The Floral Change in the Tertiary of the Rhön Mountains (Germany)
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Acta Palaeobotanica 47(1): 135–143, 2007 The fl oral change in the Tertiary of the Rhön mountains (Germany) DIETER HANS MAI Museum für Naturkunde, Humboldt Universität zu Berlin, Invalidenstraße 43, 10115 Berlin, Germany Received 9 May 2006, accepted for publication 10 December 2006 ABSTRACT. A total of 438 species from 8 stratigraphically well-dated macro- and microfloras from the Rhön mountains (Central Germany) are biostratigraphically and palaeoecologically analysed. The formations are stratigraphically discontinuous but span the age range mid/late Eocene to late Pliocene (ca. 39 Ma to 2.15 Ma). The primary compositional elements and ecological character of each formation’s fl ora is as follows: – Kaolinitic Formation: Eocene with Beckettia, Steinhauera, Sterculia, Wardensheppeya; Pollenfl ora of SPP- zone 16/17 (Bartonian). – Sieblos Formation: early Oligocene. Palynological spectrum including Boehlensipollis hohlii; invasion of Arctotertiary elements. Many Nymphaea remains. – Kühnstein Formation: “Marxheim”– pollen-spectrum of early late Oligocene. No macrofl ora. – Oberleichtersbach Formation: dated to the late Oligocene by small mammals and gastropods. 100 plant species of fruits and seeds. Mixed mesophytic forest of the Carpino-Ostryon-type; many semihumid elements and herbs. – Escheri Formation: beds south of Theobaltshof; small fl ora with Alnus julianiformis, Fagus deucalionis, Quercus drymeja and Q. kubinyi. Palynological ratio between Triatriopollenites coryphaeus and T. rurensis indi- cates early Miocene. – Kaltennordheim Formation: fossil fl oras of Kaltennordheim, Hochrain, Bauersberg and Lettengraben with more than 65 plant species, characterized by typical elements of the so called Younger Mastixioid fl oras (Eomas- tixia hildegardis); optimal warm, humid climatic phase. Latest early Miocene to early middle Miocene. – Wollbach Formation: dominated by Quercus pseudocastanea, together with Acer pseudomiyabei, Alnus ducalis, Buxus pliocenica, and Eucommia europaea. Warm temperate, deciduous broad-leaved forest of late Miocene affi nity. – Borsoni Formation: 130 plant species from six localities belonging to 59 families. Deciduous broad-leaved warm-temperate forests and different aquatic- and swamp-plant taphocoenoses with many exotic species. Marked east-European infl uence. Two different fl oral complexes document a late Pliocene warming (Gerstungen, Oberzella) and an intra-Pliocene cooling (Kaltensundheim). KEY WORDS: macrofloras, microfloras, floral change, Tertiary, Rhön mountains, Germany INTRODUCTION The Rhön mountains, a volcanic low moun- been investigated. More than 450 fossil plant tain range in the centre of Germany (Fig. 1), species have been discovered and described. lies between Bavaria, Hesse and Thuringia These plant fossils are well placed stratigraphi- (Schmeer 1964) and yield numerous Tertiary cally by association with fossil gastropods and fl oras of different ages. Knowledge of these plant mammalian remains, together with several fossils goes back to the 19th century (Zenker radiometric dates of the volcanites (Lippoldt 1833, Hassencamp 1858, 1860, Heer 1859) and 1978). The sequence of fl oras (Fig. 2) started increased after investigations in recent years with many gaps in the Eocene and terminated (Geyer 2002, Gümbel & Mai 2002, 2004, 2006, in the Upper Pliocene (Martini et al. 1994). Mai in press). Fossil fruits and seeds, leaves, The fl oral change over this long time (39 Ma pollen and spores, woods and charophytes have – 2.47 Ma) was very signifi cant. 136 Fig. 1. The distribution of volcanic rocks with the main fossiliferous places in the Rhön mountains. After Gümbel & Mai (2006) – localities, and Schmeer (1964) – volcanic rocks 137 Fig. 2. The stratigraphical assignment of the sedimentary and fossiliferous beds of the Rhön mountains (no true to time scale and to massivness of the sediments). After Martini et al. (1994), changed EOCENE Intratriporopollenites ceciliensis Krutzsch, I. minimus Mai, Labrapollis labraferus KAOLINITIC FORMATION (R. Pot.) Krutzsch, and Plicatopollis plicatus (Kr.) Krutzsch. Palaeocarpological remains were described Age. The pollen assemblage places the only from the research drilling Sieblos 1994/1 Paleogene basal layers into the Eocene. This near the Wasserkuppe in a depth of 36.65 to might be correlated with the SPP – zone 16/17 38.10 m. The macrofl ora of 16 species from after Krutzsch et al. (1992); Bartonian, ca. clayey coal seam sediment (Kaolinitic Forma- 39 Ma. tion) lying immediately above Lower Muschel- References. Krutzsch et al. (1992), Hot- kalk indicates middle to late Eocene age. tenrott (1998), Mai (1998). Flora. Beckettia mastixioides Reid & Chan- dler, Steinhauera subglobosa