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Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 259 – 269 www.elsevier.com/locate/palaeo

PTB mass extinction and earliest Triassic recovery overlooked? New evidence for a marine origin of Lower Triassic mixed carbonate–siliciclastic sediments (Rogenstein Member), Germany Oliver Weidlich ⁎ Earth Science Department, Sultan Qaboos University, P.O. Box 36, Al Khoud, PC 123, Sultanate of Oman Accepted 30 November 2006

Abstract The Central European Permo-Triassic basin was land-locked with occasional connections to the North Pangaea shelf and Tethys. A thick sequence of siliciclastic fluvial and floodplain sediments separates the Late Permian marine carbonate–evaporite cycles of the Zechstein Basin from marine Middle Triassic marls and carbonates of the Germanic Basin. Within this Latest Permian–Middle Triassic siliciclastic interval, the location of the Permian–Triassic Boundary (PTB) is difficult to recognize. The first limestones after the PTB are Induan mixed carbonate–siliciclastic oolites and microbialites of the Bernburg and Calvörde Formations (Untere Buntsandstein Group). Consensus emerged after a long-lasting controversy that the carbonates of the so-called Rogensteine are the relics of an alkaline playa lake. The idea of the marine genesis was finally rejected, because of the obvious lack of calcified metazoans. The existing depositional playa lake-model will be tested using previously unconsidered data, such as currently discussed Early Triassic recovery scenarios of marine benthic communities after the Permian–Triassic mass extinction, global patterns of Early Triassic carbonate production, Permian–Triassic tectono-sedimentary evolution of northern Pangaea and stable oxygen and carbon isotope data. The Rogenstein is interpreted as marine carbonate, showing the characteristic features of marine carbonates of the Early Triassic recovery period: – Calcified invertebrates are rare in many marine settings during the aftermath of the Permian–Triassic mass extinction. Thin shells of the oolites resemble opportunistic bivalves flourishing in marine Early Triassic oceans. – The oolites and microbialites are the product of abiotic and biotically-induced carbonate precipitation following the Permian– Triassic mass extinction while biomineralisation is insignificant; Rogenstein microbialites look like marine Early Triassic microbial reefs. – The extraordinary size of the Rogenstein ooids resembles marine Neoproterozoic ooids. The term “anachronistic” has been used in the literature to describe the similarities in the fabric and composition of Early Triassic and Early Palaeozoic/Neoproterozoic marine carbonates. – Stable carbon isotopes of least altered Rogenstein ooids and stromatolites exhibit trends similar to the composition of Triassic seawater. – The presence of flat pebble conglomerates and sediment structures similar to herring-bone cross stratification confirm the marine genesis.

⁎ Tel.: +968 24142285; fax: +968 24141405. E-mail addresses: [email protected], [email protected]. 0031-0182/$ - see front matter © 2007 Published by Elsevier B.V. doi:10.1016/j.palaeo.2006.11.046

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I propose that cool seawater transgressed during a global rise of Late Permian–Early Triassic base-level from the Barents shelf southward along reactivated extensional graben structures and flooded the Central European Permo-Triassic basin. There, the extremely hot and arid climate of the megacontinent Pangaea caused increased evaporation of seawater and subsequent supersaturation with respect to calcium carbonate. Insignificant biomineralisation and high water energy in the shallow sea give rise to largely abiotic and biotically-induced carbonate precipitation which resembles lake sediments at first sight. Benthic tropical carbonate production started with the next transgression during the Röt Formation, leading to the sedimentation of marls and limestones during the Spathian (late Olenekian). © 2007 Published by Elsevier B.V. Keywords: Early Triassic recovery; Oolites; Microbialites; Germanic basin; Germany

1. Introduction The so-called Rogenstein Member of the Bernburg Formation is a key locality to study carbonate sedimentology because the terms oolite and stromatolite have been defined by Kalkowsky (1908) in a modern sense using samples from outcrops in the vicinity of the Harz Mountains, Germany (see also Paul, 1982; Flügel, 1982; Paul and Peryt, 2000; Flügel, 2004), Fig. 1. The Induan oolites and microbialites of the Rogenstein are not pure carbonate, rather they represent a complex system of mixed carbonate–siliciclastic sediments. Probably, it is the complexity of the sedimentary environments of the red beds which has attracted the interest of sedimentologist for the last 100 years. Since the work of Kalkowsky, many aspects of the Lower Buntsandstein Group and the Rogensteine have been investigated and more than 40 peer-reviewed publications have been published, focusing on petrography, carbonate and siliciclastic sedimentology, paleontology and the nature of the obvious cyclicity of the sediments. A recent summary has been done by Paul and Peryt (2000) with emphasis on the re-investigation of the classic stromatolites of the Rogenstein Member. In this paper, preference is given to the nomenclature of Burne and Moore (1987) who regard “organosedimentary deposits formed from interaction between benthic microbial communities and detrital and chemical sediments” as microbialites. Laminated structures, including Kalkowsky's stromatolites, fulfil the definition criteria and, therefore, the term is applied to them. Despite a rapidly growing body of literature dealing with the PTB – more than 300 publications have been dedicated to this subject since 1980 – little attempt has been made to interpret the Rogenstein carbonates in the light of the Permian–Triassic mass extinction and the Early Triassic recovery period. The Permian mass extinction encompasses the end-Guadalupian (Middle Permian) and end-Lopingian (Late Permian) crises (e.g., Stanley and Yang, 1994), the latter being certainly the

