The unique Permian bivalve family Alatoconchidae has aberrant shell forms and extraordinary size up to 1 m, representing the largest bivalve group in the Paleozoic. Their occurrence is reported ...sporadically from Lower–Middle Permian shallow-marine carbonates in 9 areas in the world (Tunisia, Croatia, Oman, Iran, Afghanistan, Thailand, Malaysia, the Philippines, and Japan) that cover low-latitudes of both the Tethyan and Panthalassan domains. Alatoconchids almost always occurred in close association with large-tested fusulines (Verbeekinidae) and/or rugose corals (Waagenophyllidae) of the typical Tethyan assemblage, suggesting their preferential adaptation to shallow warm-water (tropical) environments. This “tropical trio” (Alatoconchidae, Verbeekinidae, and Waagenophyllidae) became extinct either during the Late Guadalupian or around the Guadalupian–Lopingian boundary (G–LB). Their intimate association and occurrence range suggest that these 3 taxonomically distinct clades may have shared not only a common habit but also a common cause of extinction. The shell structure of alatoconchids suggests their symbiosis with photosynthetic organisms (algae
+
cyanobacteria) in order to maintain their large body size that required high energy-consuming metabolism in contrast to smaller forms. The Alatoconchidae attained their largest size in the Wordian (Middle Guadalupian), probably maximizing the benefits of photosymbiosis. The subsequent extinction of the warm-water-adapted “tropical trio” both in Tethys and Panthalassa positively supports the explanation that a critical cooling took place on a global scale, including low-latitude oceans. The end of the gigantism in fusulines and bivalves in the Capitanian (Late Guadalupian) was likely caused by the collapse of photosymbiotic systems during a temporary temperature drop of seawater (Kamura cooling event) coupled with eutrophication that was detrimental to the tropical fauna adapted particularly to oligotrophic conditions. Gigantism of bivalves occurred several times in the Phanerozoic; e.g., Siluro-Devonian, Permian, Triassic–Early Jurassic, and Jurassic–Creataceous, mostly in warm periods. The sea-level change in the Phanerozoic apparently synchronized with the intermittent rise and decline of bivalve gigantism, suggesting that the photosymbiosis-related gigantism in low-latitudes may serve as a potential monitor of global warming/cooling in the past.
The first recovery of the conodont Hindeodus parvus from Žiri (Slovenia) a few years ago highlights this area for Early Triassic biostratigraphical study. Systematic sampling of five sections in the ...Idrija–Žiri area has yielded the new species Platyvillosus corniger sp. nov. and Neospathodus planus sp. nov. Based on these new species and other conodont elements collected here, nine discrete conodont Unitary Association (UA) zones are proposed for this area. In ascending order they are: Eurygnathodus costatus Zone (UA 1), Eurygnathodus hamadai Zone (UA 2), Foliella gardenae Zone (UA 3), Neospathodus robustus Zone (UA 4), Platyvillosus corniger Zone (UA 5), Platyvillosus regularis Zone (UA 6), Triassospathodus hungaricus Zone (UA 7), Triassospathodus symmetricus Zone (UA 8), and Neospathodus robustispinus Zone (UA 9). The conodont and δ13C data indicate that these conodonts span the Dienerian/Smithian (i.e. Induan/Olenekian) boundary interval to the Spathian, and they also indicate that Triassospathodus hungaricus Zone (UA 7) does not occur at the base of the Spathian. These conodont zones are valuable for stratigraphic correlation within Central and southern Europe, and they also promote a better correlation worldwide. Conodonts in the Idrija–Žiri area were adapted to a shallow-water environment in an epeiric ramp.
•Nine discrete conodont zones are identified for the Early Triassic in Idrija–Žiri, Slovenia.•δ13C data and conodonts indicate that these sections span the late Dienerian to Spathian.•According to δ13C data the Smithian/Spathian boundary is characterized by Foliella gardenae.•These conodonts were adapted to a shallow-water environment in an epeiric ramp.•This unique conodont sequence was probably the result of paleoecological influence and/or provincialism.
