Charles M. Henderson

Calibrating the End-Permian Mass Extinction

High-precision geochronologic dating constrains probable causes of Earths largest mass extinction. The end-Permian mass extinction was the most severe biodiversity crisis in Earth history. To better constrain the timing, and ultimately the causes of this event, we collected a suite of geochronologic, isotopic, and biostratigraphic data on several well-preserved sedimentary sections in South China. High-precision U-Pb dating reveals that the extinction peak occurred just before 252.28 ± 0.08 million years ago, after a decline of 2 per mil (‰) in δ13C over 90,000 years, and coincided with a δ13C excursion of −5‰ that is estimated to have lasted ≤20,000 years. The extinction interval was less than 200,000 years and synchronous in marine and terrestrial realms; associated charcoal-rich and soot-bearing layers indicate widespread wildfires on land. A massive release of thermogenic carbon dioxide and/or methane may have caused the catastrophic extinction.

Anomalously diverse Early Triassic ichnofossil assemblages in northwest Pangea: A case for a shallow-marine habitable zone

Early Triassic trace fossil assemblages from the northwest margin of Pangea record a diverse suite of postextinction infauna. These ichnofossil assemblages occurred within well-oxygenated, shallow-marine refuges in a Panthalassa Ocean otherwise characterized by widespread anoxia. We propose an environmentally controlled model for their distribution, in which wave aeration, enhanced by frequent storms, gave rise to an optimal zone for benthic colonization. Within this habitable zone extinction pressures were ameliorated and postextinction recovery duration was minimized.

Evolution of Permian conodont provincialism and its significance in global correlation and paleoclimate implication

The main components of Asselian through Artinskian conodont faunas found around the world are basically the same, and the provincialism is indicated only by less common endemic elements such as Gondolelloides and New Genus A Henderson in North Pangea, Sweetognathus bucaramangus around the equator and Vjalovognathus in eastern Gondwana. Provincialism is marked by differences at the species level of Mesogondolella, Neostreptognathodus and Sweetognathus during the Kungurian, and becomes very distinct with differences at the genus level during the Guadalupian and Lopingian. Three provinces of Permian conodonts, referred to as the North Cool Water Province (NCWP), the Equatorial Warm Water Province (EWWP) and the peri-Gondwana Cool Water Province (GCWP), are recognized. The NCWP is marked by Gondolelloides in the early Cisuralian, dominance of Neostreptognathodus and no or rare Sweetognathus in the late Cisuralian, dominance of Merrillina and Mesogondolella and absence of Sweetognathus in the Guadalupian, and dominance of Merrillina and Mesogondolella and absence of Iranognathus in the Lopingian. The EWWP is characterized by the absence of Gondolelloides and Vjalovognathus in the Cisuralian, abundance of Sweetognathus and Pseudosweetognathus in the Kungurian (late Cisuralian), Jinogondolella and Sweetognathus in the Guadalupian, and Clarkina and Iranognathus in the Lopingian. The GCWP is marked by Vjalovognathus, Merrillina in the Cisuralian, Vjalovognathus, Merrillina and Mesogondolella in the Guadalupian, and Vjalovognathus and Merrillina in the Lopingian. Mixed faunas are recognized in regions bordering between the EWWP and GCWP including Western Timor during the Artinskian, Pamirs during the Kungurian and the Salt Range during the Guadalupian and Lopingian. Three different conodont zonations are proposed, one for each of the three conodont provinces. Four potential horizons for inter-provincial correlation of Permian conodonts are recognized. They are in ascending order: (1) the first appearance of Sweetognathus whitei, which is closely related to the last occurrence of Carboniferous-type conodonts such as Streptognathodus and Adetognathus; (2) the first appearance of Neostreptognathodus pequopensis; (3) the base of the Jinogondolella nankingensis Zone; and (4) the base of the Clarkina postbitteri–Iranognathus erwini Zone. The spatial and temporal distribution pattern of Permian conodonts suggests that temperature is the primary controlling factor. Evolution of Permian conodont provincialism reveals a glaciation during the Asselian and Sakmarian, a global warming during the Artinskian, a climate cooling in North Pangea during the Kungurian, a continuation of Kungurian climate trends in the Guadalupian, a relatively minor warming during the Wuchiapingian, a returned cooling in the Changhsingian and Lower and Middle Griesbachian, and a global warming in the Late Griesbachian, which ended the Permian conodont lineage.

