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Coniacian to Maastrichtian changes in calcareous nannofossil assemblages have been investigated in the eastern Tethyan Shahneshin section (central Zagros Basin, Iran). The nannofossil assemblages are mainly composed of Watznaueria spp. (avg. 54%), Retecapsa spp (avg. 7.9%), Cribrosphaerella ehrenbergii (avg. 7.7%) and Micula spp. (avg. 5.7%). Throughout the late Campanian, there is a trend to lower abundances in Watznaueria spp. together with increasing abundances of C. ehrenbergii and Arkhangelskiella cymbiformis , which are considered in this basin as the main cool-water taxa. Our results reveal that, despite a diagenetic impact on calcareous nannoflora, a number of primary paleoecological trends are preserved which depict well features of the progressive Late Cretaceous cooling. The first pronounced cooling episode occurs across the late Campanian to early Maastrichtian. The onset of pronounced cooling in the eastern Tethys appears to occur prior to the Campanian/Maastrichtian Boundary event (CMBE) δ13C negative excursion, in contrast with the Boreal realm where pronounced cooling only occurs in the early Maastrichtian, postdating the onset of the CMBE. The coincidence of this earlier cooling in the Zagros Basin with an interval characterized by a significant increase in benthic foraminifera suggests an amplified response of the assemblage due to a change to shallower environments. Hence, the late Campanian calcareous nannofossil assemblage turnover in central Zagros is either a response to an early cooling trend in the eastern Tethys or to sea-level fall or both. The mid-Maastrichtian warming and late Maastrichtian cooling episodes are also delineated in the nannofossil assemblage of Shahneshin and likely correlate with similar episodes in the Boreal Realm. • The first quantitative study on the Late Cretaceous calcareous nannofossil assemblages from the Eastern Tethys (Zagros). • The first palaeoecological record of the Late Cretaceous cooling in the eastern Tethyan Realm (Zagros). • Cribrosphaerella ehrenbergii and Arkhangelskiella spp. are considered as the best cool-water indicators in the Zagros Basin in this study. • The late Campanian–early Maastrichtian cooling appears to occur earlier in eastern Tethys compared to the Boreal Realm. [ABSTRACT FROM AUTHOR]

The Early Paleogene Tethyan domain saw the development of large platform carbonates rich in large benthic foraminifera (LBF), of which the Taleh Zang Formation in Lurestan Basin, SW Iran, represents an excellent example. The LBF assemblage is dominated by alveolinids, together with a variety of foraminiferal genera such as Nummulites , Rotalia , Sackesaria , Assilina , Operculina , and Glomalveolina. Smaller benthic foraminifera, calcareous algae, gastropods, echinoids, and bivalves constitute minor components of the carbonate. Biostratigraphy analysis of the LBF is conducted on two distinct sections of the Taleh Zang Fm. The sections referred to as TZ-1 and TZ-2 have respective thicknesses of 87 m and 132 m. This analysis has constrained the formation age to the early Ypresian within Shallow Benthic Zones (SBZs) 5–7. Facies analysis supports the major accumulation of these successions in a shallow water environment within the euphotic zone. We recognize 9 distinct facies and microfacies representing four main depositional environments including tidal flat, lagoon, bioclastic shoal, and shallow open marine. These environments are distributed along a low-angle homoclinal ramp and form the foundation of a stratigraphic interpretation characterized by intervals displaying shallowing and deepening trends. Three shallowing-upward intervals have been identified within the Taleh Zang succession. The determined intervals cannot be solely attributed to global sea level fluctuations and support a significant impact of the regional structural context resulting from collision-induced uplift and variable subsidence rates. The identified intervals exhibit local and regional correlation and compatibility on the Arabian Plate, providing robust confirmation of the significant roles played by both tectonics and eustasy at a regional scale. • Taleh Zang Fm. highlights a rich LBF assemblage, shedding light on the early Eocene central Tethyan domain. • Four main carbonate depositional settings on a low angle homoclinal ramp system. • Three deepening-shallowing intervals linked to local and regional tectonic activities and global sea level changes. • Enhance understanding of LBF evolution and biodiversity patterns in the central Tethyan and Arabian Peninsula hotspots. [ABSTRACT FROM AUTHOR]

