The Nusplingen Plattenkalk and its Paleontological Background
At the beginning of the 19th century, the exploitation of pure Solnhofen-type platy limestones flourished because of their use in lithography, a method for reproducing large numbers of illustrations for books, maps or other printed forms. In the local kingdom of Wuerttemberg, which was relatively poor in mineral resources, geology and stratigraphy were recognized to be a prerequisite for the successful evaluation of potential natural resources. In 1837, Friedrich August Quenstedt (1809-1889) was employed as a professor at Tübingen University and started his studies of the Jurassic. One of his earliest students informed him about a small site close to the village of Nusplingen, where a local farmer had exploited Solnhofen-type limestones for floor tiles and similar purposes. Quenstedtʼs positive evaluation, published in 1843, resulted in several attempts at industrial exploitation of this Nusplingen Plattenkalk. However, most of the material did not have the quality required for lithography. During these efforts, a small limestone quarry was opened and interesting fossils were found, unknown from elsewhere in Swabia, but similar to those from Solnhofen in Bavaria: prawns and lobsters, cephalopods, sharks, coelacanths and other fishes, crocodilians and even pterosaurs. At that time, numerous amateur paleontologists sampled fossils from Nusplingen, and the material spread over Europe by exchange (e.g., Odin et al. 2019).
Since then, several attempts have been made to excavate this fossil site properly, first commercially by the fossil trader Bernhard Stürtz from Bonn and later by paleontologists and geologists from Tübingen University. These excavations focused on vertebrates. The results were unfortunately not very successful, because of insufficiently qualified personnel, rarity of the material as well as the lack of tools and skilled technicians for fossil extraction. It was often stated in the literature that the fossils from Nusplingen were of generally lower quality than those from Solnhofen and Eichstätt in Bavaria. As a consequence, this important site became almost forgotten.
Until the 1980s, the Nusplingen quarry was still accessible, but only the uppermost parts of the section were exposed and hence this quarry was rarely considered as a worthy destination for field trips. The situation changed completely when a team from the Stuttgart Natural History Museum evaluated the site, because the entire area had become protected and scientifically significant fossils were thought to be in danger. Despite many publications about the Nusplingen Plattenkalk and its fossils, fundamental questions concerning the age, paleoenvironment and genesis of this fossil Lagerstaette remained open. To answer these questions, the Stuttgart Natural History Museum started scientific excavations in 1993, which are still ongoing.
Location of the Nusplingen Plattenkalk Geosite
The Nusplingen Plattenkalk is well exposed in two small quarries exclusively dedicated to science, the Nusplingen quarry and the Egesheim quarry (Fig. 1), located ca. 250 m from each other on the ʻWesterbergʼ hill, west of the village of Nusplingen, atan altitude of c. 900 m above sea-level. The village and the geosite lie in the southwestern part of the Swabian Alb, within the area of the UNESCO Global Geopark Swabian Alb as well as in the Naturpark Obere Donau. The total thickness of the Plattenkalk section is 10–15 m, overlain by a few meters of brecciated olistoliths (Dietl et al. 1998; Bantel et al. 1999). Any younger Jurassic deposits have been completely eroded. The main outcrop area of the Nusplingen Plattenkalk covers less than 2.5 km2 and is mostly hidden in the subsurface of a meadow and forest landscape. A small relict occurrence of Plattenkalk crops out further to the south, along the southern foothill of the ʻGrosser Kirchbühlʼ hill. The latter site is important for reconstruction of the submarine relief during the deposition of the Plattenkalk. Siliceous sponge-microbial mounds had been tectonically uplifted and surrounded two 80–100 m deep lagoonal basins, named the ʻWesterberg-Wanneʼ and the ʻGrosser Kirchbühl-Wanneʼ (Dietl et al. 1998). Some of the uplifted mounds formed shallow islands in the Jurassic sea. Although these islands have been eroded, their former position can be reconstructed by mapping dedolomite occurrences. The Jurassic age of the formation of dedolomite was proved by dedolomitized lithoclasts occurring in breccia layers of turbidites within the Plattenkalk (Bantel et al. 1999).
Figure 1. Map showing the location and distribution of the Nusplingen Plattenkalk in the southwestern part of the Swabian Alb (modified from Klug et al. 2010a).
Nusplingen quarry (Fig. 2) can be reached by geological trails, either starting from the center of the village or from the parking lot on top of the hill, accessible by cars or small buses via a small signposted road (ca. 15 minutes by foot from there). It is accessible from early spring to late autumn, and even in winter if there is no high snow cover, although acces is then limited to times without snow, and excavations are impossible, because the limestones do not split when the ground is frozen. The Egesheim quarry, which is situated in a marginal position of the Nusplingen lagoon, is not accessible to the public, except during expert-guided field trips.
Significance of the Nusplingen Plattenkalk as a Geological Heritage
Nusplingen is one of a few sites of late Kimmeridgian age in the Upper Jurassic of southern Germany, several hundred thousand years older than the ʻclassicalʼ Solnhofen Lithographic Limestones in Franconia. In Swabia, however, it is the sole example of this type of fossil conservation Lagerstätten and one of the outstanding Jurassic geosites of the Geopark Swabian Alb. Despite the relatively small size of the outcrop area, the relatively rich and highly diverse fossil content makes Nusplingen a site of international reputation. Not only various groups of macrofossils, but also micro-, nano- and ichnofossils as well as excellently preserved terrestrial plants can be studied easily (e.g., Zügel et al. 1998; Bantel et al. 1999; Dietl & Schweigert 2004, 2011; Schweigert 2015), based on the rich fossil samples mainly housed in the collection of the Stuttgart Natural History Museum and from rock samples permanently accessible at the outcrop (hopefully also in future). All newly collected fossils and some of the historical specimens have been collected bed-by-bed thus allowing statistics on the abundance of taxa and the recognition of environmental changes through time. Most material from the ʻclassicalʼ Solnhofen Lithographic Limestones lacks such detailed information because of undocumented sources or deliberate misrepresentation by amateur collectors or fossil traders.