Species richness of foraminifera assemblages in the Permian succession, contains Dorud, Ruteh and Nessen Formations, in Central Alborz—North of Iran, was estimated and studied based on lithostratigraphy and microbiostratigraphy of Permian. We used four non-parametric estimators to investigate the species richness: Chao 2, Jackknife 1, Jackknife 2 and bootstrap. These methods estimates the species richness based on the presence/absence data of each taxon identified in the samples. We use the submenu of quadrat richness in “Past” [1] software to estimate richness in regional chronostratigraphic stages.The results show that the estimated diversity of foraminiferal assemblages with the exception of late Yakhtashian, increased constantly from Asselian to Murgabian with the highest diversity of foraminifera seen in the Murgabian. The main decrease in foraminiferal species richness happened during the Midian which corresponds to the kamura cooling event.
The number of species in a community and their relative abundance is defined as species diversity [
1) Alpha diversity: the local, in-habitat diversity, often estimated based on one sample.
2) Beta diversity: shows species composition changes within a community or in a gradient [
3) Gamma diversity: this is defined as inter-province (across regions diversity) [
Species richness is a numerical index and shows measure of alpha diversity. This means that to calculate it, the number of each species (number of individuals) in the samples is used. But, there are also other non-parametric methods for the calculation of richness that is used in this study. In these methods, the number of individuals is not need to calculate richness.
There are many examples of the application of this index in palaeontology. Sepkoski [
Alborz Mountains extend with a W-E trend along north of Iran. The two studied outcrops are located in the central part of Alborz. The first one is the type section of the Dorud Formation [
Km from Karaj-Gazvin highway. The section can be acsessed then by a roadway from Heev to Emamzadeh-Musa to the north.
The Heev section is situated at the western margin and the Dorud section approximately in the center of Central Alborz representing the middle part of Alborz Mountains in the north of Iran. Aghanabati [
According to [
To investigate the species richness of foraminifera, two sections of the Permian succession in Central Alborz have been selected and sampled systematically. Whereas biodiversity is a characterized by ecological and geological factors [
After preparation of thin sections we studied them micropalaeontologically. We identified all foraminifer genera and species in thin sections and then drew their extension line in a lithostratigraphic column (rang chart). Biostratigraphy is done based on lithostratigraphy and extension of taxa and index genus and species. We separated Permian stages (Asselian to Dzhulfian) and then inserted presence/absence data of taxa in Past [
The type section of the Dorud Formation (or Dorud Group as recommended by [
The Permian outcrop in the Heev section includes The Dorud, Ruteh and Nessen formations (
The Dorud Formation (243 m) begins with a basal fine grained conglomerate changing upward into a quartzitic weathering buff colored sandstone followed by cross bedded sandstone, silty and shaly sandstone, Fusulinid and oncoid bearing gray limestone and massive thick bedded sandstone are present in the uppermost part. We did not study the Dorud Formation in this section because of its incomplete microfauna.
The transition to the Ruteh Formation (314 m) in the studied section discon- formably overlies reddish brown Laterite zone on top of the Dorud Formation. The Ruteh Formation typically contains dark gray fossiliferous limestone bearing common macrofauna of brachiopods, corals, trilobites and Zoophycus trace fossils (
The Ruteh Formation is followed dark gray limestone (28 m) of Nessen Formation. The contact is disconformable because of laterite zone in between.
To estimate the species richness in stages we used Tetyan stages defined by Leven [
(1) Nankinella-Anderssonites-Pseudoschwagerina assemblage zone (Dorud Formation; Asselian); The age of the Dorud Formation is Gzhelian (Uppermost Carboniferous) to Sakmarian according to [
(2) Sphaeroschwagerina-Nodosinelloides pinardae-Rectogordius iranicus assemblage zone (Dorud Formation; Sakmarian); Some important genera and species appearances take place in this stage: Nodosinelloides pinardae and Dec- kerella elegans [
(3) Schubertella-Nodosinelloides cubanicus-Cribroigenerina permica assemblage zone (Ruteh Formation; late Yakhtashain); Before description of mid Permian biozonation, an important discussion about beginning age of Ruteh Formation must be considered. Despite many authors infer a Kubergandian or Murgabian age for the onset of deposition in the Ruteh Formation in Central Alborz [
(4) Protonodosaria-Pachyphloia-Hemigordius assemblage zone (Ruteh Formation; Bolorian); Bolorian is distinguished with decrease of Lagenoida abundance [
(5) Globivalvulina graeca-Neoendothyra parva asssemblage zone (Ruteh Formation; Kubergandian); We remarked lower boundary of Kubergandian with Globivalvulina graeca-Neoendothyra parva biozone, represented by [
Tetrataxis hemiovoides, Lasiodiscus sp., Agathammina sp., Agathammina asy- mmetrica, Agathammina darvasica, Minojapanella sp., Langella cukurkoyi, Pseudolangella fragilis, Pachyphloia laxa, Geinitzina minima, Climacammina sp., Neoendothyra reicheli, Deckerella clavata (
(6) Neoschwagerina-Globivalvulina Vonderschmitti Paleotextularidae as- semblage (Ruteh Formation; Murgabian); Kubergandian-Murgabian boundary characterized by appearance of lower Murgabian taxa such as Neoschwa- gerina [
(7) Hemigordius ovatus-Chusenella-Dagmarita assemblage zone (Ruteh Formation; Early Midian); Midian index taxa are: Hemigordius ovatus [
(8) Barren interval zone (Ruteh Formation; late Midian?); From biostratigraphy aspect the latest part of Ruteh Formation at studied section belongs to Midian and, a few meters of sandy limestone and sandstone that is very poor from foraminifera fauna distinguished under the top of Formation that can be assigned to late Midian and corresponded with End-Guadalopian extinction.
