scholarly journals Palynological characteristics of Givetian-Frasnian stratigraphic interval on the Southern and Middle Timan

2019 ◽  
Vol 10 ◽  
pp. 23-27
Author(s):  
O. P. Tel’nova ◽  
◽  
I. Kh. Shumilov
Keyword(s):  
Middle Timan ◽  
Stratigraphic Interval

A UNIQUE FINDING OF ZIRCON INTO BADDELEYITE TRANSFORMATION (THE ICHETJU ORE OCCURRENCE, THE MIDDLE TIMAN)

2018 ◽  
pp. 27-35
Author(s):  
S. G. Skublov ◽  
A. O. Krasotkina ◽  
A. B. Makeyev ◽  
O. L. Galankina ◽  
A. E. Melnik
Keyword(s):  
High Temperature ◽  
Experimental Studies ◽  
Middle Timan ◽  
Natural Analogues ◽  
Opposite Situation ◽  
Formation Conditions

Findings of the growth relationships between baddeleyite and zircon are rare, due to significant differences in the formation conditions of the minerals. A reaction replacement (partial to complete) of baddeleyite by zircon is possible during metamorphism accompanied by the interaction with high-Si fluids. The opposite situation, when zircon is replaced by baddeleyite, is extremely rare in the nature. Transformation of zircon from polymineral (compound) ore occurrence Ichetju (the Middle Timan) with the formation of microaggregates of baddeleyite, ratile and florencite has been found out. The size of the largest segregations of baddeleyite does not exceed 10 microns in diameter. Microaggregates are unevenly related to the rim of zircon with a thickness of 10 to 50 rfn, voids and cracks across the grain. Altered zircon rim (a mixture of newly formed minerals) is characterized by sharply increased composition of REE (especially LREE), Y, Nb, Ca, Ti. The composition of Th and U also increases. An overview of the experimental studies on the reaction between zircon and baddeleyite and single natural analogues allows to make a conclusion that the most likely mechanism of the transformation of zircon from ore occurrence Ichetju to baddeleyite (intergrowth with ratile and florencite) is due to the effect of interaction of primary zircon with high-temperature (higher than 500—600°C) alkaline fluids transporting HFSE (REE, Y, Nb, Ti). This is indirectly confirmed by the findings of zircon with anomalous high composition of Y and REE up to 100000 and 70000 ppm respectively.

scholarly journals The Souss lagerstätte of the Anti-Atlas, Morocco: discovery of the first Cambrian fossil lagerstätte from Africa

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Gerd Geyer ◽  
Ed Landing
Keyword(s):  
South China ◽  
Lower Cambrian ◽  
Northern Slope ◽  
Sea Floor ◽  
Upper Cambrian ◽  
Exceptional Preservation ◽  
West Gondwana ◽  
Regional Correlation ◽  
Animal Remains ◽  
Stratigraphic Interval

AbstractEpisodic low oxygenated conditions on the sea-floor are likely responsible for exceptional preservation of animal remains in the upper Amouslek Formation (lower Cambrian, Stage 3) on the northern slope of the western Anti-Atlas, Morocco. This stratigraphic interval has yielded trilobite, brachiopod, and hyolith fossils with preserved soft parts, including some of the oldest known trilobite guts. The “Souss fossil lagerstätte” (newly proposed designation) represents the first Cambrian fossil lagerstätte in Cambrian strata known from Africa and is one of the oldest trilobite-bearing fossil lagerstätten on Earth. Inter-regional correlation of the Souss fossil lagerstätte in West Gondwana suggests its development during an interval of high eustatic levels recorded by dark shales that occur in informal upper Cambrian Series 2 in Siberia, South China, and East Gondwana.

Lithogeochemical characteristics of metasandstones of the Chetlas series (Chetlassky Kamen, Middle Timan)

2021 ◽  
pp. 3-12
Author(s):  
N. Y. Nikulova ◽  
◽  
O. V. Udoratina ◽  
I. V. Kozyreva
Keyword(s):  
Inductively Coupled Plasma ◽  
Volcanic Rocks ◽  
Rare Metal ◽  
Weathering Crust ◽  
Terrigenous Material ◽  
Inductively Coupled ◽  
Coastal Marine ◽  
Icp Ms ◽  
Middle Timan ◽  
Destruction Of Rocks

The lithological and geochemical features of the metasandstones of the Svetlinskaya and Vizingskaya formations of the Middle Late Riphean Chetlas series in the Middle Timan, which are a substrate of rare-metal-rare-earth mineralization in several ore occurrences of the Kosyus ore cluster, have been investigated. The interpretation of the results of traditional weight chemical and mass spectrometric inductively coupled plasma (ICP MS) analyses allowed us to identify differences in the material composition of metapesanics, mainly due to changes in the degree of sedimentation maturity of terrigenous material coming from the demolition areas. The composition of metasandstones in various ratios includes both weakly weathered products of destruction of volcanic rocks of intermediate/basic composition, and altered, including under conditions of the weathering crust, metaterrigenous formations. The accumulation of sediments took place in a shallow coastal-marine environment with changing hydrodynamics, which affected the rate of destruction of rocks in paleo-catchments.

