scholarly journals Famennian carbonate microfacies from the Preslavtsi-2 well (Moesian Platform, north-eastern Bulgaria)

2019 ◽  
Vol 48 (2) ◽  
pp. 13-24
Author(s):  
Polina Andreeva
Keyword(s):  
Marine Environments ◽  
Fair Weather ◽  
Carbonate Microfacies ◽  
North Eastern ◽  
Moesian Platform ◽  
Shallow Subtidal ◽  
Carbonate Deposits

The most representative subsurface section of the Famennian carbonate succession from the Moesian Platform in Bulgaria occurs in the R-2 Preslavtsi well. Nine microfacies types (MFTs 1–9) have been distinguished and described in the intraclastic and peloidal limestone unit and the organogenic limestone unit. They are grouped in four microfacies associations: 1) protected shallow subtidal (lagoon) (MFT 1, bioclastic-peloidal packstone/grainstone; and MFT 2, oncoidal wackestone); 2) wave-dominated shallow subtidal (MFT 3, intraclastic-peloidal grainstone and rudstone; MFT 4, oncoidal rudstone; MFT 5, peloidal-bioclastic packstone and grainstone); 3) reef (MFT 6, solenoporacean-calcimicrobial-stromatoporoid boundstone; MFT 7, crinoid-stromatoporoid floatstone); and 4) open-marine (MFT 8, bioclastic wackestone/packstone with intraclasts and peloids; and MFT 9, bioclastic wackestone and packstone). The carbonate deposits are interpreted as formed in various shallow- to open-marine environments at or above the fair-weather wave base (MFTs 1–7) and below it (MFTs 8 and 9). Most of the described microfacies are comparable with Wilson’s (1975) Standard Microfacies Types.

MICROFACIES ANALYSIS OF CRETACEOUS SEDIMENTS OF DUKUL FORMATION, YOLA SUB-BASIN, NORTHERN BENUE TROUGH, NIGERIA: PALEO-ENVIRONMENTAL IMPLICATIONS

2021 ◽  
Vol 5 (2) ◽  
pp. 310-319
Author(s):  
Babangida M. Sarki Yandoka
Keyword(s):  
Sea Level ◽  
Microfacies Analysis ◽  
Fair Weather ◽  
Environmental Implications ◽  
Benue Trough ◽  
Shallow Marine ◽  
Carbonate Microfacies ◽  
Anoxic Conditions ◽  
The Mean

Carbonate microfacies analysis was conducted on the exposed sediments of Dukul Formation from Yola Sub-basin of the Northern Benue Trough with an objective to reconstruct the paleodepositional environment. The study revealed four (4) major microfacies; oyster wackestone, ostracod oyster wackestone-packestone, bioclastic wackestone and bioclastic packestone microfacies. The microfacies assemblages indicate and affirm that the Dukul Formation sediments were deposited in shallow marine (mid-inner ramp) environment under suboxic to relatively anoxic conditions due to sea-level drop. This is further supported owing to the occurence of corals, brachiopods, bivalves and ostracods immediately below the mean fair-weather wave base (FWWB)

Conodont biostratigraphy and paleoecology of Middle Ordovician rocks in eastern Oklahoma

1989 ◽  
Vol 63 (1) ◽  
pp. 92-107 ◽  
Author(s):  
Jeffrey A. Bauer
Keyword(s):  
New Species ◽  
Conodont Biostratigraphy ◽  
Middle Ordovician ◽  
Two New Species ◽  
Shallow Subtidal ◽  
Conodont Fauna ◽  
Carbonate Deposits

Conodonts from the upper Burgen, Tyner, and Fite Formations (Middle Ordovician) of eastern Oklahoma include two new species, Phragmodus harrisi and Plectodina tynerensis. The conodont fauna indicates that the upper Burgen through middle Tyner is Whiterockian (pre- to earliest Chazyan) and that the upper Tyner–Fite is probably Kirkfieldian in age.The Whiterockian Burgen–Tyner preserves a regressive succession of shoreface, lagoonal, and intertidal deposits. That change is reflected by the conodont succession, which shows replacement of a fauna dominated by species of Neomultioistodus, Scandodus?, and Paraprioniodus by one dominated by species of Phragmodus, Plectodina, and Erismodus.Carbonate deposits of the Kirkfieldian(?) upper Tyner and Fite Formations follow a major hiatus and reflect shallow, subtidal to intertidal conditions. The conodont fauna is composed of species of Aphelognathus, Plectodina, Curtognathus, Erismodus, and Oulodus, among others.

