Extinguishing a Permian World Elke Schneebeli-Hermann Palaeoecology, Department of Physical Geography, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, Netherlands At the end of the Permian, ca. 252 Ma ago, marine and terrestrial fauna were facing the most extensive mass extinction in Earth history (Raup and Sepkoski, 1982). 80%–95% of all species on Earth, on land and in the oceans, became extinct (Benton et al., 2004) within an estimated time interval of less than 200 k.y. to 700 k.y. (Huang et al., 2011; Shen et al., 2011). Among the prominent Paleozoic animal groups that vanished E<P are fusulinid foraminifera, rugose and tabulate corals, and the arthropod E>P NITC class Trilobita. The numerous hypotheses about the causes of the mass South China extinction include various environmental changes, mostly related to the SITC emplacement of the Siberian Traps large igneous province. The compila- Tethys Ocean tion of radiometric U/Pb ages for the mass extinction and the Siberian Traps demonstrate a temporal overlap of both events (Svensen et al., E>P 2009). A prominent hypothesis for the mass extinction is an accentuated E<P global climate change scenario induced by volcanic CO2 degassing (e.g., Svensen et al., 2009) that triggered biotic responses in the sea and on land. But what do we know about the climate at this time in Earth history? The two main features of climate recorded in the geological archives are temperature and humidity i.e., the moisture that is available for plant Land Mountain Tropical semi humid growth, and to a certain extent rainfall patterns. Climate simulations Cold temperate Cool temperate Subtropical arid model the general circulation patterns during Permian–Triassic times. The Warm temperate humid Tropical humid paleogeography was characterized by the supercontinent Pangea extend- ing nearly from pole to pole, with large land masses in the mid-latitudes Figure 1. Permian–Triassic Pangean paleogeography, modifi ed af- of the Northern and Southern Hemispheres, and with the Tethys Ocean in ter Smith et al. (1994). Paleogeographic position of South China and the tropics (e.g., Smith et al., 1994). Climate models and sensitivity experi- Meishan (star). Precipitation/evaporation ratio (P < E, P > E) after ments demonstrated that this paleogeography provided the preconditions Ziegler et al. (2003). Late Permian biomes and northern and southern intertropical convergence zones (NITC, SITC) modifi ed after Kutzbach for a monsoonal circulation with strong seasonality of temperatures and and Ziegler (1993). rainfall on the Tethyan coasts, and distinct northern and southern intertropi- cal convergence zones (Fig. 1) (e.g., Kutzbach and Ziegler, 1993; Parrish, 1993). Moist conditions prevailed in middle and high latitudes and along the genic apatite of tooth enamel is increasing. The oxygen isotope signature of western Pangea coast, contrasting with the year-round arid Pangean tropics. conodont apatite is little affected by post-depositional changes (Joachimski (Kutzbach and Ziegler, 1993; Parrish, 1993). Recent climate modeling for and Buggisch, 2002). New analytical techniques and better understanding the Permian–Triassic scenario tested the impact of rapid temperature change of isotopic changes during diagenesis have revealed the importance of the and showed that shifts in biomes were less pronounced during global warm- conodont paleothermometry for the reconstruction of ancient ocean tem- ing compared to global cooling (Roscher et al., 2011). For the Late Perm- peratures (e.g., Barham et al., 2012; Vennemann et al., 2002). ian oceans, sensitivity experiments with coupled atmosphere-ocean models The work of Joachimski et al. (2012, p. 195 in this issue of Geology) imply that elevated CO2 levels caused signifi cant temperature increases in uses the conodont paleothermometry to reconstruct ocean temperatures high-latitude sea-surface water masses, leading to reduced global sea-sur- of a tropical site during the largest mass extinction in Earth’s history. One face temperature (SST) gradients (e.g., Kiehl and Shields, 2005). of the best studied Permian–Triassic successions is the Global Boundary A proxy record for ancient SSTs is stable oxygen isotope data of marine Stratotype Section and Point (GSSP) in Meishan, South China. Joachim- biomineralizing fauna. During biomineralization, marine fauna incorporate ski et al. measured the oxygen isotope values of P1 elements of the con- dissolved oxygen into their hard parts (e.g., calcite, aragonite, apatite) in odont genera Clarkina (or Neogondolella) and Hindeodus recovered from or close to isotopic equilibrium with the ambient sea water (Urey, 1947; the Meishan and Shangsi sections, choosing a δ18O value of –1‰ Vienna Epstein et al., 1951). Therefore, geochemical