A New and Open CoiledValvata(Gastropoda) from the Pliocene Koobi Fora Formation of the Turkana Basin, Northern Kenya

2010 ◽  
Vol 84 (5) ◽  
pp. 996-1002 ◽  
Author(s):  
Henning Scholz ◽  
Matthias Glaubrecht
Keyword(s):  
New Species ◽  
Environmental Stress ◽  
Environmental Conditions ◽  
Lake Level ◽  
Shell Morphology ◽  
Koobi Fora ◽  
Northern Kenya ◽  
Turkana Basin ◽  
High Level ◽  
Stratigraphic Interval

New field collections allow the study and description ofValvata juliaenew species from the Pliocene upper Burgi Member of the Koobi Fora Formation of Kenya. The shell morphology of this species varies from trochospiral to planispiral to open coiled. The species is restricted to a short stratigraphic interval.Valvata juliaeis considered as an invader of the Turkana Basin during a lacustrine transgression event. The open coiling of the species is interpreted as an ecophenotypic response to a high level of environmental stress caused by lake level fluctuations and emergence of delta systems. These environmental conditions broughtValvata juliaeto extinction soon after it invaded the Turkana Basin.

Tubey or not tubey: Death beds of Ediacaran macrofossils or microbially induced sedimentary structures?

Geology ◽  
2019 ◽  
Vol 47 (10) ◽  
pp. 909-913
Author(s):  
Lyle L. Nelson ◽  
Emily F. Smith
Keyword(s):  
Environmental Conditions ◽  
Trace Fossils ◽  
Microbial Mat ◽  
Sedimentary Structures ◽  
Bedding Planes ◽  
Stratigraphic Interval

Abstract Within the upper Ediacaran Esmeralda Member of the Deep Spring Formation in southeastern California, USA, an ∼3 m stratigraphic interval contains multiple clastic bedding surfaces with enigmatic, three-dimensionally preserved corrugated tubes (<60 cm in length and 6 cm in width). When viewed as fragments and in situ on bedding planes, these resemble larger versions of annulated, tubular soft-bodied macrofossils that are common in late Ediacaran biotic assemblages regionally and globally. Despite superficial similarities to casts and molds of body fossils preserved in correlative strata, we suggest these tubes are instead previously undescribed organosedimentary structures that developed through differential compaction of rippled heterolithic interbeds bound by pyritized microbial mat layers. These distinctive structures formed within peritidal settings in the latest Ediacaran Period as the result of specific ecological and environmental conditions marked by flourishing microbial mat communities and dysoxic sediments. This interpretation may inform the biogenicity of other structures previously reported as macroscopic body or trace fossils.

First documentation of the Ordovician Guttenberg δ13C excursion (GICE) in Asia: chemostratigraphy of the Pagoda and Yanwashan formations in southeastern China

2008 ◽  
Vol 146 (1) ◽  
pp. 1-11 ◽  
Author(s):  
STIG M. BERGSTRÖM ◽  
CHEN XU ◽  
BIRGER SCHMITZ ◽  
SETH YOUNG ◽  
RONG JIA-YU ◽  
...  
Keyword(s):  
North American ◽  
First Record ◽  
Upper Ordovician ◽  
Yangtze Platform ◽  
Asian Continent ◽  
Southeastern China ◽  
Stratigraphic Unit ◽  
Baseline Values ◽  
Stratigraphic Interval

AbstractThe only published δ13C data from the Ordovician of China are from the Lower and Upper Ordovician, and only the latter records include a significant excursion, namely the Hirnantian excursion (HICE). Our recent chemostratigraphic work on the Upper Ordovician (Sandbian–Katian) Pagoda and Yanwashan formations at several localities on the Yangtze Platform and Chiangnan (Jiangnan) slope belt has resulted in the recognition of a positive δ13C excursion that has values of ~+1.5‰ above baseline values. This excursion starts a few metres above a stratigraphic interval withB. alobatusSubzone conodonts as well as graptolites of theN. gracilisZone. The distinctive conodontsAmorphognathusaff.Am. ventilatusandHamarodus europaeusfirst occur at, or very near, the excursion interval. Because these conodonts appear in the stratigraphic interval of the Guttenberg δ13C excursion (GICE) in Estonia, we identify the Chinese excursion as the GICE. This is the first record of the GICE in the entire Asian continent. It confirms that GICE is a global excursion and provides an illustration of how δ13C chemostratigraphy, combined with new biostratigraphic data, solves the problem of the previously controversial age of the Pagoda Formation and how this classical stratigraphic unit correlates with the Baltoscandian and North American successions.

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