Late Albian ammonite biostratigraphy of the Kirchrode I borehole, Hannover, Germany

Palaeogeography, Palaeoclimatology, Palaeoecology 174 (2001) 161±180

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Late Albian ammonite biostratigraphy of the Kirchrode I borehole, Hannover, Germany J. Wiedmann a,1, H.G. Owen a,b,* a

Institut und Museum fuÈr Geologie und PalaÈontologie, UniversitaÈt TuÈbingen, Sigwartstraûe 10, D-72076 TuÈbingen, Germany b Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK Received 6 May 1997; Revised 1 October 1997; Accepted for publication 17 September 2000

Abstract The ammonite biostratigraphy of the 245 m of sediments of Late Albian age traversed in the Kirchrode I (1/91) boring, situated in the south-eastern suburbs of the City of Hannover (Lower Saxony basin), is described. Correlation is made with the Actinoceramus (`Birostrina') bivalve-biostratigraphy in the part of the core of early Late Albian age and with the Inoceramus (Inoceramus) lissa-Aucellina gryphaeoides succession above. The earliest sediments of Late Albian age are of late Dipoloceras cristatum Subzone age with a good representation of the Hysteroceras orbignyi Subzone and an incomplete representation of the Hysteroceras varicosum Subzone. A notable feature of the succession is the presence of a considerable thickness (ca. 164 m) of sediments of Callihoplites auritus Subzone age. Sediments of Stoliczkaia dispar Zone age indicate the representation of the Mortoniceras (Mortoniceras) rostratum, Mortoniceras (Durnovarites) perin¯atum and Arrhaphoceras (Praeschloenbachia) briacensis Subzones. The ammonite fauna of the borehole is listed and the ammonite biostratigraphy of the clay sediments traversed is discussed. A brief comparison is made with other surface and borehole sections in northern Germany and elsewhere and the more cosmopolitan Tethyan elements of the fauna are indicated and discussed. q 2001 Elsevier Science B.V. All rights reserved. Keywords: Ammonite biostratigraphy; Albian; Lower Saxony basin; `Boreal' fauna; Faunal migration

1. Introduction Thick sediments of Albian age are present in northern Germany in the deep, west±east trending, Lower Saxony basin and have been exposed at outcrop or proved by borings (e.g. Kemper, 1973a,b; 1979). During the latest Jurassic and early Cretaceous, this basin formed a foredeep fringing the northern side * Corresponding author. Address: Department of Palaeontology, The Natural History Museum, Cromwell Road, London SW7 5BD, UK. Fax: 144-207-942-5546. E-mail address: [email protected] (H.G. Owen). 1 Now deceased.

of the emergent or shallow water Harz±MuÈnsterland± Rhenisch massifs. This foredeep was followed in turn northward by a series of highs occupying the northern German marginal area, but with marine connections to the north Sea region (Kemper, 1979). The massifs provided much of the terrigenous sediment redeposited during the Early Cretaceous in the Lower Saxony basin; subordinate amounts being derived from the northern highs until the late Middle Albian. During the Albian, arenaceous sediments, such as the upper part of the DoÈrenther, Rothenberg and Hils Sandstones and the Osning Sandstone, the Minimus Greensand and the Flammenmergel, fringe the massifs and inter®nger northward into the thick clays and marls of

0031-0182/01/$ - see front matter q 2001 Elsevier Science B.V. All rights reserved. PII: S 0031-018 2(01)00292-9

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the Gault Formation. Within the thick Gault Formation, the Early (`Lower'), Middle and Late (`Upper') Albian Substages are all represented, although discrete non-sequences occur particularly in the marginal areas of sedimentation and over the northern German highs (e.g. Kemper, 1973b, 1978, 1979; Owen, 1979). Much of our modern knowledge of the stratigraphy of the Albian sediments in this region of northern Germany is due largely to the work of Kemper (Kemper, 1973b, 1975, 1978, 1979, 1982a,b, 1984, 1989a,b; Bertram and Kemper, 1971; Elstner and Kemper, 1989; Frieg and Kemper, 1989; Frieg, Kemper and Owen, 1989; Kemper et al., 1975; Kemper and Zimmerle, 1978, 1982), the data being derived, essentially, from boreholes with additional information from mine shafts and surface quarries and cuttings. Of necessity, due to the paucity of ammonite occurrences throughout much of the succession, the biostratigraphical classi®cation and zonation of these sediments has depended largely upon microfaunas (Kemper, 1978, 1984, 1989a,b; Frieg and Kemper, 1989; Price, 1977a,b) and much work has been accomplished. The detailed ammonite zonal stratigraphy of the lower part of succession (Leymeriella tardefurcata Zone) has been established in the Hannover±Braunschweig area (Brinkmann, 1937; Kemper, 1975, 1982a,b; Kemper and Zimmerle, 1978, 1982; Owen, 1979, 1984a,b), but hitherto, there has been a paucity of ammonites in the sediments of the later Early, Middle and especially the Late Albian. One of us (Owen, 1979; Kemper, 1973b) demonstrated what was known of the ammonite faunas of the post-tardefurcata Zone sediments, bringing up to date earlier work (e.g. Althoff and Seitz, 1934; Ernst, 1922; Stolley, 1937; Spaeth, 1971, 1973). Subsequently, material from the top beds at outcrop in Misburg (Mittellandkanal) was described (Owen, 1989) together with sparse ammonite occurrences from adjacent areas in the Lower Saxony basin (Frieg et al., 1989; Keller et al., 1989). The drilling of two cored boreholes, Kirchrode I (1/ 91) and II (1/94), situated less than two kilometers apart in the south eastern suburbs of the City of Hannover, between the saltdomes of Benthe and Lehrte, has provided a cored succession through the Gault Formation of the Harz foredeep facies (BCCPGroup, 1994; Fenner et al., 1996; Fenner, 2001a).

Together, the two boreholes traversed a 370 m thick succession of clays, mudstones and marls extending in time from close to the Leymeriella tardefurcata Zone to the latest Albian Arrhaphoceras (Praeschloenbachia) briacensis Subzone (Stoliczkaia (S.) dispar Zone). Considering, the usually scattered distribution of ammonites on any given bedding plane and the relatively miniscule diameter of a borehole, the cores contain a remarkably representative ammonite fauna throughout. The ammonites consist of crushed impressions and thus, strictly speaking, many can only be referred to a species. Nonetheless, the specimens recovered by close cracking of the cores permit of a much more precise ammonite zonation of the north German Gault Formation than has been possible hitherto and the succession traversed by these boreholes is the most important yet seen in north Germany. Its nearly complete nature permits correlations to be made with scattered surface sections and borings in the Hannover±Braunschweig area, in particular and throughout the Lower Saxony basin as a whole. It provides, therefore, an ammonite biostratigraphical comparison with the previously developed micropalaeontological zonations of the north German Albian sediments, supported in part by the stratigraphical range of age-signi®cant bivalves (TroÈger in Prokoph, 1994; TroÈger in Fenner et al., 1996; Fenner, 2001a,b). Moreover, it also permits a classical macrofaunal analysis to be made for comparison with the international Albian microfaunal and micro¯oral zonations used in the dating of ocean borehole successions. It is important to note that this international standard microfaunal and micro¯oral zonation of the Albian in the Tethyan, Para-Tethyan region, does not possess a good comparative ammonite control. The present study forms part of the German research programme on biogenic sedimentation under the Boreal Cretaceous Cycles Project (BCCP), itself a part of the international ALBICORE project. In this paper, we describe the ammonite succession of the Kirchrode I boring which proved 245 m of mudstones and marls of Late Albian age, extending from the Dipoloceras cristatum Subzone to the latest Albian Arrhaphoceras (Praeschloenbachia) briacensis Subzone. A second paper will describe the ammonite succession of the sediments of Early, Middle and earlier-Late Albian age traversed by the Kirchrode II (1/94) borehole (Owen, in prep.). The study indicates

