A Dufrenoyia (Ammonoidea, Deshayesitidae) fauna from Germany: Evidence for D. furcata Zone deposits at the lower–upper Aptian boundary Jens Lehmann, Luc Bulot To cite this version: Jens Lehmann, Luc Bulot. A Dufrenoyia (Ammonoidea, Deshayesitidae) fauna from Germany: Evi- dence for D. furcata Zone deposits at the lower–upper Aptian boundary. Cretaceous Research, Else- vier, 2020, 116, pp.1-14. 10.1016/j.cretres.2020.104546. hal-03016302 HAL Id: hal-03016302 https://hal.archives-ouvertes.fr/hal-03016302 Submitted on 20 Nov 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. 1 A Dufrenoyia (Ammonoidea, Deshayesitidae) fauna from Germany: 2 Improving the correlation of the lower/upper Aptian boundary 3 4 Jens Lehmanna, Luc Georges Bulotb, c 5 With 9 figures, and 1 table 6 a Faculty of Geosciences, University of Bremen, Klagenfurter Strasse, 28357 7 Bremen, Germany. E-mail address: [email protected] 8 9 b. Aix-Marseille Université, CNRS, IRD, INRA, Collège de France, Cerege, Site 10 Saint-Charles, Case 67, 3, Place Victor Hugo, 13331 Marseille Cedex 3, France; 11 [email protected] 12 c University of Manchester, Department of Earth and Environmental Sciences, 13 North Africa Research Group, M13 9PL Manchester, UK; 14 [email protected] 15 16 ABSTRACT 17 Dufrenoyia is a relevant ammonite genus for discussing the lower/upper Aptian 18 boundary on a supraregional scale. We present the first comprehensive account 19 on the genus from Germany, recording the two index species Dufrenoyia furcata 20 and Dufrenoyia transitoria from the Ahaus area. This is based on a yet 21 undescribed historical collection by the German nineteenth century palaeontologist 22 Clemens Schlüter. Our stratigraphic conclusions improves the correlation of the 23 poorly-known highest lower Aptian in Germany, particularly with the well-known 24 successions in England and France. An alleged dimorphism in Dufrenoyia furcata 25 is discussed. 2 26 Keywords. Ammonites; lower Aptian/upper Albian; historical material; northern 27 Germany; Correlations 28 29 1. Introduction 30 Almost 60 years ago Raymond Casey recommended to place the lower/upper 31 Aptian boundary at the last occurrence of Dufrenoyia, at the top of the Tropaeum 32 bowerbanki Zone, based on the well-exposed Lower Greensand succession in 33 southern England (Casey, 1961). In fact, in the Boreal-Atlantic subrealm 34 Dufrenoyia furcata can be used as an alternative to the uppermost lower Aptian 35 zonal index Tropaeum bowerbanki (Lehmann, 2015). Although this has been 36 debated over the years (e.g. Kemper, 1971) it is now widely accepted (Reboulet et 37 al., 2011; 2018; 2014). Our current knowledge indicates that the ammonite genus 38 Dufrenoyia is a well-established marker for recognizing the lower/upper Aptian 39 boundary in the Boreal as well as in the Tethys (Raisossadat et al., 2008), 40 whereas the distribution of other important markers like Tropaeum and 41 Australiceras is comparatively restricted (Lehmann et al., 2015). 42 The Aptian ammonites of the genus Dufrenoyia from North Germany described 43 here are a part of a collection assembled in the nineteenth century. At that time, 44 many small clay pits where existing in that area from which a large number of 45 fossils were collected. Nowadays, there is hardly any outcrops left. This is the 46 main reason why only 15 papers illustrating ammonites from in situ occurrences 47 from the Aptian in North Germany were published in the past 50 years (Kemper, 48 1971a, 1973a; Kemper and Zimmerle, 1978; Gaida et al., 1978; Kemper, 1976, , 49 1982a, , 1995; Weber, 1996; Mutterlose, 1996; Owen in Mutterlose et al., 2003; 50 Hoffmann and Mutterlose, 2011; Vespermann, 2006; Mutterlose and Wiedenroth, 3 51 2009; Lehmann et al., 2012; Lehmann et al. , 2016). Among those, ammonite 52 systematic is only addressed in a couple of contributions (Owen in Mutterlose et 53 al., 2003; Hoffmann and Mutterlose, 2011) and thus each further account is 54 reasonable. 