) Rhaetian Quartzite Formation consists of (sub)arkosic sandstones and pure quartz arenites, indicating different sediment sources. The fluvio-deltaic sandstones are intercalated with silty shale, coal and bioclastic limestone, as well as mixed siliciclastic-bioclastic rocks. The depositional environment was marginal marine to shallow subtidal. The fluvio-deltaic influence decreased towards the overlying carbonates of Rhaeto-Liassic (?) age (Jomosom Formation correlative with the Kioto Limestone), when the region entered tropical paleolatitudes resulting in platform carbonates.     

Relationship between volcanism and marine sedimentation in northern Austral (Aisén) Basin, central Patagonia: Stratigraphic, U–Pb SHRIMP and paleontologic evidence

The northernmost part of the oil-producing Austral Basin, known as Aisén Basin or Río Mayo Embayment (in central Patagonian Cordillera; 43–46°S), is a special area within the basin where the interplay between volcanism and the initial stages of its development can be established. Stratigraphic, paleontologic and five new U–Pb SHRIMP age determinations presented here indicate that the Aisén Basin was synchronous with the later phases of volcanism of the Ibáñez Formation for at least 11 m.yr. during the Tithonian to early Hauterivian. In this basin marine sedimentary rocks of the basal units of the Coihaique Group accumulated overlying and interfingering with the Ibáñez Formation, which represents the youngest episode of volcanism of a mainly Jurassic acid large igneous province (Chon Aike Province). Five new U–Pb SHRIMP magmatic ages ranging between 140.3 ± 1.0 and 136.1 ± 1.6 Ma (early Valanginian to early Hauterivian) were obtained from the Ibáñez Formation whilst ammonites from the overlying and interfingering Toqui Formation, the basal unit of the Coihaique Group, indicate Tithonian, early Berriasian and late Berriasian ages. The latter was a synvolcanic shallow marine facies accumulated in an intra-arc setting, subsequently developed into a retro-arc basin.     

Distribution and facies patterns of Lower Cretaceous sediments in northern Germany: a review

Marine sediments of Early Cretaceous age (Berriasian–Albian) have a widespread distribution in the Lower Saxony Basin of northern Germany. This basin, which is about 400 km long and 100 km wide, formed the southernmost extension of the North Sea Basin. Sediments attaining a maximum thickness of up to several hundred metres are represented by shallow marine siliciclastics in the west, south and easternmost part of the basin. These interfinger with the basin facies represented by dark mudstones up to 2000 m thick. The distribution and facies patterns of the sediments as well as thicknesses are related to three factors: differential subsidence, local tectonics and sea-level changes. For various parts of the basin and certain stratigraphic intervals it is possible to distinguish between these causes. Sedimentary thicknesses are clearly a result of differential subsidence from Kimmeridgian to Albian times onwards, being controlled by tectonic movements along northwest–southeast trending faults. These result in an asymmetric trough, bound to the north and south by synsedimentary faults with sedimentation rates highest in the north. Local tectonics are clearly caused by salt diapirs mainly in the eastern part of the basin and along the western, southern and eastern margins. These areas in particular include parts of the western Emsland and the Salzgitter area. Sedimentary patterns vary considerably over less than a kilometre, showing an extreme range of different lithologies. This is ideally observed in the Salzgitter area. Sea-level changes finally are reflected by widespread facies patterns and particularly by fossils of different provenance. The following sea-level-related events can be followed throughout the basin: the Wealden regressive phase, the Early Valanginian transgression, the early Late Valanginian transgression, the mid Hauterivian transgression, the Barremian regression, deposition of the Early Aptian anoxic sediments, and accumulation of the mid Albian hemipelagic marls.     

