The geographic, environmental and phylogenetic evolution of the Alveolinoidea from the Cretaceous to the present day

The superfamily Alveolinoidea is a member of the Order Miliolida, and comprises three main families, the Alveolinidae, the Fabulariidae and the Rhapydioninidae. They are examples of Larger benthic foraminifera (LBF), which are single-celled organisms with specific characteristic endoskeletons. Alveolinoids are found globally from the Cretaceous to the present day, and are important biostratigraphic index fossils in shallow-marine carbonates. They are often associated with hydrocarbon reservoirs, and exhibit provincialism with characteristic genera often confined to one of the American, Tethyan or Indo-Pacific provinces. Previously, the systematic study of the global interrelationship between the various alveolinoid lineages has not been possible because of the absence of biostratigraphic correlation between the geographically scattered assemblages, and the scarcity of described material from the Indo-Pacific province. Here we use the literature and new material from the Americas, the French Alps, Iran, Tibet, India and South East Asia, coupled with the use of the planktonic foraminiferal zonal (PZ) correlation scheme to propose a comprehensive, global, systematic analysis of the biostratigraphic, phylogenetic and paleogeographic evolution of the alveolinoids. The alveolinoids originated in the Cretaceous in the Tethyan province. During a global sea-level low stand, a westward migration of some alveolinoids species to the Americas occurred, a behaviour previously reported in contemporaneous orbitolinid LBF. After the Cretaceous/Palaeogene (K–P) event, which saw the extinction of all Cretaceous alveolinoids, rare new forms of alveolinoids evolved again, first in the Americas and later independently in Tethys. As was found in previous studies of rotalid LBF, sea-level low stands in the Paleocene also allowed some alveolinoid forms to migrate, but this time in an eastward direction from the Americas to Tethys, and from Tethys on to the Indo-Pacific province. Alveolinoids still exist today (Borelis and Alveolinella), the former of which is cosmopolitan, while the latter is restricted to the Indo-Pacific province. Throughout their phylogenetic history, alveolinoids characteristically exhibit convergent evolution, with the repeated re-occurrence of certain morphological features. Understanding this propensity to homoplasy is essential in understanding and constructing the phylogenetic relationships within the alveolinoid superfamily

Tectono-stratigraphic correlations between Northern Evvoia, Skopelos and Alonnisos, and the postulated collision of the Pelagonian carbonate platform with the Paikon forearc basin (Pelagonian–Vardar zones, Internal Hellenides, Greece)

The Pelagonian stratigraphy of the Internal Hellenides consists of a Permo-Triassic basement and an Upper Triassic and Jurassic carbonate platform formation that has been overthrust by the Eohellenic ophiolite sheet during the Early Cretaceous. Intensive erosion, during the Cretaceous, removed most of the ophiolite and parts of the Jurassic formation. It is hypothesised that uplift and erosion of eastern Pelagonia was triggered by the break-off of the subducted oceanic leading edge of the Pelagonian plate. An investigation of the rocks that succeed the erosional unconformity shows that they constitute a shear-zone that is tectonically overlain by Cretaceous platform carbonates. Geochemical analyses of the shear-zone rocks substantiate that they are of mid-oceanic ridge and island arc provenience. Eastern Pelagonia collided with a Cretaceous carbonate platform, probably the Paikon forearc basin, as the Almopias ocean crust subducted beneath that island–arc complex. The Cretaceous platform, together with a substrate of sheared-off ocean floor mélange, overthrust eastern Pelagonia as subduction continued, and the substrate was dynamically metamorphosed into cataclastic rocks, mylonite, phyllonite and interpreted pseudotachylite. This complex of Cretaceous platform rocks and a brittle-ductile shear-zone-substrate constitute the here named Paikon–Palouki nappe, which was emplaced during Early Palaeocene. The Paikon–Palouki nappe did not reach Evvoia. Seismic tomographic models of the Aegean region apparently depict images of two broken-off ocean-plate-slabs, interpreted as Almopias-lithosphere-slabs. It is concluded that the western Almopias slab began to sink during the Early Cretaceous, while the eastern Almopias slab broke off and sank after the Paikon–Palouki nappe was emplaced in the Early Palaeocene

Climate-driven hydrological change and carbonate platform demise induced by the Paleocene–Eocene Thermal Maximum (southern Pyrenees)

