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

Palaeogeography, Palaeoclimatology, Palaeoecology 191 (2003) 301^328 www.elsevier.com/locate/palaeo

Stratigraphic versus environmental signi¢cance of Permian serrated conodonts around the Cisuralian^Guadalupian boundary: new evidence from Oman Charles M. Henderson a; , Shilong Mei a;b a

Department of Geology and Geophysics, University of Calgary, Calgary, AB, Canada T2N 1N4 b China University of Geosciences, Beijing 100083, PR China Received 20 November 2001; accepted 18 November 2002

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 deepwater 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

* Corresponding author. Fax: +1-403-284-0074. E-mail addresses: [email protected] (C.M. Henderson), [email protected] (S. Mei).

0031-0182 / 02 / $ ^ see front matter A 2002 Elsevier Science B.V. All rights reserved. doi:10.1016/S0031-0182(02)00669-7

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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. A 2002 Elsevier Science B.V. All rights reserved. Keywords: Permian; conodonts; paleoecology; provincialism; Oman; Pangea

1. Introduction Climatic e¡ects that result in profound provincialism of many Permian fossil groups hamper global correlation of late Lower to Upper Permian rocks. Conodonts have been used to de¢ne many Permian stage boundaries, but they too are subject to provincialism, which is often re£ected

in morphological variation. For example, warmwater gondolellids have small cusps relative to posterior denticle height and high, fused anterior denticles, whereas cool-water taxa have larger cusps and lower, discrete anterior denticles (Mei and Henderson, 2001 ; Fig. 1). Permian gondolellid taxa also include both serrated and non-serrated forms (Fig. 1). The ¢rst appearance of ser-

Fig. 1. Illustration of key morphologic features of Permian gondolellids that pertain to taxonomic assignment and geographic variation controlled by temperature variation. The conodonts include Jinogondolella nankingensis from West Texas on the left, Mesogondolella siciliensis from Oman in the center, and Mesogondolella idahoensis idahoensis from the Phosphoria Basin in Idaho, USA, on the right.

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PALAEO 2993 3-2-03 Fig. 2. Relative paleogeographic positions of various localities discussed in the text, Cordilleran accreted terranes, conodont provinces (modi¢ed from Mei and Henderson, 2001), and Pangea during the Guadalupian. Paleocontinental reconstruction is modi¢ed after Ziegler et al., 1997; terrane positions are based on Mei and Henderson, 2001 and Katvala and Henderson, 2002.

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rated Jinogondolella nankingensis de¢nes the base of the Middle Permian Roadian stage. The Subcommission on Permian Stratigraphy proposed that the base of the Roadian be de¢ned by the ¢rst appearance datum (FAD) of J. nankingensis, the base of Wordian by the FAD of Jinogondolella aserrata, and the base of Capitanian by Jinogondolella postserrata (Jin et al., 1997; Glenister et al., 1999; Wardlaw et al., 1999), and these stratotype de¢nitions in the Guadalupe Mountains, West Texas have been approved and rati¢ed by the ICS and IUGS. New data from Oman compared with other regions open the question as to whether the introduction of serrated gondolellids is globally synchronous or re£ects some form of climatic/oceanographic control. The essence of the argument revolves around the fact that for the interval of interest the conodonts and fusulinaceans are essentially the same in Oman, Sicily, and South China, but that these fusulinaceans and conodonts occur below the ¢rst serrated gondolellids at the Luodian section in South China. The obvious solution that we prefer is that the interval of interest is Upper Kungurian, but this correlation is problematical because of the presence of the ‘Wordian’ ammonoid Waagenoceras at Oman and Sicily; this ammonoid is not present at Luodian. If the introduction of serration is diachronous, then the interval of interest is no younger than Roadian because the ¢rst serrated gondolellids at Luodian are Jinogondolella nankingensis, which ranges throughout the entire Roadian of West Texas. Waagenoceras apparently ranges from Roadian to latest Capitanian. Advanced forms like those at Sicily and Oman have been compared to the third limestone of the Word Formation (Willis Ranch Member), which correlates with the Upper Roadian. The cephalopod limestones of the Rustaq and Ba’ad areas of Oman (Figs. 2 and 3) have yielded abundant ammonoids including Waagenoceras spp., Parapronorites konincki, Propinacoceras beyrichi, Eumedlicottia bifrons, Neogeoceras marcoui, Adrianites elegans, Aricoceras ensifer, and Tauroceras scrobiculatum as well as the conodont Mesogondolella siciliensis (Blendinger et al., 1992). These fossils have been compared with the fauna from the Sosio limestone of Sicily (Fig. 2) and

dated as Wordian (Blendinger et al., 1992, p. 14; Pillevuit, 1993; Pillevuit et al., 1997). The fauna from the Rupe del Passo di Burgio block of the Sosio Valley limestone olistostrome unit also contains the ammonoid Waagenoceras and the conodont M. siciliensis. Kozur and Davydov (1996) stated that the Sicilian block at Rupe del Passo di Burgio is of special interest because it contains ammonoids, conodonts and fusulinaceans of exclusively Wordian age. The fusulinaceans include Dunbarula a¡. nana, Kahlerina sp., Neoschwagerina ex. gr. cheni and Sumatrina ex. gr. longissima (Kozur and Davydov, 1996) and are correlated with the Midian Tethyan stage. Mesogondolella siciliensis however has a non-serrated platform and typical warm-water denticulation (Fig. 1 and Plates I^III) that is more typical of pre-Roadian faunas in Luodian, China and West Texas. This paper will examine conodonts from Oman and correlate this material with faunas from several localities around the world in an attempt to resolve these disparate age assignments.

2. Geologic setting, material, and methods 2.1. Geologic setting The geology for the interval of interest in three important regions that are referred to often in this paper is very di¡erent. The sections at Rustaq, Oman are represented by condensed, deep-water, cephalopod-bearing carbonate deposited on and intercalated with pillow lavas related to the opening of the Neotethys ocean (Baud et al., 2001a,b). At Rupe del Passo di Burgio, Sicily, isolated limestone blocks occur in a tectonically complex olistostromal unit; there are no stratigraphic sections for the interval of interest, but thick Upper Artinskian to Lower Kungurian £ysch (Catalano et al., 1992) sequences are present in the region. The Luodian section in South China is represented by a thick sequence of slope and platform carbonates that were deposited continuously (or nearly so) from the Upper Devonian to Lower Triassic and include over 600 m of Permian strata (Shi et al., 1999a,b); the Luodian section was a potential candidate for the mid-Carboniferous boundary

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3 (61992)

12 (61988) 734 (61944)

Rk3

Rk7

Fig. 3. Conodonts from Rustaq section 2 and Wadi Wasit composite. Stratigraphic column after Pillevuit, 1993. These specimens were obtained by processing samples at the University of Calgary.

because of the continuous deposition and wellpreserved conodont faunas. 2.2. New material from Oman and methods of analysis Our Oman material includes conodont samples from the cephalopod limestones of the Rustaq and Ba’ad areas that were collected by Benoit Beauchamp and Aymon Baud at some of the same levels as collections made by Heinz Kozur during the Oman Pangea Symposium in January, 2001. These samples were processed using standard acetic acid dissolution techniques at the mi-

cropaleontology laboratory at the University of Calgary. Two samples (Fig. 3), each weighing 2 kg, were collected respectively from the base of the red limestone ammonoid bed and 0.7 m above it at Section 2 of Rustaq (Baud et al., 2001b). The lower sample (Rk7 in Fig. 3) yielded 41 Pa and three ramiform elements of Mesogondolella siciliensis and one Pa element of Pseudohindeodus ramovsi. The upper sample (Rk3 in Fig. 3) yielded 303 Pa and 16 ramiform elements of Mesogondolella including Mesogondolella siciliensis and a few specimens of Mesogondolella rustaqensis (Mei and Henderson, 2002), 17 Pa elements of Pseudohindeodus ramovsi, and two Pa

