Kies- und Sandgrube Rauscheröd bei Passau. — Foto: F. Pfeil

Abstract

Collection of fossil wood

During the orogeny of the Alps, the northern foreland developed into an elongate depression, termed the Molasse Basin. Early and Middle Miocene deposits in the North Alpine Foreland Basin have preserved one of the world’s richest regional records of silicified wood. Between 1955 and 1990, more than 11.000 specimens of permineralized wood were collected from some 490 localities in southern Bavaria by Reinhard Baumgartner, Ludwig Fruth, Heinz Haberda, Peter Holleis, Ludwig Lang, Alfred Selmeier, among others. The largest portion of this material is deposited in the Bavarian State Collection of Palaeontology and Geology, Munich. The size of these wood specimens ranges from tiny pieces, to fist-size length, and to large trunk fragments, 0.6 m in diameter (750 kg). Furthermore, large collections of silicified wood specimens are known from the Austrian North Alpine Molasse Foreland.


Geological background

Of the 11.000 specimens, some 1.000 have been analyzed to date. These specimens come from 61 stratigraphically well-dated localities by using the Coexistence Approach. A database is grouped into four xylofloras: (1) Ortenburg; Late Ottnangian, (2) Southern Franconian Alb; Late Karpatian, (3) Older Series; Early Badenian, (4) Middle Series; Middle Badenian.


Taxonomic affinities

1) The Xyloflora Ortenburg (gravel pit Rauscheroed): Gymnspermae; Bombacaceae, Ebenaceae, Ericaceae, Fagaceae, Flacourtiaceae, Lauraceae, Meliaceae, Myricaceae, Platanaceae, Tiliaceae; Arecaceae (Palmae).

(2) The Xyloflora southern Franconian Alb: Cupressaceae, Podocarpaceae, Taxodiaceae; Anacardiaceae, Capparaceae, Elaeagnaceae, Fagaceae, Hamamelidaceae ?, Icacinaceae, Juglandaceae, Lauraceae, Leguminosae (Mimosoideae, Papilionoideae), Meliaceae, Periplocaceae, Platanaceae, Rosaceae, Rutaceae, Sapotaceae, Tiliaceae, Ulmaceae; Arecaceae (Palmae). These fossils predominantly occur in sandy or loamy sediments close to the surface, and were collected from farmland and waysides. Permineralized roots have not been recorded to date.


Minute anatomy

Special features of the wood specimens include insect feeding channels filled with coprolites, wood xylem with small roots of unknown plants, tile cells in the ray cellular composition, the earliest record of mineralized disjunctive ray parenchyma cell walls, a feature with only 1.16 % extant frequency (IAWA anatomical feature No.113). In addition, a few silicified Tempskya stem portions have been discovered in reworked sediments of Bavaria. 640 growth rings from15 different taxa show a variability of ring width between 0,2 and 6,9 mm (mean 0,6 - 4,6 mm).


Outlook

Unfortunately, no critical synopsis of the silicified wood from the North Alpine Molasse Basin (Austria, Germany, Switzerland) is available to date. This, however, would provide a basis for comparisons of the xylofloras to the copious leaf, seed, fruit, and pollen record that exists from this area.

Querschliff: Jungtertieres, verkieseltes Eichenholz (Quercoxylon), an der Grenze einer Zuwachszone.

© 2009 Prof. Dr. Alfred Selmeier