The Campo section in the Spanish Pyrenees is classical for shallow-water Paleocene-Eocene Thermal Maximum (PETM) studies. Despite extensive work in the last decades, the stratigraphic location of the onset of the negative carbon isotope excursion (CIE), and hence the Paleocene/Eocene (P/E) boundary, remains a matter of considerable debate in the Campo section. Here we present new biostratigraphic, sedimentological and carbon-isotopic data across the late Paleocene to Eocene strata to constrain the precise stratigraphic position of the P/E boundary and investigate environmental changes across the PETM. Foraminiferal assemblages of biozone SBZ4 found below the Claret Formation are replaced by SBZ6 assemblages above. Detailed microfacies analysis indicated that the pre-PETM upper Navarri Formation represents transgressive inner-ramp deposits, overlain unconformably by mixed carbonate-siliciclastic deposits of the syn-PETM Claret Formation, overlain unconformably in turn by renewed carbonate-ramp deposition in the post-PETM lower Serraduy Formation. The temporary demise of the carbonate ramp during the PETM is ascribed to increased siliciclastic supply associated with a significant change in regional hydrology driven by an increase in magnitude and frequency of extreme rainfall and runoff events

Shallow-water carbonate responses to the Paleocene–Eocene thermal maximum in the Tethyan Himalaya (southern Tibet): Tectonic and climatic implications

This study presents a detailed stratigraphic record of the Paleocene–Eocene Thermal Maximum (PETM) in the Gamba area of the Tethyan Himalaya, a carbonate-platform succession originally deposited along the southern margin of the eastern Tethys Ocean. The Paleocene-Eocene boundary interval is marked by a negative carbon isotope excursion at the boundary between members 3 and 4 of the Zongpu Formation. The succession is erosionally truncated at this surface, which is overlain by an intraformational carbonate conglomerate, and only the upper part of the PETM interval is preserved. Foraminiferal assemblages of Shallow Benthic Zone 4 are present below the conglomerate bed, but are replaced by assemblages of Shallow Benthic Zone 6 above the conglomerate. Depositional facies also change across this surface; below the disconformity, floatstones and packstones containing nummulitid forams record progressive transgression in an open-marine environment, whereas restricted or lagoonal inner-ramp deposits containing Alveolina and Orbitolites are typical above the disconformity. The prominent negative excursion observed in the δ13C of whole-rock carbonate (− 1.0‰ at Zongpu, − 2.4‰ at Zengbudong) and organic matter (− 24.7‰, at Zengbudong) is correlated to the characteristic PETM carbon isotope excursion. This major negative excursion in shallow-marine carbonates may have partly resulted from syndepositional alteration of organic matter. The erosional unconformity can be constrained to the lower PETM interval (between 56 and 55.5 Ma), and is identifiable throughout the Tethyan Himalaya. This widespread disconformity is attributable to tectonic uplift associated with the southward migration of an orogenic wave, originated 3 ± 1 Ma earlier in the middle Paleocene at the first site of India-Asia continent-continent collision. A possible eustatic component of the pre-PETM sea-level fall, which resulted in the excavation of incised valleys filled during the subsequent sea-level rise when the conglomerate bed was deposited, remains to be assessed

Early jurassic carbon-isotope perturbations in a shallow-water succession from the tethys himalaya, southern hemisphere

The Early Jurassic was characterized by extreme carbon-cycle perturbations that are associated with abrupt environmental and climatic change. However, the evidence mainly derives from sections in the western Tethys and northern Europe: localities situated in the northern hemisphere. This paper presents new records of biostratigraphical (large benthic foraminiferal), sedimentological and carbonate carbon-isotope (δ13Ccarb) data from the Tibetan Kioto Platform formed in the southeastern Tethys (southern hemisphere) during the Sinemurian–earliest Toarcian interval. Six foraminiferal zones have been recognized: late Sinemurian Textulariopsis sinemuriensis, Pliensbachian Planisepta compressa, Bosniella oenensis, Cyclor-bitopsella tibetica and Streptocyclammina liasica, and earliest Toarcian Siphovalvulina sp. A. Based on biostratigraphy, δ13Ccarb data allow correlation with coeval records from the western Tethys and northern Europe by the identification of both negative and positive δ13C excursions. The negative excursions characterize the Sinemurian–Pliensbachian boundary event (SPBE) and the margaritatus–spinatum zone boundary event (MSBE); the positive δ13C excursion characterizes the margaritatus zone event (ME). Facies evolution in the Early Jurassic indicates that the establishment of carbonate sedimentation on the Kioto Platform occurred in the context of a global sea-level rise partly coincident with the SPBE and that, in common with other coeval platforms, carbonate production following the negative shift was predominantly made up of skeletal carbonates. Furthermore, the spread of the Lithiotis Fauna on the Kioto Platform followed the rebound of isotopic values after the SPBE. This phenomenon has been observed in the western Tethys and suggests that the global biocalcification event represented by the flourishing of the Lithiotis Fauna may have occurred synchronously across the Tethys, possibly reflecting the creation of more favourable marine conditions after the SPBE. Biostratigraphical data indicate that certain index larger benthic foraminifera became extinct around the onset level of the MSBE, likely due to the deleterious impact of this event. However, as in more northerly localities, the Lithiotis Fauna persisted during the late Pliensbachian in the shallow-water platforms of the Tethys until its disappearance in the early Toarcian