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elements of Sweetognathus subsymmetricus. A third sample is from the ammonoid bed (Bed 2) at Wadi Wasit section (Baud et al., 2001a,b), weighed 2.7 kg, and yielded 115 Pa and 15 ramiform elements of Mesogondolella idahoensis lamberti. Three additional samples from the upper part of Rustaq Section 2 were collected by Aymon Baud (Fig. 3 : 734 (61944), 12 (61988), and 3 (61992). The lower two samples yielded abundant M. siciliensis and rare Sweetognathus subsymmetricus and P. ramovsi. The upper sample yielded abundant M. idahoensis lamberti (Fig. 3) similar to the Wadi Wasit sample.

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Before comparing the abundant Oman conodonts with faunas from other important sections in South China, Sicily, West Texas and the Phosphoria Basin it is important to highlight some pertinent conodont terminology, taxonomic problems and methods of recognizing the distinct provincialism.

dolella and absence of Sweetognathus in the Guadalupian, and dominance of Merrillina and Mesogondolella rosenkrantzi 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 (Wang et al., 1987) in the Kungurian (late Cisuralian), Jinogondolella and Sweetognathus in the Guadalupian, and Clarkina and Iranognathus in the Lopingian. The GCWP is marked by Vjalovognathus and rare Merrillina in the Cisuralian, Vjalovognathus, Merrillina and Mesogondolella in the Guadalupian, and Vjalovognathus and Merrillina or Mesogondolella sheni 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. It is remarkable that the Sweetognathus^Iranognathus^Diplognathodus lineage became con¢ned to the EWWP after the lower Kungurian. This lineage is an excellent indicator for warm-water settings (Mei and Henderson, 2001).

3.1. Conodont provincialism

3.2. Terminology for Permian gondolellids

Three provinces (Fig. 2) 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), have been recognized by Mei et al. (1999a,b) and Mei and Henderson (2001). 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 Mesogon-

Henderson and Mei (2000) revealed the systematic, stable, but minor di¡erences between Mesogondolella species of the NCWP and those from the EWWP. Late Kungurian and Early Guadalupian Mesogondolella species of the NCWP such as those reported from the Phosphoria Basin (Youngquist et al., 1951; Wardlaw and Collinson, 1984, 1986) and Sverdrup Basin (Henderson, 1981) tend to have a relatively large cusp, low and narrow carinal denticles, low and discrete

3. Age interpretation and global correlation of the Oman conodonts

Plate I. All specimens are SEM photos and magni¢ed 80U except where otherwise indicated. Letters a and b are used with the same number when both upper and lateral views of the same specimen are illustrated. 1^14.

Mesogondolella siciliensis (Kozur, 1975). 1^10, 14, Pa elements; 11, Sa element; 12, Sc1 element; 13, Pb element; all from the Luodian section, Guizhou, South China; 1^5, 11^13 from LNC-166, 6 from LNC-144; 7^10, 14 from LNC-164. Note: that specimens have high, fused denticles on the anterior blades (6b, 7a, 14b); that posterior margins exhibit di¡erent shapes including pointed (4, 10b), rounded (7b), and squared (8); that cusps are generally small, but they are higher than posterior denticles in juveniles (10a). Compare to specimens from Oman in Plate III. See Mei and Henderson, 2002 for synonomy.

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denticles on the anterior blade, and an elongate platform, as exempli¢ed by holotypes of Mesogondolella idahoensis and Mesogondolella phosphoriensis (specimens on right side of Fig. 1; Plate II, 15, 16). Mesogondolella species of the EWWP as reported from South China (Henderson et al., 1999; Wang, 1994, 2000), West Texas (Wardlaw and Grant, 1990; Lambert et al., 2000), Japan (Igo, 1981), Sicily (Kozur, 1989a; Catalano et al., 1992; Gullo and Kozur, 1992) and Slovenia (Ramovs, 1982) are marked by a relatively small cusp, and high and much more fused denticles on the anterior blade, as represented by Mesogondolella glenisteri, Mesogondolella slovenica, Mesogondolella intermedia and Mesogondolella siciliensis (Fig. 1, center) etc. These systematic and gradual geographic variations are referred to as clines that provide a tool for interprovincial correlation (Henderson and Mei, 2000). 3.3. Taxonomic problems for Permian gondolellids Kozur (1988, 1989a) divided Permian gondolellids into two genera: Mesogondolella and Clarkina. Mei et al. (1994a, 1998) and Mei and Wardlaw (1994) referred the serrated ‘Mesogondolella’ from equatorial areas such as South China and Texas (Fig. 1) to Jinogondolella, and Wardlaw and Mei (1998) proposed Pseudoclarkina to include previous Mesogondolella bitteri and Mesogondolella wilcoxi from the Phosphoria Basin. Mei

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(in Mei et al., 1998, 1999a) expanded the scope of Pseudoclarkina to include all the species of the cool-water Guadalupian gondolellid lineage from the Phosphoria Basin. Orchard and Rieber (1999) regarded Clarkina as a synonym of Neogondolella based upon a study on the multielement con¢guration. Mei and Henderson (2001) regarded Pseudoclarkina as a synonym of occasionally serrated Mesogondolella from cool-water faunas, since the con¢guration of platform and denticulation in Mesogondolella gracilis and Mesogondolella phosphoriensis cannot be di¡erentiated from Mesogondolella idahoensis, except in the partial serration within the population. However, M. bitteri and Mesogondolella wilcoxi have a more tapered anterior platform with a relatively fused anterior blade that somewhat resembles Clarkina. There is a problem and confusion in generic level taxonomy for Permian gondolellids, and detailed discussion is beyond the scope of the present paper. This paper applies: (1) Mesogondolella to all Kungurian and older Permian gondolellids as well as cool-water Guadalupian and Lopingian gondolellids with generally non-serrated and gently tapering platforms; (2) Jinogondolella to warm-water Guadalupian serrated gondolellids; (3) Clarkina to warm-water Lopingian gondolellids with nonserrated platforms that taper rapidly anteriorly; and (4) Neogondolella to late Griesbachian and younger gondolellids as de¢ned by Orchard and Rieber (1999).

Plate II. All specimens are SEM photos and magni¢ed 80U except where otherwise indicated. Letters a and b are used with the same number when both upper and lateral views of the same specimen are illustrated. 1, 5, 12.

