Palaeoceanographic differences of early Late Aptian black shale events in the Vocontian Basin (SE France)

A high-resolution study focussing on the distribution of calcareous nannofossils and carbon isotopes was carried out to improve the understanding of mid-Cretaceous black shale formation. The studied interval of the early Late Aptian is characterized by two major black shale couplets, the Niveau Noire 4 (NN4) and Niveau Noire Calcaire 2 (NNC2), of the Serre Chaitieu section in the Vocontian Basin (SE France; Bréhéret, 1997). This interval occurs within a long-term negative carbon isotope excursion of > 1.5‰ following the Early Aptian Oceanic Anoxic Event 1a (OAE1a). In contrast to the local NN4 black shales, the black shales of NNC2 are of regional significance and occur at the end of the major negative carbon isotope excursion of the early Late Aptian. Time equivalent black shales are suggested to be coeval with black shales found in the Western Tethys and Atlantic Ocean (Herrle et al., 2004). Calcareous nannofossil analyses and carbon isotopes indicate higher surface water productivity (mesotrophic), warmer surface water, and higher sea-level during the formation of the NN4 black shales. In contrast, the formation of the NNC2 black shales took place during a cooler phase, lower surface water productivity, and lower sea-level. A sea-level fall may cause a restriction of water mass exchange between the open-marine Western Tethys and the Vocontian Basin. This resulted in a longer residence time of the bottom water, decreased ventilation and less mixing of surface waters and thus enhanced preservation of organic matter at the sea floor. Our results indicate that the black shale formation of NN4 and NNC2 was caused by different processes such as increased surface water productivity and enhanced preservation of organic matter at the sea floor. Thus, we emphasize the role of different forcing factors which control the formation of local and regional black shales. The most important factors are sea-level fluctuations, increasing productivity, and changes in precipitation and evaporation rates.     

Oligocene swamp sediments of Lesvos Island,Greece (geochemistry and mineralogy)

Summary The Tertiary Lapsarna swamp sedimentary rocks include thin horizons (organic-rich sediments, up to 22% C_org). Analyses of major elements of carbonates, shaly and siliceous rocks, and a thin, intensively silicified coaly horizon were taken (10 representative samples). Pure carbonates consistalmost completely of calcite, the siliceous sediments of quartz and calcite, and the shales of montmorillonite, feldspar, quartz, dolomite and calcite. The shales contain montmorillonite as the only clay component. The presence of montmorillonite in all shales suggests that the chemistry of the clay-forming solutions lies within the stability field of montmorillonite. Geochemical data indicate that montmorillonite and associated immobile elements (La, Zr, Y, Nb) are the products of hydrolysis of volcanic material in a subtropical region. The intense silification of the coaly horizon is due to a contact with silica-rich solutions that formed during the formation of montmorillonite. Quartz is produced diagenetically by transformation of amorphous opal-A after burial.     

Feeding habits of the exotic black bullhead Ameiurus melas (Rafinesque) in the Iberian Peninsula: first evidence of direct predation on native fish species

The feeding ecology of the exotic invasive black bullhead Ameiurus melas was conducted in the Iberian Peninsula for the first time. Dietary analysis based on the stomach contents of individuals caught in several Iberian basins was carried out as a first step to evaluate its potential threat for the native Iberian ichthyofauna. Aquatic macroinvertebrates (mainly Chironomidae) dominated the black bullhead's diet in all size-classes and sites, irrespective of natural riverine or artificial lentic habitats. Secondary prey items were responsible for the observed between-sites (microcrustaceans in artificial lentic habitat; oligochaeta and caddisfly larvae in natural riverine habitats) and ontogenetic diet differences (from microcrustaceans to larger prey). These diet variations were also detected in trophic diversity values and feeding strategy plots. Black bullheads consumed plant material, terrestrial prey and co-occurring fish species (native or exotic) and thus they could be considered as generalist or opportunistic, foraging on the most abundant and available prey. There was no positive relationship between black bullhead size (total length) and fish prey size, probably indicating piscivory on dead or dying vulnerable fishes as well as predation on smaller-sized active fishes. The results showed that the black bullhead could negatively affect native Iberian ichthyofauna throughout direct predation and competition. Aspects of potential conservation and management implications of fishes resulting from the undesirable presence of the black bullhead in Iberian water bodies are discussed.     

