scholarly journals Early Famennian bryozoan fauna from the Baqer-abad section, northeast Isfahan, central Iran

2020 ◽  
Vol 100 (3) ◽  
pp. 705-718
Author(s):  
Andrej Ernst ◽  
Ali Bahrami ◽  
Ayesheh Parast
Keyword(s):  
Environmental Stress ◽  
Sediment Deposition ◽  
Upper Devonian ◽  
Central Iran ◽  
High Abundance ◽  
Low Diversity ◽  
Energy Environment ◽  
Bahram Formation ◽  
Global Patterns

Abstract A bryozoan fauna from the Upper Devonian (lower Famennian) of the Bahram Formation of the Baqer-abad section in central Iran contains four species: three trepostomes and one rhabdomesine cryptostome. Two trepostome species and one genus are new: Anomalotoechus parvus sp. nov. and Zefrehopora asynithis gen. nov. et sp. nov. The trepostome Coeloclemis zefrehensis Ernst et al., 2017 and the rhabdomesine cryptostome Euthyrhombopora tenuis Ernst et al., 2017 were recorded previously from the Upper Devonian (Frasnian) of the Bahram Formation at the Zefreh section. The fauna is dominated by the erect ramose Euthyrhombopora tenuis, accompanied by relatively frequent Zefrehopora asynithis, which developed both the erect and encrusting colonies. The bryozoans indicate low to moderate water energy environment in a middle to outer ramp position. Low diversity and high abundance of one species indicate an environmental stress apparently caused by strong sediment deposition. No significant differences in the composition of the bryozoan assemblages of the Frasnian and lower Famennian of the Bahram Formation were observed mirroring global patterns.

Sedimentary fades, depositional environments, and faunal associations of the lower Llandovery (Silurian) Beechill Cove Formation, Arisaig, Nova Scotia

1983 ◽  
Vol 20 (12) ◽  
pp. 1761-1779 ◽  
Author(s):  
R. K. Pickerill ◽  
J. M. Hurst
Keyword(s):  
Depositional Environments ◽  
Low Energy ◽  
Sedimentation Rates ◽  
Storm Activity ◽  
Distributional Patterns ◽  
Low Diversity ◽  
Energy Environment ◽  
Shallow Subtidal ◽  
Oxygen Minimum ◽  
Mudstone Facies

Six facies are recognised in the Beechill Cove Formation. These are: (1) conglomerate facies deposited as a transgressive beach lag; (2) red shale facies deposited in shoreface environments; (3) mottled mudstone facies; extensively bioturbated sediments indicative of shallow subtidal areas influenced by low sedimentation rates; (4) regular layered facies; shelf turbidites generated by storm activity and superimposed on quiescent subtidal environments; (5) lenticular facies, including a thinner bedded more persistent and a thicker bedded lenticular subfacies, induced by storm activity and deposited in shallow subtidal environments; and (6) laminated shale facies produced by sediment fallout from suspension in a low-energy environment where the oxygen, minimum layer intersected the sediment–water interface. Three faunal associations occur, which have distinct distributional patterns. The Lingula clintoni association, which is characterized by L. clintoni in life position and a moderately diverse but abundant trace-fossil assemblage, is restricted to the mottled mudstone facies. The Leptostrophia beechillensis association, a transported residue, is dominated by brachiopods and restricted to the regular layered facies. The low-diversity Dalmanella primitiva association is transported and restricted to the lenticular facies. No faunas are known from the conglomerate or laminated shale facies, and only rare trace fossils occur in the red shale facies.

scholarly journals A new paleoecological look at the Dinwoody Formation (Lower Triassic, western USA): intrinsic versus extrinsic controls on ecosystem recovery after the end-Permian mass extinction

2013 ◽  
Vol 87 (5) ◽  
pp. 854-880 ◽  
Author(s):  
Richard Hofmann ◽  
Michael Hautmann ◽  
Hugo Bucher
Keyword(s):  
United States ◽  
Environmental Stress ◽  
Beta Diversity ◽  
Mass Extinction ◽  
Western United States ◽  
Ecosystem Recovery ◽  
Diversity Pattern ◽  
Marine Habitats ◽  
Low Diversity ◽  
Permian Mass Extinction