Jinogondolella nankingensis nankingensis (Ching [Jin], 1960). 1, 12 from the Luodian section, South China, 1 from LNC-374, 12 from LNC-340; 5 is the holotype of the former Gondolella serrata, from Upper Bone Springs Formation, Texas (Clark and Ethington, 1962); now correlated with Pipeline Shale. 3, 4, 9. Mesogondolella idahoensis lamberti Mei and Henderson, 2002. 3 and 4 from LNC-340, the Luodian Section, South China; 9, U54, from the base of the stratotype Road Formation, Glass Mountains, West Texas. See Mei and Henderson, 2002 for taxonomic description and diagnosis. 2, 6^8, 10, 11, Mesogondolella siciliensis (Kozur, 1975). 2 and 11 are from LNC-279, the Luodian Section; 6^8, U54, from near 13, 14. the base of Cathedral Mountain Formation, Split Tank, Glass Mountains, West Texas, adopted from Wardlaw (2001); 10, U54, from the middle Cathedral Mountain Formation, Split Tank, Glass Mountains, West Texas; 10 and 11 are adopted from Wardlaw (2001); 13 and 14 from W90-41 of middle Cathedralian, West Texas, USA. 15. Mesogondolella idahoensis idahoensis (Youngquist et al., 1951). SEM photo of the holotype specimen of Youngquist et al. (1951), from just below cap rock, Montpelier Canyon, Idaho. 16. Mesogondolella phosphoriensis (Youngquist et al., 1951). SEM photo of the holotype specimen of Youngquist et al. (1951), from the upper part of Meade Peak Phosphatic Shale, Paris Canyon, Idaho. Note the very large cusps on specimens 15 and 16 from the NCWP compared to other specimens, which are all from the EWWP.

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3.4. Age of Oman conodonts We interpret the age of the Oman conodonts to be Upper Kungurian or Upper Kungurian and/or Lower Roadian and reject previous Wordian age assignments. A full analysis of this di⁄cult correlation problem requires comparison with other conodont successions as well as with associated fusulinaceans and ammonoids in Section 4. Jinogondolella aserrata, the de¢ning species for Wordian, belongs to the J. nankingensis-J. aserrata-J. postserrata-J. altudaensis-J. prexuanhanensisJ. xuanhanensis-J. granti lineage that can be easily recognized by the anterior platform serration (Mei et al., 1994a,b, 1998; Wardlaw, 2000) in both South China (Fig. 4) and in the Guadalupian Global Stratotype sections in West Texas (Fig. 5). This lineage has not been reported from either Oman or Sicily. The Wordian age for Mesogondolella siciliensis is therefore di⁄cult to substantiate on the basis of conodonts alone since it has not been found from the Roadian as de¢ned by J. nankingensis, the Wordian as de¢ned by J. aserrata, or from the Capitanian as de¢ned by J. postserrata in South China (Fig. 4 ; Mei et al., 1994a,b, 1998, 1999c) or West Texas (Fig. 5 ; Glenister et al., 1992, 1999; Kozur, 1992c, 1995b; Wardlaw, 2000). In contrast, M. siciliensis has been found in beds underlying the ¢rst appearance of J. nankingensis in both South China (Fig. 4 and Plate I) and Texas (Fig. 5), and should therefore be Late Kungurian in age (Henderson et al., 1999; Mei et al., 1999a; Mei and Henderson, 2001). Kozur et al. (2001) have indicated that

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M. siciliensis is not present in West Texas and that our recognition of this species by synonomy (Fig. 5) is the crux of our argument. We acknowledge that we have not seen a lot of material from the Cathedral Mountain Formation, but ¢gured specimens ¢t our interpretation of M. siciliensis when viewed in terms of population, stable characters like denticulation, and from the viewpoint of geographic clines (Plate II, 6^8, 10, 11, 13, 14). Mesogondolella siciliensis has a long range in the Luodian section of South China and clearly predates the ¢rst serrated gondolellids identi¢ed as Jinogondolella nankingensis. This would indicate that M. siciliensis from South China is Upper Kungurian, if the ¢rst occurrence of J. nankingensis correlates with the true FAD. If the ¢rst occurrence of J. nankingensis at Luodian does not correlate with the FAD of that taxon then M. siciliensis could range into the Roadian. Although we believe that the ¢rst occurrence at Luodian is near the true FAD based on the presence of a few specimens of Mesogondolella idahoensis lamberti immediately below the ¢rst serrated forms, we acknowledge that it is possible that M. siciliensis could range into the Roadian. A 50 m thick interval at Luodian (Fig. 4, Mesogondolella idahoensis lamberti-Sweetognathus subsymmetricus-Sweetognathus hanzhongensis Zone) contains very shallow-water carbonates and is dominated by sweetognathids; paleoecologic distributional controls may have limited the presence of gondolellid taxa. As a result we suggest an alternative lower position for the base of the Roadian at the Luodian section (Fig. 4, column

Plate III. All specimens are SEM photos and magni¢ed 80U except where otherwise indicated. Letters a and b are used with the same number when both upper and lateral views of the same specimen are illustrated. 1^8, 10^12.

9.

Mesogondolella siciliensis (Kozur, 1975). All are Pa elements showing ontogeny and intra-population variation; from RK3, which is 0.7 m above the base of the red limestone ammonoid bed of the Al Jil Formation at Section 2 of Rustaq, Oman (Baud et al., 2001a,b). Note: that specimens have high, fused denticles on the anterior blades (5a, 7a, 8a, 11a, 12a); that posterior margins exhibit di¡erent shapes including pointed (7b), rounded (10b), and squared (12b); that cusps are generally small, but they are higher than posterior denticles in juveniles (1^3). Compare to specimens from Luodian, South China in Plate I. See Mei and Henderson, 2002 for synonomy. Mesogondolella rustaqensis Mei and Henderson, 2002. Pa element, holotype; from RK3, which is 0.7 m above the base of the red limestone ammonoid bed of the Al Jil Formation at Section 2 of Rustaq, Oman (Baud et al., 2001a,b). Note: that anterior denticles are more discrete and lower and that middle denticles on the carina are more fused compared to Mesogondolella siciliensis. See Mei and Henderson, 2002 for taxonomic diagnosis and description. Specimens of this type were not common.

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D, at Bed 35; see Section 4.2 for an elaboration of this argument). Adopting this position would mean that the introduction of serrated gondolellids is diachronous. Furthermore, this new position is within some of the shallowest facies at Luodian and before a transgressive event in beds 42^46. In contrast, the base of the Roadian at the stratotype section (Fig. 5, column B) is within the transgressive El Centro Member of the Cuto¡ Formation. We include ¢gures of M. siciliensis from West Texas, Luodian, South China and Oman for comparison in our plates. Mei and Henderson (2002) provide descriptions and synonomy lists for these taxa. Kozur (1998) suggests that the Roadian should be de¢ned in the open-sea Tethys by the ¢rst occurrence of the paleopsychrospheric (cryophilic in Leven, 2001) taxon Mesogondolella saraciniensis, which Mei and Henderson (2002) regard as synonymous with Mesogondolella siciliensis (see Section 3.5); this would mean that M. siciliensis ranges through the entire Roadian and Wordian. Kozur (1998) indicates that cool-water faunas do not occur just in high latitudes, but also in opensea environments in the tropical Tethys, if the water depth was below 200 m and the areas were connected to cold bottom-water currents as indicated by the presence of paleopsychrospheric ostracods. Our research from South China (Henderson et al., 1999), West Texas, Oman, and Canada shows that non-serrated Mesogondolella species assigned to Wordian by Kozur from Western Sicily (in Catalano et al., 1992; Gullo and Kozur, 1992), by Wang from South China (Wang, 2000), and probably those from Bolorian through lower Midian strata in the Pamirs (Fig. 6) and Darvas (Kozur et al., 1994) appear to be correlative with the uppermost Kungurian and/or Lower Roadian. In all of those areas, Mesogondolella species bear a platform and denticulation pattern typical of warm-water settings that is very di¡erent from