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Table 1 Ammonite zonal and subzonal scheme for the Late Albian±European province Late Albian zone

Subzone

Stoliczkaia (Stoliczkaia) dispar

Arrhaphoceras (Praeschloenbachia) briacensi Mortoniceras (Durnovarites) perin¯atum Mortoniceras (Mortoniceras) rostratum

Mortoniceras (Mortoniceras) in¯atum

Callihoplites auritus (early part & later interval with Mortoniceras (Cantabrigites) minor) Hysteroceras varicosum Hysteroceras orbignyi Diploceras cristatum later part of the Subzone only

that there are signi®cant differences in the previous correlation of certain Albian microfaunal zones with the ammonite/bivalve biostratigraphy. The ammonite zonal and subzonal scheme is given in Table 1 and discussed below. The study of the ammonite fauna of the Kirchrode I borehole was largely undertaken by the late Professor Jost Wiedmann with collaboration from H.G. Owen until the former's untimely death in 1993. Jost Wiedmann's extensive work in the Tethyan realm was particularly germane to the ALBICORE project (Herm and TroÈger, 1996). 2. The Gault Formation in the Hannover region The outcrop of the Gault Formation in the Hannover region (Lower Saxony) is strongly affected by faulting associated with salt-dome kinetics and much of the succession is cut-out at surface. Previous borings have proved part of the succession and these have been zoned micropalaeontologically (e.g. Price, 1977a,b; Frieg and Kemper, 1989). Sediments of very late Albian age containing an ammonite fauna had been proved in a section along the Mittellandkanal at Misburg (Owen, 1989). More recent exposures in this area have proved even later sediments of Albian age with ammonites indicating the later part of the Arrhaphoceras (Praeschloenbachia) briacensis Subzone. The Late Albian succession of the Kirchrode I boring extends our knowledge of the ammonite zonal stratigraphy substantially. The uppermost clays and marlstones of the borehole succession are situated not far beneath basal Cenomanian sediments. Ammonites of the earlier part of the Arrhaphoceras

(Praeschloenbachia) briacensis Subzone appear in the core at a depth of 15.28 m and correspond to the faunule described from Misburg (Owen, 1989). The Kirchrode I boring terminates, downward, at 245 m depth in marls of late Dipoloceras cristatum Subzone age. The most notable feature of the succession is the approximately 164 m thickness of sediments of Callihoplites auritus Subzone age. The lithological succession in this region has been called Gault in the older literature, but this term also included clays of Aptian age (Kemper, 1973b). In more recent years, the Gault as a formation name in the Lower Saxony basin, was restricted to the sediments of the Middle Albian and the Late Albian with the exception of the sediments of the Stoliczkaia (S.) dispar Zone grouped as `Vraconne' (Kemper, 1978, p.160, tabelle 1). This use of the term Gault in the formational sense thus coincided with that employed in England (Price, 1879). The subdivisions `Unter Alb', `Mittel Alb' and `Oberes Alb' used by Kemper (e.g., 1979 and later), although regarded by him as Substages, are used in a lithostratigraphical sense for the clays, mudstones and marls of the Gault Formation of the basinal area. These names are chronostratigraphic in concept and to accord with current lithostratigraphic nomenclatorial practise, Member names are required. The Upper Albian sediments of the Kirchrode borings correspond closely to the clays, mudstones and marls of the English Upper Gault (e.g. Owen, 1976; 1996b). Kemper (1978, 1979) originally included Late Albian, Stoliczkaia (S.) dispar Zone, sediments in the Bemeroder Beds. Subsequently, he gave detailed reasons for considering that the lower part of this member was wholly of early Upper

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Cretaceous age (Kemper, 1984). The uppermost beds in the Kirchrode I borehole are, lithologically, somewhat reminiscent of the Bemeroder facies, albeit with a latest Albian microfauna and micro¯ora (Weiû, 1997; Tyszka and Thies, 2001; Prauss, 2001). It is clear that a new Member name is required for the marls of the `Oberes Alb' which characterise the Late Albian succession in the deeper-water area of the Lower Saxony basin. These Late Albian marls traversed in the Kirchrode I borehole, with possibly slightly higher sediments in the Mittellandkanal sections at Misburg, are grouped here as the Kirchrode Marls Member. 2.1. Kirchrode Marls Member Proposed herein for the light-gray to olive-gray marls, olive-gray to dark-gray marly clays with marlstone beds at the top of the succession, forming the upper part of the Gault Formation in the central axial area of the Lower Saxony basin of northwest Germany. The stratotype is the succession traversed in the Kirchrode I borehole, the detailed lithological succession of which has been described by Prokoph (1994 from the original logs made by British Plaster Board Ltd) and Fenner (2001b). The Member is wholly of Late Albian age and intervenes between the Concentricus Beds of Kemper (e.g. 1978) of Middle Albian age and the Cenomanian Bemeroder Beds (Kemper, 1984). 3. The ammonite zonation of the Late Albian In this section of the paper, a more general account of the ammonite zonal scheme of the Late Albian of the European faunal province (Table 1) is given, while its more precise application to the Kirchrode I borehole succession and to other sections in northwest Germany, is given later (Sections 5 and 6). A thorough review of the development of the zonal scheme and the variations to it, which have been proposed, has been given by Mikhailova and Saveliev (in Bogdanova et al., 1989). The scheme in Table 1 has developed, essentially, from the work of Spath (1923a±43, 1923b, 1926) on the Ammonoidea of the Gault and Upper Greensand Formations of England and of Breistroffer (1936, 1940, 1947, 1965) on the Albian of France. Spath's ®nal scheme (1923a±1943, 668, 671±3) has been modi®ed by Scholz (1973), Owen (1976) and Gale et al. (1996) to produce that given

