Sakineh Arefifard

The Permian-Triassic transition (∼252 million years ago) marks the most severe mass extinction in Earth’s history, followed by a protracted interval of environmental instability and delayed biological recovery. Although elevated atmospheric carbon dioxide (CO ₂ ) from extensive volcanism is widely invoked, the role of continental weathering feedbacks in regulating global climate has not been effectively constrained. Here, we present high-resolution lithium isotope records from marine carbonates and terrestrial deposits through the Permian-Triassic transition. Combined with an Earth-system model, our data reveal notable decreases in global continental weatherability following the end-Permian mass extinction, inferred to associations with widespread deforestation (extinction of deep-rooted plants) and the collapse of terrestrial ecosystem. This diminished weathering response to volcanic carbon emissions likely contributed to prolonged high atmospheric CO ₂ and global temperature during the Early Triassic. The sustained greenhouse conditions, in turn, inhibited contemporaneous marine and terrestrial ecosystem recoveries. Our findings highlight the importance of terrestrial ecosystem in modulating global carbon cycle stability, and its effects on Earth’s habitability.

Fossil benthic foraminifera are essential proxies of Jurassic marine environmental change, yet their distribution and palaeoecological significance across northeastern Iran remain insufficiently understood. This study presents a detailed, high‐resolution quantitative investigation of Middle‐Upper Jurassic (Bajocian‐mid Tithonian) benthic foraminiferal assemblages from the Dalichai Formation recorded at the Baqi section of the Binalud Mountains. The analysis integrates foraminiferal data with microfacies characteristics to reconstruct palaeoenvironmental evolution and relative sea‐level history within the northern Tethyan margin. Fifty species representing twenty‐seven genera and organised into twelve foraminiferal morphogroups were identified, defining seven successive ecostratigraphic intervals (A‐G) that mark distinct ecological and depositional stages. Interval A (Bajocian) represents a shallow‐neritic, reduced‐salinity environment dominated by agglutinated taxa. Interval B, a red‐shale bed at the Bajocian‐Bathonian boundary, corresponding to the Ammonitico Rosso facies, records a rapid transgressive pulse linked to early rifting. Interval C and D (Bathonian–lower Oxfordian) capture maximum deepening, with pelagic and gravity‐flow deposits associated with horst‐and‐graben formation and an abrupt diversity decline. Interval E (upper Oxfordian‐lower Kimmeridgian) reflects partial shallowing and renewed agglutinated dominance. Interval F (Kimmeridgian) demonstrates open‐marine, oxygen‐rich conditions with abundant calcareous epifauna. And Interval G (upper Kimmeridgian‐mid Tithonian) indicates progressive shallowing and enhanced siliciclastic delivery. The reconstructed sea‐level curve reveals a major transgression from the Bajocian to early Oxfordian and regression from the Kimmeridgian to Tithonian, broadly conforming to global eustatic trends but punctuated by tectonically induced fluctuations. This integrated approach refines our understanding of Jurassic sequence development in the Binalud Basin and underscores the ecological response of benthic foraminiferal communities to coupled eustatic and tectonic controls within the marginal Tethyan system.

Stratigraphic variations in the carbon isotope composition of marine limestones (δ¹³C_carb) have been widely reported from the Guadalupian, particularly in the uppermost Capitanian, but the extent to which they reflect global carbon cycle dynamics remains in dispute. Resolving these uncertainties is critical for interpreting the dynamics of the carbon cycle during the Guadalupian as well as for testing hypothesized circumstances of the marine extinction event during the Capitanian (latest Guadalupian). To assess the local versus global causes of stratigraphic variations in δ¹³C_carb, here we report δ¹³C_carb values from Guadalupian strata in the Hambast Valley, Abadeh region, southwest Iran, in two sections. We then compare the data from the two sections (Abadeh-1 and Abadeh-2) to data from numerous other well-studied sections that were distant from central Iran at the time of deposition. In the Hambast sections, there are broad excursions of δ¹³C_carb, of up to 3‰. However, the δ¹³C_carb values do not show any remarkable shifts across the Wordian/Capitanian or Capitanian/Wuchiapingian boundaries in the Abadeh-1 section. An excursion occurs near the Capitanian/Wuchiapingian boundary in the Abadeh-2 section but is associated with elemental and oxygen-isotope evidence for diagenetic resetting. The lack of reproducibility in the δ¹³C_carb shifts between the two studied sections at Abadeh and evidence for diagenetic resetting in association with negative excursions are consistent with evidence from other, previously reported, study sites that negative excursions can be accounted for by local primary or diagenetic factors and do not require any global perturbation of the carbon cycle through this interval. When carbonate values are compared with previously published organic carbon isotope data and carbonate sections are compared for shared isotope features, the primary global signal that is supported by the data is one of stable and relatively heavy values of δ¹³C_carb in marine limestone during the Guadalupian.