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those in high-latitude settings. In addition, co-occurring specimens of Sweetognathus guizhouensis, Sweetognathus adjunctus (Leonova and Dmitriev, 1989) and Sweetognathus subsymmetricus further support the warm-water interpretation as this genus is typical of shallow warm-water environments (Mei et al., 2002). Sweetognathus subsymmetricus is recognized in Sicily (Catalano et al., 1992 ; from the Kubergandian and just below M. siciliensis according to their table 2), in Oman associated with M. siciliensis (Fig. 3), and in Luodian, South China (Fig. 4; in association with M. siciliensis and Kubergandian to Murgabian fusulinaceans). Another long-ranging species found in Oman in association with M. siciliensis is Pseudohindeodus ramovsi. This species is found in Sicily (Gullo and Kozur, 1992; reported from Chihsian to ‘Wordian’ in the Rupe del Passo di Burgio block) and in West Texas (Wardlaw, 2000). Wardlaw (2000) indicates that the species occurs sporadically from the Road Canyon Formation to the Altuda Formation ( = Upper Kungurian to Capitanian). The Mesogondolella idahoensis previously reported from the Kungurian in South China and West Texas has a di¡erent carina from the holotype of M. idahoensis idahoensis (Plate II, 15) in denticulation and the latest Kungurian specimens are referred to as M. idahoensis lamberti. We do not agree with the reported occurrence of Mesogondolella phosphoriensis, the holotype of which has a typical NCWP denticulation (Plate II, 16), in Sicily, South China and probably the Pamirs, because all Mesogondolella specimens that we have seen from these regions bear the warm-water type denticulation. The specimen identi¢ed and ¢gured as M. phosphoriensis by Wang (2000 ; his pl. 1, ¢g. 4) is dissimilar from the holotype and bears a warm-water type denticulation. Wang (2000) illustrates a specimen identi¢ed as M. idahoensis (his pl. 1, ¢g. 12; bed 25b at Luodian) that Kozur et al.

Fig. 4. Conodont distribution and zones and fusulinacean zones from the Luodian section, Guizhou, South China (modi¢ed after Mei et al., 1999a). Chronostratigraphic correlations are as follows: (A) preferred in this paper; (B) Tethyan stages based on fusulinaceans at Luodian and Leven et al., 1996 and Leven, 2001; (C) standard stages as correlated to Tethyan stages by Leven et al., 1996 and Leven, 2001; (D) an alternative correlation of the Global and Tethyan stages that is discussed in this paper. Correlation of Oman conodont fauna from Fig. 3 is indicated in the black box.

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Fig. 6. Conodonts from the Pamirs as reported by Kozur et al., 1994 and our interpretations of the faunas. *We question the identi¢cation of Jinogondolella postserrata and suggest that if these are the ¢rst gondolellids bearing serrations they could be Early Roadian Jinogondolella nankingensis, but diachroneity cannot be discounted. According to Fig. 4 Late Midian may correlate with Late Roadian to Capitanian.

Fig. 5. Conodonts, ammonoids and fusulinaceans in the Glass Mountains, Texas (A) and Guadalupe Mountains (B). (C) Permian stages as currently rati¢ed. Conodont zones are slightly modi¢ed after Wardlaw (1996) and Mei et al. (1998). Range for Mesogondolella siciliensis is based on ranges for Mesogondolella idahoensis and Mesogondolella zsuzsannae, which we regard as synonymous. Fusulinacean distribution is from Yang and Yancey, 2000. Ammonoids are from Lambert et al., 2000 and Lambert, 2002a,b

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(2001) refer to as a slightly serrated form transitional between Mesogondolella idahoensis and Jinogondolella nankingensis. However, this specimen is a juvenile that has been magni¢ed to look as large as an adult specimen from the same bed (Wang, 2000; his pl. 1, ¢g. 13). Juvenile specimens of many gondolellid taxa are very similar and the hint of ‘serration’ referred to previously is actually the lack of platform margin development typical of juveniles. There has been a strong desire to ¢nd M. phosphoriensis or serrated ‘mesogondolellids’ from bed 25b at Luodian since this level is associated with Kubergandinian fusulinaceans. However, the ¢gured specimens do not support the argument and extensive samples processed at the University of Calgary yield only M. siciliensis with a typical warm-water denticulation and without serration (Plate I, 1^14). Rare specimens from Oman identi¢ed as Mesogondolella rustaqensis have lower and more discrete denticles on the anterior blade that is somewhat reminiscent of colder-water denticulation. Furthermore, a few conodont specimens from Oman do show an asymmetric pointed posterior platform outline that resembles somewhat the Wordian, Jinogondolella aserrata, but these are rare morphotypes (Plate IV 7). Two specimens show some very subtle serration (Plate IV, 6 and 7) on the anterior platform surface that is typical of transitional types prior to the FAD of Jinogondolella nankingensis, which is one of the characters supporting our Mesogondolella idahoensis lamberti

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identi¢cation. Jinogondolella nankingensis is de¢ned when these serrations can be seen on the lateral pro¢le as well as the upper surface; this is clearly not the case in these specimens (Plate IV, 6a). Such serration was extremely rare (1%) in our Oman samples and our ¢gured specimens are the best that we observed. 3.5. Comparison of Sicily and Oman conodont faunas We agree with other workers (e.g. Gullo and Kozur, 1992; Kozur, 1989b, 1998; Kozur and Davydov, 1996) that the conodonts from Rustaq, Oman can be correlated and compared with the conodont fauna recovered from olistostromal limestones in Sicily. We disagree however with respect to the age assignment and in part with the taxonomic assignments. Our taxonomic approach emphasizes stable characters including denticulation within the entire population whereas in the past many Permian conodont workers, including us, have emphasized the platform outline. For example, Mesogondolella siciliensis, Mesogondolella zsuzsannae and Mesogondolella siciliensis saraciniensis ( = Mesogondolella saraciniensis in Kozur, 1998) were named and di¡erentiated mainly based on platform outline (Kozur, 1989b). In di¡erentiating M. siciliensis and M. zsuzsannae, Kozur (1989b, p. 399) stated: ‘‘Mesogondolella siciliensis siciliensis (Kozur, 1975) has a di¡erent platform shape with stronger

Plate IV. All specimens are SEM photos and magni¢ed 80U except where otherwise indicated. Letters a and b are used with the same number when both upper and lateral views of the same specimen are illustrated. 1^8, 11, 12.

9.

10.

Mesogondolella idahoensis lamberti Mei and Henderson, 2002. All are Pa elements showing intra-population variation; 6 and 7 are transitional to Jinogondolella nankingensis nankingensis, and 8 is a very rare specimen with a round posterior platform end. 1^6, 8, 11, 12 are from 3 (61992), which is 2.3 m above the base of the red limestone ammonoid bed of the Al Jil Formation at Section 2 of Rustaq, Oman (Baud et al., 2001a,b); 7 is from 12 (61988), which is 1.3 m above the base of the red limestone ammonoid bed of the Al Jil Formation at Section 2 of Rustaq, Oman (Baud et al., 2001a,b). Compare to specimens from Texas in Plate II (3, 4, 9). See Mei and Henderson, 2002 for diagnosis and description. Transitional form between Sweetognathus subsymmetricus Wang, Ritter and Clark 1997 and Sweetognathus hanzhongensis (Wang, 1978). Pa element, from 12 (61988), which is 1.3 m above the base of the red limestone ammonoid bed of the Al Jil Formation at Section 1 of Rustaq, Oman (Baud et al., 2001a,b). Compare to the temporal range at Luodian (Fig. 4). Pseudohindeodus ramovsi Gullo and Kozur, 1992. Upper view of Pa element, U100, from 12 (61988), which is 1.3 m above the base of the red limestone ammonoid bed of the Al Jil Formation at Section 1 of Rustaq, Oman (Baud et al., 2001a,b).