in Table 1. Variations to this scheme have been proposed by a number of authors re¯ecting either their national successions (e.g. Mikhailova and Saveliev in Bogdanova et al., 1989; Scholz, 1979a,b) or perceived phylogenies (e.g. Amedro, 1981, 1992). Throughout the Middle and Late Albian Substages, the European province was characterised by the ammonite genera belonging to the Family Hoplitidae. These genera include Hoplites, Euhoplites, Discohoplites, Hyphoplites, Anahoplites, Dimorphoplites, Daghestanites, Epihoplites, Semenovites, Callihoplites, Arraphoceras and Pleurohoplites, which are restricted to the European shelf seas and do not occur outside of it. Thus, the name `hoplitid faunal province' was coined by one of us (Owen, 1971) for this region. During the Middle Albian, there were relatively few incursions of ammonites from the Tethyan Province, but the more notable short-lived occurrences, such as Lyelliceras lyelli in the earliest Middle Albian and Dipoloceroides subdelaruei in the later Middle Albian, are marked within the subzonal scheme (Owen, 1971). In the earliest Late Albian, however, there commenced a more general incursion of Tethyan Province genera and these tended to co-exist with the endemic hoplitid ammonites. These Tethyan-derived genera include, in the earliest Subzone of the Late Albian, Dipoloceras of the cristatum group, early Hysteroceras (including transitions from the Middle Albian species of Brancoceras) and very rare Oxytropidoceras (Spath, 1923a±43; Owen, 1971). The arrival of the more cosmopolitan elements of the ammonite fauna in the D. cristatum Subzone coincided with the rapid morphological change in the inoceramid bivalve Actinoceramus (formerly Birostrina see Crampton, 1996) from the concentrically ornamented Actinoceramus concentricus (Parkinson), characteristic of the Middle Albian, to the radially ribbed form Actinoceramus sulcatus (Parkinson), characteristic of the D. cristatum and H. orbignyi Subzones. This morphological change from Actinoceramus concentricus to Actinoceramus sulcatus is geographically very widespread in occurrence and the intercontinental distribution of A. sulcatus makes it of value as a zonal fossil. The early Late Albian interval in which A. sulcatus occurs is widely represented by sediments within the various boreholes and mine shafts in north Germany (e.g. Kemper, 1984).

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The Subzones of Hysteroceras orbignyi and Hysteroceras varicosum, like that of D. cristatum, are capable of geographically very widespread recognition outside of the European province. Within them one sees the appearance of Mortoniceras (with subgenera Mortoniceras and Deiradoceras) and later, of Prohysteroceras. The inoceramid bivalve Actinoceramus sulcatus reverts back to the concentricus form at the end of the H. orbignyi Subzone and survives in that form until the end of the H. varicosum Subzone (Owen, 1996a,b). In the opinion of one of us (HGO), Crampton (1996) has misinterpreted the nature of this morphological change in the single species Actinoceramus concentricus. Its distribution through time, the morphological changes it undergoes in the earliest D. cristatum Subzone and at the end of the H. orbignyi Subzone, indicated in our paper, is based on observations made in continuous sediment successions (e.g. Owen, 1971; 1996a,b). The Subzone of Callihoplites auritus, when ®rst introduced (Spath, 1923a±43), re¯ected a time interval in which the hoplitid ammonites became dominant again in the European Province. However, newer sections in East Anglia in the United Kingdom (Gallois and Morter, 1982; Woods et al., 1995) show that the Subzone can be divided into an earlier period, in which Callihoplites tended to dominate and a later part in which the more Tethyan elements become common, co-existing alongside the endemic hoplitids. One sees the appearance of Mortoniceras (Cantabrigites), such as M. (C.) minor Spath, in this later part of the C. auritus Subzone, but it would be premature to recognise two distinct Subzones at present. Apart from changes in the ammonite faunas, there is a marked change in the bivalve fauna in England with Inoceramus (Inoceramus) lissa Seeley characterising the lower part of the Subzone, replaced by Aucellina gryphaeoides in the upper part of the Subzone (Gallois and Morter, 1982; Morter and Wood, 1983). This division into early and late intervals in the C. auritus Subzone is apparent also in the succession of the Kirchrode I boring together with the change in the bivalve fauna (TroÈger in Fenner et al., 1996; and Table 2 herein). It should be noted that the typical Mortoniceras (Mortoniceras) in¯atum (J. Sowerby) is an ammonite of C. auritus Subzone age. Although the D. cristatum Subzone is included in the M. (M.) in¯atum Zone, Mortoniceras is not present in that Subzone. The early form of M. (M.)

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in¯atum appears in the H. varicosum Subzone and a late form is present in the Mortoniceras (M.) rostratum Subzone of the Stoliczkaia (S.) dispar Zone. A signi®cant change in the ammonite fauna occurs at the end of the auritus Subzone with the appearance of Mortoniceras (Mortoniceras) of the rostratum group and Stoliczkaia (Stoliczkaia), marking the base of the S. (S.) dispar Zone. Three Subzones can be recognised in Europe, the equivalents of which are capable of widespread recognition within the Tethyan belt also (e.g. Cooper and Kennedy, 1979). The M. (M.) rostratum Subzone, while containing the hoplitids, Callihoplites, Lepthoplites and Discohoplites, characteristic of the European Province, possesses a much more cosmopolitan fauna than that of the C. auritus Subzone, with Puzosia additionally forming a common element (Owen, 1976). The Subzone is represented widely in Europe by relatively uncondensed sediments. However, the succeeding Subzone of Mortoniceras (Durnovarites) perin¯atum and, if represented at all, the Late Albian terminal Subzone of Arrhaphoceras (Preschloenbachia) briacensis (Scholz, 1973) are often condensed into phosphatic pebble beds. The ammonite fauna of the latest S. (S.) dispar Zone belongs to a Subzone which Owen (1989) recognised was present in southern England and elsewhere in Europe, but was not suf®ciently delimited or its fauna known, for it to be formerly named. Recent work carried out on the thick late Albian to early Cenomanian succession at Mont Risou near Rosans (DroÃme, SE France) by Gale et al. (1996), provides a much more precise stratigraphic framework for the middle and late parts of the S. (S.) dispar Zone. They employ the subzonal index name Arrhaphoceras (Praeschloenbachia) briacensis of Scholz (1973) for the latest S. (S.) dispar Zone. This is now used here, but with reservation, because the index species A. (P.) briacensis is of limited range, occurring towards the end of this assemblage Subzone. With rare exceptions, it is only in the areas of the deeper basins in Europe, where sediments have escaped early Early Cenomanian erosion, that uncondensed sediments of middle and late S. (S.) dispar Zone age are known. It is apparent that a similar succession of sediments of M. (D.) perin¯atum and A. (P.) briacensis Subzones age to that described by Gale et al. (1996) in the Vocontian basin, is present in the Hannover district of the Lower Saxony basin.