During the earliest Triassic microbial mats flourished in the photic zones of marginal seas, generating widespread microbialites. It has been suggested that anoxic conditions in shallow marine ...environments, linked to the end‐Permian mass extinction, limited mat‐inhibiting metazoans allowing for this microbialite expansion. The presence of a diverse suite of proxies indicating oxygenated shallow sea‐water conditions (metazoan fossils, biomarkers and redox proxies) from microbialite successions have, however, challenged the inference of anoxic conditions. Here, the distribution and faunal composition of Griesbachian microbialites from China, Iran, Turkey, Armenia, Slovenia and Hungary are investigated to determine the factors that allowed microbialite‐forming microbial mats to flourish following the end‐Permian crisis. The results presented here show that Neotethyan microbial buildups record a unique faunal association due to the presence of keratose sponges, while the Palaeotethyan buildups have a higher proportion of molluscs and the foraminifera Earlandia. The distribution of the faunal components within the microbial fabrics suggests that, except for the keratose sponges and some microconchids, most of the metazoans were transported into the microbial framework via wave currents. The presence of both microbialites and metazoan associations were limited to oxygenated settings, suggesting that a factor other than anoxia resulted in a relaxation of ecological constraints following the mass extinction event. It is inferred that the end‐Permian mass extinction event decreased the diversity and abundance of metazoans to the point of significantly reducing competition, allowing photosynthesis‐based microbial mats to flourish in shallow water settings and resulting in the formation of widespread microbialites.
After the end‐Permian mass extinction, microbialites filled the ecological niche previously occupied by metazoan reefs. The factors that allowed microbialite‐forming microbial mats to flourish are, however, hotly debated. By investigating the faunal composition and depositional setting of Permian/Triassic boundary microbialites, we propose that the impact of the extinction event on the abundance of metazoans suppressed the biological controls that were previously excluding microbialite development from subtidal environments.
Middle Triassic deposits in the Karst Dinarides (south Lika area, near Gračac) were investigated for petrological, sedimentological and biostratigraphic determinations. Within two continuously ...recorded sections of sedimentary carbonates and interlayered pyroclastic rocks (Mali Kunovac and Kunovac sections) reflecting variable sedimentary-magmatic environments, valuable cephalopod fauna ranging from the middle Illyrian to the upper Illyrian age was found. The most significant was the recovery of the ammonoids Asseretoceras sp., indicating the upper part of the Illyrian Paraceratites trinodosus Zone, and Reitziites reitzi species which marks the upper part of the Illyrian Reitziites reitzi Zone. The discovery of the Reitziites reitzi species was not known from the Karst Dinarides until this finding.
In order to document paleoenvironmental conditions of the equatorial western Paleo-Tethys during the late Middle Permian prior to the end-Guadalupian mass extinction, chemostratigraphic analysis ...using stable carbon isotopes was conducted for the Guadalupian rocks at Brusane in the Velebit Mtn., central Croatia. By analyzing 72 carbonate samples of the Capitanian (Upper Guadalupian) Velebit Formation, we found an interval with unusually high δ
13C
carb values (+
4 to +
6‰) in the ca. 150
m-thick
Yabeina (fusuline) Zone. The present find clarifies that the primary productivity and burial rate into the sediments were considerably high during the Capitanian in westernmost Paleo-Tethys. This chemostratigraphic signal is properly correlated with the “Kamura event” detected in a mid-Panthalassan paleo-atoll limestone in Japan. The present results identify the Capitanian “Kamura event” for the first time in European Paleo-Tethys on the opposite side of the globe from the mid-Panthalassan paleo-seamount, and prove the global context of the event as well as its utility in chemostratigraphic correlation. In order to enhance bioproductivity on a global scale, the increase in nutrient supply is inevitable. In addition to riverine run-off from Pangea, active oceanic circulation, in particular upwelling of deep-sea water enriched in nutrients, was likely vital both in Panthalassa and Paleo-Tethys. The extinction of some Guadalupian fauna, in particular photosymbiotic community (large-tested fusulines, large bivalves, rugose corals), was likely related to a temporary cooling coupled with eutrophication in low-latitude shallow marine environments of Paleo-Tethys and Panthalassa.
Six samples of Gröden sandstones (Middle Permian) were analysed: Five of them were from Pikovac Creek valley (in the vicinity of Brusane village at Velebit Mts., Croatia) and one was from the locus ...typicus Gröden/Val Gardena (Italy). Based on the micropetrographical characteristics of sandstones, as well as on the modal composition and heavy mineral association, origin of material, weathering index of source rocks, climate and relief in the period of deposition have been supposed. Four samples from Pikovac Creek were petrographicaly determined as lithic greywackes, one as densely packed lithic arenite, while a specimen from Gröden locus typicus represents feldspar greywacke. Lithic greywackes/arenites imply very low maturity and suggest a close proximity of source rocks as well as the active tectonics in the hinterland of the depositional basin. Heavy mineral association in the samples from Pikovac Creek valley, with a large amount of fairly rounded stable grains (zircon, tourmaline and rutile), indicate that clastic material was derived from recycled orogen, and probably from reworked sedimentary rocks. The presence of kyanite and chlorite in the heavy mineral assemblage suggest their origin is from metamorphic rocks. This data assumes that Gröden sandstones from Pikovac Creek were possibly deposited in the fan delta or braided delta depositional environment as a part of a riftsystem (recycled orogen). The composition of the sample Gröden s. locus typicus (light and heavy mineral fractions) suggests the vicinity of magmatic rocks in the source area. All analysed samples are red coloured and have a large amount of limonitized grains in the heavy mineral assemblage, that point to the arid climate at the time of deposition. A weathering index diagram for Pikovac sandstones implies an arid/semiarid climate and high relief of the source area where metamorphic or sedimentary rocks dominate, while an arid/semiarid climate and high relief with plutonic source rocks were supposed for the provenance of Gröden s. locus typicus.