The Dinwoody Formation of the western United States represents an important archive of Early Triassic ecosystems in the immediate aftermath of the end-Permian mass extinction. We present a systematic description and a quantitative paleoecological analysis of its benthic faunas in order to reconstruct benthic associations and to explore the temporal and spatial variations of diversity, ecological structure and taxonomic composition throughout the earliest Triassic of the western United States. A total of 15 bivalve species, two gastropod species, and two brachiopod species are recognized in the study area. The paleoecological analysis shows that the oldest Dinwoody communities are characterized by low diversity, low ecological complexity and high dominance of few species. We suggest that this low diversity most likely reflects the consequences of the mass extinction in the first place and not necessarily the persistence of environmental stress. Whereas this diversity pattern persists into younger strata of the Dinwoody Formation in outer shelf environments, an increase in richness, evenness and guild diversity occurred around the Griesbachian–Dienerian boundary in more shallow marine habitats. This incipient recovery towards the end of the Griesbachian is in accordance with observations from other regions and thus probably represents an interregional signal. In contrast to increasing richness within communities (alpha-diversity), beta-diversity remained low during the Griesbachian and Dienerian in the study area. This low beta-diversity reflects a wide environmental and geographical range of taxa during the earliest Triassic, indicating that the increase of within-habitat diversity has not yet led to significant competitive exclusion. We hypothesize that the well-known prevalence of generalized taxa in post-extinction faunas is primarily an effect of reduced competition that allows species to exist through the full range of their fundamental niches, rather than being caused by unusual and uniform environmental stress.

scholarly journals Review of the Ordovician stratigraphy and fauna of the Anarak Region in Central Iran

2015 ◽  
Vol 65 (4) ◽  
pp. 403-435 ◽  
Author(s):  
Leonid E. Popov ◽  
Vachik Hairapetian ◽  
David H. Evans ◽  
Mansoureh Ghobadi Pour ◽  
Lars E. Holmer ◽  
...  
Keyword(s):  
North China ◽  
Cold Water ◽  
Central Iran ◽  
Metamorphic Complex ◽  
North African ◽  
Northern Margin ◽  
Faunal Assemblages ◽  
Lower Ordovician ◽  
Low Diversity ◽  
Sedimentary Succession

Abstract The Ordovician sedimentary succession of the Pol-e Khavand area, situated on the northern margin of the Yazd block, has important differences from those in other parts of Central Iran. It has been established that the presumably terminal Cambrian to Lower Ordovician volcano-sedimentary Polekhavand Formation, exposed in the Pol-e Khavand area, has non-conformable contact with greenschists of the Doshakh Metamorphic Complex. The succeeding, mainly siliciclastic Chahgonbad Formation contains low to moderately diverse faunal assemblages, including brachiopods, cephalopods, trilobites and tentaculitids. The Darriwilian age of the lower part of the formation is well established by the co-occurrence of brachiopod genera Camerella, Phragmorthis, Tritoechia and Yangtzeella. The associated rich cephalopod fauna is different from the Darriwilian cephalopod associations of the Alborz terrane and may show some affinity with warm water faunas of North China and South Korea. It is likely that the Mid Ordovician fauna recovered from the lower part of the Chahgonbad Formation settled in the area sometime during a warming episode in the late Darriwilian. By contrast the low diversity mid Katian brachiopod association includes only three taxa, which occur together with the trilobite Vietnamia cf. teichmulleri and abundant, but poorly preserved tentaculitids questionably assigned to the genus Costatulites. This faunal association bears clear signatures linking it to the contemporaneous cold water faunas of the Arabian, Mediterranean and North African segments of Gondwana. Four brachiopod species recovered from the Chahgonbad Formation, including Hibernodonta lakhensis, Hindella prima, Lomatorthis? multilamellosa and Yangtzeella chupananica are new to science.

scholarly journals Palaeoecology of a hypersaline Carboniferous ostracod fauna

1987 ◽  
Vol 6 (2) ◽  
pp. 29-33 ◽  
Author(s):  
Chris P. Dewey
Keyword(s):  
Nova Scotia ◽  
Population Growth ◽  
Reproductive Strategy ◽  
Growth Parameters ◽  
High Abundance ◽  
Rapid Population Growth ◽  
Lower Carboniferous ◽  
Low Diversity ◽  
Combined Data

Abstract. A high abundance, low diversity ostracod fauna has been collected from the Lower Carboniferous Dimock and Phillips limestones in Nova Scotia, Canada. The ostracod fauna consists of Paraparchites sp. aff. P. kellettae Sohn and Beyrichiopsis lophota Copeland, as well as rare specimens of Acratia acuta (Jones & Kirkby), Bythocypris aequalis (Jones & Kirkby), and Chamishaella suborbiculata (Munster).Growth parameters for the dominant ostracod, Paraparchites sp. aff. P. kellettae, show that a multi-generation, progenetic, parthenogenetic population developed. This reproductive strategy caused rapid population growth and thereby allowed the species to take advantage of the available environmental resources.When considered together, the ostracod fauna and the sedimentology indicate that physiologically stressful hypersaline conditions prevailed. The combined data therefore provide evidence for hypersalinity tolerance and heterochronous development amongst Carboniferous ostracods.