most severe Phanerozoic bioevent. The recovery period of marine ecosystems following the mass extinction was extraordinarily prolonged and for metazoan reefs took until the early Middle Triassic (Flügel, 2002; Weidlich, 2002; Weidlich et al., 2003). The impact of the Permian mass extinctions on biodiversity and ecosystems has been analyzed in detail (Erwin et al., 2002 and further references herein). Lopingian sponge microbial and dendroid coral reefs persisted until the end of the Permian. After the PTB probably during the late Griesbachian, the microbialites flourished in an area comparable to the latest Permian reef domain, including marine settings of the Tethys and Panthalassa Transcaucasus, China, Iran, Afghanistan, Turkey, Oman, Mexico, USA (Weidlich, 2002; Weidlich et al., 2003; Baud et al., 2005; Pruss and Bottjer, 2005), see Fig. 1. Metazoan reefs started to colonize the shelves not before the Anisian (Middle Triassic) in an extended equatorial zone (Figs. 1, 2). The main objective of this paper is to re-interpret the depositional environment of the carbonates of the Lower Buntsandstein Group in the light of the end-Permian mass extinction and the Early Triassic recovery period. Samples studied were collected at Harlyberg (near Vienenburg). Details of the study area have been already published (study area: Paul and Peryt, 2000, Fig. 1, location Harly; location of samples: Paul and Peryt, 2000, Fig. 14, upper part of section). 2. Geological setting THE Central European Permo-Triassic basin reflects the evolution from the Southern Zechstein basin (or Southern Permian basin) during the Permian to the Germanic basin during the Triassic. The latter basin reflects, at least at its beginning, the paleogeography of the precursor basin which extended from the southern North Sea to Lithuania and Belarus and from Denmark to southern Germany and eastern Poland (Ziegler, 1990), Fig. 1. During the Permian–Triassic, seawater

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Fig. 1. Late Permian–Early Triassic paleogeography. (1) Map showing the location of Early Triassic marine microbialites. Rectangle shows position of the Germanic basin (Central European Triassic basin). Dark gray = land masses, light gray = flooded shelves; data from Weidlich et al. (2003), Haas et al. (2004) and Weidlich and Bernecker (2007). (2) Close-up view of the Germanic basin. Carbonates of the Altmark–Eichsfeld High have been investigated for this paper. Other locations are discussed in the text and simplified logs are presented in Fig. 2. MNS-RF High = Mid North SeaRingköbing-Fyn High.

Fig. 2. Chronostratigraphy and lithologic logs of a cross section from the southeastern Germanic basin (locations 1–4) to the northern Barents gateway. Carbonate production is restricted to the Germanic basin; note the obvious change in the Triassic from biotically-induced to bioticallycontrolled carbonate precipitation. The area of investigation is the Altmark–Eichsfeld High; su = Lower Buntsandstein Group, sm = Middle Buntsandstein Group, so = Upper Buntsandstein Group; z = Zechstein; Vol.–Det. = Volpriehausen and Detfurth Formations; sea level curve from Jin et al. (1994); the asterisk highlights the position of the study locality Harlyberg.

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occasionally flooded the land-locked continental depression along reactivated rift structures from the north (Barents gateway), the southwest (Hessian–Burgundian gateway) and the southeast (East Carpathian and Silesian–Moravian gateways). The exact position of the PTB is difficult to locate, because of poor outcrops. Early Triassic clay-rich sandstone of the Calvörde Formation (Lower Buntsandstein Group) conformably overlies sandy silt- and claystone of the Late Permian Bröckelschiefer. The position of the PTB is based on sporomorph and conchostracan associations (Kozur, 1998; Bachmann and Kozur, 2004); distinct sedimentological changes have not been reported (Menning, 1995). During the Early Triassic, the Germanic basin was almost completely land-locked, except for some shortlived rift-induced phases with connections to the North Pangea shelf and probably the Tethys (Fig. 1). Buntsandstein red beds exceeding 1200 m thickness were deposited under terrestrial, lacustrine and to some extent shallow-marine conditions in the center of the basin. Up to 450 m of siliciclastic sediment intercalated with carbonate accumulated during the Lower Buntsandstein Group (Ziegler, 1990; Aigner and Bachmann, 1992). Carbonate siliciclastic intercalations have been interpreted as fining-upward cycles (Szurlies et al., 1998), high-frequency cyclicity is probably related to base-level fluctuations and climate instability. Whether or not orbital forcing directly or indirectly controlled the cyclicity of the Lower Buntsandstein sediments is beyond the scope of this contribution. However, it has been reported that that short eccentricity cycles are important (Bachmann and Kozur, 2004). The ideal cycle comprises the transition from sandstone to carbonate and finally to siltstone with sandstones representing a fluvial environment (Paul and Peryt, 2000). It has been argued that during wet periods, lake level transgressed over fluvial deposits and, after a lag time, oolites with varying siliciclastic input and stromatolites precipitated from the probably alkaline lake. The carbonates in turn are commonly overlain by reddish mudstones with desiccation and/or syneresis cracks, which are attributed to the shift from a permanent to an ephemeral lake system and indicate falling lake level. Predominantly oolites and microbialites with varying percentages of siliciclastic grains form an approximately 200 km wide belt extending from the southern North Sea to Lithuania. This unit reaches a maximum thickness of 100 m in the southern North Sea (Rhys, 1975) and developed a thickness of 45 m near the Altmark–Eichsfeld high (Fig. 2, AEH). The AEH is the key area of carbonate precipitation with carbonate beds reaching a maximum thickness of 3.5 m. Here,