The Teočak section in Bosnia and Herzegovina (Sava-Vardar Zone) composed of the Upper Permian Bellerophon Formation and the Lower Triassic “Werfen Formation” was studied sedimentologically and ...micropaleontologically by using foraminifers and conodonts. The Bellerophon Formation was deposited in a shallow subtidal lagoon rich in biota characterized by typical Changsingian foraminiferal species. Deposition on a shallow epicontinental ramp with pronounced long-term transgression is proposed for the Lower Triassic strata. The recovered conodont faunas are assigned to the Late Permian praeparvus (Changhsingian) and to the Early Triassic isarcica-staeschei (Griesbachian), costatus (? latest Dienerian-early Smithian) and hungaricus (early Spathian) Zones. The studied strata include the Permian-Triassic Boundary as well as the Induan-Olenekian Boundary. The introduced conodont biozonation in the Teočak section is for the first time proposed for the region and is an important contribution for paleobiogeographic correlation of Western Tethys.
•Uppermost Permian and Lower Triassic strata of the Teočak section were studied.•The section is composed of the Bellerophon Formation and the “Werfen Formation”.•The recovered conodont faunas enabled identification of four conodont zones.•Foraminifers of the Bellerophon Formation are marked by typical Changhsingian taxa.•A deposition on a shallow epicontinental ramp is proposed for the Triassic strata.
Conodont ecology of the Early Triassic Smithian–Spathian transition is still poorly understood. Here we use oxygen isotope ratios of monogeneric conodonts from Omani samples to reveal the differences ...of oxygen isotopic composition between different taxa. Oxygen isotope analyses from Oman reveal that Neogondolella inhabited a deeper part of the water column relative to neospathodids and Icriospathodus. This indicates that species of Neogondolella lived in an environment ca. 1.7 °C cooler than where neospathodids lived. The investigation of conodonts from these Smithian and Spathian sections has also enabled the first recovery of some rarely reported species (e.g., Icriospathodus zaksi, Paullella omanensis sp. nov. Chen and Gladigondolella laii sp. nov. Chen) from Oman. Paullella omanensis sp. nov. was further recovered from Plavno, Croatia, indicating a large geographic distribution, and its value for biostratigraphic correlations. The discovery of these species in both Oman and Croatia expands their geographical distribution.
•Conodont ecology of the Early Triassic Smithian-Spathian transition is revealed via isotopic composition.•Neogondolella inhabited a deeper part of the water column relative to neospathodids and Icriospathodus.•Species of Neogondolella lived in ca. 1.7 °C cooler environment than where neospathodids lived.•The investigation has enabled the recovery of two new conodont species.
Upper Permian and lowermost Triassic strata of the Masore section in western Slovenia have been restudied by means of bio- and lithostratigraphy. This section is mainly characterized by a carbonate ...succession of the Bellerophon Formation deposited in a shallow marine ramp environment that was located in the western part of the Paleotethys. The Permian-Triassic boundary (PTB) transition is marked by laminated microbialites – stromatolites interpreted to reflect a deeper ramp environment. The conodont elements recovered enabled the recognition of the Hindeodus praeparvus Zone of the uppermost Permian (Upper Changhsingian) in the Bellerophon Formation. Gondolellids are documented in the PTB transitional interval with microbial microfacies, whereas the Isarcicella isarcica Zone (Lower Griesbachian, Lower Triassic) is recognized in the tectonically separated Werfen Formation just above the microbial microfacies part of the section. The lowermost part of the microbialites is characterized by Late Permian species of foraminifers indicating that at least this part of the section is still Upper Permian.
•The Masore section in Slovenia has been restudied.•The PTB transition is marked by laminated microbialites – stromatolites.•Three conodont faunas are recognized based on Clarkina, Hindeodus and Isarcicella.•Abundant and diverse Changhsingian foraminifers are documented.•The Masore area was located in the western Paleotethyan carbonate ramp-like edge.
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