Carbonate drowning successions of the Bird's Head, Indonesia

Drowning unconformities and their related strata are important records of key tectonic and environmental events throughout Earth’s history. In the eastern Bird’s Head region of West Papua, Indonesia, Middle Miocene strata record a drowning unconformity present over much of western New Guinea, including several offshore basins. This study records platform carbonate strata overlain by mixed shallow- and deep-water units containing benthic and planktonic foraminiferal assemblages in several outcrop locations across the eastern Bird’s Head region. These heterolithic beds are interpreted as drowning successions that are terminated by a drowning unconformity. We define a succession exposed along the Anggrisi River in the eastern Bird’s Head as a stratotype for carbonate platform drowning in the Bird’s Head, analogous to similar faunal turnovers identified in its offshore basins. Detailed facies analyses, biostratigraphic dating, and paleoenvironmental interpretations using larger benthic and planktonic foraminifera collected from the Anggrisi River succession help to constrain the drowning event recorded onshore as beginning in the Burdigalian and ending in the Serravallian. The cause of platform drowning in the Bird’s Head is attributed to a reduction in the rates of carbonate accumulation due to the presence of excess nutrients in the depositional environment. Already foundering carbonate platforms due to environmental deterioration were left vulnerable to submergence and eventually succumbed to drowning. Low rates of carbonate production were outpaced by the rate of relative sea-level rise caused by high-amplitude oscillations in global glacio-eustatic sea-level change and/or regional tectonic subsidence. The duration of the drowning event across the entire Bird’s Head region is interpreted to have lasted a duration of approximately 9.5 My, between 18.0 and 8.58 Ma. This has implications when interpreting timings of sedimentary basin fill across western New Guinea and in other basins where carbonate platform drowning is recorded

Sea level, biotic and carbon-isotope response to the Paleocene–Eocene thermal maximum in Tibetan Himalayan platform carbonates

During the Paleocene–Eocene Thermal Maximum (PETM, ~56 Ma), a large, negative carbon-isotope excursion (CIE) testifies to a massive perturbation of the global carbon cycle. Shallow-marine settings are crucial to understand the environmental and ecological changes associated with the PETM and the connection between continental and open-marine environments. Detailed sedimentological, paleontological, and geochemical analysis of a quasi-continuous succession of shallow-marine carbonates in the Tethys Himalaya of southern Tibet indicates that a relative rise in sea level coincided with PETM onset, continued through PETM core, and terminated with a regression at PETM recovery. At PETM onset, corresponding to the SBZ4/SBZ5 boundary, no obvious impact on biota and specifically on larger benthic foraminifera (LBF) is observed. The major biotic change occurs later on at PETM recovery, corresponding to the SBZ5/SBZ6 boundary. Our data suggest that relative sea level, rather than temperature, exerted the main control on benthic biota during the PETM. Although the δ13Corg values of organic matter are similar in the deep sea and shallow-marine continental margins, the δ13Ccarb value of bulk carbonates are significantly 13C-depleted, which we attribute to environmental change driven by relative sea-level fluctuations

Discovery of the Paleocene-Eocene Thermal Maximum in shallow-marine sediments of the Xigaze forearc basin, Tibet: A record of enhanced extreme precipitation and siliciclastic sediment flux

The Paleocene-Eocene Thermal Maximum (PETM, ~56 Ma) was one of the major global deep-time hyperthermal events of the past. Studies of shallow-marine PETM records are crucial to understand the continental hydrological response to current global warming. This study presents the first detailed documentation of the PETM in the Xigaze forearc basin located along the northern active continental margin of the eastern Tethys Ocean, and illustrates the associated environmental and hydrological changes. Based on carbon-isotope stratigraphy, foraminiferal biostratigraphy, and zircon Usingle bondPb chronostratigraphy, the PETM event was identified within a siliciclastic unit in the largely calcareous Jialazi Formation. Foraminiferal assemblages of Shallow Benthic Zone 4 are present below the siliciclastic unit, but are replaced by Shallow Benthic Zone 6 assemblages above the siliciclastic unit. High-resolution microfacies analysis indicates that the pre-PETM deposits consist of carbonate-ramp sediments followed by a sudden change to syn-PETM siliciclastic rocks, followed in turn by renewed post-PETM carbonate-ramp deposition. The siliciclastic supply increased notably during the PETM, as indicated by the thickness of both sandstone and shale intervals, resulting in a temporary demise of the carbonate ramp. Provenance analysis does not indicate any major change in the source areas of terrigenous detritus through the early Paleogene. Increasing siliciclastic supply is thus chiefly ascribed to the intensification of seasonal precipitation and consequently increased hydrological circulation in the Gangdese arc during the PETM event