stromatolites occur frequently and ooids reach extraordinary sizes with maximum diameters up to 20 mm. These carbonates have been called “Rogensteine” (roestone) by Kalkowsky (1908) who presented the first detailed description of oolites and stromatolites. Two stratigraphically different carbonate units of have been recognized in the Germanic basin on the basis of lithostratigraphic correlations. The first unit of oolitic limestone encompasses the Griesbachian Lower Buntsandstein Group (Fig. 2, su: Unterer Buntsandstein) and the Bunter Shale Formation (Beutler and Schüler, 1987; Röhling, 1991). It consists of basal thin carbonates of the Calvörde Formation and of the thicker succession of the Rogenstein Member of the lower Bernburg Formation. The second unit of oolites has been found in the Middle Buntsandstein Group (Fig. 2, sm: Mittlerer Buntsandstein), notably the Volpriehausen, Detfurth, and Solling Formations. Investigations of this paper focus on unit 1, notably the Rogenstein of the Bernburg Formation at the Harlyberg locality. The genetic processes, which led to the deposition of mixed carbonate–siliciclastic sediments of the Lower Buntsandstein Group, have been discussed. Although there has been the idea of a marine origin of the carbonates (e.g., Usdowski, 1962; Langbein, 1985), the suggestion of a closed lacustrine depositional system has been widely accepted because of the lack of marine biota (e.g., Paul, 1982; Paul and Peryt, 2000; Hauschke and Wilde, 2000; Becker, 2005; Knaust and Hauschke, 2005; Korte and Kozur, 2005). In addition, conchostracans from fine-grained siliciclastic sedimentary rocks were used to confirm a non-marine genesis of the Rogenstein. 3. Local data favoring a re-interpretation 3.1. Mode of carbonate production The scarcity of bioclasts indicates that biomineralisation was minor despite the presence of carbonatesecreting metazoans. From the quantitative point of view, calcified metazoans were insignificant for carbonate production, while ooids and microbialites were dominant. Paul and Peryt (2000) who revisited Kalkowsky's “stromatolites” provided valuable data on their formation. The growth started on ripples of oolitic grainstone, which had been already stabilized by cementation. Characteristic of the microbialites are sponge-fenestrate and fan-like microfabrics, which may reflect different microbe populations (Paul and Peryt, 2000). Sediment texture of oolites ranges from

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packstone to float/rudstone, locally with strong bimodality in ooid size. Oolite groundmass contains varying percentages of detrital quartz, micas and carbonate cement. Ooid types comprise normal ooids, regenerated ooid fragments, superficially incrusted ooid clasts and cerebroid ooids. The latter probably resulted from

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microbial activity because of their asymmetric layers (Figs. 3.3, 4.1–2). The cortex of ooids consists of concentric and radial-fibrous microfabrics with changes within one individual ooid. The proposed textural and compositional heterogeneities within individual ooids as well as within oolite beds suggest rapid changes of water energy and chemistry over short periods of time. The mode of carbonate production of the Rogensteine has to be re-evaluated in the light of the endPermian mass extinction and the Early Triassic recovery period. Generally, marine carbonate precipitation represents a continuum of processes with (quasi-)abiotic (spontaneous mineralization), (non-enzymatic) biotically-induced and (enzymatic) biotically-controlled precipitation as end members (Webb, 2001; Schlager, 2003). Gradational boundaries exist especially between biotically-induced and -controlled carbonate precipitation exist. Environmental perturbations may cause a change in carbonate production from biotically-controlled to biotically-induced or even abiotic carbonate production. This change is typical of the Early Triassic recovery period following PT mass extinctions and controls the deposition of so-called “anachronistic” sediments (e.g., Lehrmann et al., 1998, 2001) which are similar in appearance to Early Paleozoic or Neoproterozoic sediments. Interestingly, “anachronistic” Early Triassic carbonates from the Great Bank of Guizhou are similar, because of the lack of bioturbation and the presence of flat pebble conglomerates (Lehrmann et al., 1998, 2001). Early Triassic microbialites known from a variety of marine settings of the Tethys and Panthalassa (Fig. 1) are a convincing testimony of changed carbonate production during the aftermath of the PTB. Oolites and microbialites of the Rogenstein Member coincide with biotically-induced carbonate production. The information presented here sheds new light on the oolites and microbialites of the Lower Buntsandstein Group and makes a marine genesis very likely. 3.2. Calcified shells of metazoans

