PalZ DOI 10.1007/s12542-017-0345-9 RESEARCH PAPER Graptolites from glacial erratics of the Laerheide area, northern Germany 1 2 Jo¨rg Maletz • Heinrich Scho¨ning Received: 24 November 2016 / Accepted: 12 March 2017 Ó The Author(s) 2017. This article is an open access publication Abstract Ordovician and Silurian glacial erratics of the Material vermutlich stammt, nur selten zu finden. Die Laerheide area (Lower Saxony, north-western Germany) Graptolithen finden sich in Kalken des Oberen Ordovizi- bear well-preserved graptolites. The faunas provide ums (Sandbium–Katium) und Schwarzschiefern des Kati- important information on the origin and transport direction ums. Ha¨ufiger sind jedoch die kalkigen oder siltig-sandigen of the sediments preserved in a kame, representing the Geschiebe des ‘Gru¨nlich-Grauen Graptolithengesteines’ Drenthe stadial of the Saalian glaciation. The faunas even mit Graptolithen des Oberen Wenlock bis Ludlow (Oberes include species not commonly encountered in the succes- Silur). sions of mainland Sweden, from where the erratics pre- sumably originated. The most common graptolites are from Schlu¨sselwo¨rter Geschiebe Á Mora¨nen Á Kame Á Drenthe- Upper Ordovician (Sandbian to Katian) limestones and Stadium Á Deutschland Á Pala¨ozoikum Á Graptolithen from Katian black shales. More common, however, are greenish limestones, sand- and siltstones, often combined in the term ‘Gru¨nlich-Graues Graptolithengestein’, in Introduction which upper Wenlock to Ludlow (upper Silurian) grapto- lites are common. Fossil-bearing glacial erratics have long been used to doc- ument transport and flow directions of glacial ice sheets Keywords Glacial erratics Á Moraines Á Kame Á Drenthe- from the place of origin of the material (e.g. Roemer Stadium Á Germany Á Palaeozoic Á Graptolites 1862, 1885), even though modern methods like satellite imaging are now superseding this seemingly ‘old-fashioned’ Kurzfassung Gut erhaltene Graptolithen ko¨nnen in ordo- method (e.g. Boulton et al. 2001). ‘Leitgeschiebe’ are still vizischen und silurischen Geschieben aus der Laerheide regarded as important tracers for the origins of North Ger- (Niedersachsen) gefunden werden. Sie bieten Informatio- man glacial deposits (see Ehlers 2011) and include both nen zu Ursprung und Transportrichtung der Sedimente, die sedimentary and crystalline rocks. The investigation of heute in einer Kamestruktur des Drenthe-Stadiums der sedimentary erratics has been dominated by the collection Saale-Vereisung erhalten sind. Manche dieser Formen sind and description of the fossils. These identify unambiguously auch in den skandinavischen Abfolgen, aus denen das the age of the sedimentary rocks and their origin if the sedimentary rock types are still exposed in the area of their origin. Spectacular fossils such as Xenusion auerswaldae Handling editor: Mike Reich. Pompeckj, 1927 (probably originating from the Lower Cambrian Kalmarsund Sandstone of southern Sweden: Jae- & Jo¨rg Maletz ger and Martinsson 1967; Hauschke and Kretschmer 2015) [email protected] have been found in glacial erratics, and new taxa are even 1 Department of Geological Sciences, FU Berlin, now being described from glacial(?) erratics originating Malteserstrasse 74-100, 12249 Berlin, Germany from the Palaeozoic succession of Scandinavia (e.g. Botting 2 Am Spielplatz 3, 34613 Schwalmstadt, Germany and Rhebergen 2011). 123 J. Maletz, H. Scho¨ning Graptolites are relatively common and highly diverse in Fig. 1 Graptolites from North German glacial erratics. a Saetograp-c glacial erratics (Fig. 1). The earliest illustration of a glacial tus leintwardinensis (Hopkinson in Lapworth, 1880), SMF 68294, Nienhagen bei Rostock, Ludlow, Silurian. b, c Saetograptus chimaera erratic block with graptolites may be by Walch (1771, (Barrande, 1850), SMF 75783, SMF 75784, Nienhagen bei Rostock, suppl. IVc, Fig. 5) from Stargard, Mecklenburg. It took Ludlow, Silurian. d Corynites wyszogrodensis (Kozłowski, 1956), nearly a century, however, before Heidenhain (1869) and SMF 75785, Berlin, coll. Ku¨hne, Katian, Ordovician. e Bohemograp- Haupt (1878) described these faunas in more detail. tus sp., proximal end, SMF 75786, B9/96, Bramsche, Mecklenburg- Vorpommern, Ludlow, Silurian. f Dicranograptus clingani (Car- Gu¨mbel (1878) may have been the first to isolate grapto- ruthers, 1868), SMF 75787, Slg. Weil Nr. 18, Kieler Bucht, Katian, lites chemically from their calcitic matrix based on this Ordovician. g Spinograptus spinosus (Wood, 1900), MB.G. 1078, kind of material. A great time for graptolite research started Hiddensee, Ru¨gen, scanning electron microscope (SEM) photo, with Wiman (1895), who described in detail the con- Ludlow, Silurian. h Plectograptus toernquisti (Bates et al., 2006), SMF 