Palaeoenvironmental and sequence-stratigraphic analysis of the Middle–Late Devonian carbonates (Bahram Formation) of Anarak, western Central Iran

2020 ◽  
Vol 171 ◽  
pp. 103938
Author(s):  
Mohammad Ali Salehi ◽  
Ali Bahrami ◽  
Sanaz Moharrami ◽  
Hossein Vaziri-Moghaddam ◽  
Hamid Reza Pakzad ◽  
...  
Keyword(s):  
Central Iran ◽  
Late Devonian ◽  
Sequence Stratigraphic ◽  
Stratigraphic Analysis ◽  
Bahram Formation

Lingulid brachiopods and Lingulichnus from a Silurian shelf–slope carbonate sequence, Delorme Group, Mackenzie Mountains, Northwest Territories

1988 ◽  
Vol 25 (3) ◽  
pp. 465-471 ◽  
Author(s):  
D. Jeffrey Over
Keyword(s):  
Northwest Territories ◽  
Substrate Surface ◽  
Benthic Fauna ◽  
Low Energy ◽  
High Abundance ◽  
Energy Conditions ◽  
Bottom Current ◽  
Shelf Slope ◽  
Low Diversity ◽  
Carbonate Sequence

Structures assigned to the ichnogenus Lingulichnus, commonly containing the burrow-forming brachiopod, were collected from an argillaceous unit in a Silurian shelf dolostone sequence (Delorme Group). The sediments, benthic fauna, and inclined orientation of all lingulid burrows indicate the presence of a bottom current and restricted conditions on the margin of the Selwyn Basin. High-abundance–low-diversity faunas of lingulids and Lingulichnus are indicative of limiting conditions at the substrate surface. Under low-energy conditions, they seem to be indicative of the Zoophycos ichnofacies.

scholarly journals Diversity of mollusks (bivalves and gastropods) in degraded mangrove ecosystems of Kolaka District, Southeast Sulawesi, Indonesia

2020 ◽  
Vol 21 (12) ◽  
Author(s):  
Fajar Hasidu ◽  
Jamili Jamili ◽  
Gaby Nanda Kharisma ◽  
Arif Prasetya ◽  
Maharani Maharani ◽  
...  
Keyword(s):  
Diversity Index ◽  
Mangrove Ecosystem ◽  
Marine Ecosystems ◽  
High Abundance ◽  
Line Transect ◽  
Mangrove Ecosystems ◽  
Evenness Index ◽  
Low Diversity ◽  
Filter Feeders ◽  
Molluscan Species

Abstract. Hasidu LOAF, Jamili, Kharisma GN, Prasetya A, Maharani, Riska, Rudia LOAP, Ibrahim AF, Mubarak AA, Muhasafaat LO, Anzani L. 2020. Diversity of mollusks (bivalves and gastropods) in degraded mangrove ecosystems of Kolaka District, Southeast Sulawesi, Indonesia. Biodiversitas 21: 5884-5892. Mollusks are one of the mangrove organisms whose classes are bivalves and gastropods. It plays an important role in mangrove and marine ecosystems as filter feeders, predators, and herbivores. This study aims to knows the diversity and abundance of mollusks (bivalves and gastropods) in several mangrove ecosystems in the Kolaka coastline as well as the similarity of these locations. This study was conducted in mangrove ecosystems of Induha Village, Mangolo Village, Tahoa Village, and Towua Village of Kolaka District, Southeast Sulawesi, Indonesia, from July to August 2019. This is a transect method stretched along a 100 m line perpendicularly from the seaward. The size of the mollusks subplot was 1 m2 and placed along the line transect. Each line transect comprises 10 subplots. To analyze the diversity index, evenness index, and its abundance, Kaleida Graph 4.0 version was used. This research indicates that the mollusks consist of 4 families of bivalves with 6 species and 10 families of gastropods with 182 species. It also found out 23 species of mollusks scattered to each location. The molluscan species which spread in all four mangrove ecosystems were Terebralia sulcata, Nerita planospira, and Batillaria multiformis. In Induha, the mollusks species were Anadara notabilis and Drupella margariticola. Meanwhile, Saccostrea cucullata, Pirenella incisa, Clithon oualaniensis, and Clithon pulchellum were only found in Towua. The diversity index of bivalves in each location was categorized as low diversity index category, as well as gastropods were categorized as medium diversity index. The highest diversity index of gastropods was in Induha (H' = 1.96). It was supported by the good mangrove ecosystem for mollusks' habitat. The lowest diversity index of gastropods was in Towua (1.41). This research depicts that three kinds of species with high abundance rate whose rates were >1 ind/m2are located in two different locations namely; P. incisa (3.9 ind/m2) and S. cucullata (3.2 ind/m2) in Towua and followed by B. multiformis (2 ind/m2) and Isognomon ephippium (1.2 ind/m2) in Mangolo.

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