Fig. 3. Photomicrographs of a microbialite of the Rogenstein Member, Harlyberg, Lower Buntsandstein (The sample is from the upper part of the Harly section, see Paul and Peryt, 2000, Fig. 14). See Fig. 1 for location and Fig. 2 for chronostratigraphy. 3.1 Overview, showing bivalve bioclasts which have been trapped within the microbialite. Scale bar = 10 cm; 3.2 Close-up view of the bivalve bioclasts. 3.3 A cerebroid ooid becomes part of the microbialite. Scale bar = 0.5 cm.

Remains of vertebrates and invertebrates are rare in the Lower Buntsandstein Group, only conchostracans, notostracan triosids, xiphosurans, limulids and fish remains have been reported (Kozur, 1998; Hauschke and Wilde, 2000). No calcified shells of metazoans have been described or figured. However, within microbialites (Fig. 3.1–2) and oolites (Fig. 4.1, 3–5), shell debris of skeletal metazoans has been preserved under favorable conditions (e.g., rapid cementation). Bioclasts of shells have been trapped within microbialites, which resemble opportunistic bivalves despite micritization of the shell

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Fig. 4. Photomicrographs and polished slab of oolites of the Rogenstein Member, Harlyberg, Lower Buntsandstein (The sample is from the upper part of the Harly section, see Paul and Peryt, 2000, Fig. 14). See Fig. 1 for location and Fig. 2 for chronostratigraphy. 4.1 Polished slab with bimodal size of ooids. The large ooids are cerebroid ooids (see text for details). Note the skeletal fragment (arrow). Scale bars in centimeter. 4.2 Close-up view of a partly recrystallized cerebroid ooid. Scale = 1 cm. 4.3 Overview of a bimodal oolite containing bioclasts. The dark rectangles show the exact position of Figs. 4.4–5. Scale bar = 2 cm. 4.4 Ooid with a bivalve fragment as nucleus. Scale bar = 1.0 mm; 4.5 Groundmass with ostracods. Scale bar = 0.5 mm.

microstructure. In addition, shells of bivalves and/or brachiopods or ostracods may form nuclei of ooids. Also, ostracods may be even preserved in the siliciclastic-rich matrix of oolites. Bivalves and ostracods have been reported from marine and lacustrine environment since the Paleozoic, however, no published data of Early Triassic lacustrine bivalves and ostracods exist. During the aftermath of the Permian–Triassic mass extinction, opportunistic bivalves are a widespread phenomenon of marine environments. Considering this issue, a marine environment is much more likely than a playa lake.

3.3. Stable isotopes Stable carbon and oxygen isotopes have been measured from least altered ooid cortices and microbialite laminae (Fig. 5). With the exception of one data point, all δ18 O and δ13 C measurements are concentrated in a narrow field. Values of δ13 C vary between + 0.77 and − 1.44 and are within the lower field of marine δ13 C measurements (e.g., Baud et al., 1989; Veizer et al., 1999 (68% sample interval), Payne et al., 2004, Korte et al., 2005; Corsetti et al., 2005). Korte

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Fig. 5. Cross plot of δ18O and δ13C data of the Rogenstein Member (black dots) in comparison with a selection of published data (Baud et al., 1989; Veizer et al., 1999; Payne et al., 2004; Corsetti et al., 2005; Korte et al., 2005). See text for interpretation. Least altered samples have been selected on the basis of petrography.

and Kozur (2005) provided bulk rock data of the Lower Buntsandstein carbonates and recognized trends similar to marine sections. Their values of δ13 C vary between + 1 and − 2. However, they support the playa like hypothesis. The interpretation of δ18O data is ambiguous (Veizer et al., 1999) and not used to interpret primary signals. Comparison with published data shows that the δ18O values of the Rogenstein samples plot within the field of marine seawater of Veizer et al. (1999). Comparison with recently published data (Korte et al., 2005), however, indicate that diagenetic overprint of ooids and microbialites cannot be ruled out. 3.4. Sedimentary structures and trace fossils A large number of sedimentary structures has been described from the red beds of Lower Buntsandstein Group. Sedimentary structures of siliciclastic sediments comprise horizontal, cross, lenticular and wavy bedding and ripples; mud cracks and syneresis cracks are typical of clay- and siltstones. Sediment structures described from the oolites comprise oscillation ripples, cross bedding and flat pebble conglomerates (Paul and Peryt, 2000). Flat pebble conglomerates have been regarded as typical sediments of the aftermath following the Permian–Triassic mass extinction (Wignall and Twitchett, 1999; Pruss et al., 2005) and they thought to form in strom-dominated shelf environments in the western US (S. Pruss, pers. communication). During field work, sediment structures resembling herring-bone cross

