R EPORTS synergistic combination of these (6), among Abrupt and Gradual Extinction Among others. An important test of any mechanism is a consideration of the pattern of extinc- Late Permian Land Vertebrates in the tions. The marine extinctions are well de- scribed in several areas, notably Meishan, China (7). Here, we report new chemostrati- Karoo Basin, South Africa graphic, biostratigraphic, and magnetostrati- Peter D. W ard,1* Jennifer Botha,3 Roger Buick,2 graphic data from multiple stratigraphic Michiel O. De Kock,5 Douglas H. Erwin,6 Geoffrey H. Garrison,2 sections located in the K aroo basin of South Africa that provide an exceptionally detailed Joseph L. Kirschvink,4 Roger Smith3 record of the terrestrial extinctions. The Karoo basin of South Africa exposes a succession of Upper Permian to Permian-Triassic (P-T) strata in the central Lower Triassic terrestrial strata containing abundant terrestrial vertebrate K aroo basin provide the most intensively fossils. Paleomagnetic/magnetostratigraphic and carbon-isotope data allow investigated record of vertebrate fossils from sections to be correlated across the basin. With this stratigraphy, the verte- 1Department of Biology, 2Department of Earth and brate fossil data show a gradual extinction in the Upper Permian punctuated Space Sciences, University of Washington, Seattle, by an enhanced extinction pulse at the Permian-Triassic boundary interval, WA 98195, USA. 3Karoo Paleontology, Iziko: South 4 particularly among the dicynodont therapsids, coinciding with negative African Museum, Cape Town, South Africa. Division of Geological and Planetary Sciences, California carbon-isotope anomalies. Institute of Technology, Pasadena, CA 91125, USA. 5Department of Geology, Rand Afrikaans University, Johannesburg, South Africa. 6Department of Paleo- The Permian extinction is universally por- ses include climate change due to increased biology, MRC-121 Smithsonian Institution, Washing- trayed as the most catastrophic of all atmospheric CO2 and/or CH4 (2), the effects ton, DC 20013, USA. Phanerozoic mass extinctions (1), yet its of extraterrestrial impact (3–5), the effects of *To whom correspondence should be addressed. cause remains problematic. V arious hypothe- the eruption of the Siberian Traps, and some E-mail: [email protected] www.sciencemag.org SCIENCE VOL 307 4 FEBRUARY 2005 709 R EPORTS the Upper Permian through the Triassic (8). identified a reversed polarity magnetozone Arctic. Although there is some uncertainty These strata are dominantly fluvial overbank (R1) È5 m beneath the Unit I-II contact about the reversal pattern near the P-T sediments deposited near the center of a (14). At Lootsberg and Wapadsberg, the boundary (16), recent records in Europe subsiding retroarc foreland basin (9). We have normal-polarity zone extends well up into suggest that the boundary occurs just above sampled across 200 m of the Palingkloof the Katberg Formation (Unit IV). At Loots- the base of a reversed-to-normal-polarity Member of the Balfour Formation and the berg, where the youngest strata were transition in Germany, although there has overlying Katberg Formation, where we sampled of all the sections, there is a change been a recent report placing it slightly lower, recognize four units spanning the Upper to reversed polarity (R2) above about 130 m in the uppermost part of the reversed chron Permian and Lower Triassic (10). Fossils and a final switch back to normal (N2) at the (17). The base of Unit II is thus approxi- were collected from these strata at five top. Given paleontological constraints (8), mately coincident with the P-T boundary. different areas. Hence, correlating the sec- we correlate the long normal found in Units These correlations were tested by mea- 13 tions, which is difficult between fluvial II, III, and most of IV with magnetozone suring sedimentary carbon isotope (d Ccarb 13 sections and has been notably problematic in SN1 of the classic German Trias sections and d Corg) stratigraphy at all the sections at the Karoo (11), is critical. (15) and thus define the top and bottom of meter or submeter sampling frequency (12) To correlate the stratigraphy, we obtained the Griesbachian stage in the Karoo. The (Fig. 2), a finer resolution than has been a magnetostratigraphic record (Fig. 1) (12) superjacent reversal at Lootsberg Pass is done before (18). This earlier P-T isotope from three sections Esome data are also in most parsimoniously correlated with magne- study in the Karoo found a single negative ^ 13 (13) . Samples from Unit II and Unit III are tozone SR1 of central Germany, R2 of the d Ccarb excursion approximately coincident all of normal polarity (Chron N1), and we Southern Alps, and GR1 of the Canadian with the last occurrence of the latest Permian Fig. 1. Magnetostratigraphic correlation across the Karoo basin. The dashed lines represent the correlated positions between the stratigraphic sections. 