Exotic facies episodes of a carbonate platform: implications for middle and late Cambrian ecosystems and impact of bioturbation in the Alborz Basin, Iran

2021 ◽  
pp. SP522-2020-269
Author(s):  
Aram Bayet-Goll ◽  
Mehdi Daraei ◽  
Gerd Geyer ◽  
Carlos Neto de Carvalho ◽  
Nasrin Bahrami
Keyword(s):  
Environmental Stress ◽  
Environmental Conditions ◽  
Carbonate Platform ◽  
Northern Iran ◽  
Virtual Absence ◽  
Late Cambrian ◽  
Physico Chemical ◽  
Stage 4 ◽  
Middle And Late Cambrian ◽  
Spice Event

AbstractThe sedimentological and ichnological data of the Mila Group in the Alborz Basin, northern Iran indicate that the appearance of exotic facies and resurgence of microbialites resulted from the development of extraordinary palaeoceanographic conditions with widespread environmental stress and enhanced precipitation of CaCO3. Inhospitable environmental conditions in the Mila Group platform led to a considerable reduction in ichnodiversity, bioturbation intensity, depth and size of burrows, which led to periods of dominating calcimicrobe ecology. The development of exotic, or anachronistic facies started around the Cambrian Stage 4-Wuliuan boundary, probably simultaneous with the SPICE event whereas the Furongian exotic facies period probably took place simultaneous with the HERB event. Biotic and physico-chemical changes in the ocean during these events may have led as well to the virtual absence of the mixed layer and infaunal ecospace utilisation in the deposits of the Mila Group. Nevertheless, the local presence of metazoan-microbial build-ups that established between the two suggested exotic facies developments indicates that these periods started at the Cambrian Stage 4-Wuliuan boundary interval, but a fluctuation of abnormal palaeoceanographic conditions and ambient normal marine conditions took place during the Miaolingian and Furongian in the Alborz Basin as a representative of northern Gondwanan margin.

Latest Middle Cambrian metazoan reef from northern Iran

1995 ◽  
Vol 132 (4) ◽  
pp. 367-373 ◽  
Author(s):  
B. Hamdi ◽  
A. Yu. Rozanov ◽  
A. Yu. Zhuravle
Keyword(s):  
Northern Iran ◽  
Middle Cambrian ◽  
Middle Ordovician ◽  
Late Cambrian ◽  
The Family ◽  
Middle And Late Cambrian

AbstractMiddle and Late Cambrian reefs were built mainly by cyanobacterial communities. A few reefs with a metazoan as well as an algal component, however, are known from this interval. A Middle Cambrian reef formed primarily by spicular demosponges is described here from the Mila Formation in the Elburz Mountains, northern Iran. The reef is enclosed within calcareous grainstones which contain terminal Middle Cambrian (late Mayan) trilobites. The Mila Formation reef was constructed by sponges of the family Anthaspidellidae and bacterial (algal?) sheaths, and is the earliest metazoan reef to be documented from the interval after the demise of archaeocyath sponges. The reefal community is typical of subsequent reefal communities of Early–Middle Ordovician age. The Ordovician examples differ only by the incorporation of additional metazoan elements.

scholarly journals Marine Antibiotics 2020

Marine Drugs ◽  
2021 ◽  
Vol 19 (6) ◽  
pp. 351
Author(s):  
Yannick Fleury
Keyword(s):  
Environmental Conditions ◽  
Light Pressure ◽  
Marine Life ◽  
Physico Chemical

The range of environmental conditions in marine life is tremendous at different physico-chemical criteria (temperature, light, pressure and salinity) [...]

scholarly journals Stability of Fe-oxide nanoparticles coated with natural organic matter under relevant environmental conditions

2014 ◽  
Vol 70 (12) ◽  
pp. 2040-2046 ◽  
Author(s):  
L. Chekli ◽  
S. Phuntsho ◽  
L. D. Tijing ◽  
J. L. Zhou ◽  
J.-H. Kim ◽  
...  
Keyword(s):  
Organic Matter ◽  
Natural Organic Matter ◽  
Environmental Conditions ◽  
Divalent Cations ◽  
Oxide Nanoparticles ◽  
Fe Oxide ◽  
Coated Nanoparticles ◽  
Aggregation Behaviour ◽  
Physico Chemical ◽  
The Stability

Manufactured nanoparticles (MNPs) are increasingly released into the environment and thus research on their fate and behaviour in complex environmental samples is urgently needed. The fate of MNPs in the aquatic environment will mainly depend on the physico-chemical characteristics of the medium. The presence and concentration of natural organic matter (NOM) will play a significant role on the stability of MNPs by either decreasing or exacerbating the aggregation phenomenon. In this study, we firstly investigated the effect of NOM concentration on the aggregation behaviour of manufactured Fe-oxide nanoparticles. Then, the stability of the coated nanoparticles was assessed under relevant environmental conditions. Flow field-flow fractionation, an emerging method which is gaining popularity in the field of nanotechnology, has been employed and results have been compared to another size-measurement technique to provide increased confidence in the outcomes. Results showed enhanced stability when the nanoparticles are coated with NOM, which was due to electrosteric stabilisation. However, the presence of divalent cations, even at low concentration (i.e. less than 1 mM) was found to induce aggregation of NOM-coated nanoparticles via bridging mechanisms between NOM and Ca2+.