stratification were discovered. They were observed within a thick, mixed carbonate–siliciclastic oolite at Harlyberg (Fig. 6.1–2). The bimodal flow direction of tidal currents which is indicated by the different orientation of the foreset laminae is favored as interpretation despite the fact that trough cross bedding cannot be excluded. The ichnofauna of the Lower Buntsandstein Group consists of a variety of genera, including Planolites, Skolithos, Fuersichnus, Phycodes, Diplichnites, Rusophycus, Cruziana, Diplopodichnus, Tambia and Gyrochorte. The interpretation of trace fossils is challenging, because some sedimentary structures easily might be misinterpreted as trace fossils (Knaust and Hauschke, 2004). No trace fossils were discovered within the oolites. Fine-grained siltstone yields trace fossils similar to the ichnogenus Planolites (alternatively Gyrochorte isp. has been suggested as ichnotaxon, A. Goetz, pers. communication). In cross section the epirelief is cylindrical and has no walls. The diameter of the tubes is 0.8–1.1 cm. The trace fossil is parallel to bedding and consists of slightly bent tubes which are simple and lack bifurcations or branches (Fig. 7.1). The tubes resemble with respect to size and morphology Planolites from the marine Myophoria beds of the Röt and Muschelkalk (Fig. 7.2; see Fig. 2 for Germanic Triassic stratigraphy). It is crucial that morphologically similar trace fossils of the Lower Buntsandstein Group and the Röt siltstones have a similar size and did not undergo a dramatic reduction of size (Lilliput effect), a phenomenon observed from Early Triassic trace fossils (Twitchett

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influence is questioned. More likely, the Rogenstein units represent marine carbonate deposited during shortlived marine transgressions, as they show the characteristic features of Early Triassic anachronistic carbonates described from many marine settings: – The oolites and microbialites are the product of abiotic and biotically-induced carbonate precipitation while biomineralisation is insignificant; Earliest Triassic reefs of the Tethys and Panthalassa are very similar. – The sometimes extraordinary size of the Rogenstein ooids resembles marine Neoproterozoic ooids. The term “anachronistic” has been used in the literature to describe the similarities in the fabric and composition of earliest Triassic and Early Palaeozoic/Neoproterozoic carbonates.

Fig. 6. Sediment structure regarded as herring-bone cross stratification (HBCS), Harlyberg, Lower Buntsandstein (The sample is from the upper part of the Harly section, see Paul and Peryt, 2000, Fig. 14). See Fig. 1 for location and Fig. 2 for chronostratigraphy. 6.1 Outcrop photograph, HBCS is part of the lower part of a massive oolite bed at Harlyberg. Scale = 10 cm. 6.2 Photomicrograph, HBCS is overlain by low-angle cross stratification. Scale = 1 cm.

and Barras, 2004; Pruss et al., 2004). Early Triassic terrestrial trace fossils have been described in the literature (Bromley and Asgaard, 1979; Gradzinski and Uchman, 1994). These ichnocoenoses, which contain Planolites-like trace fossils, are restricted to both marine and terrestrial siliciclastic sediments and have not been described from carbonates. 4. Regional and global perspectives — PTB mass extinction and earliest Triassic recovery overlooked? Considering (i) currently discussed Early Triassic recovery scenarios of marine benthic communities, (ii) global patterns of Early Triassic carbonate production, (iii) Permian–Triassic tectono-sedimentary evolution of northern Pangaea, (iv) new outcrop and microfacies data and, finally, (v) stable oxygen and carbon isotope data, the existing depositional playa lake-model has been tested. The current understanding of a lack of marine

Fig. 7. Photographs of trace fossils similar to Planolites isp., Lower Buntsandstein (the sample is from the upper part of the Harly section, see Paul and Peryt, 2000, Fig. 14) and Röt Formation. See Fig. 1 for location and Fig. 2 for chronostratigraphy. 7.1 Bedding plane with trace fossil resembling Planolites, Harlyberg. Note that two generations of trace fossils (arrows) overlap despite their scarcity. Scale bar = 2 cm; 7.2 Bedding plane with Planolites isp. from the marine Röt Formation. Note the increase in density and the variation in diameter. Scale bar in centimeters.

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– Newly found debris of thin shells resembles opportunistic bivalves flourishing in Early Triassic oceans. – Stable carbon isotopes of least altered Rogenstein ooids and stromatolites exhibit trends very similar to the composition of Triassic seawater. – The presence of flat pebble conglomerates and sediment structures similar to herring-bone cross stratification confirm marine conditions. – Trace fossils of fine-grained clastic sediments of the Rogenstein show striking similarities to marine Planolites of the Middle Triassic Muschelkalk (it is important to mention that Planolites is not necessarily an indicator of marine conditions).