Upper Ladinian to Lower Carnian sedimentary evolution in the Idrija-Cerkno Region,Western Sovenia

Summary An Upper Ladinian to Lower Carnian succession in the Idrija-Cerkno region (W Slovenia) is described and correlated with similar successions in the Dolomites. Structurally, the area belongs to the Rodne unit (Trnovo nappe, NW Dinarides). The succession was reconstructed from three stratigraphically superimposed sections. The Orehovska Grapa section is characterised by finegrained turbidites composed of sandy mudstones with intercalations of lenses and beds of trachy-andesite tuff and resedimented tuffs. Beds of hemipelagic light grey wackestone are rarely interstratified. These rocks are correlative with the Upper Ladinian Wengen Group. The Police1 section is composed of black shaly marls and mudstones, hemipelagic wackestone, tuffaceous sand-stones, and in the upper part, of calciturbidites overlain by black laminated shales. The section is correlated with the lower part of the San Cassiano Formation. The Police 2 section consists mainly of wavy bedded peloidal and bioclastic limestone, alternating with thin interbeds of shaly mudstones and marls. The limestone and mudstones are interpreted as tempestites and gradually pass into bedded and massive dolomite of Early Carnian age. This succession is similar to the transition from the San Cassiano Formation to the Cassian Dolomite. The studied succession represents a shallowing upward basinal sequence capped by carbonate platform deposits. Palaeogeographically it is a Late Ladinian transition from the carbonate platform in the south to the typical basinal area in the north.     

Geochemistry and palaeogeography of upper Ordovician glaciogenic sedimentary rocks in the Table Mountain Group, South Africa

Evidence for a late Ordovician glaciation is best known from northern Africa and locally in South Africa, and western South America. The South African glacial deposits (Pakhuis Formation of the Table Mountain Group) are present in the western part of the Cape Fold Belt. Two thin diamictites are succeeded by a coarsening upward shale-siltstone unit known as the Cedarberg Formation. These glaciogenic rocks are associated with one of the world's greatest accumulations of mature sandstones. The diamictites are under- and overlain by shales and sandstones that have undergone extensive alteration, presumably as a result of chemical weathering. Some diamictite samples have low values for a Chemical Index of Alteration (CIA), in keeping with their inferred glacial origin. Immediately above the glaciogenic diamictites, black shales, comprising the basal Soom Member of the Cedarberg Formation preserve an unusual soft bodied fauna and are enriched in Mo, U and other trace elements. The unusual chemical composition of these shales is attributed to starved basin conditions and a reducing environment during a rapid sea level rise that accompanied demise of the late Ordovician glaciers. The late Ordovician glacial deposits of western South Africa are widely regarded as the distal deposits of a large continental ice sheet centred on North Africa but they may have been partly derived from piedmont glaciers that descended from highlands formed as a result of late Ordovician orogeny.     

Surveillance of habitats and plant diversity indicators across a regional gradient in the Iberian Peninsula

Located in the west of the Mediterranean and with high environmental heterogeneity, the Iberian Peninsula represents a challenging region for designing and implementing observation systems for landscape, habitat and species diversity indicators. Within the framework of a project designed to set up a European Biodiversity Observation Network (EBONE), a standardized protocol for field survey was used in pilot sites located across a major gradient in Portugal and Spain. Results are presented and compared to assess the efficiency of the method in detecting patterns along this gradient. These sites represent different types of Iberian landscapes selected using a stratified random procedure implemented in the Madrid province (Spain) and in the north of Portugal. Species and habitat richness and diversity (as well as their components) are compared in their relation to environmental gradients and survey area. Results from spatial analyses of landscape heterogeneity are also presented and discussed in relation to appropriate indicators. The implications for setting up cost-efficient observation schemes that capture the key indicators effectively are discussed. Perspectives for integration with complementary monitoring schemes targeted at key species, habitat and landscape indicators are also discussed in order to optimize the power and efficiency of these observation networks.     