55 56 2. Geological setting 57 All specimens referred to here have been obtained from the vicinity of the city of 58 Ahaus in northern Germany. During the Early Cretaceous this area was at the 59 western rim of the Lower Saxony Basin (LSB in the following; Fig. 1). The LSB 60 contains a several thousand meters thick sedimentary succession, spanning a 61 time interval from the latest Jurassic to the Late Cretaceous. During Aptian times, 62 the LSB was subdivided by small swells and islands into subbasins, but generally 63 it constituted a large epicontinental sea extending to the Proto-North Sea area, 64 and connected to the (proto-)Atlantic Ocean in the southwest and northwest 65 (Kemper, 1979; Ziegler, 1990). In the distal areas predominately shales were 66 deposited, including the local expression of OAE 1a (e.g. Lehmann et al., 2012), 67 whereas towards the basin margin, silty to sandy dark-grey claystone prevailed 68 (Mutterlose and Böckel, 1998). The material described here comes from a 69 restricted southernmost extension of the LSB called the Alstätte Bay (e.g. 70 Lehmann et al., 2012; von Bargen and Lehmann, 2014; Schlak et al., 2016; 71 =Alstätte Embayment of Kemper, 1973b and Herngreen et al., 1994). It represents 72 one of several small bays at the southwestern margin of the LSB (Wolburg, 1954; 73 Schott et al., 1969). Sediments of the Alstätte Bay were poorly exposed for many 74 decades and thus very little research was done for many years. This changed 75 fairly recently and a whole series of papers on the temporary EGW section in 4 76 Ahaus-Alstätte that was exposed from 2009 to 2019 was published (Hoffmann and 77 Mutterlose, 2011; Lehmann et al., 2012; Bottini and Mutterlose, 2012; Mutterlose 78 and Bottini, 2012; von Bargen and Lehmann, 2014; von Bargen et al., 2016; 79 Mutterlose et al., 2014; Schlak et al., 2016; Lübke and Mutterlose, 2016; Lehmann 80 et al., 2016). However, the Ahaus area became a classic area for Aptian 81 palaeontology in Germany already in the 19th century due to a large number of 82 fossiliferous, but now abandon clay pits (e.g. Ewald, 1861; Hilbck, 1867; Ziegler, 83 1873). It is quite surprising that the material focussed on herein can add quite a 84 few new data to this classical and seemingly well-explored area of 85 palaeontological research in Central Europe. 86 Figure 1 somewhere near here 87 88 3. Material and conventions 89 3.1 Previously known material 90 Dufrenoyia is a very rarely reported ammonite from Early Cretaceous deposits of 91 Germany. Already von Strombeck (1858: 444) reported an ammonite, erroneously 92 referred to as Ammonites Deshayesi, that is a Dufrenoyia since the cross section 93 shows a distinct ventrolateral edge (“Die Kante zwischen Rücken und Seite pflegt 94 dagegen bis ins höchste Alter hervorzustechen“). 95 First finds attributed to a species that is now included in Dufrenoyia were 96 mentioned by Ewald (1861: 338; not 1860 as cited by von Koenen 1902) from the 97 Ahaus area (Barler Berg) as Ammonites furcatus. The same specimens were later 98 briefly described by von Koenen (1902: 202-204), referring to them as Hoplites 99 furcatus Sowerby. Besides 10 specimens from the Ahaus area von Koenen (1902) 100 mentions two doubtfully conspecific specimens from Weenzen, Duingen area, in 5 101 the Hildesheim district. More recently, Kemper (1964: 42) referred to one of these 102 specimens in the University of Münster collection as Dufrenoya dufrenoyi 103 (d'Orbigny, 1840) [sic] – apparently the only specimen that survived until then. 104 Kemper (1971: pl. 26, fig. 2) figured Dufrenoyia furcata and since his figure 105 captions refers to being a part of the University of Münster collection it can be 106 assumed that he refers to the same specimen and actually revised his earlier 107 identification. In fact, this historical specimen remained the only material depicted 108 in the literature from Germany and consequently Kemper (1976: pl. 24, fig. 1 and, 109 1995: pl. 5, fig. 2) refigured this important find. 110 111 3.2 New material and conventions 112 One of us (JL) was visiting the historical collection of Clemens August Schlüter 113 (Fig. 2A) as a part of the University of Bonn collection in 2016, recognizing that the 114 Aptian/Albian part of this collection was scientifically not explored yet. All of the 115 material is housed in the Goldfuß-Museum für Paläontologie, University of Bonn, 116 Germany. Its acronym is IGPB (for “Institut für Geowissenschaften, Paläontologie, 117 Bonn”). Since these specimens are of historical importance additional to their 118 scientific value, no preparation works have been done to reveal the suture lines. 119 However, IGPB KrU16-5 is a slightly worn internal mould that shows the suture. 120 We used the suture terminology of Wedekind (1916), as applied by Kullmann and 121 Wiedmann (1970) and modified by Korn et al. (2003): E - external lobe, A - 122 adventive lobe (that is L of traditional nomenclature), U - umbilical lobe (I - internal 123 lobe is not applicable for the present material). The E/A (that is E/L of traditional 124 nomenclature) is the saddle between E and A and A/U (L/U of traditional 125 nomenclature) and corresponds to the saddle between A and U.