Acknowledgments

This body of data supports the idea of a shallow marine environment in the area of the Altmark– Eichsfeld high and suggests that most of the Rogenstein carbonates are the product of short-lived marine transgressions. The absence of marine biota is not a useful criterion. In addition, spirorbids, gastropods and rare foraminifers found within microbialites and oolites have been interpreted as marine indicators in the eastern Germanic Triassic basin (western Poland: Peryt, 1974, 1975). The marine re-interpretation is backed by a global rise in sea level during the Late Permian–Early Triassic (Fig. 2) and Early Triassic transgressive successions in the realm of the Barents gateway, notably East Greenland (Stemmerik et al., 1992; Wignall and Twitchett, 1996; Twitchett et al., 2001), southern Barents shelf (Mork, 1998), see Figs. 1, 2. Unfortunately, unequivocal criteria of Early Triassic marine sediments are absent from the northern North Sea because of local erosion. The presence of reactivated graben structures (Fisher and Mudge, 1998), however, makes marine ingressions from the north very likely. In conclusion, the following model is proposed: Cool water transgressed during a global rise of Late Permian– Early Triassic sea level from the Barents shelf southward along reactivated extensional graben structures and flooded the Central European Permo-Triassic basin. There, the extremely hot and arid climate of the megacontinent Pangaea caused increased evaporation of seawater and subsequent supersaturation with respect to calcium carbonate. Insignificant biomineralisation and high water energy in the extremely shallow sea gives rise to rapid and discontinuous abiotic and biotically-induced carbonate precipitation. Benthic tropical carbonate production started with the next transgression during the Röt Formation, causing the sedimentation of marls and limestones during the Spathian (late Olenekian).

References

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This study was partly financed by the German Science Foundation (project We1804/8-1,2). I thank Michael Weiss (Freie Universität Berlin) for guidance in the field, thin sections and fruitful discussion. Michaela Bernecker (Universität Erlangen-Nürnberg) and Manfred Menning (GeoForschungsZentrum Potsdam) improved with their comments the manuscript. The help and enthusiasm of the editors of this volume is greatly acknowledged. Reviews of Tom Algeo, Carl Brett, Annette Götz and Sara Pruss improved the manuscript. Annette Götz provided additional literature.

Aigner, T., Bachmann, G.H., 1992. Sequence-stratigraphic framework of the German Triassic. Sedimentary Geology 80, 115–135. Bachmann, G.H., Kozur, H., 2004. The Germanic Triassic: correlation with the international chronostratigraphic scale, numerical ages and Milankovitch cyclicity. Hallesches Jahrbuch für Geowissenschaften B 26, 17–26. Baud, A., Margaritz, M., Holser, W., 1989. Permian–Triassic of the Tethys: carbon isotope studies. Geologische Rundschau 78, 649–677. Baud, A., Richoz, S., Marcoux, J., 2005. Calcimicrobial cap rocks from the basal Triassic units: western Taurus occurrences (SW Turkey). Comptes Rendus Palevol 4, 501–514. Becker, A., 2005. Facies and sedimentary cycles in the lower Volpriehausen Formation (Middle Buntsandstein, Triassic) in the clay pit Baalberge near Bernburg (south-eastern Subhercynian Basin, Saxony-Anhalt). Hallesches Jahrbuch für Geowissenschaften B, Beiheft 19, 107–118. Beutler, G., Schüler, F., 1987. Probleme und Ergebnisse der lithostratigrahischen Korrelation der Trias am Nordrand der Mitteleuropäischen Senke. Zeitschrift für Geologische Wissenschaften 15, 421–436. Bromley, R.G., Asgaard, U., 1979. Triassic freshwater ichnocoenoses from Calsberg Fjord, East Greenland. Palaeogeography, Palaeoclimatology, Palaeoecology 28, 39–80. Burne, R.V., Moore, L.S., 1987. Microbialites: organo-sedimentary deposits of benthic microbial communities. Palaios 2, 241–254. Corsetti, F.A., Baud, A., Marenco, P.J., Richoz, S., 2005. Summary of Early Triassic carbon isotope records. Comptes Rendus Palevol 4, 405. Erwin, D.H., Bowring, S.A., Jin, Y., 2002. End-Permian mass extinctions: a review. In: Koeberl, C., MacLeod, K.G. (Eds.), Catastrophic Events and Mass Extinctions: Impacts and Beyond. Geological Society of America Special Paper, vol. 256. Geological Society of America, Boulder, CO, pp. 363–383. Fisher, M.J., Mudge, D.C., 1998. Triassic. In: Glennie, K.W. (Ed.), Petroleum Geology of the North Sea. Blackwell, London, pp. 212–244. Flügel, E., 1982. Microfacies Analysis of Limestones. Springer Verlag, Berlin, pp. 1–633. Flügel, E., 2002. Triassic reef patterns. In: Kiessling, W., Flügel, E., Golonka, J. (Eds.), Phanerozoic Reef Patterns. Tulsa, Society of Economic Petroleum Geologists and Mineralogists Special Publication, vol. 72. SEPM (Society for Sedimentary Geology), Tulsa, OK, pp. 391–463. Flügel, E., 2004. Microfacies of Carbonate Rocks — Analysis, Interpretation, and Application. Springer Verlag, Berlin, pp. 1–976.