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Table 2 Ammonite occurrences, and the range of age-signi®cant bivalves derived from TroÈger (in Prokoph 1994; BCCP Group 1994), in the Late Albian sediments of the Kirchrode I borehole

4. The ammonite fauna and zonation of the Late Albian, Kirchrode marl member, of the Kirchrode I borehole The succession of ammonite occurrences listed below is arranged in descending order with depths recorded. They are further grouped within the established ammonite zones and subzones recognised for the European ammonite faunal province (Table 1). Most of the ammonites are crushed ¯at and strictly, therefore, can only be referred to a given species. However, a number of these (Plates 1±5) are as well preserved as those illustrated previously by one of us (Owen, 1989) from the highest Gault at Misburg, Hannover. The age-signi®cant bivalves associated

with the ammonites in the core samples are indicated between brackets in the lists below. The distribution of age-signi®cant ammonites and bivalves is shown graphically in Table 2 and representative specimens of the ammonites recovered from the cores are ®gured in Plates 1±5. 4.1. Ammonite occurrences Stoliczkaia dispar Zone, Arraphoceras (Praeschloenbachia) briacensis Subzone Depth (m) Identi®cation 15.28 Anahoplites (Lepthoplites) cantabrigiensis Spath 15.75 Anahoplites (Lepthoplites) proximus Spath

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21.10

Scaphites (Scaphites) cf. simplex Jukes± Browne

Stoliczkaia dispar Zone, Mortoniceras (Durnovarites) perin¯atum Subzone 28.92 30.72 32.52 33.70 35.60 36.41 36.87

Inoceramus sp. Mortoniceras (Cantabrigites) sp. Mortoniceras (Cantabrigites) subsimplex Spath Callihoplites cf. pulcher Spath Mortoniceras (Cantabrigites) cf. subsimplex Spath Mortoniceras (Durnovarites) sp. Mortoniceras (Cantabrigites) sp.

Stoliczkaia dispar Zone, Mortoniceras (Mortoniceras) rostratum Subzone 36.90 38.50 39.13 40.15 48.74 49.87 50.20 51.00 55.38 59.66 61.60 61.52 63.25

Mortoniceras (Mortoniceras) sp. juv. Scaphites (Scaphites) sp. Mortoniceras (Cantabrigites) cantabrigiense Spath Lechites gaudini (Pictet and Campiche) Mortoniceras (Mortoniceras) sp. juv. Lechites gaudini (Pictet and Campiche) Lechites cf. gaudini (Pictet and Campiche) Idiohamites aff. dorsetensis Spath Idiohamites cf. elegantulus Spath Lechites sp. Stoliczkaia (Stoliczkaia) sp. Idiohamites tuberculatus (J. Sowerby) late form (Aucellina sp. M. rostratum Subzone form) Callihoplites leptus (Seeley) (Aucellina sp. M. rostratum Subzone form)

Mortoniceras in¯atum Zone, Callihoplites auritus Subzone later part of the Subzone 64.25 68.66 70.28 71.08 72.16 75.03 75.27 80.59

Prohysteroceras (Neoharpoceras) coptense Spath Callihoplites robustus Spath Idiohamites cf. subspiniger Spath Idiohamites cf. turgidis (J. Sowerby) (Aucellina sp. late C. auritus Subzone form) Callihoplites cf. glossonotus (Seeley) Spath (Aucellina sp. late C. auritus Subzone form) Lechites moreti Breistroffer (Aucellina sp.) Lechites sp. Lechites sp.

81.80 82.60 90.32 92.08 94.19 96.16 96.67 100.75 103.19 103.62 104.20 104.78 105.02 105.15 106.97 108.98 109.38 111.64 111.88 112.58 114.10 115.06 117.70 120.28 121.20 122.50 126.15 126.22

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Lechites cf. gaudini (Pictet and Campiche) (Aucellina sp. late C. auritus Subzone form) Hamites parkinsoni (Fleming) Lechites cf. moreti Breistroffer juvenile heteromorph cf. Lechites juvenile heteromorph cf. Lechites Idiohamites sp. juvenile heteromorph cf. Lechites Idiohamites sp. Idiohamites cf. favrinus (Pictet) Idiohamites cf. desorianus (Pictet) Idiohamites favrinus group (Aucellina sp. late C. auritus Subzone form) Idiohamites cf. turgidis (J. Sowerby) Idiohamites sp. nov. cf. Puzosia sp. Scaphites (Scaphites) simplex Jukes Browne cf. Puzosia sp. juv. Idiohamites sp. Idiohamites cf. desorianus (Pictet) Callihoplites sp. Hamites cf. virgulatus (Pictet and Campiche) Idiohamites cf. turgidus (J. Sowerby) Idiohamites cf. turgidus (J. Sowerby) cf. Idiohamites sp. Prohysteroceras (Goodhallites) sp juv. Euhoplites cf. vulgaris Spath Callihoplites variabilis Spath Anahoplites (Lepthoplites) cf. ornatus Spath Hamites charpentieri (Pictet)

earlier part of the Subzone 129.24 Callihoplites cf. variabilis Spath 130.40 Hysteroceras binum group Mortoniceras (Mortoniceras) commune Spath Prohysteroceras (Goodhallites) sp. juv. 131.47 Callihoplites cf. strigosus Spath juv. 131.99 Hamites sp. 134.90 Callihoplites sp. juv. 136.82 Anahoplites (Lepthoplites) pseudoplanus Spath 137.20 Idiohamites sp. indet. 149.55 juv. cf. Idiohamites 156.53(63) Callihoplites cf. strigosus Spath juv. 161.10 Puzosia cf. communis Spath 182.50 Callihoplites cf. leptus (Seeley) 204.08 Euhoplites vulgaris Spath 206.10 Euhoplites cf. alphalautus Spath 206.54 Euhoplites sp. vulgaris±alphalautus group

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210.25 211.10 212.65 215.50 217.70 221.60 225.50 226.25 228.85

Euhoplites sp. Callihoplites strigosus Spath Callihoplites formosus Spath Euhoplites alphalautus Spath Callihoplites auritus (J. Sowerby) Callihoplites strigosus Spath Callihoplites auritus (J. Sowerby) Callihoplites cf. variabilis Spath Callihoplites sp.

Mortoniceras in¯atum Zone, Hysteroceras varicosum Subzone 229.03 (Actinoceramus concentricus (Parkinson), H. varicosum Subzone form) 229.36 Prohysteroceras (Goodhallites) cf. falcifer Spath 230.23 Euhoplites sp. Mortoniceras in¯atum Zone, Hysteroceras orbignyi Subzone 231.40 Euhoplites trapezoidalis Spath (Actinoceramus sulcatus (Parkinson)) 232.07 Hysteroceras cf. orbignyi (Spath) (Actinoceramus sulcatus (Parkinson)) 232.10 Hysteroceras sp. (Actinoceramus sulcatus (Parkinson)) 232.36 Hysteroceras subbinum Spath (Actinoceramus sulcatus (Parkinson)) 232.45 Euhoplites serotinus±trapezoidalis group (Actinoceramus sulcatus (Parkinson)) 232.55 Epihoplites sp. ind.