The Iberian Peninsula: ancient history of a hot spot of mite harvestmen (Arachnida: Opiliones: Cyphophthalmi: Sironidae) diversity

The Iberian Peninsula represents a hot spot of cyphophthalmid (mite harvestman) disparity, with four of the eight genera currently recognized in the family Sironidae represented in the region – a generic diversity and morphological disparity not found in any other region of the World so far. From these, two genera (Iberosiro and Odontosiro) are monotypic, and are restricted to the western side of the peninsula. Parasiro is restricted to the north‐east region, from the Catalonian Coastal Ranges and both sides of the Eastern Pyrenees, in areas where the annual rainfall surpasses 1000 mm, and mostly restricted to areas with Paleozoic and Variscan rocks, with other species of the genus extending to Corsica, Sardinia, and the Italian Peninsula. A second species of the genus Paramiopsalis, Paramiopsalis eduardoi sp. nov. from Fragas do Eume, is described here along with a re‐diagnosis of the genus. Paramiopsalis species, together with Odontosiro, inhabit the north‐west corner of the Iberian Peninsula, an area with some of the highest recorded annual rainfall, and with Paleozoic rocks from the Iberian Massif or Variscan granitoid rocks. A phylogenetic analysis of the members of the family Sironidae using four molecular markers, despite not including all of the Iberian genera, clearly shows the non‐monophyly of the Iberian Cyphophthalmi, indicating that the Iberian Peninsula is home to multiple ancient lineages of mite harvestmen. The two Paramiopsalis species form a sister clade to the Balkan genus Cyphophthalmus, whereas Parasiro constitutes the first lineage of the sironids represented.     

Origin, sequence stratigraphy and depositional environment of an upper Ordovician (Hirnantian) deglacial black shale, Jordan

The upper Ordovician succession of Jordan was located 60°S, less than 100 km from the Hirnantian ice sheet margin. New graptolite dates indicate glaciation ended in Jordan in the late Hirnantian (persculptus Biozone). The succession records two glacial advances within the Ammar Formation and the subsequent deglaciations. Organic-rich black shales (Batra Formation) form part of the final deglacial transgressive succession that in-filled an existing low stand glacial continental shelf topography. The base of the black shale is coincident with the maximum flooding surface. During transgression, interfluves and sub-basin margins were breached and black shale deposition expanded rapidly across the region. The top of the black shales coincides with peak highstand. The “expanding puddle model” (sensu Wignall) for black shale deposition, adapted for the peri-glacial setting, provides the best explanation for this sequence of events.

We propose a hypothesis in which anoxic conditions were initiated beneath the halocline in a salinity stratified water column; a fresher surface layer resulted from ice meltwater generated during early deglaciation. During the initial stages of marine incursion, nutrients in the monimolimnion were isolated from the euphotic zone by the halocline. Increasing total organic carbon (TOC) and δ¹³C_org up section indicates the organic carbon content of the shales was controlled mainly by increasing bioproductivity in the mixolimnion (the Strakhov model). Mixolimnion nutrient levels were sustained by a continual and increasing supply of meltwater-derived nutrients, modulated by obliquity changes in high latitude insolation. Anoxia was sustained over tens to hundreds of thousands of years. The formation of black shales on the north Gondwana shelf was little different to those observed in modern black shale environments, suggesting that it was the nature of the Ordovician seas that pre-disposed them to anoxia.     

Trace fossils of the Jurassic,blue Lias,Lyme Regis,Southern England

The Lower Jurassic, Blue Lias Formation at Lyme Regis, Dorset, England is rhythmically bedded with symmetrical rhythms consisting of laminated black shale followed by dark then pale marls (sometimes cemented into pale limestones) and back to laminated black shale. Its trace fossil fauna includes nine ichno‐genera and represents a shallow shelf paleoenviron‐ment. The ichnofauna occurs in three assemblages named after consistently occurring ichnogenera. A Chondrites assemblage (diversity = 1 ichnogenus) and a Chondrites‐Arenicolites assemblage (diversity = 2–3 ichnogenera) are typical of dark marls but may penetrate tops of laminated black shales. A thalassi‐noides‐Chondrites‐Arenicolites assemblage (diversity up to 7 ichnogenera) is typical of pale marls or limestones. Blue Lias limestones are diagenetic: dark laminated limestones and pale bioturbated limestones are cemented equivalents of laminated black shales and pale marls, respectively. However, pale burrow fills in darker sediments and vice versa confirm the rhythms are primary. Rhythms represent redox cycles, fluctuating from anoxic laminated black shales lacking mac‐robenthos or infauna (bioturbation index = 0) to oxic, bioturbated, pale marls or limestones with large mac‐robenthos such as Gryphaea or Plagiostoma and diverse infauna (bioturbation index = 5).     