268

O. Weidlich / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 259–269

Gradzinski, R., Uchman, A., 1994. Trace fossils from interdune deposits — an example from the Lower Triassic aeolian Tumlin Sandstone, central Poland. Palaeogeography, Palaeoclimatology, Palaeoecology 108, 121–138. Haas, J., Hips, K., Pelikán, P., Zajzon, N., Götz, A.E., Tardi-Filácz, E., 2004. Facies analysis of marine Permian/Triassic boundary sections in Hungary. Acta Geologica Hungarica 47, 297–340. Hauschke, N., Wilde, V., 2000. Limulid remains from the Lower Buntsandstein (Bernburg Formation, Lower Triassic) of SaxonyAnhalt, Germany. Hallesches Jahrbuch für Geowissenschaften B 22, 87–90. Jin, Y.G., Zhang, J., Shang, Q., 1994. Two phases of the end-Permian mass extinction. In: Embry, A.F., Beauchamp, B., Glass, D.J. (Eds.), Pangea: Global Environments and Resources. Canadian Society of Petroleum Geologists Memoir, vol. 17, pp. 813–822. Kalkowsky, E., 1908. Oolith und Stromatolith im norddeutschen Buntsandstein. Zeitschrift der Deutschen Geologischen Gesellschaft 60, 68–125. Knaust, D., Hauschke, N., 2004. Trace fossils versus pseudofossils in Lower Triassic playa deposits, Germany. Palaeogeography, Palaeoclimatology, Palaeoecology 215, 87–97. Knaust, D., Hauschke, N., 2005. Living conditions in a Lower Triassic playa system of central Germany: evidence from ichnofauna and body fossils. Hallesches Jahrbuch für Geowissenschaften B, Beiheft 19, 85–106. Korte, C., Kozur, H., 2005. Carbon isotope trends in continental lake deposits of uppermost Permian to Lower Olenekian: Germanic Lower Buntsandstein (Calvörde and Bernburg Formations). Hallesches Jahrbuch für Geowissenschaften B, Beiheft 19, 87–94. Korte, C., Kozur, H., Veizer, J., 2005. δ13C and δ18O values of Triassic brachiopods and carbonate rocks as proxies for coeval biotically induced and palaeotemperature. Palaeogeography, Palaeoclimatology, Palaeoecology 226, 287–306. Kozur, H.W., 1998. Some aspects of the Permian Triassic Boundary (PTB) and of the possible causes for the crisis around this boundary. Palaeogeography, Palaeoclimatology, Palaeoecology 143, 227–272. Langbein, R., 1985. Fluvial-marine transitional depositional environment influencing the diagenesis in the Buntsandstein of Thuringia (Germanic Democratic Republic). In: Mader, D. (Ed.), Aspects of Fluvial Sedimentation in the Lower Triassic Buntsandstein of Europe. Lecture Notes of Earth Sciences, vol. 4. Springer Verlag, Berlin, pp. 561–590. Lehrmann, D.J., Wei, J., Enos, P., 1998. Controls on facies architecture of a large Triassic carbonate platform: the Great Bank of Guizhou, Nanpanjiang Basin, South China. Journal of Sedimentary Research 68, 311–326. Lehrmann, D.J., Wang, Y., Wei, J., Yu, Y.Y., Xiao, J., 2001. Lower Triassic peritidal cyclic limestone: an example of anachronistic carbonate facies from the Great Bank of Guizhou, Nanpanjiang Basin, Guizhou province, South China. Palaeogeography, Palaeoclimatology, Palaeoecology 173, 103–123. Menning, M., 1995. A numerical time scale for the Permian and Triassic periods: an integrative analysis. In: Scholle, P.A., Peryt, T.M., UlmerScholle, D. (Eds.), The Permian of Northern Pangea. Springer Verlag, pp. 77–97. Mork, A., 1998. Lower and Middle Triassic Rocks cored in the SouthWestern Barents sea. Hallesches Jahrbuch für Geowissenschaften. Reihe B: Geologie, Paläontologie, Mineralogie 5, 121–122. Paul, J., 1982. Der Untere Buntsandstein des Germanischen Beckens. Geologische Rundschau 71, 795–811.