232.55±60 Euhoplites cf. boloniensis Spath juv. Hysteroceras sp. juv. (Actinoceramus sulcatus (Parkinson)) 232.61 Euhoplites sublautus monocantha Spath (Actinoceramus sulcatus (Parkinson)) 232.79 (Actinoceramus sulcatus (Parkinson)) 233.07 Hysteroceras sp. 233.15 Euhoplites cf. trapezoidalis Spath (Actinoceramus sulcatus (Parkinson)) 234.36 Euhoplites sublautus Spath 235.29 Hysteroceras cf. orbignyi (Spath) 236.12 (Actinoceramus sulcatus (Parkinson)) 236.63 Hamites cf. intermedius (J. Sowerby) (Actinoceramus sulcatus (Parkinson)) 236.73 (Actinoceramus sulcatus (Parkinson)) (Inoceramus (Inoceramus) sp.) 238.25 Hamites cf. intermedius (J. Sowerby) (Neohibolites sp.) 239.13 Euhoplites cf. armatus Spath (Actinoceramus sulcatus (Parkinson)) 240.31 Euhoplites cf. inornatus Spath 240.85 Euhoplites inornatus Spath Mortoniceras in¯atum Zone, Dipoloceras cristatum Subzone 241.75 Anahoplites (Anahoplites) sp. juv. planus group 241.00±245.00 m (Actinoceramus sulcatus (Parkinson)). It should be noted that the core below 242.30 m is slickensided (Fenner, 2001b), the hole terminating at 245 m depth.

PLATE I. Late Albian Stoliczkaia (Stoliczkaia) dispar Zone ammonites from the Kirchrode I (1/91) boring. (A) Anahoplites (Lepthoplites) cantabrigiensis Spath (Kirchrode I, 15.28 m) A. (P.) briacensis Subzone X1 (P.C. 2). (B) Anahoplites (Lepthoplites) proximus Spath (Kirchrode I, 15.75 m) A. (P.) briacensis Subzone X1.5 (J.W. 1). (C) Mortoniceras (Cantabrigites) cantabrigiense Spath (Kirchrode I, 39.13 m) M. (M.) rostratum Subzone X1 (P.C.). (D) Mortoniceras (Durnovarites) sp. (Kirchrode I, 36.41 m) M. (D.) perin¯atum Subzone X2 (J.W.). (E) Callihoplites leptus (Seeley) (Kirchrode I, 63.25 m) M. (M.) rostratum Subzone X1.25 (J.W.). (F) Mortoniceras (Cantabrigites) cf. subsimplex Spath (Kirchrode I, 35.60 m) M. (D.) perin¯atum Subzone X1 (P.C.). (G) Lechites gaudini (Pictet and Campiche) (Kirchrode I, 48.74 m) M. (M.) rostratum Subzone X1 (P.C.). (H) Stolickzkaia (Stoliczkaia) sp. (Kirchrode I, 59.66 m) M. (M.) rostratum Subzone X1 (P.C.). (I) Idiohamites sp. nov. aff. dorsetensis Spath (Kirchrode I, 50.20 m) M. (M.) rostratum Subzone X1 part and counterpart (P.C.). (J) Idiohamites tuberculatus (J. Sowerby) late form (Kirchrode I, 61.60 m) M. (M.) rostratum Subzone X1.15 (J.W.).

2

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In Figs. 1±5 (P.C.) indicates photographs by Phil Crabbe, (J.W.) indicates photographs by Jost Wiedmann.

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PLATE II. Late Albian ammonites from the Mortoniceras (Durnovarites) perin¯atum Subzone and the Callihoplites auritus Subzone of the Kirchrode I (1/91) boring. (A) Mortoniceras (Cantabrigites) subsimplex Spath (Kirchrode I, 32.52 m) M. (D.) perin¯atum Subzone X1 (P.C.). (B) Idiohamites sp. nov. (Kirchrode I, 105.15 m) late C. auritus Subzone X1 (P.C.). (C) Anahoplites (Lepthoplites) pseudoplanus Spath (Kirchrode I, 136.82 m) early C. auritus Subzone X1 (P.C.). (D) Callihoplites cf. variabilis Spath (Kirchrode I, 129.24 m) early C. auritus Subzone X1 (P.C.).

5. Biostratigraphical classi®cation and correlations 5.1. Stoliczkaia (Stoliczkaia) dispar zone 5.1.1. The Arrhaphoceras (Praeschloenbachia) briacensis subzone The lithology of the core around 2.60 m depth in

the Kirchrode I boring, suggests classi®cation with the lowest part of the Bemerode Beds, which Kemper (1984) regards as basal Cenomanian in age (CenomanMergel). However, the microfauna of the Kirchrode core succession above 15.28 m, the depth of the ®rst ammonite occurrence, indicates a latest Albian age for these sediments (Weiû, 1997). New sections

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along the Mittellandkanal at Misburg, which show a similar lithology to that of the uppermost part of the Kirchrode I core, have yielded an Albian ammonite fauna of Arrhaphoceras (Praeschloenbachia) briacensis Subzone age including A. (P.) briacensis Scholz. This new fauna is later in age than the ammonite fauna described by one of us from Section 4.1 at Misburg (Owen, 1989), who originally placed their position in the early part of the Mortoniceras (Durnovarites) perin¯atum Subzone. The earlier section at Misburg (Owen, 1989) can be correlated with the Kirchrode I core between 15.28 and 21.10 m depths, but strictly speaking, the ammonite subzonal age of the top 15 m of sediments in Kirchrode I is uncertain. Gale et al. (1996) refer the earlier Misburg faunule (which is not in a Flammenmergel facies as they state) to the A. (P.) briacensis Subzone, but the absence of Hyphoplites sp. in this faunule and their presence both at Mont Risou and at Uplyme, Dorset, suggests an early briacensis Subzone age. The specimen ®gured by Owen (1989, 375, 378, Taf 1 ®g. 12a,b) from Misburg as cf. Worthoceras is identical to Worthoceras pygmaeum Bujtor (1991) of late S. (S.) dispar Zone age in Hungary and at Mont Risou (Gale et al., 1996, ®g. 30 d±n). It is particularly useful that the relative position of the earlier Misburg faunule has now been established in the Kirchrode I core and it is clearly later than the M. (D.) perin¯atum Subzone date previously assigned to it. Apart from the Mittellandkanal sections at Misburg of early A. (P.) briacensis Subzone age, mentioned above, the only other sediments of this age in the Hannover area were probably traversed by test borings for the Hannover U-Bahn (numbers 250± 254) which correspond to the broad foraminiferal Zone eight of Price (1977a). Elsewhere in northern Germany in the area ¯anking the Harz, MuÈnsterland and Rhenisch massifs, sediments of the A. (P.) briacensis Subzone have not been proved in these more marginal sediments of Flammenmergel facies which have yielded ammonites. In all these cases, sediments of M. (D.) perin¯atum Subzone age are overlain by Cenomanian sediments (e.g. Owen, 1979; Frieg et al., 1989). This underlines the effect of the early Cenomanian phases of erosion on sediment successions. The latest Albian is preserved in an uncondensed succession, normally, only within relatively deep basinal areas; the shallower regions being subject to