Age and growth of Alitta succinea (Polychaeta; Nereididae) in a tropical estuary of Brazil

2013 ◽  
Vol 93 (8) ◽  
pp. 2123-2128 ◽  
Author(s):  
C.S.C. Sette ◽  
R.A. Shinozaki-Mendes ◽  
T.L. Barros ◽  
J.R.B. Souza
Keyword(s):  
Growth Parameters ◽  
Length Distribution ◽  
Information Criteria ◽  
Age And Growth ◽  
Distribution Data ◽  
Tropical Estuary ◽  
Von Bertalanffy ◽  
Eastern Brazil ◽  
North Eastern ◽  
Shallow Subtidal

The aim of this work was to study the dynamics of Alitta succinea population growth in a tropical estuary. The organisms were collected in the polyhaline area of Pina Basin, north-eastern Brazil, in lower and shallow subtidal consolidated substrates, from October 2009 to March 2011. Fifteen samples with a size of 0.01 m2 were collected every month. A total of 2064 A. succinea individuals were measured for growth analysis, and the measure used was the length from prostomium to the 25th setiger. Growth parameters were estimated by the frequency–length distribution data from three different functions (i.e. von Bertalanffy, Gompertz and Richards). The differences in the densities of A. succinea were significant between the months of the dry and the rainy season, with the rain pattern being the factor that most affects the A. succinea life cycle. According to Akaike information criteria, the von Bertalanffy and Gompertz models were the ones that presented the best fit with the growth curve of A. succinea for the studied period. Using the Bhattacharya method for the analysis of modal progression, we identified eight cohorts. The lowest recruitment values were found in July and August 2010, respectively, and the remaining months had numbers of recruits that were representative of the total population. The growth performance index (Ø′) found was 2.86. The maximum longevity indicates that specimens of A. succinea live between 586 and 953 d, and the instantaneous mortality rate (Z) is 1.53 yr−1.

Permineralized Fossils from the Terminal Proterozoic Doushantuo Formation, South China

1998 ◽  
Vol 72 (S50) ◽  
pp. 1-52 ◽  
Author(s):  
Yun Zhang ◽  
Leiming Yin ◽  
Shuhai Xiao ◽  
Andrew H. Knoll
Keyword(s):  
South China ◽  
Secular Variation ◽  
Biological Diversity ◽  
Marine Environments ◽  
Fair Weather ◽  
Doushantuo Formation ◽  
Carbonaceous Shales ◽  
Stratigraphic Ranges ◽  
Late Neoproterozoic ◽  
Large Animals

Permineralized fossils of the terminal Proterozoic (600–550 Ma) Doushantuo Formation, China, provide an unusually clear window on biological diversity just before the Ediacaran radiation. In the eastern Yangtze Gorges region, cherts in lower and upper Doushantuo carbonates preserve prokaryotes and protists from subtidal marine environments below and above fair weather wave base, respectively. Phosphorites in the Weng'an district to the south contain diverse acanthomorphic acritarchs as well as cellularly preserved thalloid algae. Twelve taxa of probable cyanobacteria are recognized. None is endemic to the Doushantuo Formation, and most have long stratigraphic ranges. The apparent restriction of two species to late Neoproterozoic and Cambrian rocks may reflect secular variation in taphonomic circumstance rather than evolution. Thirty-one species of spheromorphic and acanthomorphic acritarchs are recognized, about half of which occur elsewhere in rocks of the same approximate age. At least some of the eight formally described species of multicellular algae can be assigned with confidence to the Rhodophyta; these fossils provide a glimpse of structural and reproductive diversity in Neoproterozoic algae that is, to date, unique. Several reports of Doushantuo animal fossils have been published; most compelling are triact spicules identified in chert nodules. Along with more than two dozen taxa of compressed macrofossils preserved in carbonaceous shales from the top of the formation, Doushantuo permineralizations indicate that large animals radiated into a world rich in prokaryotic, protistan, and, even, multicellular diversity.

scholarly journals Shallow subtidal macroalgae in the North-eastern Atlantic archipelagos (Macaronesian region): a spatial approach to community structure

2018 ◽  
Vol 53 (1) ◽  
pp. 83-98 ◽  
Author(s):  
Carlos Sangil ◽  
Gustavo M. Martins ◽  
José Carlos Hernández ◽  
Filipe Alves ◽  
Ana I. Neto ◽  
...  
Keyword(s):  
Community Structure ◽  
The North ◽  
Spatial Approach ◽  
North Eastern ◽  
Shallow Subtidal

Neurotropic enteroviruses co-opt “fair-weather-friend” commensal gut microbiota to drive host infection and central nervous system disturbances

2019 ◽  
Vol 42 ◽  
Author(s):  
Kevin B. Clark
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Gut Bacteria ◽  
Infection Cycle ◽  
Fair Weather ◽  
Host Health ◽  
Microbe Interactions ◽  
Animal Hosts ◽  
Host Infection ◽  
Neuropsychiatric Conditions

Abstract Some neurotropic enteroviruses hijack Trojan horse/raft commensal gut bacteria to render devastating biomimicking cryptic attacks on human/animal hosts. Such virus-microbe interactions manipulate hosts’ gut-brain axes with accompanying infection-cycle-optimizing central nervous system (CNS) disturbances, including severe neurodevelopmental, neuromotor, and neuropsychiatric conditions. Co-opted bacteria thus indirectly influence host health, development, behavior, and mind as possible “fair-weather-friend” symbionts, switching from commensal to context-dependent pathogen-like strategies benefiting gut-bacteria fitness.

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