Origin of mid-cretaceous black shales in the benue through, Nigeria

Black and dark-gray laminated shales with large amounts of both terrestrial and marine organic material are common in upper Cenomanian to lower Santonian rocks of the Benue Trough. These shales were deposited during global mid-Cretaceous marine transgressions when widespread high organic carbon sedimentation took place. The Benue Trough in those times was the site of a shallow, density-stratified, anoxic epeiric sea with estuarine-type circulation. From this reservoir, nutrient-rich oxygen-depleted waters were fed into the northern parts of the South Atlantic Ocean.     

论陡山沱组的年代

三峡地区震旦系的三层式地层结构 (冰积层 ,陡山沱组特色的大型带刺疑源类组合层 ,埃迪卡拉生物化石层 )在世界其它地区是常见的。通过生物和化学地层对比我们认为陡山沱组及其化石组合层是在马雷诺恩 ( Marinoan)冰期之后、埃迪卡拉生物群分异之前沉积的。根据这一地层对比方案以及西伯利亚、纳米比亚和阿瓦龙半岛 ( Avalon Peninsula)新元古代地层的精确放射性同位素测年资料 ,陡山沱组的沉积年龄很可能在五亿五千万年至六亿年之间。这一估计要新于以前发表的铷锶法或钾氩法测定的陡山沱组黑色页岩或海绿石年龄。更精确地估算陡山沱组的沉积年龄还有待于在陡山沱组地层中发现火山灰以及对火山灰的精确年龄测定 ,但我们根据地层对比估算的陡山沱组年龄 ,为评估庙河和瓮安陡山沱组生物群的演化意义提供了必要的地层框架。     

塔里木柯坪地层区中-上奥陶统萨尔干组碳酸盐岩微相和古地理

塔里木板块西北柯坪地层区中-上奥陶统萨尔干组的分布和相变受控于当时西浅东深的海底深度差异。萨尔干组的厚度10米左右,为富含有机物的黑色页岩并夹少量灰岩薄层或透镜体。位于研究区西南的伽师西克尔剖面缺失大部分奥陶纪地层,上奥陶统铁热克阿瓦提组碎屑岩不整合于下-中奥陶统鹰山组灰岩之上,中-晚奥陶世的大部分时段属于暴露海面的剥蚀区;北部乌什的亚科瑞克剖面无萨尔干组岩性单元,为红色居多且粒度偏粗的碎屑岩夹白云岩薄层,属于近岸带碎屑岩为主的沉积区。西克尔向东北延伸150km至柯坪羊吉坎亦无萨尔干组,与萨尔干组同期沉积的地层在此表现为大湾沟组上部浅海灰岩的相变,且与上奥陶统桑比阶坎岭组偏深水相的红色薄层含泥瘤状灰岩之间呈整合接触;由西向东出露于柯坪苏巴什沟、柯坪大湾沟、阿克苏四石厂3个剖面的萨尔干组黑色泥页岩指示典型的滞流盆地相,而夹含于萨尔干组下部和上部的薄层灰岩之微相特征差异甚为显著,表现为该组下部可见数层密集砂屑颗粒形成泥粒状灰岩或颗粒灰岩,可解释为西部相邻的浅海碳酸盐岩台地区灰岩经重力流搬运后的再沉积;而该组上部含生屑泥状灰岩则属滞流盆地相区类似于黑色页岩环境的正常沉积。从羊吉坎灰岩台地到苏巴什沟滞流盆地相之间距离仅20余千米,坡度偏大是导致重力流形成的主要原因。     

