REVUE DE MICROPALEONTOLOGIE最新文献

The eastern Mediterranean Sea is a partially isolated sea where excess evaporation over precipitation or riverine discharge results in large north to south gradients in temperature and salinity. Eastern Mediterranean Sea surface sediment samples from 28 locations spanning from the North Aegean to the Levantine Sea have been examined for recent planktonic foraminiferal distribution. In addition to determining the relative abundance of 12 species that have been identified, the average intraspecific size along with the size of the overall faunal pattern was also examined. The quantitative analysis performed on >125 μm fraction reveals pronounced and complex changes in planktonic foraminiferal assemblages that do not parallel the intraspecific size variation and sea surface temperature (SST). On the contrary, foraminifera most of the times are slightly larger in the colder and fresher North Aegean and become progressively smaller toward the warmer Levantine Sea. We conclude that the relationship between planktonic foraminifera shell size and abundance or SST are either absent or weaker than previously reported for other regions and that in E. Mediterranean assemblages size may be mainly related to nutrient availability.

The Aptian–Albian boundary has long been difficult to identify along the foreland basin of the Tunisian Atlas, although ammonites occur in the Fahden Formation. The revision of Aptian–Albian series from Jebel Sidi Salem, in the northeastern part of the Tunisian Ridge, provides new data for the recognition of this boundary. The Jebel Sidi Salem section contains a rich succession of planktic foraminifers’ index species which document a complete marine record of Aptian–Albian boundary with no sign of redeposition. Six zones of planktic foraminifera have been identified through the late Aptian to middle Albian; including Globigerinelloides algerianus Zone, Hedbergella trocoidea Zone, Planomalina cheniourensis Zone, Paraticinella eubejaouensis/Ticinella roberti Zone, Hedbergella planispira Zone and Ticinella primula Zone.

The morphological abnormalities caused on the agglutinated foraminifera Ammobaculites texanus CUSHMAN extracted from the Lower Kharga Member of the Dakhla Formation (Upper Maastrichtian) deposits may be caused due to environmental factors such as high organic flux, high terrigenous input and low salinity as indicated by the presence of Ammoastuta together with A. texanus agglutinated foraminifera, which suggested hyposaline environments.

The deformations described in this work are several types of morphological abnormalities, including irregular chamber shape (lobate peripheral outline), abnormal size or shape of the last chambers, high spire giving a spiroconvex test and irregular coiling, and additional chambers (elongated axes of rotation). Some studied species of A. texanus show compaction and the collapse of the inner microgranular layer, the compaction indicates the binding of quartz grains with a deformable substance before cementation.

Climatic oscillations during the Pleistocene were controlled by glacial/interglacial cycles. Such oscillations are commonly imprinted into sediments and fossils from transitional marine environments, as is also the case in Sousaki Basin (Eastern Gulf of Corinth, Greece). Nevertheless, the records become scarcer as we go back in time. During the Lower Pleistocene, Sousaki Basin (Eastern Gulf of Corinth, Greece), was dominated by transitional marine environments. Micropalaeontological analysis has been carried out in sedimentary sequences to identify the evolution of the palaeoenvironments in an area where intense tectonic activity occurred, being at the western end of the Hellenic volcanic arc and at the eastern end of the Corinth rift. The recovered ostracod assemblage revealed a primarily brackish environment. Deposition took place in a coastal lagoon which was subjected to constant salinity changes. The palaeoenvironment in the basin evolved from a delta fan environment to an outer lagoon with possible connection to a sublittoral marine environment at the top. This evolution coincides and therefore is attributed to minor climate oscillations that occurred during the Early Pleistocene.

Abundant specimens of the orbitolinid Dictyoconus turriculus Hottinger and Drobne from Thanetian shallow-water carbonates of the Zagros Zone, SW Iran, allow new taxonomic insights. With a high conico-cylindrical test, lacking a prominent eccentric initial spire and the occurrence of a distinct zone of only primary beams between the marginal zone (with subepidermal network) and central zone, this species always stood out from a morphological perspective among the other species of the genus Dictyoconus Blanckenhorn. However, its generic status was never challenged. The aligned arrangement of the main radial partitions and also of the pillars to a large extent, rules out a possible inclusion of this species in a rigorous classification framework within the genus Dictyoconus Blanckenhorn and therefore, the subfamily Dictyoconinae Moullade because its members display an alternating pattern of the respective structural elements. In addition, intercalary elements also occur and account for the partly irregular pattern, a pattern similar with that of Dictyorbitolina Cherchi and Schroeder. The new genus Schroedericonus is introduced with the new combination Schroedericonus turriculus (Hottinger and Drobne) and assigned to the Dictyorbitolininae Schroeder. As a consequence of this taxonomic review, there are no other species of Dictyoconus in the Paleocene. The distributional pattern of Dictyoconus (upper Cretaceous and Eocene) can be considered as a classical example of iterative evolution.