Evidence for a diachronous Late Permian marine crisis from the Canadian Arctic region

A high-resolution chemostratigraphic study of a 24-m-thick section at West Blind Fiord on Ellesmere Island (Canadian Arctic) documents stepwise environmental deterioration in the marine Sverdrup Basin during the late Changhsingian (late Late Permian) as a result of volcanic disturbances to surrounding landmasses. A horizon within the upper Lindstrom Formation (datum A) is characterized by increased Fe-oxyhydroxide fl uxes and weathering intensity as well as modest shifts toward more reducing watermass conditions and higher marine productivity, recording an initial disturbance that washed soils into the marine environment. The contact between chert of the Lindstrom Formation and silty shale of the overlying Blind Fiord Formation, which is 1.6 m higher and ~50 k.y. younger than datum A, records a large increase in detrital sediment fl ux, more strongly enhanced marine productivity, and a regional extinction of siliceous sponges, herein termed the “Arctic extinction event.” The horizon equivalent to the latest Permian mass extinction of Tethyan shallow-marine sections is 5.6 m higher and ~100 k.y. younger than the Arctic extinction event, demonstrating the diachronous nature of the marine biotic and environmental crisis at a global scale; it is associated with intensifi ed anoxia and possible changes in phytoplankton community composition in the study section. Marine environmental deterioration in the Sverdrup Basin, probably triggered by terrestrial ecosystem deterioration and elevated detrital sediment fl uxes, was under way by the early part of the late Changhsingian, well before the onset of main-stage Siberian Traps fl ood basalt volcanism. The event sequence at West Blind Fiord may record the deleterious effects of early-stage explosive silicic eruptions that affected the Boreal region, possibly through deposition of toxic gas and ash within a restricted latitudinal band, while having little impact on marine ecosystems in the peri-equatorial Tethyan region.

Evolution and distribution of the conodonts Sweetognathus and Iranognathus and related genera during the Permian, and their implications for climate change

Abstract The conodont genus Sweetognathus , which is characterized by pustulose ornamentation on a wide, flat-topped carina, originated in the earliest Permian as S. expansus from Diplognathodus edentulus . The Asselian through Artinskian part of the Sweetognathus lineage is well represented in Kansas by the successive evolution of S. expansus , S. merrilli , S. aff. S. merrilli , S. whitei and S. bucaramangus . Sweetognathus and Iranognathus lineages were mainly confined to tropical areas from the Kungurian onward. The Kungurian and Guadalupian part of the Sweetognathus lineage is well represented in South China by the successive evolution of S. whitei (Artinskian), S. guizhouensis (lower Kungurian), S. subsymmetricus (upper Kungurian), S. iranicus hanzhongensis (Roadian) and S. fengshanensis (Capitanian). An additional lineage in West Texas is represented by the evolution of S. sulcatus to S. aff. adjunctus to S. adjunctus and to S. bicarinum . In the Urals and northwestern Pangea, the late part of the Sweetognathus lineage is represented by rare specimens of S. bogoslovskajae (upper Artinskian–lower Kungurian). During the late Artinskian, S. whitei radiated into S. toriyamai and S. bucaramangus , and also gave rise to Neostreptognathodus pequopensis and probably Pseudosweetognathus costatus . Neostreptognathodus ? exsculptus may have evolved from Adetognathus paralautus through Adetognathus ? telfordi sp. nov. Iranognathus , characterized by a narrow carina with poorly developed denticles and bearing subtle and smaller pustulose micro-ornament, replaced Sweetognathus at or near the Guadalupian/Lopingian boundary. It probably also evolved from Diplognathodus in the topmost Guadalupian. A lineage of Iranognathus ? sp. nov. A to I. erwini can be recognized for the Guadalupian and Lopingian boundary interval. A lineage of Iranognathus ? sp. nov. A to I. movschovithschi to I. sosioensis to I. tarazi is found throughout the Guadalupian and Lopingian boundary interval and the Wuchiapingian of South China. Sweetognathus and Iranognathus tend to develop homeomorphic accessory nodes iteratively during lowstand periods of global sea level near the Artinskian/Kungurian and Guadalupian/Lopingian boundaries and in the late Wuchiapingian. Sweetognathus and Iranognathus seem to be equatorial warm-water inhabitants. Distribution patterns reflect glaciation in Gondwana during the Asselian and Sakmarian, a warm climate during the Artinskian, cooling in North Pangea during the Kungurian and later Permian, slight amelioration during the Guadalupian, warming during the Wuchiapingian, and cooling during the Changhsingian in the peri-Gondwana region. Definitions for most of the important Sweetognathus species are refined. Three new species and subspecies, Iranognathus ? sp. nov. A , Adetognathus ? telfordi sp. nov., Gullodus duani sp. nov., are described.