75496, Bramsche, Mecklenburg-Vorpommern, Ludlow, Sil- struction of graptolite tubaria (an replacement term for urian. i Rectograptus gracilis (Roemer, 1861), PMU 31641, Ro¨sta˚nga, rhabdosomes: Mitchell et al. 2013, p. 34) based on chem- Scania, Sweden, partial relief specimen filled with pyrite, obverse ically isolated graptolites from glacial erratics, but also view (not from glacial erratic), Katian, Ordovician. j–l Monograptus from samples collected in situ from a number of Scandi- priodon (Bronn, 1835), SMF 75780, Kiesgrube Basedow, Mecklen- burg-Vorpommern, coll. R. Klafack, j, k coated with ammonium navian localities. One of the most detailed descriptions of chloride to better show the details, note preservation of fuselli in (k), chemically isolated graptolites remains Kraft’s (1926) Wenlock, Silurian. Scale bars represent 1 mm in all photos investigation of Rectograptus gracilis, but the important works of Kozłowski (1938, 1949) on Tremadocian benthic taxa and Urbanek (1958) of Silurian monograptids are also Ordovician graptolites from glacial erratics provide highlights of graptolite research. There is no doubt that the important constructional information due to the excellent study of Silurian retiolitids (e.g. Mu¨nch 1931; Eisenack preservation as relief specimens. One of the reasons for the 1935; Kozłowska-Dawidziuk 1995; Maletz 2008, 2010) previously poor record may be the lack of interest in this would not have been possible without chemically isolated fossil group, but also the difficulty for most fossil collectors material, including that from glacial erratics (Fig. 1g, h). to get answers to questions on taxonomy and to find the Kowalski (1964, 1966a, b, 1968a, b, 1969, 1984) pro- relevant literature. Despite this, graptolites can provide vided overviews on the graptolites found in glacial erratics important information for dating glacially deposited sedi- in a number of short review papers. These show the most ments and for the origination of the fossil-bearing rocks important taxa encountered, but unfortunately, the illus- (Kalbe and Maletz 2015, p. 5). Unfortunately, the record of trated material is often not specimens of glacial origin, but graptolites in glacial erratics has been limited to identifi- based on available published illustrations from various cation and taxonomic description (e.g. Kraft 1926; Gothan sources, and therefore may be misleading. It appears that 1934; Eisenack 1935; Urbanek 1959; Zessin et al. 1994), many of the taxa listed in various publications as origi- and further evaluation of the enclosing sediments and their nating from North German glacial erratics have never been (palaeo-)geographical origin has not been undertaken. properly described or illustrated from these erratics. Research on graptolites from glacial erratics has con- Available descriptions and illustrations are not sufficient centrated mostly on the Silurian faunas (see Jaeger for modern identification (e.g. Heidenhain 1869; Haupt 1959, 1978, 1991), as the ‘Gru¨nlich-Graues Grap- 1878; Roemer 1885), and the specimens are unfortunately tolithengestein’ (cf. Roemer 1862, p. 608) became not available for re-identification. famous—at least in Germany—for the presence of three- Glacial erratics with Ordovician graptolites are either dimensionally and well-preserved graptolites (Fig. 1a–e). It rarely encountered or have not attracted much attention, is also the most commonly encountered graptolitiferous even though they may also bear excellently preserved rock type in glacial erratics of Scandinavian origin. Jaeger faunas and even provide information on taxa not known (1991) and Maletz (2008) indicated that the time interval from other sources. This is shown by the descriptions of covered by this lithology ranges from the Homerian Archiretiolites regimontanus by Eisenack (1935) and Co- (Wenlock) Cyrtograptus lundgreni Biozone to the Lud- rynites wyszogrodensis by Kozłowski (1956) (Fig. 1d), fordian (Ludlow) Bohemograptus cornutus/praecornutus species that have been found only once or twice and are Biozone. Quite a number of Silurian monograptids have unknown from successions in situ. Other species have been been described—in some cases exclusively—from glacial described from Scandinavian successions, but important erratics (e.g. Jaekel 1889;Ku¨hne 1955; Urbanek 1958; details were revealed only by isolated material, for exam- Jaeger 1991). In particular, glacial erratics from northern ple of Gymnograptus linnarssoni from western Pomerania, Germany have yielded excellently preserved material of a Poland (Urbanek 1959). Ordovician graptolites may be number of monograptids (Mu¨nch 1938;Ku¨hne 1955; Jae- more common in glacial erratics than previously indicated ger 1959, 1991; Maletz 1999). Mu¨nch (1938) was one of (Fig. 2). the first