Lithostratigraphy,biostratigraphy and sedimentary dynamics of the Lower Cretaceous deposits on the northern side of the western High Atlas (Morocco)

The analysis of a sedimentary succession on the northern side of the western High Atlas, from Essaouira to Amizmiz, has enabled us to identify, and describe, thirteen formations ranging in age from Tithonian to Clansayesian. The collection and determination of ammonite and echinoid faunas has allowed us to attribute a precise age to most of these units. Lower Cretaceous formations are organized into six main depositional sequences: Late Jurassic-Berriasian; Valanginian; Hauterivian-Barremian; Bedoulian; Gargasian; Clansayesian-Albian. This organization, the characteristics of the major discontinuities and the geometry of sedimentary succession allows recognition of the following events: a Late Berriasian distensive phase; a period of sea-level change and basin infilling during Valanginian, Hauterivian, Barremian and Bedoulian times under essentially eustatic control; an intra-Aptian tectonic phase; and a period of relative sea level rise and topographic levelling during Gargasian-Albian. This is essentially linked to the evolution of the North Atlantic ocean during the Early Cretaceous.     

Development of carbonate platforms on an extensional (rifted) margin: the Valanginian–Albian record of the Prebetic of Alicante (SE Spain)

Within the upper Valanginian to upper Albian deposits of the easternmost part of the Prebetic Zone of the Betic Cordillera (Iberian Peninsula), seven lithostratigraphic formations made up of shallow-water carbonate and carbonate-siliciclastic sediments and of outer-platform hemipelagic sediments have been recognized. These formations were deposited in the most distal part of a platform that developed on the Southern Iberian Continental Palaeomargin. The geodynamic context was a margin affected by extensional or transtensional faults that produced tilted blocks. The interval studied records three major second-order transgressive-regressive facies cycles: (I) A late Valanginian to earliest Aptian cycle, mostly represented by hemipelagic and condensed sedimentation, with the development of a tectonically controlled high without sedimentation that separated two sectors with different sedimentary evolution and that ended with an episode of shallow-water carbonate platform development; (II) An earliest to latest Aptian cycle, with a transgressive phase represented by a retrogradational shallow-water carbonate platform capped by a drowning event leading to hemipelagic sedimentation, which was affected by an anoxic event (OAE 1a); the regressive phase is represented by progradation and aggradation of shallow-water carbonate deposits. Finally (III) a latest Aptian to early-late Albian cycle that records the expansion of mixed platform deposits in the entire area, ending with a phase of shallow-water carbonate platform development. Extensional tectonics leading to spatial and temporal changes in subsidence patterns is envisaged as the main control on sedimentation at a local scale, resulting in notable lateral changes in thickness as the main signature. Tectonics exerted a strong control on the distribution of sedimentary environments only during Cycle I. At a higher order, sea-level fluctuations are responsible for sequential organization, and environmental factors determined shallow-water carbonate platform development and demise, as well as oceanic anoxic events. The relevant continuity of the stratigraphic record in the distal part of the Prebetic platform has led to the recognition of events related to cycle boundaries, which result mainly from a combination of tectonics and sea-level changes.     

Revision of Valanginian Steinmanellinae bivalves from the Neuquén basin,West-central Argentina,and their biostratigraphic implications

We present a new species of Steinmanella Crickmay from the Valanginian of the Neuquén Basin, west-central Argentina, and at the same time update a Valanginian–earliest Barremian bivalve zonation which is integrated into the local, Chilean and European standard ammonoid zonations. Steinmanella caicayensis sp. nov. presents a moderately inflated shell, a subtriangular outline, well-developed carinae and a straight to moderately convex anterior margin. Steinmanella is very abundant in the Tithonian–Barremian interval in the basin and thus provides an ideal opportunity to perform detailed taxonomic and stratigraphic studies; a former zonation based on these trigonioids is here revised and expanded with a thorough revision of Valanginian occurrences based on new material. Two new zones are proposed, namely the S. quintucoensis and S. caicayensis zones, encompassing Valanginian times. The proposed bivalve zonation encompassing the Valanginian–earliest Barremian time interval can be useful in correlating with other southwestern Gondwanan regions, such as Perú, Chile, South Africa, Tanzania, and India, where Steinmanella has been recorded.     