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widening before the platform midlength. The platform is often slightly constricted in front of the posterior end, or at least in this part no or indistinct widening occurs’’. In di¡erentiating M. siciliensis saraciniensis and M. zsuzsannae, Kozur (1989b, p. 399, 400) stated: ‘‘Mesogondolella siciliensis saraciniensis Gullo and Kozur n. subsp. has a similar platform outline to M. zsuzsannae n. sp., but the posterior platform end is mostly rounded, rarely obliquely blunt’’. In di¡erentiating M. siciliensis saraciniensis and Mesogondolella siciliensis siciliensis, Kozur (1989b, p. 399) stated: ‘‘Mesogondolella siciliensis siciliensis (Kozur, 1975) has mostly no platform brim at the posterior end (only in very wide forms with bifurcated end of carina a narrow platform brim behind the carina may be present). The platform widening before the mid-length is stronger, and the increase of the platform width from the posterior end to its widest part is not so continuous, because often a slight constriction is present before the posterior end; for this part of the platform no or only very few widening of platform can be observed’’. Kozur (1989b) also referred specimens with a pointed posterior platform end (Kozur, 1989b, pl. 4, ¢g. 4) to Mesogondolella slovenica. However, in our samples from Oman, all of these platform outline forms are found to be intergrading with each other and they all have identical denticulation in what appears to us to be a single population (Plate III, 1^8, 10^12). Kozur’s (1989b, pl. 1, ¢gs. 1^4; pl. 2, ¢gs. 1^4; pl. 4, ¢gs. 2^6; pl. 5, ¢gs. 1^7; pl. 6, ¢gs. 1^7; pl. 7, ¢g. 1) illustrations also indicate that all of the Pa elements for the above mentioned species have identical denticulation with a cusp that in adult specimens is slightly bigger than or the same size as the posterior denticles, a carina with denticles that are increasingly closely spaced to fused towards the anterior, and an anterior blade with largely fused and high denticles. The use of the platform outline as the primary taxonomic character for discrimination can lead to misidenti¢cation of homeomorphic taxa. For example, Capitanian specimens of Jinogondolella altudaensis were at one time identi¢ed as Lopingian Clarkina changxingensis based on the extremely similar platform outline (Kozur, 1992a,b). As Mei et al. (1998) and Henderson (2001) indi-

cated, the denticulation con¢guration is the most stable character in a population for species discrimination and high-resolution stratigraphic correlation. As a result, we believe that specimens illustrated by Kozur (1989b, pl. 1, 1^4; pl. 2, ¢gs. 1^4; pl. 4, ¢gs. 2^6; pl. 5, ¢gs. 1^7; pl. 6, ¢gs. 1^7; pl. 7, ¢g. 1) actually represent di¡erent morphotypes of a M. siciliensis population, and thus we regard M. zsuzsannae and M. saraciniensis as junior synonyms (Mei and Henderson, 2002). The specimens referred to M. phosphoriensis and M. idahoensis by Kozur (1989b, pl. 2, ¢gs. 5,6; pl. 4, ¢gs. 1,2; pl. 5, ¢g. 1) are mostly juvenile specimens and cannot be di¡erentiated from juvenile or young specimens of M. siciliensis. Conodonts from shallow carbonate platform rocks of the Saiq Formation include Hindeodus excavatus (sensu Wardlaw and Collinson, 1984; identi¢ed by A. Nicora in Baud et al., 2001a). Wardlaw and Collinson (1984) show a range for H. excavatus of Upper Kungurian to Upper Wordian. Wardlaw (2000) has split this taxon into two taxa including H. excavatus (Upper Kungurian to mid-Roadian) and Hindeodus wordensis (midRoadian to Upper Capitanian). The latter taxon relates to specimens ¢gured in Wardlaw and Collinson (1984, 1986). Conodont faunas from the Khu¡ Formation of southeastern Oman (Angiolini et al., 1998) may correlate with the Saiq Formation (conodonts are not de¢nitive), but they do not appear to correlate with specimens from Rustaq or Sicily, despite the fact that faunas from these areas have been dated as Wordian. We agree that the Khu¡ fauna including H. excavatus, Merrillina praedivergens, and Sweetina sp. is indicative of a Late Wordian (and/or earliest Capitanian) age based on the presence of M. praedivergens. Furthermore, the latter two taxa are characteristic of a cool-water province (Mei and Henderson, 2001), which supports the mixed/transitional Gondwanan/Tethyan brachiopod fauna indicated by Angiolini et al. (1998). These rocks appear to be younger than those from Rustaq and possibly the Saiq, which may account for the cooler-water nature given the progressive cooling occurring in the northern hemisphere during the Permian (Beauchamp, 1994; Beauchamp and Baud, 2002).

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4. Comparison with associated biota Further development of our argument regarding age correlation requires comparison to other fossil groups including fusulinaceans and ammonoids. 4.1. Comparison with associated ammonoid faunas and age of Waagenoceras The Wordian stage was traditionally correlated as the stage of Waagenoceras (Furnish, 1973). Clifton (1945) and King (1947) reported Waagenoceras from the lower limestone of the Word Formation (now Road Canyon Formation), but the relative stratigraphic position to beds of the lower limestone containing the ammonoid Perrinites is uncertain ; King (1947) suggested that both genera were near the respective lower and upper limits of their range. These lower occurrences of Waagenoceras are now usually referred to Demarezites based on sutural variations (Glenister and Furnish, 1987). This unit also includes distinctive brachiopods (Cooper and Grant, 1966). According to the o⁄cial stage de¢nition, the Road Canyon Formation correlates with the upper Kungurian and lower Roadian (Wardlaw, 1996; Lambert et al., 2000). Lambert et al. (2000) assumed that reports of Waagenoceras from low in the Road Canyon Formation (Upper Kungurian) most likely represent occurrences of Demarezites, but stated that study of additional specimens will be required to con¢dently resolve this separation (Lambert et al., 2000, p. 178). Lambert et al. (2000; p. 178) also regarded a new species of Waagenoceras found from the Pipeline Shale Member of the basal Brushy Canyon Formation as an index ammonoid for the Roadian. The Pipeline Shale Member includes specimens with sutures advanced for Demarezites and primitive for Waagenoceras that may represent sympatric species preserved soon after a major speciation event (Lambert, 2002a; Lambert, 2002b in Rohr et al., 2002). These specimens of primitive Waagenoceras occur about 20 m above the FAD of Jinogondolella nankingensis in the middle of the El Centro Member of the Cuto¡ Formation (Fig. 5) and over 300 m below the FAD of Jinogondolella aser-