Stratigraphy, Paleoecology, and Origin of Lower Devonian (Emsian) Carbonate Mud Buildups, Hamar Laghdad, Eastern Anti-Atlas, Morocco, Africa

ABSTRACT Recent debates concerning the origin of Emsian carbonate mud buildups exposed at Hamar Laghdad in the eastern Anti-Atlas of Morocco centre around geochemical studies that suggest authigenic or chemosynthetic processes induced precipitation of mud from hydrothermal fluids. Geochemical data alone cannot be used to demonstrate conclusively the origin of the mud comprising the buildups, but an in situ source and early cementation can be inferred from morphology, internal architecture, and sedimentary structures. Morphological types vary from symmetrical mounds up to 12 m high to asymmetrical pinnacles that locally coalesced, forming elongate multicored complexes up to 56 m high. Their steep-sided nature (margins dipping up to 54°) and sporadic occurrence of erect invertebrates suggest localized production of mud rather than hydrodynamic piling or baffling from suspension. Irregular nodular beds that thicken internally imply centralized production and a local source for the mud. Displaced nodules and slump folds indicate early cementation of mud to at least a firm consistency, followed by downslope movement. Abrupt termination of carbonate production during late transgression resulted in drowning of the mud buildups and adjacent platform. Except for a thin condensed bed deposited during maximum flooding, the buildups and platform (transgressive systems tract deposits) remained uncovered for an extended period (upper inversus-laticostatus to lower serotinus zones) before being buried beneath progradational clinoforms of nodular limestone and marlstone (regressive systems tract deposits). Overlying Middle Devonian carbonates contain evidence of hydrothermal seepage, based on the occurrence of solemyid and anomalodesmatan bivalves, which are thought to be chemosymbiotic. These bivalves occur in a mud buildup rooted on an Emsian counterpart, suggesting periodic hydrothermal activity beneath the buildups. A hydrothermal origin for the Hamar Laghdad mud buildups appears to be consistent with other mud buildups of similar age in other parts of northwest Africa. Vast deposits of coeval Minette-type ooidal ironstones, which also have a seep origin in the Tindouf Basin, south of the Anti-Atlas, testify to occasional widespread hydrothermal activity along the northwest margin of Gondwana during much of the Devonian. End_Page 217------------------------

Stratigraphic versus environmental significance of Permian serrated conodonts around the Cisuralian–Guadalupian boundary: new evidence from Oman

Abstract Conodonts from the cephalopod limestones of Rustaq and Ba’ad, Oman, have for many years been dated as Wordian because of the presence of the ammonoid, Waagenoceras. Revised definitions for Guadalupian stages and major differences of conodont morphology among apparently coeval faunas necessitate a review of this age assignment. The lack of serration within the Oman conodont faunas as well as from Waagenoceras-bearing limestone blocks in Sicily differs markedly from conodonts in the Guadalupian stratotype sections of West Texas. These differences have previously been interpreted to be the result of upwelling ‘cold bottom-water’ that may have restricted the distribution of serrated, warm-water Jinogondolella species. However, our samples from Oman are dominated by species with a carinal configuration that is comparable to gondolellids from the Equatorial Warm Water Province (EWWP). Abundant species include Mesogondolella siciliensis in the lower ammonoid beds and Mesogondolella idahoensis lamberti in the upper ammonoid beds. If cold bottom-water currents were present at Oman then these taxa must have been pelagic, living in warm surficial water. In contrast, the North Cool Water Province (NCWP) includes coeval conodonts that have a different carinal configuration and are dominated by long-ranging Mesogondolella idahoensis idahoensis. These taxa and their morphologic variations represent a geographic cline between the EWWP and NCWP. In addition, Early Roadian serrated gondolellids have been recognized in temperate cool-water settings in the Jilin Province, NE China, the Phosphoria Basin, Idaho, USA, and the Sverdrup Basin, Arctic Canada. These serrated forms extend above the Lower Roadian in only the Phosphoria Basin, indicating a distribution into temperatures cooler than previously thought, at least during the Early Guadalupian. Other conodonts from the deep-water cephalopod limestones of Oman include rare, shallow warm-water sweetognathids, suggesting that these too must have been pelagic; if true, then cold bottom-waters probably played little role in conodont distribution. The identified conodont taxa at Oman best correlate with the uppermost Kungurian at the Luodian section of South China and in the Guadalupe Mountains of West Texas, suggesting that the lack of serration is not a result of cold water but rather of a stratigraphic position prior to the evolution and expansion of serrated gondolellids in the Roadian. It is possible that other paleoecologic controls affected distribution, and an alternative age assignment of Early Roadian is considered for these conodonts. The ammonoids, including advanced species of Waagenoceras, suggest that the best correlation is with the third limestone of the Word Formation (Willis Ranch Member), which correlates with the Upper Roadian according to ratified global stage definitions. There is still an apparent discrepancy between conodont and ammonoid ages, but discounting previous Wordian ages has considerably reduced this. Associated fusulinaceans cannot resolve this argument because of profound provincialism, but they can contribute to correlation of the global stages with Tethyan stages. It is here suggested that the Kungurian correlates with the Upper Bolorian to Upper Murgabian and that the Roadian correlates with the Lower Midian or Upper Murgabian and Lower Midian.