吐哈盆地十红滩铀矿床构造特征及其与铀矿化时空关系研究

在分析了十红滩矿床地质构造背景、主要断裂和褶皱构造特征的基础上,提出了吐哈盆地十红滩矿床具有断块构造活动的特点,并将该区划分为4个不同特点的断块区,论述了各断块构造的地质特征和对地下水及铀矿化的控制作用;将盆地演化与铀矿化划分为盆地基底形成、沉积建造形成、盆地改造及铀矿化3个大的阶段和若干次级阶段,指出了盆后构造对铀矿化的分布和矿体的产出状态有明显的控制作用.     

Cretaceous Rocks of the Penzhina Bay: Mineralogy,Petrography, and Geodynamic Sedimentation Conditions

Cretaceous sedimentary and volcanosedimentary rocks from northwestern Kamchatka are considered. The stadial analysis has revealed variable impacts of three major provenances upon the Cretaceous Penzhina sedimentary basin. The provenances were composed of volcanic and volcanosedimentary rocks (Uda–Murgal island arc and Okhotsk–Chukotka volcanic belt) and granitic–metamorphic rocks (the mature Asian continental margin). Sediments were largely accumulated owing to the erosion of island-arc volcanics during reactivation of the Uda–Murgal island arc (Hauterivian–Barremian) or the Okhotsk–Chukotka volcanic belt (middle Albian–Cenomanian). Eroded granitic–metamorphic rocks of the mature Asian continental margin (Berriasian–Valanginian) or Asian metamorphic–volcanic rocks (Santonian–Campanian) were supplied to the basin during tectonically quiet periods (Berriasian–Valanginian and late Cenomanian–Campanian). Compositional changes in provenances were related to active tectonic processes at the continental margin, including evolution and closure of the Uda–Murgal island-arc system and origin of the Okhotsk–Chukotka volcanic belt. The postsedimentary modification of Cretaceous rocks deposited in forearc trough beyond the tectonically active accretionary prism is characterized by a low degree of clastic component alteration.     

Nannostratigraphy and palaeoecology of uppermost Mozduran Formation in the Kopeh-Dagh range (NE Iran)

The Mozduran Formation includes light-coloured, thick-bedded to massive limestone and porous dolomitic limestone and dolomite. In this study, 13 samples from the uppermost Mozduran Formation were taken from two localities and examined for calcareous nannofossils. A total of 19 species and 12 genera were identified in the Mozduran section and19 species and 13 genera for the Taherabad section. Based on these assemblages, the uppermost Mozduran Formation is assignable to Sissingh's (1977) biozone CC1 (Early Berriasian) at the Mozduran section and to biozone CC3 (Late Valanginian) at the Taherabad section. Thus, the formation is younger from east to west across the basin.     

Luminescence chronometry and geomorphic evidence of active fold growth along the Kachchh Mainland Fault (KMF), Kachchh, India: Seismotectonic implications

The Kachchh region of Western India is a pericratonic basin experiencing periodic high magnitude earthquakes events. In 2001 a catastrophic seismic event occurred at Bhuj measuring M_w = 7.7. The epicenters of both the 1956 and 2001 earthquakes were along the Kachchh Mainland Fault (KMF), proximal to the eastern end of the Northern Hill Range (NHR). The latter is a topographic expression of an active fault related fold on the hanging wall, and is controlled by a south dipping blind thrust.The present study deals with the eastern sector of NHR and uses optical dating to reconstruct the chronology of tectonically caused incisions. Along the backlimb of the NHR, incision ages on, channel fills and valley fill terraces progressively decrease from  12 ka to 4.3 ka. This age progression along with geomorphic evidences (decrease in topographic relief, drainage capture and drainage migration across the fold nose) suggests an active vertical and lateral fold growth along the KMF. Optical ages suggest that during the Late Holocene, the average uplift rate along the eastern NHR was 10 ± 1 mm/a. Recent GPS based estimates on crustal shortening are  12 mm/a.The KMF and the South Wagad Fault (SWF) represent the bounding faults of a transtensional basin that formed during the initial rifting. This basin is termed as the Samakhiali basin. The compressive stresses on account of structural inversion from normal to reverse phase resulted in lobate-shaped anticlines along KMF and SWF zone. These anticlines subsequently coalesced and formed linked and overlap segments. The present study suggests that eastward lateral deformation across the eastern portion of KMF has continued and has now resulted in its interaction with a left step over transfer fault called the South Wagad Master Fault (SWMF). This implies an increasing transpersional deformation of the Samakhiali basin. We therefore, suggest that the eastward NHR ridge propagation along KMF resulted in the thrust faulting on the south dipping SWMF resulting in the Bhuj 2001 event. The increasing strain on this basin may cause enhanced seismicity in the future along the eastern KMF and Wagad region.     