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current scour with pebble-fauna accumulations or a complete non-sequence. 5.1.2. The Mortoniceras (Durnovarites) perin¯atum and Mortoniceras (Mortoniceras) rostratum subzones Sediments of M. (D.) perin¯atum Subzone age are present in the Kirchrode I core from 30.72 to 36.87 m depth. From 36.90 to 63.25 m, the marls contain an ammonite and Aucellina fauna indicating a Mortoniceras (M.) rostratum Subzone age. Ammonites indicating both of these Subzones are present in the upper part of the marginal Flammenmergel in the Harz and MuÈnsterland (e.g. Owen, 1979, 1989; Frieg et al., 1989). 5.2. Mortoniceras (Mortoniceras) in¯atum zone 5.2.1. Callihoplites auritus subzone Hitherto, no ammonites of Callihoplites auritus Subzone age have been recorded with absolute certainty from the basin facies in northern Germany, although there is certainly room for sediments of this age in the succession of marls. There is better evidence of the presence of this Subzone in the marginal Flammenmergel facies (Owen, 1979; Frieg et al., 1989). The interval in the `Ober-Alb' of the Lower Saxony basin which contains Aucellina (e.g. Kemper, 1984; Frieg and Kemper, 1989) could be of late C. auritus Subzone and S. (S.) dispar Zone age, but no ammonite dating has been possible hitherto. This is particularly the case in the Konrad 101 boring (Frieg and Kemper, 1989). In the Kirchrode I borehole, sediments of C. auritus Subzone age with a good ammonite control, occur between 64.25 and 228.85 m depth and are present also in the Kirchrode II boring (Owen, in preparation). This is an exceptional thickness (over 164 m) and the suspicion that faulting has produced a repetition of strata must be addressed. However, in East Anglia in the United Kingdom, Gallois and Morter (1982) have recognised distinct early and late time intervals in the C. auritus Subzone. These two intervals are present in the Kirchrode cores; the later from 64.25 to 126.22 m depth in Kirchrode I and the earlier in Kirchrode I from 130.40 to 228.85 m. Inoceramus (Inoceramus) lissa Seeley is a common bivalve in the early part of the C. auritus Subzone and this is evident in the Kirchrode succession (BCCP Group, 1994; TroÈger, in Fenner et al.,

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1996). It should be noted that elsewhere in north west Europe, there is evidence of substantial erosional events at the beginning and particularly, at the end of C. auritus Subzone times associated with block fault movements (Owen, 1996b). Where sediments of C. auritus Subzone age are preserved in downfaulted basins in northwest Europe, they are relatively thick, but none compare with the proven Kirchrode succession in thickness. North of Hannover, in the Schacht Stafforst 1, SchwaffoÈrden, Euhoplites alphalautus Spath and Euhoplites vulgaris Spath were recorded at depths between 841.5 and 843 m and were taken by Owen (1979, 576 and in a report to the Bundesanstalt, Hannover, 1972) to indicate the presence of the Hysteroceras varicosum Subzone. These two ammonites range in age through the varicosum Subzone into the C. auritus Subzone. In the absence of species of Callihoplites of auritus Subzone age at Schacht Stafforst 1, an H. varicosum Subzone age is still to be preferred, but it has to be borne in mind that the absence there of Callihoplites could be a collecting artefact. 5.2.2. The Hysteroceras varicosum, Hysteroceras orbignyi and Dipoloceras cristatum subzones In Kirchrode I, the undoubted sediments of Hysteroceras varicosum Subzone age are thin and probably very incomplete, when successions elsewhere in north west Europe are taken into account (e.g. Owen, 1996b). Elsewhere, in this region of Germany, the marl sediments of this Subzone, such as at Schacht Stafforst 1, are of comparable thickness to that of the Kirchrode I borehole (Owen, 1979). Sediments of this Subzone are absent in the marginal Flammenmergel facies. The character and thickness of the sediments of the

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Hysteroceras orbignyi and Dipoloceras cristatum Subzones in both the Schacht Stafforst 1 and Mastbruch railway cuttings (Owen, 1979), suggests strongly that the earliest D. cristatum Subzone is not represented by sediments in the Kirchrode borings. Kemper (e.g. 1984, 1989a,b) has demonstrated the widespread occurrence in borings in the Lower Saxony basin of an interval at the base of the `Oberes Alb' containing Birostrina sulcata, now to be called Actinoceramus sulcatus (Crampton, 1996). Unlike the Kirchrode succession, this interval in the various borings has not provided ammonite evidence of exact age and the degree of representation of the D. cristatum and H. orbignyi Subzones remains uncertain. However, a very thick succession of these sediments is indicated for part of the Scheerhorn Oil®eld (Kemper, 1984, 480; Elstner and Kemper, 1989; Frieg and Kemper, 1989), surmounted by a relatively thin interval of Aucellinabearing sediments when compared to the Kirchrode pro®le. It is interesting to note that Kemper does not record the interval containing the H. varicosum Subzone form of Actinoceramus concentricus, or the early C. auritus Subzone interval containing Inoceramus (Inoceramus) lissa, which together intervene between the Actinoceramus sulcatus bearing sediments and those with Aucellina. This suggests a thin development of the varicosum Subzone as in the Kirchrode borings, or its absence altogether, and perhaps also, the absence of early C. auritus Subzone sediments.

6. The in¯ux of Tethyan ammonites into the European province One of the principal objectives of the BCCP

PLATE III. Late Albian, late Callihoplites auritus Subzone ammonites from the Kirchrode I(1/91) boring. (A) Prohysteroceras (Neoharpoceras) coptense Spath (Kirchrode I, 64.25 m) X2 (J.W.). (B) Hamites parkinsoni (Fleming) (Kirchrode I, 82.60 m) X2 (J.W.). (C) Prohysteroceras (Goodhallites) sp. juv. (Kirchrode I, 120.28 m) X2 (J.W.). (D) Idiohamites cf. desorianus (Pictet) (Kirchrode I, 103.62 m) X1 (P.C.). (E) Lechites moreti Breistroffer (Kirchrode I, 75.03 m) X1 (P.C.). (F) Idiohamites sp. nov. (Kirchrode I, 105.15 m) X1.25 (J.W.). (G) Callihoplites robustus Spath (Kirchrode I, 68.66 m) X1 (P.C.). (H) Euhoplites cf. vulgaris Spath (Kirchrode I, 121.20 m) X2 (J.W.). (I) Hamites charpentieri (Pictet) (Kirchrode I, 126.22) X2 (J.W.). (J) Anahoplites (Lepthoplites) cf. ornatus Spath (Kirchrode I, 126.15 m) X1 (J.W.). (K) Callihoplites variabilis Spath (Kirchrode I, 122.50 m) X2 (J.W.).