A detailed palynostratigraphic study of two Somincor/Lundin Mining exploration drill holes intercepting the Phyllite-Quartzite (PQ) Formation in the geological basement of the Neves-Corvo mine region (Portuguese sector of the Iberian Pyrite Belt – IPB) allowed to first recognise the oldest ages for this formation in this region, ranging from midGivetian/midFrasnian (base unknown) to late Famennian. The TA Miospore Biozone (Cristatisporites triangulatus-Ancyrospora ancyrea) of middle Givetian age (Middle Devonian) was identified in NK30B-1 drill hole (Lombador North mine sector), whereas the BM Miospore Biozone (Verrucosisporites bulliferus-Lophozonotriletes media) and IV Miospore Biozone (based in the first occurrence of Rugospora bricei and Diducites cf. poljessicus) of middle Frasnian (Late Devonian) age were both recognised in drill hole SJ32 (Corvo-Semblana mine sector). The common presence of Early-Middle Devonian reworked spores, as well as similar inherited zircon ages may suggest that the lower PQ Formation age is not yet known.

At Neves-Corvo mine, the Volcano-Sedimentary Complex is deposited directly above the PQ basement, spanning different ages, pointing out two major unconformities, a VSC/upper and/or lower PQ sequences and an upper PQ/lower PQ sequences.

A palynostratigraphic correlation of the lowermost Phyllite-Quartzite Formation across the IPB is established. Phyllite-Quartzite Formation palynoassemblage of Neves-Corvo region is compared with lowermost PQ assemblages recovered in the NW sector of IPB (S. Francisco da Serra and Lousal-Caveira mine structures, Portugal) and in E sectors of the IPB in Spain (Gerena-El Garrobo section). The similar palynological record (also including the same reworked taxa signature) and ages obtained, suggests identical sedimentary provenance, close paleogeographic domain and temporal affinity throughout the lowermost IPB Phyllite-Quartzite Formation.

The paleoenvironmental evolution of Lake Ismarida in Thrace (Northern Greece) is revealed by the combined lithological, micropaleontological (benthic foraminifera, pollen and NPPS), molluscan analyses, magnetic susceptibility measurement and radiocarbon dating of a 5.8-m long sediment core. The mid Holocene evolution of the lake area is evidenced by the documentation of four sedimentary Units in the core ISMR-2, corresponding to four distinct evolutionary stages: (1) during ∼5500-3500 cal yr BP the lake area was a shallow marine environment characterized by an Ammonia beccarii, small rotaliids, miliolids, Bittium reticulatum and Veneridae spp. assemblage, marine dinoflagellate cysts, and low magnetic susceptibility values; (2) during ∼3500-3000 cal BP the environment is gradually tending to more isolated conditions forming an open lagoon, characterized by marine and euryhaline fauna and low magnetic susceptibility values; (3) during 3000 cal yr BP, the open lagoon presented a transition to an oligohaline inner lagoon, characterized by an Ammonia tepida, Haynesina germanica, Aubignyna perlucida, Pirenella conica, Cerastoderma glaucum and Abra spp. assemblage, sedges and aquatic vegetation. This restricted, entirely isolated from the sea inner lagoon could be definitely used as the landmark of the Lake Ismaris from Heorodotus, while describing the march of Xerxes through Thrace in 480 B.C.; (4) since ∼2000 cal yr BP to the present, the Lake Ismarida is formed, characterized by fresh-water indicators and aquatic pollen, Pseudoschizaea and high magnetic susceptibility values. Finally, the progradation of the Filiouris River deltaic deposits resulted to a 4 km wide deltaic plain between Lake Ismarida and the nowadays coastline. Pollen assemblages record the dominance of a rather rich deciduous forest in the area with traces of human presence in the lower part of the sequence, whereas the opening of the plant landscape under the increasing human pressure is evidenced after ∼ 3000 cal yr BP. Finally, an open vegetation pattern, contemporaneous with the retreat of forest vegetation, is evidenced in the area already before 2000 cal yr BP.

Mediterranean mountain ecosystems have been attractive to human societies due to their valuable resources, but are also susceptible to environmental and climate changes. The Rhodope Mountain Range hosts one of the least disturbed natural forests of Europe and is a conservation priority area in the Southern Balkans. Located in the borderlands of the plain of Macedonia, the forest ecosystem development of Rhodope Mountains was shaped not only by Late Holocene climatic variability, but also by changes in human activities since Byzantine times. Palynological and microscopic charcoal analysis of the Livaditis ombrotrophic bog record offers unique insights into vegetation and landscape evolution under the influence of human land-use practices in the south Rhodope area during the last c.a. 1100 years. The findings show a forested landscape, with well-developed Pinus and Abies forests of in the montane zone and mixed deciduous oak forests below that flourished in the area until 900 AD. The expansion of human activity in mountainous areas during the period of Byzantine economic growth (ca. 1000 AD) is evidenced by forest clearance through fire, affecting mainly the Abies populations. The Livaditis record bears evidence about both, arboriculture and cereal cultivation as well as animal husbandry during the first period of human activities in the uplands, while a shift towards pastoralism is most likely associated with the establishment of the Vlach population in the region (ca. 1200 AD). Subsequently, a short-lived expansion of the Pinus percentages could be attributed to the afforestation of abandoned pasture land during the Little Ice Age. Finally, a further intensification of pastoralism is most likely concurrent with the population expansion documented during the Ottoman period (after 1500 AD). The Livaditis pollen record shows significant vegetation shifts in the upland area of southern Rhodope Mountains that could be associated with changes in climate, population mobility and density, as well as evolving land-use practices.