Early Cretaceous volcaniclastic and quartzose sandstones from north central Nepal: composition,sedimentology and geotectonic significance

Early Cretaceous sandstones and shales from the Thakkhola region (Chukh and Tangbe Formations) were deposited on the subsiding northern (Tethyan) margin of Gondwana; current directions indicate a source area to the south. Whereas the Berriasian Chukh Formation is dominated by quartz arenites, volcaniclastic sandstones and minor conglomerates dominate the Tangbe Formation of Valanginian to Aptian age. Upsection, the composition of the volcaniclastic components changes from mainly basaltic to dominantly dacitic/rhyolitic. Magmatism was preceded and accompanied by strong uplift in the source area of the Chukh and Tangbe clastics, resulting in the erosion of probably more than several hundred meters of pre-Cretaceous sedimentary, metamorphic and plutonic rocks. A geochemical whole rock analysis of basaltic pebble fragments shows their alkaline character and suggests a within-plate geotectonic setting for the volcanic source. This volcanotectonic event is probably related to rifting between Australia and Greater India, where seafloor spreading began in late Valanginian/Hauterivian times.     

Multi-proxy record of orbital-scale changes in climate and sedimentation during the Weissert Event in the Valanginian Bersek Marl Formation (Gerecse Mts., Hungary)

The Valanginian positive carbon isotope excursion and associated environmental changes, known as the Weissert Event, is the first in the series of Cretaceous Earth system perturbations. Here, we develop a multiproxy cyclostratigraphy from a 31.2-m-thick Upper Valanginian to lowermost Hauterivian section of the Bersek Marl Formation in Gerecse Mountains, Hungary, comprising alternating marlstone layers of varying clay and carbonate content. The bulk carbonate δ¹³C signal shows sustained, elevated values (up to 2.7‰) up to 19.2 m, followed by a decreasing trend upsection. Together with biostratigraphic data, this suggests that the lower part of the section was deposited during the plateau phase of the Late Valanginian Weissert Event. Spectral analyses of the multiproxy dataset, including magnetic susceptibility measurements and gamma-ray spectroscopy on the lower part of the section, led to the identification of precession, obliquity, and long and short eccentricity signals. A mean sedimentation rate of 14 m/Myr was calculated based on astronomical tuning. The cyclicity in the proxy signals reflects dilution cycles induced by the fluctuating rate of detrital runoff into the basin. This supports the idea that orbitally-forced humid-arid cycles controlled the pelagic alternating sedimentation during the Early Cretaceous throughout the Tethyan area.     