Detailed studies of upper Cisuralian (i.e., upper lower Permian) fusulinids make it possible to decipher the paleobiogeographic relations of central Iran, as part of the Cimmerian terranes, with other Paleotethyan regions. Two sections, Bagh-e Vang and Shesh Angosht, located in east-central Iran, are revised. Four local fusulinid biozones are distinguished: upper Yakhtashian Pamirina darvasica and Sakmarella spp. Zone, lower Bolorian Misellina (Brevaxina) dyrhenfurthi Zone, mid-Bolorian Cuniculinella Zone, and upper Bolorian Misellina (Misellina) cf. M. (M.) termieri Zone (probably equivalent to the traditional Misellina (Brevaxina) parvicostata Zone). Taxonomically, the main results are as follows: (1) a clarification is provided of the fusulinid genus or subgenus “Cuniculina,” the name of which is pre-occupied, and its synonymy with Cuniculinella; and (2) a lectotype is designated for Darvasites (Alpites) sinensis (Chen, 1934). The mid-Bolorian Cuniculinella Zone is recognized for the first time in Iran. Among the Bolorian fusulinids, Cuniculinella is reported in SE Pamir, Karakoram, central Afghanistan, SW Japan, central Japan, and California, confirming the faunal affinity of the study area in east-central Iran with both Paleotethyan and Panthalassan bioprovinces. Such a distribution is considered to have resulted from combined effects of global warming during the upper Cisuralian, warm oceanic currents along the Paleotethys Ocean, and the northward drift of the Iran block toward lower paleolatitudes.

The foraminiferal biostratigraphy and precise geological ages of the late Wordian, Capitanian, and Wuchiapingian strata in the Abadeh region of Iran have remained poorly constrained, despite evidence that they contain one of the most complete marine records of this important time interval. The purpose of this study is to provide a more complete documentation about the foraminiferal community preserved in these deposits, to assess their correlation with other Tethyan shelves, and to address implications for paleobiogeography. The foraminifers and calcareous algae from two measured stratigraphic sections allowed us to re‐evaluate the biostratigraphy of the poorly studied upper part of the Surmaq Formation and the entire Abadeh Formation in the Hambast Valley, Abadeh region, Iran. Foraminiferal assemblages consist of 72 species belonging to 34 genera. Calcareous algae and botanical incertae sedis include seven species from four genera, of which two species are new: Eogoniolina kordeae n. sp. and Sphairionia stellata n. sp. Four foraminiferal biozones are identifed in both sections: upper Wordian‐lower Capitanian Altineria bacillaeformis‐Baisalina pulchra‐“Hemigordius” aff. japonicus‐Sphairionia stellata Zone, upper Capitanian Baisalina cf. guizhouensis‐Hemigordius giganteus Zone, uppermost Capitanian Hemigordius irregulariformis Zone, and Wuchiapingian Pseudodunbarula‐Codonofusiella kwangsiana‐Reichelina cf. changhsingensis Zone. According to the foraminiferal assemblages, the beginning of the Wuchiapingian is placed at the lower part of the subunit 4b, which is contrary to the previous study reporting the base of unit 5 of the Abadeh Formation or the base of the unit 6 of the Hambast Formation as lower Wuchiapingian. Coeval biozones have been described in Transcaucasia in the former USSR. The similarity of foraminiferal assemblages in the Abadeh region and Transcaucasia reveals a proximity between these two regions, at least during Capitanian and Wuchiapingian time. Furthermore, the resemblance of foraminiferal faunas between Abadeh region and South China is more likely through palaeocurrent gyres, which facilitated the faunal exchange between these two regions despite their great geographic distances.

Eopolydiexodina and Monodiexodina individuals from the Middle Permian lower Dalan Member of the Dalan Formation in the Zard‐Kuh Mountains, southwest Iran, are quantitatively studied using histograms, normal probability plots, test of normality, and parametric (PCA and PCoA) and non‐parametric (NMDS) ordination techniques, in order to determine the accuracy of previously identified Eopolydiexodina and Monodiexodina species based on traditionally defined fusulinid parameters. Specimens of the genus Eopolydiexodina recorded in the lower Dalan Member have been previously assigned to one species and those of Monodiexodina are subdivided into one species and one subspecies. In the present study, 35 specimens from an Eopolydiexodina‐bearing bed in unit 11 and 40 individuals from a Monodiexodina‐bearing bed in unit 17 of the lower Dalan Member are selected. Observations of the histograms, normal probability plots, and test of normality for all the measured variables reveal that Eopolydiexodina and Monodiexodina individuals follow generally a normal distribution. The results of the principal component analysis (PCA), principle coordinate analysis (PCoA), and non‐metric multidimensional scaling (NMDS) suggest that the distribution of the studied individuals cannot be divided into different groups and only one species for Eopolydiexodina (E. aff. persica) and one species for Monodiexodina (M. aff. kattaensis) are identifiable. This study provides an example to show how the identification and definition of fusulinid species can be well constrained using both the traditional description approach and modern morphometric techniques together.