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rata in the Getaway Member of the Cherry Canyon Formation and are therefore correlated with a position low in the Roadian. Advanced Waagenoceras including W. dieneri (Lambert, 2002a) are abundant in the Willis Ranch Member (third limestone of the Word Formation ; Wardlaw, 2002) several metres below the ¢rst appearance of J. aserrata (Glenister et al., 1999, p. 8) and are therefore Late Roadian (Fig. 5) in age; Waagenoceras does continue up into the Wordian. Wardlaw (1996) and Lambert et al. (2000) con¢rmed this age range for Waagenoceras in the type locality of the Word Formation in the Glass Mountains, Texas, and in Coahuila, Mexico by Wardlaw et al. (2000). In South China, Waagenoceras sp. has been found to occur with the latest Capitanian Clarkina postbitteri hongshuiensis (Henderson et al., 2002; Jin et al., 1998, 2001; Mei et al., 1999d). In conclusion, this indicates that Waagenoceras, as a genus, may range from Roadian to latest Capitanian. Therefore the genus Waagenoceras cannot be regarded as simply Wordian; more re¢ned ages will require species level correlation. This brings into question the proposed Wordian age for the Sicily and Oman faunas based on Waagenoceras since none of the species present in Sicily and Oman are represented in the West Texas region. Miller and Furnish (1940) indicated that 70 species within 20 genera are recognized in the classic localities for Waagenoceras in Sicily and correlate them with the Word Formation. Miller (1933, 1945) and Furnish (1966) have made detailed comparisons indicating that the Sicily fauna best compares to the third limestone of the Word Formation (#1^4 in Fig. 5 lithologic column; the Road Canyon Formation or limestone #1 was originally regarded as a member of the Word Formation) or Willis Ranch Member. It is true that there is some discrepancy regarding which is the third limestone (Lambert et al., 2000 indicate that the Willis Ranch is the second limestone), but the classic literature typically names the Willis Ranch unit (con¢rmed by Wardlaw, 2002; Lambert et al., 2002a left out the China Tank Member in their ¢gures). The Willis Ranch Member encompasses the upper range of Jinogondolella nankingensis and is therefore Upper Roadian. Our inter-

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pretation, based on identi¢cations by ammonoid workers, is that with one exception, none of the species from Sicily are identical to those from West Texas; in contrast, Sicily and Oman share many species. The following discussion highlights some of these species as discussed primarily by Miller and Furnish (1940), but is by no means exhaustive. Waagenoceras mojsisovicsi and Waagenoceras stachei are found in Sicily, but not in West Texas. Waagenoceras dieneri from the third Word limestone to the South Wells (Upper Roadian to mid-Wordian) is compared to the Sicily species. Miller and Furnish (1940) indicate that specimens from the ¢rst limestone of the Word Formation (Road Canyon; Upper Kungurian to Lower Roadian) are probably referable to W. dieneri, but subsequent workers (Glenister and Furnish, 1987) refer them to Demarezites based on sutural variations. Miller and Furnish (1940) did not compare a second species from West Texas, Waagenoceras guadalupense from the South Wells to Pinery and Lower Capitan limestone (midWordian to earliest Capitanian), to the Sicily fauna. Medlicottia bifrons and Medlicottia verneuili are present in Sicily, but not in West Texas. Medlicottia burckhardti from the second (China Tank Member ; see Fig. 5) and third Word limestones up to the South Wells Member (mid-Roadian to mid-Wordian) is compared to the Sicily species. Paraceltites hoeferi is present in Sicily, but not in West Texas. This species is compared to Paraceltites multicostatus from the Word Formation (Upper Kungurian to mid-Wordian), but an exact position within the Word cannot be determined; many early references to localities are di⁄cult to interpret because of the lack of depicted sections. The only species present in both Sicily and West Texas that we can determine is Propinacoceras beyrichi. This species is from the Leonardian Bone Springs Limestone and Willis Ranch Member ranging from Kungurian to Upper Roadian; a precise location is not clear from Miller and Furnish (1940). This species is also present in the Cache Creek Group in British Columbia. Two localities within terranes of the western Cordillera of British Columbia are pertinent to the discussion; sections are rarely present within these tectonically accreted terrane rocks. Nassi-

chuk (1977) described ammonoids from the Cache Creek Group near Atlin and near Kamloops (the latter locality is now referred to the Harper Ranch Group of the Quesnell terrane), British Columbia. Among the list of ammonoids from the Kamloops locality are Propinacoceras beyrichi, Agathiceras suessi (present in Sicily), and Waagenaceras cf. W. girtyi. The Kamloops locality has also yielded Parafusulina spp. (C.A. Ross in Nassichuk, 1977) that are comparable to species from the Late Kungurian and Roadian of West Texas. Nelson and Nelson (1985) reported Guadalupian Tethyan fusulinaceans (identi¢cations by C.A. Ross: Dunbarula laudoni, Boultonia sp., and Minojapanella sp.) and waagenophyllid corals associated with Leonardian brachiopods from the same bed. Orchard and Forster (1988) reported that the youngest conodonts in the region yielded Mesogondolella (Neogondolella formerly) idahoensis and M. idahoensis n. subsp. A; they suggested a Late Leonardian (Kungurian) age. The exact juxtaposition of these three separate reports (ammonoids, fusulinaceans and corals, conodonts) cannot be con¢rmed, but they all represent the youngest reported elements of each group in this structurally complex area. Specimens illustrated by Orchard and Forster (1988) as M. idahoensis n. subsp. A (their pl. 3, ¢gs. 18^20) are identical to Mesogondolella idahoensis lamberti from Oman (Plate IV, 11) and from Luodian, South China (Plate II, 3) and similar to Mesogondolella siciliensis from Luodian (Plate I, 8). The Kamloops conodont fauna is identical in our view with conodonts from Oman and Sicily and from the Upper Kungurian of West Texas and Luodian, South China. Among the list of ammonoids from the Atlin locality are Eumedlicottia burckhardti, Agathiceras girtyi, Stacheoceras mediterraneum (present in Sicily), Waagenoceras canadensis, Waagenoceras dieneri, and Waagenoceras girtyi. We are not aware of reports of conodonts from the Atlin locality, but the fusulinaceans include Yabeina spp. and were correlated with the Neoschwagerina Zone (Ross in Nassichuk, 1977). This fusulinacean fauna is typical of the Tethyan province and is distinct from the Harper Ranch Group, which shows a mixed a⁄nity. If the ammonoids from the two BC localities are the same

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age then there is a potential correlation between warm-water Parafusulina and Tethyan Yabeina and Neoschwagerina ; however, normally in the Tethys, Parafusulina occurs below the latter two genera. 4.2. Comparison with associated fusulinaceans The fusulinacean connection within these two terrane localities is an important one because comparison of fusulinaceans between West Texas and the Tethys cannot be made directly because of distinct provincialism. The fusulinaceans from the interval of interest in West Texas (Fig. 5) are dominated by Parafusulina spp. whereas in Sicily and South China they are dominated by Neoschwagerina spp. (Upper Murgabian to Lower Midian). Fusulinaceans are the primary tool for correlation of the Tethyan stages and when correlated with the Tethyan stages like Murgabian and Midian that age cannot be disputed. However, the correlation with the International Standard is problematic. Yang and Yancey (2000) indicate that Parafusulina rothi, which is found in West Texas just above the FAD of Jinogondolella nankingensis has been found occasionally in South China associated with Neoschwagerina simplex; this would indicate that the Roadian of West Texas is correlative with the Lower Murgabian and not Kubergandian as indicated by Leven (2001). This does not support our interpretation as N. simplex occurs well below the FAD of J. nankingensis (Fig. 4), but it does demonstrate the problematic nature of these correlations. Midian age Yabeina have been reported from Luodian in rocks that we regard as uppermost Roadian to Capitanian (Fig. 4). Kozur et al. (2001) indicate that Yabeina is found in the Capitanian of West Texas and never below. However, Yang and Yancey (2000) indicate that Yabeina texana does not provide direct evidence for correlation to the Tethyan province and that the West Texas specimens are probably an aberrant form adapted to unusual environmental conditions. The Luodian section (Fig. 4) includes a normal Tethyan succession of fusulinaceans, and this has not been disputed; however, the correlation of these zones with the global Permian stages on the basis of