Cretaceous stratigraphy of the Ionian Zone,Hellenides, western Greece

The Cretaceous sedimentary successions of the Ionian Zone, Hellenides, western Greece, are composed of pelagic limestones intercalated with cherty layers. The micritic and biomicritic beds with abundant chert nodules and cherty horizons, which were deposited during late Tithonian to early Santonian times, belong to the Vigla Limestone Formation, while the sediments deposited during the late Santonian to Maastrichtian, formed clastic limestone beds in which chert nodules also occur sparsely.In the Cretaceous beds calpionellids, planktonic and benthonic foraminifera characteristics of the Tethyan realm, and radiolaria have been recorded. The calpionellids, together with radiolaria, colonized the entire basin during the Berriasian to early Valanginian, the latter becoming dominant during the Hauterivian to early Albian as a result of anoxia. Planktonic foraminifera first appeared in the basin during the late Albian and persisted until the Maastrichtian. The numbers decreased, however, during the Cenomanian-early Turonian interval, when radiolaria increased owing to anoxic conditions, and during the Campanian-Maastrichtian interval because the basin became shallow. During this interval larger benthonic foraminifera colonized the basin. Zonal markers have been recognized in calpionellid and planktonic foraminiferal assemblages on the basis of which two calpionellid zones are distinguished, viz. the Calpionella alpina and Calpionellopsis Zones (Berriasian-early Valanginian) along with seven planktonic foraminiferal zones, viz. the Rotalipora ticinensis, Rotalipora appenninica (late Albian), Rotalipora brotzeni (early Cenomanian), Helvetoglobotruncana helvetica (early to middle Turonian), Marginotruncana sigali(late Turonian to early Coniacian), Dicarinella concavata (late Coniacian to early Santonian) and Dicarinella asymetrica (late early-late Santonian) Zones.The anoxic conditions that prevailed in the Ionian basin during the Barremian-early Albian, Cenomanian-early Turonian and Coniacian-Santonian intervals probably arose as a result of (a) the accumulation of large amounts of organic matter because the palaeotopography of the basin periodically hindered the circulation of water from the ocean and (b) the oxygen content of the intruding oceanic waters was low.     

THE PROBLEM OF OIL-GAS SATURATION IN THE MESOZOIC SEDIMENTS OF THE LOWER YENISEI

Exploratory drilling in Mesozoic argillites, sandstones, and shales of the still-subsiding Yenisei basin located numerous gas and oil occurrences. Contained organic-oil content of Lower Jurassic sediments is 1.5 percent; of Middle Jurassic, 1.8 (locally 3.7 percent in Bajocian sediments); of Upper Jurassic, 1.4 percent; and of Valanginian, 1 percent. Maximum gas flow from Bajocian and Valanginian sandstone was 13,000 m³ per 24 hours; gas flowed at a rate of 76,000 m³ in 24 hours at depth of 612 to 627 m from Middle Jurassic sandstone. These and other factors, including evidence that the sediments were largely accumulated in shallow-water and reducing conditions, indicate that the Jurassic and Valanginian sediments of the Ust-Yenisei basin are potential oil producers. --G. E. Denegar.     

The Valanginian history of the eastern part of the Getic Carbonate Platform (Southern Carpathians,Romania): Evidence for emergence and drowning of the platform

Lower Cretaceous successions that crop out in the eastern part of the Getic Carbonate Platform (Southern Carpathians, Romania) preserve records of the Valanginian events in different settings of the platform. The integrated sedimentological, biostratigraphical, geochemical and mineralogical analysis of the upper Berriasian–Valanginian successions reveal successive stages in the evolution of the carbonate platform: (a) pre-drowning stage of the shallow-shelf and slope settings of the platform; (b) subaerial exposure and karstification; and (c) incipient flooding and drowning of the carbonate platform. Following the subaerial exposure, starting in the middle early Valanginian, the eastern part of the Getic Carbonate Platform experienced a drowning phase documented by iron oxyhydroxides, phosphate and glaucony mineralized discontinuity surface and glaucony-rich sediments disposed on the discontinuity surface. Recognition of the diachronous intra-Valanginian discontinuity surface within the studied successions is based on clear evidences (facies contrast, depositional and diagenetic features, biostratigraphic and taphonomic data, and geometrical relations). The negative–positive carbon isotope excursion is correlated with the global perturbations of the carbon cycle related to the Valanginian “Weissert” episode, and it is documented for the first time in the shallowest parts of the Getic Carbonate Platform. Tectonic activity and eustatic sea-level fluctuations were most probably the main factors that led to fault-block tilting, local emersion and subsequent drowning of the eastern part of the Getic Carbonate Platform during the Early Cretaceous. We infer that the eastern part of the Getic Carbonate Platform was affected by late Berriasian–early Hauterivian extensional tectonics that could be related to the Neo-Cimmerian movements with effects generally recognized in the northern peri-Tethyan areas.     