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Programme is to determine the nature and degree of Tethyan faunal and micro¯oral migrations into north Germany during the Albian. The ammonite faunas of the Albian show distinct geographical provincialism with separate Arctic (gastroplitid), European (hoplitid) and Tethyan (brancoceratid) provinces being recognisable in the Early, Middle and Late Albian (Owen, 1971, 1973, 1979, 1984b, 1988a, 1996c). Palaeogeographic maps of the more northerly regions of the Earth in the Late Albian, Dipoloceras cristatum Subzone and Stoliczkaia (Stoliczkaia) dispar Zone have been given by Owen (1996c, ®gs. 4 and 5). The only known ammonite link with the Arctic (gastroplitid) faunal province occurs in the earliest Late Albian (D. cristatum Subzone), with the unique occurrence of the Canadian Arctic genus Gastroplites in Bed VIII of the Gault at Folkestone, Kent (Spath, 1923a±43; Owen, 1973; Jeletzky, 1980). No further links with the Arctic province are known for certain in the later Late Albian. On the other hand, in the Late Albian there are many more ammonite links between the European and Tethyan faunal provinces. In the Middle Albian these Tethyan incursions had been few and relatively short-lived. In the Late Albian, however, there was a general migration of Tethyan faunal elements into the European Province to co-exist with the endemic hoplitids and this is re¯ected in the ammonite zonation (Table 1). Our intention here is not to speculate on the causes and conditions under which migration of Tethyan ammonite faunas spread into the European Province during the Late Albian. We indicate, merely, the extent of it in relation to the Tethyan-derived ammonite occurrences in the sediments of the Kirchrode I boring. The migration of these Tethyan ammonites occurred along relatively narrow seaways, which connected the European shelf seas, including the Albian North Sea, to the growing North Atlantic via the western approaches to the Anglo-Paris basin.

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The Lower Saxony basin was in marine connection to the Albian North Sea and thus open to these migration routes from the Tethyan province (Schott, 1967, 1969; Owen, 1996c). Connections to the Mediterranean region occurred via southern France and the Polish trough (Owen, 1996c ®gs. 4 and 5). Our work in Spain (see Herm and TroÈger, 1996; Wiedmann, 1996) and the southern margin of Europe, shows that these regions belong to the Tethyan (brancoceratid) ammonite faunal province, whereas the remainder of the European shelf seas during the Late Albian were characterised by the endemic hoplitid ammonites. We stated above, that the ammonite genera of the Family Hoplitidae, including Hoplites, Euhoplites, Discohoplites, Anahoplites (with its subgenus Lepthoplites), Dimorphoplites, Epihoplites, Semenovites, Callihoplites, Arrhaphoceras (with its subgenus Praeschloenbachia) and Pleurohoplites, evolved within and are restricted to, the European shelf seas throughout the Middle and Late Albian. The hoplitid ammonites present in the sediments of Late Albian age in the Kirchrode borings, listed in Section 3, show that the Lower Saxony basin falls geographically well within the hoplitinid faunal province. Four Late Albian groups of ammonites belonging to the families Lyelliceratidae (Subfamily Stoliczkaiinae), Brancoceratidae and Mojsisovicsiidae (Subfamilies Mojsisovicsiinae and Mortoniceratinae) (sensu Owen, 1988b), occurring in the Kirchrode borings, are characteristic, essentially, of the Tethyan and Southern faunal provinces (the brancoceratid faunal province). The Subfamily Stoliczkaiinae contains the later Late Albian subgenus Stoliczkaia (Stolickzkaia), Brancoceratidae includes the earlier to middle Late Albian Hysteroceras and the Subfamily Mortoniceratinae contains the subgenera Mortoniceras (Mortoniceras), M. (Durnovarites) and M. (Cantabrigites), Prohysteroceras (Goodhallites) and P. (Neoharpoceras), all

PLATE IV. Late Albian early Callihoplites auritus Subzone ammonites from the Kirchrode I (1/91) boring. (A) Hysteroceras sp. binum group, Mortoniceras (Mortoniceras) cf. commune Spath (Kirchrode I, 130.41 m) X1.15 (J.W.). (B) Callihoplites cf. strigosus Spath juv. (Kirchrode I, 131.47 m) X2 (J.W.). (C) Euhoplites vulgaris Spath (Kirchrode I, 204.08 m) X1 (J.W.). (D) Callihoplites auritus (J. Sowerby) (Kirchrode I, 225.50 m) X1 (J.W.). (E) Callihoplites strigosus Spath (Kirchrode I, 211.10 m) X1.15 (J.W.). (F) Euhoplites alphalautus Spath (Kirchrode I, 215.50 m) X1.5 (J.W.).

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of which are present in the Kirchrode I boring and elsewhere in northern Germany (Owen, 1979, 1989). Among the heteromorph ammonites which might be of Tethyan provincial origin, the interprovincial genus Worthoceras is notable and is represented at Misburg, in sediments of earliest A. (P.) briacensis Subzone age, by Worthoceras pygmaeum Bujtor (identi®ed as cf. Worthoceras Owen, 1989, 375, 378, Taf 1 ®g. 12a,b). The sediments classi®ed with the Dipoloceras cristatum Subzone in the Kirchrode cores have not yielded Dipoloceras although this genus is known from Mastbruch (Stolley, 1937, 17, 30). However, the relatively thin sediments of the Hysteroceras orbignyi Subzone have yielded species of Hysteroceras and those of the Hysteroceras varicosum Subzone have yielded Prohysteroceras (Goodhallites), typically Tethyan genera. Thus, both the H. orbignyi and H. varicosum Subzones show the in¯ux of Tethyan forms. Within the sediments of the earlier part of the Callihoplites auritus Subzone, with the exception of the Tethyan immigrant desmoceratid Puzosia cf. communis at a depth of 161.10 m, the only Tethyan ammonites recovered from the Kirchrode I core occur towards the top of a succession otherwise dominated by hoplitid ammonites. These are the species recorded as Hysteroceras binum group, Mortoniceras (Mortoniceras) commune, and Prohysteroceras (Goodhallites) sp. juv. in the faunal lists. The succession in the later part of the C. auritus Subzone in Kirchrode I is characterised essentially by the heteromorph ammonites, such as Hamites, Idiohamites and Lechites, with subordinate Callihoplites. However, Prohysteroceras (Goodhallites) is present

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at 120.28 m, Puzosia at 108.98 and 105.15 m and Prohysteroceras (Neoharpoceras) at 64.25 m at the top of the succession, all indicating a Tethyan in¯uence. The Tethyan element is more marked by the ammonite occurrences within the sediments of the Stoliczkaia (S.) dispar Zone. Stoliczkaia and Mortoniceras (Mortoniceras and Cantabrigites) are present within the Mortoniceras (M.) rostratum Subzone sediments and M. (Cantabrigites) and M. (Durnovarites) are present within the Mortoniceras (Durnovarites) perin¯atum Subzone. Within the Flammenmergel facies to the south, in the Harz, sediments of M. (M.) rostratum and M. (D.) perin¯atum Subzone age are present containing Stolickzkaia (Stoliczkaia), Mortoniceras (Mortoniceras and Durnovarites) and Puzosia (Owen, 1979, 1989; Scholz, 1979a). Although the sediments of Arrhaphoceras (Praeschloenbachia) briacensis Subzone age in the Kirchrode I boring have not yielded Tethyan origin ammonites, similar sediments of this age at Misburg (Mittellandkanal) have yielded Puzosia, Stolickzkaia (Stoliczkaia) and the heteromorph ammonite Worthoceras pygmaeum Bujtor associated with hoplitid ammonites (Owen, 1989). The above reports the known occurrences of tethyan-derived faunal elements in the Late Albian ammonite fauna of the Kirchrode I borehole. However, a borehole core represents only a 10 cm diameter circle of a bedding plane and the chance of it encompassing an ammonite scattered on that bedding plane becomes a matter of good fortune; indeed of luck. When correlating the intervals of microfaunal and micro¯oral Tethyan elements with the ammonite evidence, the observation in the preceding sentence