(9) paraglobivalvulina-Reichelina assemblage zone (Nessen Formation; Dzhulfian); As mentioned upper Permian identified by Nessen Formation in Alborz and it differentiates from Ruteh Formation by a Bauxit-Laterit zone usually and at studied section too. We aged Nesen Formation early to late Dzhulfian that characterize by Reichelina [
ottoman, Frondina permica, Ichtyolaria primitiva, Codonofusiella laxa, C. schu- betelloides, C. tenussima, Dagmarita sp. (
There are different methods to measure species richness. In the simplest case, it is equal to the number of observed species in the sample: R = S where R is richness and S is number of species counted in samples. However there are many examples of using other taxonomic levels in palaeontology. Two general approaches to calculate (estimate perhaps better expression) index there are: (1) by measuring the presence or absence of species in samples and (2) by counting the number of individuals of each species (abundance) in samples. We used the first method, where some random standard samples are selected and then species presence/absence data are extracted and richness in total of samples is calculated. The four important equations for richness calculation in this method are [
1) Chao 2 =
2) Jackknife 1 =
3) Jackknife 2 =
4) Boot strap =
where:
Sobs: total number of observed species
L: the number of species that are present in a sample
M: the number of species that exist in the two samples
Pi: proportion of specimens containing species i
n: the number (size) of samples
To estimate the indices with “Past” software [
The trend of species richness shows that all of four computational approaches have quite similar trends and slight differences in their amounts are the result of different equations used. The chart is showing a species richness increase from As- selian to Murgabian with a maximum value in the Murgabian. This is comparable
Bootstrap | Jackknife 2 | Jackknife 1 | Chao 2 | STAGE/INDICES |
---|---|---|---|---|
39.5829 | 40.3183 | 43.05 | 39.5583 | Asselian |
50.6274 | 51.6023 | 53.9491 | 48.7298 | Sakmarian |
36.5139 | 39.8958 | 40.5877 | 36.9017 | Late Yakhtashian |
40.9539 | 44.0983 | 46.4391 | 40.3577 | Bolorian |
42.8021 | 46.2039 | 48.3411 | 41.8466 | Kubergandian |
85.711 | 90.6918 | 92.7912 | 86.3454 | Murgabian |
62.5244 | 65.5872 | 69.1833 | 62.8149 | Early Midian |
63.3563 | 66.5916 | 69.8441 | 61.6377 | Dzhulfian |
with high productivity in low latitude ocean [
Medadi, M., Mosaddegh, H., Aleali, S.M. and Majidifard, M.R. (2017) Estimation of Species Richness of Permian Foraminifera in Non-Parametric Methods and Investigation of Its Change Trend in Central Alborz, Western Tethys. Open Journal of Geology, 7, 666-682. https://doi.org/10.4236/ojg.2017.75045
Submit or recommend next manuscript to SCIRP and we will provide best service for you:
Accepting pre-submission inquiries through Email, Facebook, LinkedIn, Twitter, etc.
A wide selection of journals (inclusive of 9 subjects, more than 200 journals)
Providing 24-hour high-quality service
User-friendly online submission system
Fair and swift peer-review system
Efficient typesetting and proofreading procedure
Display of the result of downloads and visits, as well as the number of cited articles
Maximum dissemination of your research work
Submit your manuscript at: http://papersubmission.scirp.org/
Or contact ojg@scirp.org