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conodonts has caused considerable consternation (Leven, 2001). To explain the disparate ages, Kozur et al. (2001) have indicated that the conodonts, but not the fusulinaceans, from Luodian must be reworked and that they have surface textures indicating reaction with freshwater and subaerial exposure. The specimens illustrated from Luodian in this paper are well preserved and the surface textures are mostly pristine (Plate I, for example). We are not aware of any surface texture that can be attributed with certainty to subaerial exposure and freshwater alteration. The lack of reworking is also supported by the presence of specimens of various sizes and of associated ramiform elements indicating the lack of size sorting. Luodian conodonts from the upper part of beds 22 to 41 and below the ¢rst occurrence of serrated Jinogondolella in bed 42 correlate with conodonts from Sicily, Oman and the Upper Kungurian of West Texas (Fig. 4). This suggests that the fusulinacean zones of Missellina to Neoschwagerina craticulifera (Kubergandinian to Murgabian) correlate with the Upper Kungurian and possibly lowest Roadian. Kozur (1998, p. 210) has stated that he preferred the traditional base of the Wordian at the FAD of Waagenoceras and felt that the FAD of Jinogondolella aserrata (his Mesogondolella) may cause problems for Tethyan correlations. Obviously this forms the primary basis upon which to date the associated Mesogondolella siciliensis and other conodonts as Wordian (Kozur, 1993, 1995a, 1997, 1998; Kozur and Davydov, 1996; Catalano et al., 1991, 1992; Gullo and Kozur, 1992) and the main reason why the Upper Murgabian and Lower Midian are correlated with the Wordian. Earlier (Section 3.4) we suggested that the ¢rst occurrence of Jinogondolella nankingensis may be diachronous and indicated an alternative position for the base of the Roadian at the Luodian section (Fig. 4; bed 35). At this section, this would indicate that Upper Murgabian fusulinaceans (Neoschwagerina craticulifera and Afghanella schencki) were correlative to the Lower Roadian. This coincides closely with the Chihsian^Maokouian subseries boundary de¢ned at the base of the Afghanella schencki Zone by Zhu and Zhang

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(1994). This interval at Luodian (beds 35^41) is represented by shallow marine facies and occurs just before a major transgressive unit (bed 42). In two other Tethyan sections of more proximal marine aspect this interval may be absent. At the Tieqiao section near Laibin, South China a major transgressive surface (base of bed 112 in ¢g. 2 of Wardlaw and Mei, 1998) separates Roadian J. nankingensis associated with Midian Sumatrina cf. fusiformis from Kungurian Sweetognathus subsymmetricus associated with Parafusulina kwangsiana and Rusiella pulchra. A di¡erent fusulinacean biofacies is indicated by the succession of Misellina claudiae, Nankinella orbicularia, Schwagerina chihsianensis, and Parafusulina kwangsiana; apparently no Cancellina or Neoschwagerina simplex at this locality. Zhu and Zhang (1994) point out the biofacies problems of correlating fusulinaceans from restricted shelf to open shelf to slope. Another section at Khojagor, Afghanistan (Leven, 1997 ; see p. 17) shows an unconformity with transgressive deposits above (units D, E) associated with Midian Eopolydiexodina sp., Neoschwagerina margaritae, Afghanella schencki, Afghanella tumida, and Sumatrina cf. S. anna (among others) and shallow-water carbonates below associated with Lower Murgabian Parafusulina sp., Eopolydiexodina afghanensis, Neoschwagerina simplex tenuis and Presumatrina schellwieni (among others) ; apparently the Upper Murgabian Neoschwagerina craticulifera and possibly A. schencki zones are missing. No conodonts are reported from this location.

5. Paleoecologic implications for Permian gondolellid correlations Kozur (1997, p. 151) indicated that serrated Mesogondolella (that we refer to Jinogondolella) are partly or totally replaced by smooth Mesogondolella of the Mesogondolella phosphoriensis-Mesogondolella siciliensis lineage in regions with cool or cold water (e.g. peri-Gondwana Tethys, Boreal realm except brie£y in the Roadian of Arctic Canada’s Sverdrup Basin; Fig. 1), with cold upwelling waters as in the Phosphoria Basin of western USA (Fig. 2), and in tropical open sea

deep-water environments connected with the cold oceanic bottom currents (Sicily) ; he indicates that serrated forms are found only in semi-restricted basins with warm bottom-waters and on the upper shelf in tropical areas. We do not agree that there is an evolutionary relationship between M. phosphoriensis and M. siciliensis ; they have totally di¡erent carinal denticulation. We do agree, however, that cool-water areas generally display non-serrated forms, but interestingly, serrated forms do occur early in the Guadalupian in the Sverdrup Basin, Arctic Canada (Henderson, 1981; Mei and Henderson, 2002), in the Phosphoria Basin, Idaho, and in NE China (Wang et al., 2000). Wang et al. (2000) correlated the latter locality in Jilin Province (Fanjiatun Formation) to the Wordian or early Capitanian and named several new taxa including Mesogondolella changcunensis, Mesogondolella jilinensis, Mesogondolella multiserrata, and Mesogondolella pseudoaltudaensis. Some of these taxa have serrated margins whereas others are smooth and most have a relatively large cusp and moderately low and discrete anterior denticles typical of cool-water areas, which supports the temperate zone identi¢ed by Wang et al. (2000). Mesogondolella jilinensis, M. changcunensis, and M. multiserrata are very similar to specimens (including several juveniles) identi¢ed by Behnken et al. (1986) as Neogondolella gracilis and Neogondolella serrata (referred to as Jinogondolella nankingensis gracilis in Mei and Henderson, 2002) from the Roadian Meade Peak Formation of Idaho, USA. During the Early Roadian, early in the evolution of Permian serrated gondolellids, these forms migrated into relatively cool-water areas of the NCWP. All younger Guadalupian specimens of Mesogondolella in the Sverdrup Basin are smooth, whereas rare serrated specimens do occur in younger Guadalupian rocks of the Phosphoria. Why then are serrated forms excluded from the open-sea areas of the Tethys? Although serrated Mesogondolella ( = Jinogondolella) are common in shallow warmwater settings, we do not agree that they are restricted to such areas for the following reasons: (1) South China was a low-lying microcontinent at the middle of the eastern opening of the Tethys Ocean, and the South China Permian basin was