Paul, J., Peryt, T.M., 2000. Kalkowsky's stromatolites revisited (Lower Triassic Buntsandstein, Harz Mountains, Germany). Palaeogeography, Palaeoclimatology, Palaeoecology 161, 435–458. Payne, J.L., Lehrmann, D.J., Wei, J., Orchard, M.J., Schrag, D.P., Knoll, A.H., 2004. Large perturbations of the carbon cycle during recovery from the end-Permian extinction. Science 305, 506–509. Peryt, T.M., 1974. Spirorbid algal stromatolites. Nature 249, 239–240. Peryt, T.M., 1975. Significance of stromatolites for the environmental interpretation of the Buntsandstein (Lower Triassic) Rocks. Geologische Rundschau 64, 143–158. Pruss, S.B., Bottjer, D.J., 2005. The reorganization of reef communities following the end-Permian mass extinction. Comptes Rendus Palevol 4, 485–505. Pruss, S., Fraiser, M., Bottjer, D.J., 2004. Proliferation of Early Triassic wrinkle structures: implications for environmental stress following the end-Permian mass extinction. Geology 32, 461–464. Pruss, S., Corsetti, F.A., Bottjer, D.J., 2005. The unusual sedimentary rock record of the Early Triassic: a case study from the southwestern United States. Palaeogeography, Palaeoclimatology, Palaeoecology 222, 33–52. Rhys, G.H., 1975. A proposed standard lithostratigraphic nomenclature for the Southern North Sea. In: Woodland, A.W. (Ed.), Petroleum and the Continental Shelf of North–West Europe. Geology, vol. I, pp. 151–164. Röhling, H.-G., 1991. A lithostratigraphic subdivision of the Lower Triassic in the northwest German lowlands and the German sector of the North Sea, based on gamma-ray and sonic logs. Geologisches Jahrbuch A 119, 3–24. Schlager, W., 2003. Benthic carbonate factories of the Phanerozoic. International Journal of Earth Sciences 92, 445–464. Stanley, S.M., Yang, X., 1994. A double mass extinction at the end of the Paleozoic era. Science 266, 1340–1344. Stemmerik, L., Christiansen, F. G., Piasecki, S., Jordt, B., Marcussen, C., Nohr-Hansen, H., 1992. Depositional history and petroleum geology of the Carboniferous to Cretaceous sediments in the northern part of East Greenland. In: T.O. Vorren, Bergsager, E., Dahl-Stamnes, O. A., Holter, E., Johansen, B., Lie, E., Lund, T. B. (Eds.), Arctic Geology and Petroleum Potential, NPF Special Publication. Norwegian Petroleum Society (NPF), Elsevier, Amsterdam, pp. 67–87. Szurlies, M., Menning, M., Nowaczyk, N.R., 1998. Magnetostratigraphy and cyclic stratigraphy of the Lower Buntsandstein (Northern Foreland of the Harz Mts., Central Germany). Hallesches Jahrbuch für Geowissenschaften. Reihe B: Geologie, Paläontologie, Mineralogie 5, 171–172. Twitchett, R.J., Barras, C.G., 2004. Trace fossils on the aftermath of mass extinction events. In: McIlroy, D. (Ed.), The Application of Ichnology to Palaeoenvironmental and Stratigraphic Analysis. Geological Society of London Spec. Publ., vol. 228. Geological Society of London, London, pp. 397–418. Twitchett, R.J., Looy, C.V., Morante, R., Visscher, H., Wignall, P.B., 2001. Rapid and synchronous collapse of marine and terrestrial ecosystems during the end-Permian biotic crisis. Geology 29, 351–354. Usdowski, H.-E., 1962. Die Entstehung der kalkoolithischen Fazies des norddeutschen Unteren Buntsandsteins. Beiträge zur Mineralogie und Petrographie 8, 141–180. Veizer, J., Ala, D., Azmy, K., Bruckschen, P., Buhl, D., Bruhn, F., Carden, G.A.F., Diener, A., Ebneth, S., Godderis, Y., Jasper, T., Korte, C., Pawellek, F., Podlaha, O.G., Strauss, H., 1999. 87Sr/86Sr, d13C and d18O evolution of Phanerozoic biotically induced. Chemical Geology 161, 59–88.

O. Weidlich / Palaeogeography, Palaeoclimatology, Palaeoecology 252 (2007) 259–269 Webb, G.E., 2001. Biologically induced carbonate precipitation in reefs through time. In: Stanley, G.D. (Ed.), The History and Sedimentology of Ancient Reef Systems. Kluwer Academic/ Plenum Publishers, New York, pp. 159–203. Weidlich, O., 2002. Middle and Late Permian reefs — distributional patterns and reservoir potential. In: Kiessling, W., Flügel, E., Golonka, J. (Eds.), Phanerozoic Reef Patterns. Society of Economic Petroleum Geologists and Mineralogists Special Publication, vol. 72, pp. 339–390. Weidlich, O., Bernecker, M., 2007. Differential severity of Permian– Triassic environmental changes on Tethyan shallow-water carbonate platforms. Global and Planetary Change 55, 209–235.

269

Weidlich, O., Kiessling, W., Flügel, E., 2003. The Permian–Triassic boundary interval as a model for forcing marine ecosystem collapse by long-term atmospheric oxygen drop. Geology 31, 961–964. Wignall, P.B., Twitchett, R.J., 1996. Oceanic anoxia and the end Permian mass extinction. Science 272, 1155–1158. Wignall, P.B., Twitchett, R.J., 1999. Unusual intraclastic limestones in Lower Triassic carbonates and their bearing on the aftermath of the end-Permian mass extinction. Sedimentology 46, 303–316. Ziegler, P.A., 1990. Geological atlas of western and central Europe. Shell Internationale Petroleum Maatschappij B.V., pp. 1–239.