(In part adapted from Moser 1978 and Binsteiner 1990b)
|Geographical setting:||Of the four areas in Southern Germany where cherts of knappable quality occur, the region around Kelheim/Regensburg, also known as the "Altmühl-Alb", is without a doubt the most important. Here, in the Southwestern part of the so called Franconian Alb, there are at least 20 localities with Upper Jurassic (Malm) chert that count as possible sources (see also our clickable map of sampled sites in the region). On three of them, Baiersdorf, Abensberg-Arnhofen and Lengfeld large-scale prehistoric exploitation has been proven. Archaeological excavations on the latter two uncovered extensive flint mines, with Abensberg being the largest Neolithic mining site in Germany.
The Franconian Alb is, together with its Eastern extension the Swabian Alb, the major geographical feature of Southern Germany. It is more or less the continuation of the Swiss and French Jura Massives, running for about 400 kilometres between the Black Forest in the Southwest and the Frankenwald region around Bayreuth in the Northeast. The lowish range, rising to a maximum of about 1 000 meters is mostly not more than forty to fifty kilometres wide and separates the Central German Uplands form the Danube Valley and the Alpine Foreland. The traditional geographical divide between the Swabian Alb and the Franconian Alb is the Ries near Nördlingen, a very large Tertiary crater formed by the impact of a big meteorite in the Upper Miocene. The whole region is characterized by a landscape of scarp and vale, with locally steep cliffs of limestone.
The geology of the region is quite complex and uses a local stratigraphy which seems to be made especially to confuse geologists foreign to the region. In the first place, instead of using the international division of Lower, Middle and Upper Jurassic, the period is divided into "Schwarzer" (Black), "Brauner" (Brown) and "Weißer" (White) Jura. Every epoch is divided in five stages numbered form α (alpha) to ζ (zeta), which in some cases are further subdivided in numbers. In giving the age of a formation, the old Epoch-names Lias, Dogger and Malm are used, so the Upper Kimmeridgian would be Malm ε, but the Lower Tithonian Malm ζ1. In the following text and in the material-pages, we will be mostly using the local stratigraphy with the approximate international designation added in brackets, following Geyer & Gwinner 1984. We hope to be able to present a more precise correlational table on these pages in the future.
If you think the European Jurassic geology can be equalled with the large-scale sedimentation in the Thetys, with the Franconian and Swabian Alb this is certainly not the case. Although the area belongs to the Thetys in a wider sense, it is the Northern shelf of the oceanic basin, mostly characterized by small basins separated by reefs. This small-scaledness causes the high variety of chert-types in the region, but within the basins there can be a marked variation in types and forms too depending on the facies of the sediments. Within these basins, two zones can be distinguished, the reef and the basin itself with the cherts mainly occurring in the limestones bordering directly on the reef.
|Similarities and differences:||
In the area under discussion here, at least three of these small basins mentioned above are important: around Painten in the North, the small area of Abensberg-Pullach in the South and in between the larger Hienheim-Kelheim-Basin. All cherts in this geographical area date from Upper Jurassic ("Weißer Jura"/Malm), and are to be found predominantly in platy limestones of the Malm ζ1/2 (Lower and Middle Tithonian) at the edge of the basins.
From the basin around Painten, the so called "Paintner Wanne", come predominantly thin plates with a hard cortex, mostly markedly different in structure on both sides of the piece. Incorrectly, this material is known as the Baiersdorf-type or plain Baiersdorf, after the most important source in the area, but as it is probably impossible to discern the platy material from the different localities in this basin, it is better to speak of the "Paintener-Wanne-type" (de Grooth 1994 and pers. com. 2002).
Another typical material that can't be confused with any other type is the tabular chert of the Abensberg-type, being very fine in structure, typically grey striped, with a very thin and even cortex. All other types of chert in the region can come from a variety of sources: nodular striped chert has been found in Abensberg, Lengfeld and Alling as well as in Thalhof and has given rise to a general lumping of material from several sources into the Abensberg-Lengfeld-type (e.g. Grillo 1997). This seems a very bad idea, as very similar material can be found in the Eichstätt-region and the tabular material from Abensberg is distinguishable from all other types. Also the very dark chert with secondary colouring which was thought to be typical of the source at Lengfeld, has been found at Abensberg and Thalhof too.
|Extractability and prehistoric use:||
As pointed out above, it will be very difficult to distinguish the material from different sources in the larger region, without calling it lapidary "Jurassic chert from the Southern Franconian Alb", so estimating which sources were used and when during prehistory is accordingly difficult. All types are used locally and regionally in the Palaeolithic, but no evidence of mining or active extraction is known from this period. Probably most of the raw material was taken from the river gravels or picked up from the surface of the chert-bearing residual loams that cover large areas in the region.
More widespread use of all types, but especially the tabular chert from Abensberg and all types of high quality nodular material, starts with the onset of the Neolithic, in the Linear Pottery Culture. In this period there is, judging from the amount of material in circulation, already some more active extraction, possibly even mining, going on. With the Middle Neolithic Stichbandkeramik, the use of the Abensberg-type reaches its greatest popularity and the mining in Abensberg-Arnhofen must be in full swing, although there are currently no dates from the mining area to confirm this. The distribution of this tabular chert is very wide indeed, with some pieces reaching Lake Constance, Eastern and Northern Germany, whereas in the majority of Bohemia and most of Southern Germany it is the most popular lithic material.
Of the eight sites mapped as flint mines (Weisgerber et al. (eds.) 1999), excavations have been carried out on only two (Lengfeld and Abensberg) with additional geophysical surveying at Baiersdorf where mining can be considered proven too. On all three locations, the material was extracted from secondary deposits, only in Baiersdorf there might been some mining into the underlying limestone.
|Last modified on:
February 7, 2002
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