PLATE V. Late Albian early Callihoplites auritus, Hysteroceras varicosum, Hysteroceras orbignyi and late Dipoloceras cristatum Subzones ammonites from the Kirchrode I(1/91) boring. (A) Callihoplites strigosus Spath (Kirchrode I, 221.60 m) C. auritus Subzone X1.5 (J.W.). (B) Callihoplites formosus Spath (Kirchrode I, 212.65 m) C. auritus Subzone X1 (J.W.). (C) Callihoplites auritus (J. Sowerby) (Kirchrode I, 217.70 m) C. auritus Subzone X1 (J.W.). (D) Prohysteroceras (Goodhallites) cf. falcifer Spath (Kirchrode I, 229.36 m) H. varicosum Subzone X1.5 (J.W.). (E) Euhoplites sp. serotinus±trapezoidalis group, Actinoceramus sulcatus (Parkinson) (Kirchrode I, 232.45 m) H. orbignyi Subzone X1.15 (J.W.). (F) Euhoplites trapezoidalis Spath (Kirchrode I, 231.40 m) H. orbignyi Subzone X1.15 (J.W.). (G) Hysteroceras sp. juv., Actinoceramus sulcatus (Parkinson) (Kirchrode I, 232.55±60 m) H. orbignyi Subzone X1.15 (J.W.). (H) Hysteroceras subbinum Spath (Kirchrode I, 232.36 m) H. orbignyi Subzone X1 (P.C.). (I) Anahoplites (Anahoplites) cf. planus (Mantell) juv. (Kirchrode I, 241.75 m) late D. cristatum Subzone X2 (J.W.). (J) Euhoplites inornatus Spath (Kirchrode I, 240.85 m) basal H. orbignyi Subzone X1 (P.C.). (K) Hamites cf. intermedius (J. Sowerby) (Kirchrode I, 238.25 m) H. orbignyi Subzone X1 (P.C.).

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should be kept strongly in mind. Nonetheless, the amount of ammonite evidence of dating and the degree to which it has proved possible to delimit the ammonite zonation in these cores is quite remarkable. 7. Conclusions The drilling of the Kirchrode I (1/91) and II (1/94) boreholes has provided for the ®rst time a good ammonite succession and zonation for the Upper Albian sediments of the Lower Saxony basin. The Upper Albian of the Kirchrode I borehole shows that all Late Albian ammonite Zones and Subzones are represented within the Kirchrode Marls. In sediments of Mortoniceras (Mortoniceras) in¯atum Zone age, there is an incomplete development of the Dipoloceras cristatum Subzone, thin developments of both the Hysteroceras orbignyi and Hysteroceras varicosum Subzones and a very thick development of the Callihoplites auritus Subzone capable of division into an early and late time interval. In sediments of the Stoliczkaia (Stoliczkaia) dispar Zone, the Mortoniceras (Mortoniceras) rostratum Subzone is well developed, the Mortoniceras (Durnovarites) perin¯atum Subzone is less well known, together with the terminal Albian Subzone of Arrhaphoceras (Praeschloenbachia) briacensis. The presence of ammonites of Tethyan faunal province origin is apparent throughout the succession with the exception of sediments of Dipoloceras cristatum Subzone age. However, the presence of the bivalve Actinoceramus sulcatus, of cosmopolitan distribution in the D. cristatum and H. orbignyi Subzones, suggests a failure of the borehole to strike a scattered shell of Dipoloceras or early Hysteroceras. These Tethyan faunal elements coexisted with the endemic hoplitid ammonites throughout the succession. The new ammonites biostratigraphical data from Kirchrode I provides an opportunity to compare the previously recognised Actinoceramus/Inoceramus (Inoceramus)/Aucellina bivalve macro-zonation and the micropalaeontological and microphytological zonations previously developed for the northwest German Albian deposits. Acknowledgements We wish to acknowledge helpful discussions and

collaboration with Edwin Kemper over many years and with colleagues in the University of TuÈbingen and elsewhere and in particular Karl-Armin TroÈger; the Bundesanstalt fuÈr Geowissenschaften und Rohstoffe and particularly Juliane Fenner and her team; the Natural History Museum in London and particularly Andy Gale and Martin Jakubowski, Ramues Gallois of the British Geological Survey, Adrian Morter and Chris Wood. H.G.O. is particularly grateful to Professor JuÈrgen Kullmann for his efforts in tracing and sending him Jost Wiedmann's relevant notes and photo-negatives of his work on the Kirchrode I core in order to continue the study. Andreas Prokoph provided copies of the detailed lithological log of the Kirchrode I boring, measured and produced by British Plaster Board Ltd. Phil Crabbe of the Natural History Museum has exercised much skill in the photography of additional crushed and dif®cult ammonite material and Nick Hayes of this Museum has reprinted Jost Wiedmann's negatives. Peter Bengtson (University of TuÈbingen), Juliane Fenner (BGR) and Jim Kennedy (University of Oxford) provided helpful criticisms of the ®rst draft of this paper. H.G.O. would also like to pay tribute to the memory of Jost Wiedmann whose untimely death robbed Science of a bright star and himself of a good friend. References Althoff, W., Seitz, O., 1934. Die gliederung des albium bei bielefeld. Abh. Westf. Prov. Mus. Naturk. 5 (3), 5±26. Amedro, F., 1981. Actualisation des zonations d'ammonites dans le CreÂtace moyen du bassin Anglo-parisien. Essai d'une zonation phyleÂtique du l'Albien au turonien. Cretac. Res. 2, 261±269. Amedro, F., 1992. L'Albien du bassin Anglo-parisien: ammonites zonation phyleÂtique, seÂquences. Bull. Centres Rech. Explor.Prod. Elf-Aquitaine 16, 187±233. BCCP-Group, 1994. The upper Albian of northern Germany: results from the Kirchrode 1/91 borehole, boreal cretaceous cycles project (BCCP). Zentral. Geol. PalaÈontal. 1 (7/8), 809±822. Bertram, H., Kemper, E., 1971. Das Alb von Hannover. Beih. Ber. Nathist. Ges. Hannover 7, 27±74 3 plates. Bogdanova, T.N., Egoyan, V.L., Kakabadse, M.V., Kotetishvili, E.V., Mikhailova, I.A., Pokhialainen, V.P., Prozorovsky, V.A., Saveliev, A.A., Sakharov, A.S., Shulgina, N.I., 1989. Zon'i MelovoõÈ system'õÈ v SSSR. NizhniõÈ Otdel. Nauka, Leningrad, 240 pp. Breistroffer, M., 1936. Les subdivisions du Vraconien dans le SudEst de la France. Bull. Soc. GeÂol. Fr. 6 (5), 63±68. Breistroffer, M., 1940. ReÂvisions des Ammonites du Vraconien de

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