The Late Cretaceous is marked by geodynamical changes including Africa-Eurasia convergence that resulted in the narrowing of the Tethys Ocean and in ophiolite obduction along the southern margin of the various continental blocks in eastern Tethys. Geochemical and mineralogical analyses were performed on the Shahneshin section (Zagros Basin - eastern Tethys), to explore the consequences of this evolution on oceanic circulation, and to estimate the role of ophiolite weathering that can impact climate through atmospheric CO 2 drawdown. [Ni] and [Cr] sharply increase in the uppermost Campanian – Maastrichtian interval and are not coeval with an increase in the Nd isotope composition (ɛ Nd) of the detrital fraction of the sediments. This is interpreted as reflecting weathering of the mantellic, ultramafic part of the ophiolite sequence at that time, implying that ophiolites were exposed on the continents as soon as the Coniacian in the vicinity of the Zagros Basin. Hence their weathering could have contributed to the Late Cretaceous climatic cooling. Clay mineralogy reveals an alternation of kaolinite-rich humid periods (Coniacian/Santonian and late early Campanian to latest Campanian) and kaolinite-depleted arid periods (early Campanian and the latest Campanian to late Maastrichtian). The ɛ Nd(t) of bathyal waters (carbonate leached fraction) appears quite radiogenic, in the range of -3.4 to -5.2 ɛ-units, about 2 to 4 ɛ-units higher than the detrital fraction. Changes in the ɛ Nd(t) of detrital material delivered to the Zagros Basin appear to control the ɛ Nd(t) of the local bottom waters from the Coniacian to the middle Campanian. By contrast, decoupling of detrital ɛ Nd(t) from that of the local bottom waters from the middle Campanian to the Maastrichtian points to increasing fluxes of westward flowing Pacific radiogenic water masses into the eastern Tethys at that time. These results support an intensification of the Tethyan Circumglobal Current, likely related to the narrowing of the Tethyan seaway. • Alternating humid and arid periods throughout the Late Cretaceous of Zagros. • Ophiolite sequence was aerially exposed as soon as the Coniacian in the Zagros area. • Intensification of the TCC from the middle Campanian to the Maastrichtian. [ABSTRACT FROM AUTHOR]

During the Cretaceous-Paleogene (KPg) transition about 66 million years ago, eruptions of the Deccan Traps magmatic province released massive amounts of carbon dioxide and acid aerosols into the atmosphere, leading to global warming, environmental acidification and biological crisis. However, how this acidification affected the biosphere and was recorded in marine sediments is still poorly constrained. Here we investigated the unusual occurrence of a low magnetic susceptibility interval overlying the KPg boundary at Galanderud, Iran, and constituted by clays alternating with three limestone beds. On a global scale, the base of the Danian (biozone P0) represent a period of low biological productivity at the aftermath of the KPg mass extinction, and thus the occurrence of these three carbonate beds is unusual. Our results show that the basal Danian clays are characterized by anomalously low content of magnetite compared to Maastrichtian and upper Danian marls, as well as by a relative higher abundance of mercury (20-30 ppb) than the interbedded carbonates. Absence of significant correlation between mercury and total organic content comforts the contribution of the Deccan volcanism. Carbonates are constituted by microcrystalline calcite, with no or very few nannofossils, suggesting a diagenetic or early calcite precipitation origin. We hypothesized that these clay/carbonate alternations represent periods of acidification induced by the Deccan volcanism, where acid rains led to the dissolution of iron oxides inland and in surficial seawater and resulted in the deposition of magnetite-depleted clays. To test this hypothesis we conducted a set of simulations using a biogeochemical model coupled to a General Circulation Model (GCM). Results shows that dissolution of continental and shallow water carbonates would have led to the rapid injection of Ca2+ and CO32- into the ocean, triggering ocean carbonate saturation overshoot, resulting in the precipitation of the abiotic carbonates. The occurrence of three successive and rapid pulses of Deccan eruptions may further explains the enigmatic clay/carbonates alternations in the basal Danian. These findings represent an unprecedented piece of evidence of the climate perturbation of the Deccan volcanism in the Tethys realm.Publication supported by FCT- project UID/GEO/50019/2019 - Instituto Dom Luiz [ABSTRACT FROM AUTHOR]