signals preserved in marine standard mean ocean water for their temperature calculation. They demon- invertebrate shells and skeletal parts can be used as a proxy for SST, if the strate that in the Meishan area, SST increased by 1–5 °C, from an average isotope composition of the ambient water is known (although isotope frac- temperature of 22 °C, before the main extinction event. Thereafter, tem- tionation during biomineralization and diagenetic alteration need to be con- peratures remained fairly stable up to the extinction event, where oxygen sidered). Oxygen isotopes measured on unaltered brachiopod shells from isotopes indicate another distinct warming by 5–8 °C, up to SST of 32–35 the Late Permian Bellerophon Formation, and from a single sample from °C in the earliest Triassic. The data of Joachimski et al. are an important the overlaying basal Werfen Formation, in southern Italy were interpreted advance in the discussion of the Permian–Triassic climate change, as they to represent a rise of 6–10 °C of tropical SST (Kearsey et al., 2009 and quantify SST change in a stratigraphically well-constrained framework. references therein). However, the resolution and stratigraphic constraints of The documented oxygen isotope shift (i.e., the warming) coincides with these data are limited. In the search for unaltered archives for oxygen iso- a negative shift in carbon isotope ratios over a period of possibly only tope records for paleotemperature reconstructions, the signifi cance of bio- ~110 k.y. (Shen et al., 2011). © 2012 Geological Society of America. For permission to copy, contact Copyright Permissions, GSA, or [email protected]. GEOLOGY,Geology, March March 2012; 2012 v. 40; no. 3; p. 287–288; doi: 10.1130/focus032012.1. 287 Downloaded from http://pubs.geoscienceworld.org/gsa/geology/article-pdf/40/3/287/3543910/287.pdf by guest on 23 September 2021 Permian macrofl ora (distribution of biomes) largely support the of diversity gradients: Palaeogeography, Palaeoclimatology, Palaeoecology, general climate zone distribution with strong seasonality for the Late v. 239, p. 374–395, doi:10.1016/j.palaeo.2006.02.003. Epstein, S., Buchsbaum, R., Lowenstam, H., and Urey, H.C., 1951, Carbonate-water Permian, as derived from climate models (Rees et al., 2002). The glob- isotopic temperature scale: Geological Society of America Bulletin, v. 62, ally less-differentiated Early Triassic fl ora were interpreted to indicate no. 4, p. 417–426, doi:10.1130/0016-7606(1951)62[417:CITS]2.0.CO;2. warm-temperate climate up to 70°N (Ziegler et al., 1993). Unfortunately, Hermann, E., Hochuli, P.A., Bucher, H., Brühwiler, T., Hautmann, M., Ware, D., the time constraint of most macrofl oral records to infer detailed climate Weissert, H., Roohi, G., and Yasseen, A., ur-Rehman, K., 2012, Climatic os- evolution is limited by the lack of calibration. Higher chronological reso- cillations at the onset of the Mesozoic inferred from palynological records from the North Indian Margin, Journal of the Geological Society, London, lution is achieved by implementing palynological data. Despite uncertain- doi:10.1144/0016-76492010-130. ties regarding the botanical affi nities of 250 Ma spores and pollen, the Hochuli, P.A., Vigran, J.O., Hermann, E., and Bucher, H., 2010, Multiple cli- approach of distinguishing sporomorphs according to the requirements matic changes around the Permian-Triassic boundary event revealed by an of their parent plants with respect to water availability has been applied expanded palynological record from mid-Norway: Geological Society of America Bulletin, v. 122, p. 884–896, doi:10.1130/B26551.1. successfully to describe relative changes in humidity (e.g., Hochuli et al., Huang, C., Tong, J., Hinnov, L., and Chen, Z.Q., 2011, Did the great dying of life 2010). In Norway, chemostratigraphically calibrated palynological records take 700 k.y.? Evidence from global astronomical correlation of the Permian- indicate a distinct shift from pollen-dominated (conifers and seed ferns) Triassic boundary interval: Geology, v. 39, no. 8, p. 779–782, doi:10.1130/ to spore-dominated (ferns and lycophytes) assemblages across the Perm- G32126.1. Joachimski, M.M., and Buggisch, W., 2002, Conodont apatite δ18O signatures in- ian–Triassic transition. This change has been interpreted as a shift to more dicate climatic cooling as a trigger of the Late Devonian mass extinction: humid conditions in the earliest Triassic (Hochuli et al., 2010). Also, in the Geology, v. 30, p. 711–714, doi:10.1130/0091-7613(2002)030<0711:CAOSIC monsoon-dominated region of the southern subtropics, increasing spore >2.0.CO;2. abundances occur toward the Early Triassic (Hermann et al., 2012). Thus, Joachimski, M.M., Lai, X., Shen, S., Jiang, H., Luo, G., Chen,