710 4 FEBRUARY 2005 VOL 307 SCIENCE www.sciencemag.org R EPORTS zonal index fossil Dicynodon. The global d13C ues maintain a broad minimum in Unit II, a of these sections are extensively intruded by 13 record for the P-T boundary period is known pattern similar to global marine d Ccarb re- Mesozoic dolerite dikes and sills. We suggest in varying detail from several dozen marine cords. The lowermost negative excursion in that this igneous activity has homogenized the 13 13 and fewer nonmarine sites (e.g., 19, 20). In- d Ccarb observed in the Karoo most parsi- primary d Corg record at these two sections. tensively sampled sections show a gradual moniously correlates with the singular, lower Fossil vertebrate biostratigraphy confirms 13 12 13 decline in the sedimentary C: Cratio Griesbachian negative d Ccarb excursion that Unit II is essentially contemporaneous upward through the Upper Permian, then a reported recently from a Late Permian–Late across the Karoo basin. At all sections, the sudden decline of 92° at or near the pa- Triassic carbonate platform in the Nanpan- highest occurrence of the uppermost Permian leontologically defined extinction boundary, jiang Basin, Guizhou Province, China (22). zonal index, Dicynodon lacerticeps, is found 13 13 followed by a gradual increase in d C. The Furthermore, the broad swings in d Ccarb either immediately below (at the fossiliferous sudden d13C decline precedes the formal P-T values that were measured higher in the Karoo Lootsberg, Wapadsberg, and Bethulie sections) boundary based on the first occurrence of the sections (Fig. 2) appear to be consistent with or at most several meters below the base of 13 Triassic conodont Hindeodus parvus at the Smithian and Spathian age d Ccarb excur- Unit II (at the fossil-poor Carlton Heights 13 global stratotype section and point (GSSP) sions in the same marine d Ccarb record. and Kommandodrift Dam sections). Dicynodon P-T stratotype in Meishan, China, where the The bulk sedimentary organic carbon lacerticeps was never found in or above Unit 13 boundary has been placed at Bed 27. At isotope records (d Corg) from the Carlton II, and the first Triassic fossil common to all Meishan, the lowest d13C values are found in Heights and Lootsberg sections provide fur- sections—Lystrosaurus sp. C—was found in Bed 25 (7), coincident with the level of ther support for these conclusions (Fig. 2). The the lower strata of Unit III but never in Unit II. maximal species disappearance (94% loss of data also supports the magnetostratigraphic In summary, three independent correlation then-extant marine invertebrates). Thus, the correlation of Unit II between the northern methods support our contention that Unit II is mass extinction and sharp negative excursion (Carlton Heights and Bethulie regions) and both essentially isochronous across the Karoo in d13C are slightly older than the formal southern (Lootsberg and Wapadsberg re- basin and also time equivalent with the P-T stratigraphic boundary. gions) parts of the basin. At the Carlton boundary in China. This allows us to use this 13 We sampled both bulk sediment and Heights and Lootsberg sections, d Corg de- unit as a datum surface against which our carbonate paleosol nodules for carbon iso- creases from È –24° Vienna Pee Dee vertebrate range taxa can be plotted and to tope stratigraphy from our measured sec- belemnite (VPDB) to È –26° VPDB across compare the patterns of extinction with those 13 13 tions. Soil carbonate d C(d Ccarb)isa the uppermost meter of Unit I and remains observed at other P-T sections. function of both the d13C of atmospheric there through Unit II and into Unit III. Over a period of 7 years, we collected 13 13 CO2 (d CCO2) and the partial pressure of Between 15 m and 22 m (Unit III), d Corg 126 skulls assigned to 21 vertebrate taxa È ° CO2 in the atmosphere (pCO2), and thus soil increases in both sections to –21 and from the sections shown here (reptile or 13 È ° d Ccarb records can be more scattered than then decreases 1 at the base of Unit IV. amphibian) (Fig. 3) (23). We treat these taxa 13 13 marine d Ccarb records (21). Nevertheless, This pattern is typical of P-T d C records as species, although further study will prob- 13 the d Ccarb results show a prominent drop measured elsewhere in the world. The ably result in an even greater number of taxa. 13 within Unit I that is consistent with our Wapadsberg and Bethulie d Corg records do We found 13 taxa in Unit I (Upper Permian), assessment that Unit I/Unit II contact marks not show any substantial negative excursions, only 4 of which persist into Unit II, and 12 13 the P-T extinction (Fig. 2). The d Ccarb val- particularly not at the P-T boundary, but both taxa in Units II to IV. Six of the 13 taxa 13 13 Fig.