Discovery of agglutinated benthic foraminifera in Devonian black shales and their relevance for the redox state of ancient seas

Agglutinated foraminifera are benthic organisms that occur in marginal marine to bathyal environments. Though some taxa can live in oxygen deficient environments, they require at least some oxygen in order to persist at the seafloor. The discovery that they occur widely in Late Devonian black shales has a bearing on the boundary conditions required for episodes of extensive carbon sequestration in marine sediments and their connection to atmospheric composition and global climate. Devonian black shales of the eastern US have been studied extensively to determine the fundamental controls on carbon burial, and a range of mechanisms has been proposed. Finding agglutinated benthic foraminifera in these black shales refocuses the debate about their origin and points to limitations of earlier models.     

The origins of Iberian horses assessed via mitochondrial DNA

Despite a number of recent studies that have focused on the origin of domestic horses, genetic relationships between major geographical clusters still remain poorly understood. In this study we analyzed a 296 bp mtDNA fragment from the HVI region of 171 horses representing 11 native Iberian, Barb, and Exmoor breeds to assess the maternal phylogeography of Iberian horses. The mtDNA haplogroup with a CCG motif (nucleotide position 15,494 to 15,496) was the most frequent in Iberian and Barb breeds (0.42 and 0.57, respectively), regardless of geographic location or group of breeds. This finding supports the close genetic relationship between the ancestral mare populations of the Iberian Peninsula and Northern Africa. Phenotypic differences among the Northern and Southern Iberian groups of breeds are not explained by population subdivision based on maternal lineages. Our results also suggest that Northern Iberian ponies--which are phenotypically close to British ponies, especially Exmoor--are the result of an introgression rather than population replacement.     

Cenomanian–Turonian carbonate and organic-carbon isotope records, biostratigraphy and provenance of a key section in NE Sicily, Italy: Palaeoceanographic and palaeogeographic implications

In eastern Sicily, a series of highly organic-rich black shales occur as exotic blocks (~ 100 m across) floating in tectonized sediments (Argille Varicolori Unit containing olistoliths of Cretaceous–Palaeogene age). A 19-metre section, through one of these blocks near the town of Novara di Sicilia, includes cyclically bedded black shales, marlstones and claystones, which have been dated using planktonic foraminiferal and nannofossil biostratigraphy. On this basis, the section is assigned to the latest Cenomanian and clearly represents a manifestation of the Oceanic Anoxic Event characteristic of that interval. Total organic-carbon values range up to 23% and the relatively high hydrogen indices record the presence of marine organic matter of low thermal maturity. High-resolution carbonate and organic-carbon isotope curves are comparable with those recorded elsewhere in indicating a significant positive excursion and confirm that, in the Novara di Sicilia section, the black shales are latest Cenomanian in age. By comparison with Cenomanian–Turonian black shales exposed elsewhere in Italy (Calabianca section, western Sicily; Livello Bonarelli, Bottaccione Gorge, Gubbio, Marche–Umbria), the section of Novara di Sicilia is different in being more stratigraphically expanded. However, this section from eastern Sicily does resemble extremely closely coeval sediments cropping out in Tunisia and Morocco. This association is taken as evidence that the Argille Varicolori Unit includes elements that were initially deposited on the north African shelf during Cretaceous time.     

一种濒危大疣蛛的潜在分布区域以及气候变暖的影响

本研究的目的是i)确定伊比利亚半岛一种大疣蛛(Macrothele calpeiana)分布的气候相关性以预测其潜在分布,ii)详细阐述该物种在伊比利亚半岛的分布假说,iii)通过推断模型预测确认该物种在北非和整个地中海地区的适合区域,iv)预测气候变暖对蜘蛛潜在分布区的影响。基于物种的存在、远离目前环境条件下的可能缺失以及其它的气候参数,使用广义线性模型发展了潜在分布的可预测模型。蜘蛛在伊比利亚半岛上的潜在分布远大于目前已知的分布区,延伸到尚未发现蜘蛛分布的葡萄牙广大地区。本文提出了该种大疣蛛在适合分布区域内没有分布的历史因素。北非具有适合该物种的条件但却没有该属物种的分布支持了大疣蛛(Macrothele)祖先的东方起源假说。对地中海地区蜘蛛分布的推断突出显示了阿根廷地区有合适的分布区,该地区也发现有另一种欧洲大疣蛛。气候变暖将对现存于伊比利亚的M.calpeiana种群产生负面影响,因为气候变暖将减少并破碎化蜘蛛在北非的潜在栖息地。目前,急需确认在葡萄牙广大地区是否存在蜘蛛物种,发展对该属的系统发育研究以确定大疣蛛属起源和扩散史的理论。     