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not restricted (Ziegler et al., 1997). The western Tethys region in Sicily must also be restricted if South China is restricted on the eastern margin (Fig. 2). In addition, we wonder whether upwelling in Oman would be signi¢cant, as it appears to be isolated from the Panthalassa ocean thermohaline circulation generated from Pangea poles (Fig. 2). Furthermore, shelf carbonates in the Wadi Sahtan section (Saiq Formation) of Oman contain a warm-water fauna of fusulinaceans, calcareous algae, and corals (Baud et al., 2001a); the presence of coral boundstones preclude the presence of cool upwelling currents (Ziegler et al., 1997). (2) Abundant Guadalupian serrated conodonts have been recovered from outer shelf, slope and basinal facies in South China (Mei et al., 1994a,b,c, 1998) and they are comparable with those from the Delaware Basin in Texas zone by zone (Mei, 1995; Mei et al., 1999b; Mei and Henderson, 2001). It is di⁄cult to imagine gene £ow between these two regions if the taxa are found only in restricted to semi-restricted basins. (3) The Cache Creek Terrane (Fig. 2) in British Columbia, Canada and the Baker Terrane (Fig. 2) in Eastern Oregon, USA are similar to the Hawasina Nappes in Oman and the Sosio limestone in Sicily in terms of tectonic and sedimentary settings. The Cache Creek Terrane is represented by abundant Jinogondolella and less abundant Sweetognathus in the Guadalupian (Beyers and Orchard, 1991; Orchard et al., 1999, 2000). In the Baker Terrane, Nestell and Orchard (2000; no illustrations in the paper, but M.K. Nestell showed us SEM photos) reported a late Kungurian conodont fauna with Mesogondolella idahoensis and two species of Sweetognathus. The specimens they referred to as Mesogondolella idahoensis have a small cusp, closely spaced to fused denticles on the middle carina, and largely fused and high denticles on the anterior blade. These specimens are almost identical to specimens we ¢nd from the upper Kungurian in South China (Plate I, 1^14 and Plate II, 2, 11) and from Oman (Plate III, 1^8, 10^12) referred to as Mesogondolella siciliensis (Mei and Henderson, 2001). The fusulinacean found in the same locality as the conodont fauna in the Baker Terrane contains Neoschwagerina, which is also found in shelf car-

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bonates in Oman and the Sosio limestone in Sicily. It is well accepted that faunas from the Cache Creek and Baker terranes are typical of warm-water settings. (4) Warm-water elements such as Sweetognathus and Neostreptognathodus exculptus (Mei and Henderson, 2001; Mei et al., 2002 ; the latter can range into temperate settings, see Katvala and Henderson, 2002) have also been found in Sicily in association with Mesogondolella bearing typical warm-water type denticulation (Kozur, 1997). (5) In Sicily, as well as in South China and Texas, there are ‘shallow warm-water’ environments as indicated by the occurrence of Sweetognathus and fusulinaceans in Sicily (Gullo and Kozur, 1992; Kozur, 1997; Kozur and Davydov, 1996), South China (Mei et al., 1998, 1999a) and West Texas (Wardlaw, 2000). There should be both non-serrated and serrated Mesogondolella found in each of these regions along a corridor from shelf to slope to basin in coeval strata, if we assume a model comparable to Kozur (1997). However, this is not the case (Henderson, 1981; Lambert et al., 2000; Mei et al., 1994a,c, 1998; Wardlaw, 2000; Wardlaw and Collinson, 1984, 1986; Wardlaw and Grant, 1990; Wardlaw and Mei, 1998; Wardlaw et al., 2000). (6) During the Roadian in the Sverdrup Basin cool temperate to cold climatic conditions prevailed (Beauchamp, 1994), yet the conodonts bear serration for a short interval in the lower Assistance Formation (Henderson, 1981; Mei and Henderson, 2002). (7) In Oman, the co-occurrence of shallow warm-water conodonts like Sweetognathus and smooth mesogondolellids with warm-water denticulation in relatively deep-water cephalopod limestones of the Rustaq Formation may suggest that both of these taxa were pelagic and unaffected by cold bottom-water currents.

6. Conclusion The lack of serration within Oman conodont faunas di¡ers markedly from conodonts in the Guadalupian stratotypes of West Texas. Environmental factors do control the distribution of Per-

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mian gondolellids, but upwelling ‘cold bottomwater’ does not appear to be signi¢cant based on our samples from Oman, which are dominated by species with a carinal con¢guration that is comparable to gondolellids from the EWWP. If cold bottom-water currents were present at Oman then these taxa must have been pelagic, living in warm sur¢cial water. Early Roadian serrated gondolellids have been recognized in temperate coolwater settings of the NCWP in Jilin Province, Phosphoria Basin, and the Sverdrup Basin. These serrated forms extend above the Lower Roadian in only the Phosphoria Basin indicating a distribution into cooler temperatures than previously thought, at least during the Early Guadalupian. Other conodonts from the deep-water cephalopod limestones of Oman include shallow, warm-water sweetognathids; these too must have been pelagic. Our Oman samples yielded Mesogondolella siciliensis, Mesogondolella rustaqensis, Mesogondolella idahoensis lamberti, Sweetognathus subsymmetricus, and Pseudohindeodus ramovsi. This fauna is identical to that obtained from Sicily at Rupe del Passo di Burgio in association with Upper Murgabian to Lower Midian fusulinaceans. The fauna is also virtually identical to specimens from the Upper Kungurian Cathedral Mountain and lower Road Canyon formations of West Texas and from the Luodian section in South China (beds 22 to lower 42; see Fig. 4) in association with Kubergandian to Murgabian fusulinaceans. This interval at Luodian has been correlated as Upper Kungurian because of its position below the FAD of Jinogondolella nankingensis. It is possible that the top part of this interval may be correlated with the Lower Roadian since other paleoecologic controls (setting was too shallow for gondolellids) may result in diachroneity of the ¢rst occurrence of J. nankingensis. The overall conodont succession indicates that the Kungurian and possibly the Lower Roadian correlates with the Upper Bolorian to Murgabian (Fig. 4, columns B, D). This is very di¡erent from previous correlations between the standard stages and the Tethys stages. The linchpin to the entire argument is the occurrence of Waagenoceras and/or Demarezites with these conodonts and fusulinaceans and their presumed correlation with Wordian

and Roadian respectively, since the conodonts and fusulinaceans seem to be in agreement everywhere they co-occur. Perhaps these ammonoid genera have longer ranges than previously recognized. The best correlation of advanced species of Waagenoceras from Oman and Sicily is with the third limestone of the Word Formation (Willis Ranch Member), which correlates with the Upper Roadian according to rati¢ed global stage de¢nitions. The ammonoid species vary between all of the important sections and no detailed evolutionary succession depicting the relative positions within well-constrained sections appears to exist. No one would correlate the Kungurian or the Murgabian or any other Permian stage on the basis of the conodont genus Mesogondolella unless it was identi¢ed at the speci¢c level. The end result of these new correlations, if correct, is that the standard stages will be correlated di¡erently with the Tethyan stages, which will enhance our ability to interpret the geological history of the world during Late Cisuralian and early Guadalupian time. There is still an apparent discrepancy between conodont (Upper Kungurian or Upper Kungurian to Lower Roadian) and ammonoid (Upper Roadian) ages, but discounting previous Wordian ages has considerably reduced this.

Acknowledgements C.H. and S.M. acknowledge funding from the industry-supported Applied Stratigraphy Research Group at the University of Calgary. S.M. also acknowledges support from a key state project funded by the Ministry of State Science and Technology of China (G2000077705 and SSER). Lorraine Bloom of the Department of Geology and Geophysics, University of Calgary, is thanked for processing and picking the Oman conodont samples. Benoit Beauchamp and Aymon Baud are thanked for collecting and providing the Oman conodont samples. Critical reviews from Aymon Baud, Benoit Beauchamp, Leopold Krystyn, Alda Nicora, and Mike Orchard improved this article, but the authors remain responsible for the ¢nal content and any errors it may contain.

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