Search results for "Crust"

Changes in epizoic crustacean infestations during cetacean die-offs: the mass mortality of Mediterranean striped dolphins Stenella coeruleoalba revis…

2006

In the summer and autumn of 1990, a cetacean morbillivirus caused a massive epizootic mortality of striped dolphins Stenella coeruleoalba in the western Mediterranean. Previous circum- stantial evidence suggested that the disease could also have increased host susceptibility to infesta- tions with epizoic crustaceans. In this study we provide strong evidence supporting this hypothesis. We examined striped dolphins stranded along the Mediterranean central coast of Spain from 1981 to 2004 (n = 136), and recorded data on prevalence, intensity of infestation, size and reproductive status of 2 sessile crustacean species specific to cetaceans, the phoront cirriped Xenobalanus globicipitis and the…

DNA taxonomy of the potamid freshwater crabs from Northern Africa (Decapoda, Potamidae)

2020

The Mediterranean area, from southern Balkans to western Maghreb, is inhabited by the Potamon subgenus Euthelphusa, with three currently recognised species. The Maghrebian species P. (E.) algeriense is isolated from other Potamon species by the Mediterranean Sea and the Sahara Desert, and nearly no molecular data are currently available for this taxon. Present study investigated the mtDNA and nuDNA diversity in Potamon algeriense s.l. with the aims of exploring its molecular diversity pattern throughout its known distribution range, and testing the possible presence of cryptic taxa currently lumped under this binomen. The phylogenetic and DNA taxonomy analyses showed the presence of two wel…

Chapter 5.2 The Ancient Gneiss Complex of Swaziland and Environs: Record of Early Archean Crustal Evolution in Southern Africa

2007

Publisher Summary This chapter discusses the record of early Archean crustal evolution in Southern Africa. Southern Africa preserves one of the most complete and detailed records of early Precambrian crustal evolution, and the Ancient Gneiss Complex (AGC) of Swaziland and the related rocks along the southern margin of the 3.5–3.2 Ga Barberton Greenstone Belt (BGB) have played a prominent role in models for the early evolution of continental crust. The AGC is separated from the BGB by a large granitoid sheet-like pluton some 3 Ga in age and known as the Mpuluzi Batholith. In northwest Swaziland, however, small inliers of AGC gneisses occur in faulted and sheared contact with BGB rocks, and t…

Detrital and igneous zircon ages for supracrustal rocks of the Kyrgyz Tianshan and palaeogeographic implications

2014

Abstract We report detrital zircon ages for Precambrian and early Palaeozoic metasediments from the Tianshan orogen in Kyrgyzstan, an important component of the Central Asian Orogenic Belt and compare these with published ages from the Chinese Tianshan and the Tarim craton. These data provide information on possible source terrains and suggest that Precambrian basement is widespread in the Tianshan and may, at least in part, represent continental fragments rifted off the Tarim craton during the early history of the Central Asian Orogenic Belt. Distinct differences in the Precambrian zircon age distribution between the North and Middle Tianshan of Kyrgyzstan support earlier ideas that these …

Precambrian basement around Wadi Halfa, Sudan: a new perspective on the evolution of the East Saharan Craton

1994

This paper provides new geochemical and isotopic data on the evolution of the western foreland to the Nubian shield of north-east Africa. There is abundant evidence for early to middle Proterozoic crust west of the River Nile, but this was severely affected by the Pan-African (~ 500-900 Ma) orogenic cycle. The results are reported of Rb-Sr whole rock and zircon evaporation geochronological studies and whole rock Sm-Nd and feldspar Pb isotopic analyses for four rock units around Wadi Halfa in northern- most Sudan. These results indicate the presence of heterogeneous pre-Pan-African crustal components, preserved in mylonitic gneisses and in conglomerates that unconformably overlie the gneisse…

Composition, structure and evolution of the early Precambrian lower continental crust: constraints from geological observations and age relationships

1986

EARLY NEOPROTEROZOIC CRUST FORMATON IN THE DZABKHAN MICROCONTINENT, CENTRAL ASIAN OROGENIC BELT

2017

The Dzabkhan microcontinent was defined by [Mossakovsky et al., 1994] as a cratonic terrane with an early Precambrian basement that combines highgrade metamorphic complexes of the Songino, Dzabkhan, Otgon, Baidarik, Ider and Jargalant Blocks. However, early Precambrian ages have so far only been recognized in the Baidarik and Ider blocks [Kozakov et al., 2007, 2011; Kroner et al., 2015].

Zircon U–Pb and Hf isotopic study of gneissic rocks from the Chinese Altai: Progressive accretionary history in the early to middle Palaeozoic

2008

Abstract Gneissic rocks in the Chinese Altai Mountains have been interpreted as either Paleozoic metasedimentary rocks or Precambrian basement. This study reports geochemical and geochronological data for banded paragneisses and associated gneissic granitoids collected along a NE–SW traverse in the northwestern Chinese Altai. Petrological and geochemical data suggest that the protoliths of the banded gneisses were possibly immature sediments with significant volcanic input and that the gneissic granitoids were derived from I-type granites formed in a subduction environment. Three types of morphological features can be recognized in zircons from the banded gneisses and are interpreted to cor…

Zircon ages and Hf isotopic compositions of plutonic rocks from the Central Tianshan (Xinjiang, northwest China) and their significance for early to …

2014

We present new zircon ages and Hf-in-zircon isotopic data for plutonic rocks and review the crustal evolution of the Chinese Central Tianshan (Xinjiang, northwest China) in the early to mid-Palaeozoic. The Early Ordovician (ca. 475–473 Ma) granitoid rocks have zircon eHf(t) values either positive (+0.3 to +9.5) or negative (−6.0 to −12.9). This suggests significant addition of juvenile material to, and coeval crustal reworking of, the pre-existing continental crust that is fingerprinted by numerous Precambrian zircon xenocrysts. The Late Ordovician–Silurian (ca. 458–425 Ma) rocks can be assigned to two sub-episodes of magmatism: zircon from rocks of an earlier event (ca. 458–442 Ma) has neg…

Cadmium-binding proteins in midgut gland of freshwater crayfishProcambarus clarkii

1989

Metallothioneins, metal binding proteins, were originally isolated and characterized by Margoshes and Vallee. These proteins have a high affinity for various heavy metals, particularly cadmium and mercury and have extensively been studied in mammals. Metal binding proteins have been observed in a variety of marine invertebrates; however, there is very little information available on metal binding proteins in freshwater invertebrates, and particularly in freshwater crustaceans. Cadmium is an ubiquitous non essential element which possesses high toxicity to aquatic organisms. Cadmium binding proteins observed in invertebrates have similar characteristics to mammalian metallothioneins. In 1978…