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.

scholarly journals A missing link in the peri-Gondwanan terrane collage: the Precambrian basement of the Moroccan Meseta and its lower Paleozoic cover

2018 ◽  
Vol 55 (1) ◽  
pp. 33-51 ◽  
Author(s):  
Dominik Letsch ◽  
Mohamed El Houicha ◽  
Albrecht von Quadt ◽  
Wilfried Winkler
Keyword(s):  
Carbonate Platform ◽  
Source Area ◽  
Source Rocks ◽  
Lower Paleozoic ◽  
Northern Margin ◽  
Precambrian Geology ◽  
The North ◽  
Late Cambrian ◽  
Paleozoic Rocks ◽  
Rifted Margin

This article provides stratigraphic and geochronological data from a central part of Gondwana’s northern margin — the Moroccan Meseta Domain. This region, located to the north of the Anti-Atlas area with extensive outcrops of Precambrian and lower Paleozoic rocks, has hitherto not received much attention with regard to its Precambrian geology. Detrital and volcanic zircon ages have been used to constrain sedimentary depositional ages and crustal affinities of sedimentary source rocks in stratigraphic key sections. Based on this, a four-step paleotectonic evolution of the Meseta Domain from the Ediacaran until the Early Ordovician is proposed. This evolution documents the transition from a terrestrial volcanic setting during the Ediacaran to a short-lived carbonate platform setting during the early Cambrian. The latter then evolved into a rifted margin with deposition of thick siliciclastic successions in graben structures during the middle to late Cambrian. The detritus in these basins was of local origin, and a contribution from a broader source area (encompassing parts of the West African Craton) can only be demonstrated for postrifting, i.e., laterally extensive sandstone bodies that seal the former graben. In a broader paleotectonic context, it is suggested that this Cambrian rifting is linked to the opening of the Rheic Ocean, and that several peri-Gondwanan terranes (Meguma and Cadomia–Iberia) may have been close to the Meseta Domain before drifting, albeit some of them seem to have been constituted by a distinctly different basement.

scholarly journals Marine anoxia and sedimentary mercury enrichments during the Late Cambrian SPICE event in northern Scotland

Geology ◽  
2019 ◽  
Vol 47 (5) ◽  
pp. 475-478 ◽  
Author(s):  
Sara B. Pruss ◽  
David S. Jones ◽  
David A. Fike ◽  
Nicholas J. Tosca ◽  
Paul B. Wignall
Keyword(s):  
Late Cambrian ◽  
Spice Event

Evidence of a large δ13Ccarb and δ13Corg depth gradient for deep-water anoxia during the late Cambrian SPICE event

Geology ◽  
2018 ◽  
Vol 46 (7) ◽  
pp. 631-634 ◽  
Author(s):  
Dandan Li ◽  
Xiaolin Zhang ◽  
Dongping Hu ◽  
Xiaoyan Chen ◽  
Wei Huang ◽  
...  
Keyword(s):  
Deep Water ◽  
Depth Gradient ◽  
Late Cambrian ◽  
Spice Event

scholarly journals Bacterial Cell Wall Quality Control during Environmental Stress

mBio ◽  
2020 ◽  
Vol 11 (5) ◽  
Author(s):  
Elizabeth A. Mueller ◽  
Petra Anne Levin
Keyword(s):  
Quality Control ◽  
Cell Wall ◽  
Cell Surface ◽  
Environmental Stress ◽  
Environmental Conditions ◽  
Bacterial Cell ◽  
Cell Shape ◽  
Bacterial Cell Wall ◽  
Peptidoglycan Synthesis ◽  
Peptidoglycan Cell Wall

ABSTRACT Single-celled organisms must adapt their physiology to persist and propagate across a wide range of environmental conditions. The growth and division of bacterial cells depend on continuous synthesis of an essential extracellular barrier: the peptidoglycan cell wall, a polysaccharide matrix that counteracts turgor pressure and confers cell shape. Unlike many other essential processes and structures within the bacterial cell, the peptidoglycan cell wall and its synthesis machinery reside at the cell surface and are thus uniquely vulnerable to the physicochemical environment and exogenous threats. In addition to the diversity of stressors endangering cell wall integrity, defects in peptidoglycan metabolism require rapid repair in order to prevent osmotic lysis, which can occur within minutes. Here, we review recent work that illuminates mechanisms that ensure robust peptidoglycan metabolism in response to persistent and acute environmental stress. Advances in our understanding of bacterial cell wall quality control promise to inform the development and use of antimicrobial agents that target the synthesis and remodeling of this essential macromolecule. IMPORTANCE Nearly all bacteria are encased in a peptidoglycan cell wall, an essential polysaccharide structure that protects the cell from osmotic rupture and reinforces cell shape. The integrity of this protective barrier must be maintained across the diversity of environmental conditions wherein bacteria replicate. However, at the cell surface, the cell wall and its synthesis machinery face unique challenges that threaten their integrity. Directly exposed to the extracellular environment, the peptidoglycan synthesis machinery encounters dynamic and extreme physicochemical conditions, which may impair enzymatic activity and critical protein-protein interactions. Biotic and abiotic stressors—including host defenses, cell wall active antibiotics, and predatory bacteria and phage—also jeopardize peptidoglycan integrity by introducing lesions, which must be rapidly repaired to prevent cell lysis. Here, we review recently discovered mechanisms that promote robust peptidoglycan synthesis during environmental and acute stress and highlight the opportunities and challenges for the development of cell wall active therapeutics.

Sign in / Sign up

Export Citation Format

Share Document