Presl, Sterculia subovoidea (Reid & Chandl.) Mai, and War- OLIGOCENE densheppeya marginata (Chandl.) Eyde are most important species. The palynological SIEBLOS FORMATION investigation of the borehole Sieblos 1994/1 yielded microfl oras only from the underlying The abandoned coal mine of Sieblos at the substratum. Signifi cant pollen are Composit- Wasserkuppe was famous for its fossil contents oipollenites rhizophorus (R. Pot.) R. Potonié, already during the 19th century and has been 138 accepted as a classical locality of the German Hottenrott (1988, 1998), Martini & Rothe palaeobotany. Since most of the fossils so far (1998, 2005). collected were from mining dumps, they could not be positioned into a relative stratigraphi- KÜHNSTEIN FORMATION cal succession. The Tertiary period was re-exa- At the bend of the street no. 284 south-east mind by scientifi c drillings in the years 1994, of the Wasserkuppe near Gersfeld in a land- 1998, and 1999. The results of the investiga- slide a small deposit of brown-coal clay and tions of the whole Sieblos Formation were pub- dysodile was investigated in 1975. This was lished in monographical studies. Many details named after the neighbouring hill as Kühn- about the sedimentology, palaeoecology, vol- stein beds. canology, and geochemistry of this remarkable Flora. A microfl ora (only 56 species) freshwater deposit in the Oligocene of Central from these beds shows very characteristical Europe are well known. The structure Sieblos amounts of Sparganiaceaepollenites, Cyper- is suggested as a suberosional depression. aceaepollis, Alnus and Platanus pollen grains. Flora. A dysodile bed of Sieblos has Very typical elements are also Polypodiaceois- included many plants of intrazonal vegetation, porites marxheimensis (Mürr. & Pfl ug) Krut- predominantly Nymphaea nymphaeoides (Ett.) zsch, Diplopollis kockelii Pfl anzl (= Calamus), Weyland (= N. rhoenensis Kurtz 1894), and Momipites punctatus (R. Pot.) Nagy (= Engel- Spirematospermum wetzleri (Heer) Chandl. hardia), and Tricolporopollenites cingulum The association of Glyptostrobus europaeus (R. Pot.) R. Pot. & Pfl ug. One uncertain speci- (Brongn.) Heer – Nyssa disseminata (Ludw.) men of Boehlensipollenites hohlii Krutzsch Kirchh. verifi ed the swampy forest, possibly possibly indicates early late Oligocene. together with Myrica banksiaefolia Unger, Age. The differences between this “Marx- and the fern Lygodium cf. kaulfussii Heer. heim pollen spectrum” of the Kühnstein For- The zonal vegetation was characterized by the mation and the younger microfl oras of Hesse members of a mixed mesophytic forest. Impor- and the Rhön mountains are evident. No mac- tant elements of this forest were Tetraclinis rofl ora has been discovered. salicornioides (Ung.) Kvaček, Carya rostrata The lithological composition, thickness, and (Schloth.) Schimper, Engelhardia orsbergensis regional extent of the Kühnstein Formation is (Wessel & Web.) Jähnichen et al., Quercus unknown. Therefore nothing can be said about lonchitis Ung., Tilia irtyshensis (Shaparenko) the overlapping with volcanites (tuffs) and their Grubov, Zanthoxylum europaeum Ung., and radiometric age. The eruptions in the region of many Lauraceae. This is very similar to the the Wasserkuppe started approximately before conditions known from the volcanodetritic 25.0 Ma., that is in accordance with the new series in the Bohemian mountain range. The time scale late Oligocene (Chattian). macrofl ora of only 32 species contrasts with References. Hottenrott (1992), Krutzsch a richer microfl ora of 48 species with typical (1993), Hottenrott et al. (1998). elements as Cicatricosisporites paradorogensis Krutzsch, Momipites quietus (R. Pot.) Nichols., OBERLEICHTERSBACH FORMATION and Boehlensipollis hohlii Krutzsch, verifying unambiguously older Oligocene. Worth men- The fossil remains at the locality Oberleich- tioning is the strong invasion of Arctotertiary tersbach near Bad Brückenau (Bavarian Rhön) elements as in the “fl oral complex Valeč” at the derive from a blue-black clayey sediment of same time. the fi lling of a doline in the Muschelkalk. This Age. The palynological picture, mainly sediment is very rich in fossil fruits and seeds, Boehlensipollis, demonstrates typical Oli- ostracods, snails, shells, and mammal bones in gocene. Based on recently found teeth of excellent preservation. smaller mammals, especially by the presence Age. Based on gastropods, e.g. the strati- of Melissiodon (family Melissiodontideae) the graphically important Ferussina (Stropho- age of the Sieblos Formation can be deter- nema) tricarinata M. Braun, and a great mined more precisely as early Oligocene. diversity especially of small mammals the References. Hassencamp (1858, 1860), sediments can be placed in the latest late Heer (1859), Schenk (1891), Kurtz (1894), Oligocene (Neochattian, Paleogene mammal