黑龙江东部鸡西盆地构造层序划分与盆地动力学演化

依据钻孔及露头资料,对黑龙江东部鸡西盆地进行了构造层序划分及研究,共划分了1个Ⅰ级、2个Ⅱ级、5个Ⅲ级构造层序,在此基础上讨论了鸡西盆地动力学演化机制,证实鸡西盆地主要由敦密断裂在白垩纪左旋走滑拉分而成。纵向上表现为两个构造演化阶段：早白垩世早中期表现为断陷盆地特点,控制了鸡西群含煤层序的生长和发育;早白垩世晚期-晚白垩世早期表现为坳陷盆地特征,控制了桦山群红层的生长、发育。该盆地的层序划分及动力学分析对黑龙江东部白垩纪地层对比、构造作用及成矿作用的分析提供了重要依据。     

Oligocene–Miocene formation of the Haifa basin: Qishon–Sirhan rifting coeval with the Red Sea–Suez rift system

During mid-Oligocene to early-Miocene times the northeastern Afro-Arabian plate underwent changes, from continental breakup along the Red Sea in the south, to continental collision with Eurasia in the north and formation of the N–S trending Dead Sea fault plate boundary. Concurrent uplift and erosion of the entire Levant area led to an incomplete sedimentary record, obscuring reconstructions of the transition between the two tectonic regimes. New well data, obtained on the continental shelf of the central Levant margin (Qishon Yam 1), revealed a uniquely undisturbed sedimentary sequence which covers this time period. Evaporitic facies found in this well have only one comparable location in the entire eastern Mediterranean area (onland and offshore) over the same time frame — the Red Sea–Suez rift system. Analysis of 4150 km of multi and single-channel seismic profiles, offshore central Levant, shows that the sequence was deposited in a narrow basin, restricted to the continental shelf. This basin (the Haifa Basin) evolved as a half graben along the NW trending Carmel fault, which at present is one of the main branches of the Dead Sea fault. Re-evaluation of geological data onland, in view of the new findings offshore, indicates that the Haifa basin is the northwestern-most of a larger series of basins, comprising a failed rift along the Qishon–Sirhan NW–SE trend. This failed rift evolved spatially parallel to the Red Sea–Suez rift system, and at the same time frame. The Carmel fault would therefore seem to be related to processes occurring several million years earlier than previously thought, before the formation of the Dead Sea fault. The development of a series of basins in conjunction with a young spreading center is a known phenomenon in other regions worldwide; however this is the only known example from across the Arabian plate.     

Report on the 5th International Meeting of the IUGS Lower Cretaceous Ammonite Working Group,the Kilian Group (Ankara,Turkey, 31st August 2013)

The 5th meeting of the IUGS Lower Cretaceous Ammonite Working Group (the Kilian Group) held in Ankara, Turkey, 31st August 2013, discussed the Mediterranean ammonite zonation, and its calibration with different ammonite zonal schemes of the Boreal, Austral and Central Atlantic realms. Concerning the standard zonation, that corresponds to the zonal scheme of the West Mediterranean province, some changes have been made on two stages. For the Valanginian, the Busnardoites campylotoxus Zone was abandoned; the upper part of the lower Valanginian is now characterised by the Neocomites neocomiensiformis and Karakaschiceras inostranzewi zones. For the upper Barremian, the former Imerites giraudi Zone is here subdivided into two zones, a lower I. giraudi Zone and an upper Martellites sarasini Zone. The I. giraudi Zone is now subdivided into the I. giraudi and Heteroceras emerici subzones, previously considered as horizons. The current M. sarasini and Pseudocrioceras waagenoides subzones correspond to the lower and upper parts of the M. sarasini Zone, respectively. The Anglesites puzosianum Horizon is kept. The Berriasian, Hauterivian, Aptian and Albian zonal schemes have been discussed but no change was made. The upper Hauterivian zonal scheme of the Georgian (Caucasus) region (East Mediterranean province) has been compared with the standard zonation. Discussions and some attempts at correlations are presented here between the standard zonation and the zonal schemes of different palaeobiogeographical provinces: the North-West European area for the Valanginian and Hauterivian, the Argentinean region for the Berriasian, Valanginian and Hauterivian, and the Mexican area for the Valanginian–Hauterivian and Aptian–lower Albian. The report concludes with some proposals for future work.