The regional record of Albian oceanic anoxic events at the Apulian Platform Margin (Gargano Promontory, southern Italy)

The Gargano Promontory, located on the eastern margin of the Apulia Platform, represents a distinctive Tethyan area where the transition from carbonate platform to adjacent basin is exposed on land. The Albian stratigraphic record, represented by shallow-water, slope and deep-water deposits, provides a good opportunity to investigate the regional response to oceanic anoxic events (OAEs) in different depositional settings by using an integrated, high-resolution micropalaeontological (planktonic foraminifers and calcareous nannofossils) approach. Results show that organic matter preservation is confined to the more distal areas (Marne a Fucoidi Formation), and consists of black shale intervals from the middle and late Albian (Ticinella primula/Prediscosphaera columnata Zones; upper Ticinella praeticinensis Subzone/R. achlyostaurion Zone, respectively). Integrated biostratigraphic data correlate the intervals of black shale deposition to the Urbino and Amadeus levels, previously identified and named in the Umbria-Marche Basin. These black shales record the effects of OAEs 1b and 1c. The biotic changes in the pelagic Albian succession of the Apulian Platform Margin provide evidence for episodes of eutrophication that correlate to the deposition of these black shales. Genetic models for the two episodes of organic matter preservation are proposed, taking into account both global and local controlling factors.     

Formation of large carbonate concretions in black cherts in the Gufeng Formation (Guadalupian) at Enshi,South China

The formation of carbonate concretions is a cementation process which passively infills the pore spaces within sediments. They record the original environments of deposition and diagenetic conditions of the host rocks. Little is known about the precise mechanisms responsible for the precipitation of carbonate concretions. The most common host rocks are mudstones/shales, sandstones, and limestones. This study presents an example of large carbonate concretions from an unusual host rock, the black bedded cherts of the Gufeng Formation (Guadalupian) at Enshi on the northern Yangtze Platform, South China. Petrographic observations (X‐ray diffraction, optical microscopy, scanning electron microscopy) and multiple geochemical analyses (pyrite‐ and carbonate‐associated‐sulfate (CAS)‐sulfur isotopes, carbon isotopes) indicate that (a) the studied carbonate concretion are mainly composed of micritic calcite with subordinate dolomite; (b) the concretions may have been mainly formed in the bacterial sulfate reduction (BSR) zone during very early diagenesis near the sediment–water surface; (c) the paleo‐bottom water overlying the sediments during formation of the concretions was mainly euxinic; and (d) the growth of the studied concretions proceeded via a pervasive model, where later cementation phase initiated in the lower part of the concretions and progressed upward.     

Migration and winter distribution of Iberian and central European black storks Ciconia nigra moving to Africa across the Strait of Gibraltar: a comparative study

This paper compares the migratory movements of Iberian and central European satellite‐tagged black storks Ciconia nigra moving to Africa across the Strait of Gibraltar. Results show that the populations differ in departure dates from breeding areas (central European birds start to move 15 d before Iberian birds), cross the Strait of Gibraltar together and reach the Sahel on similar dates. This synchronic arrival to the Sahel may be related with the onset of suitable conditions for the species after summer rains, when many pools are available for fishing. In this area, Iberian birds occupied westernmost localities compared to central European birds crossing the Strait of Gibraltar, which were distributed closer to those storks arriving in Africa across the Bosporus. This suggests that the parallel distribution of breeding and wintering areas results from posterior rearrangements of the two populations crossing Gibraltar. These patterns appear to be linked to the increasing population of central European black storks located on the western side of the migratory divide that moves throughout the western flyway to sectors of the Sahel close to their ancestral wintering grounds.