Presently the highway BAB 38 is under construction, which runs close to the southern slopes of the Harz mountains and across the shell limestone uplands of the Querfurt plate. Several streams, among them Weida and Weitzschkerbach between the towns of Eisleben and Querfurt, have dug themselves into this plate, exposing Triassic strata.
The valleys have to be crossed with bridges (Fig.1). At the Weitzschkerbach crossing, the exposed strata cover a geologic time span from Lower Shell Limestone (Upper "Wellenkalk", "Schaumkalk") through Middle Shell Limestone (Upper Dolomite) to Upper Shell Limestone (lower strata of "Trochitenkalk").

The two valleys make a beautiful setting and have been protected as a nature reserve for a long time. As fossil collecting is explicitly forbidden by the regulations, it has to be restricted to sites of earthwork. In 2004, pits for the pillar foundations of the two bridges were dug, with the spoils deposited nearby. Additional earthwork was done in the Weitzschkerbach region (Fig.1).

						Fig.1: constuction site of the Weitzschkerbach valley viaduct
						Fig.2: stromatolite consisting of sponge and microbial layers
						Fig.3: stromatolite consisting of sponge and microbial layers, with crystal druse

In addition to the typical shell limestone fossils, the dolomitic strata on the rock pile in the Weitzschkerbach valley yielded chert samples, too. They were of the type already shown at the 3rd Chert Meeting, silicified debris layers from the boundary between Lower and Upper Shell Limestone. As a feature not observed with previous finds, some samples contained silicified stromatolites (Fig.2 & Fig.3).

Stromatolites are also known from rocks 3.5 Billion years old. Often they are the only fossils in old rocks. Much younger stromatolites serve as indicators of highly saline environments where microbe-eating creatures like snails could not live. Stromatolites can be preserved as "normal" petrefacts but also as cherts.

text & photographs: H.HUHLE/Roeblingen