Quantifying the Process and Abruptness of the End-Permian Mass Extinction

Abstract Studies of the end-Permian mass extinction have suggested a variety of patterns from a single catastrophic event to multiple phases. But most of these analyses have been based on fossil distributions from single localities. Although single sections may simplify the interpretation of species diversity, they are susceptible to bias from stratigraphic incompleteness and facies control of preservation. Here we use a data set of 1450 species from 18 fossiliferous sections in different paleoenvironmental settings across South China and the northern peri-Gondwanan region, and integrate it with high-precision geochronologic data to evaluate the rapidity of the largest Phanerozoic mass extinction. To reduce the Signor-Lipps effect, we applied constrained optimization (CONOP) to search for an optimal sequence of first and last occurrence datums for all species and generate a composite biodiversity pattern based on multiple sections. This analysis indicates that an abrupt extinction of 62% of species took place within 200 Kyr. The onset of the sudden extinction is around 252.3 Ma, just below Bed 25 at the Meishan section. Taxon turnover and diversification rates suggest a deterioration of the living conditions nearly 1.2 Myr before the sudden extinction. The magnitude of the extinction was such that there was no immediate biotic recovery. Prior suggestions of highly variable, multi-phased extinction patterns reflect the impact of the Signor-Lipps effect and facies-dependent occurrences, and are not supported following appropriate statistical treatment of this larger data set.

ENVIRONMENTAL CONTROLS ON THE GENESIS OF MARINE MICROBIALITES AND DISSOLUTION SURFACE ASSOCIATED WITH THE END-PERMIAN MASS EXTINCTION: NEW SECTIONS AND OBSERVATIONS FROM THE NANPANJIANG BASIN, SOUTH CHINA

Abstract A widespread marine microbialite and underlying truncation surface occur in Permian–Triassic sections of South China. We interpret the microbialite to have formed as a shallow, open-marine benthic framework stimulated by high seawater CaCO3 saturation. The widespread distribution across platform interiors and lack of asymmetry or thickening toward platform margins is incompatible with an alternative hypothesis, that microbialite deposition was stimulated by upwelling anoxic, alkaline waters. The truncation surface beneath the microbialite is irregular with overhangs and small caverns extending up to 30 cm beneath the surface indicating a dissolutional origin. Petrographic observations refute the interpretation that strata immediately beneath the surface contain pendant cements, meniscus cements, and vadose silt. Measurements of the anisopachous fibrous cements show that thickened areas have random, not downward orientations. Pores retain the pointed geometry consistent with isopachous cement. Carbon and oxygen isotope measurements, from immediately beneath the surface, do not show a negative shift as would be expected with subaerial exposure. Also incompatible with a subaerial origin is the occurrence of only one truncation surface within a subtidal succession ~ 50 m thick below the surface and the limited vertical penetration of dissolution. The surface closely resembles a hardground containing a micritized alteration zone with stromatolites encrusted on the surface. We interpret the surface to have formed by submarine dissolution driven by a pulse of ocean acidification associated with Siberian Traps eruptions and the end-Permian extinction. After a hiatus of ~ 30–100 kyr, seafloor dissolution would have brought seawater back to saturation coupled with increased delivery of calcium to the oceans as the result of elevated continental weathering and caused a rebound in carbonate saturation and precipitation of microbialites.

Comments on some Permian conodont faunas reported from Southeast Asia and adjacent areas and their global correlation

Abstract Some important conodont faunas, reported from Southeast Asia, excluding South China and Japan, are re-evaluated on the basis of the improved taxonomy and resulting newly established provincialism. These faunas are representative of either the Equatorial Warm Water Province (EWWP) or the peri-Gondwana Cool Water Province (GCWP), except that the fauna from Jilin, North China represents the North Cool Water Province (NCWP). The GCWP is marked by Vjalovognathus and/or Merrillina in the Cisuralian, Vjalovognathus , Merrillina and Mesogondolella in the Guadalupian, and Vjalovognathus and Mesogondolella sheni or Merrillina in the Lopingian. The EWWP is characterized by the absence of Gondolelloides and Vjalovognathus in the Early and Middle Cisuralian, abundance of Sweetognathus and Pseudosweetognathus in the Kungurian (Late Cisuralian), dominance of Jinogondolella and Sweetognathus in the Guadalupian, and dominance of Clarkina and Iranognathus in the Lopingian. Mixed faunas are recognized in regions on the border between the EWWP and GCWP including Western Timor during the Artinskian, southeast Pamirs during the Kungurian and the Salt Range during the Guadalupian and Lopingian.