Lower Palaeozoic stratigraphy at Lyby and Tängelsås, central Scania, southern Sweden

Abstract

Lithological and stratigraphical data from two new percussion borings at Lyby mosse and Tängelsås in central Scania, provide valuable information on the Middle Cambrian to Lower Ordovician succession. The drilling at Lyby mosse was stopped in the Alum Shale Formation at a depth of 55 m after penetrating a sequence of Upper Didymograptus Shale and Komstad Limestone. The stratigraphical assignment of the limestone is based on conodonts from cuttings. The conodont fauna is virtually the same as in the Komstad Limestone in SE Scania. The presence of a few Tremadocian specimens in the lower part of the limestone indicates either the existence of a very thin bed of the Bj⊘rkåsholmen Formation, or the presence of an erosional residue of specimens between the Alum Shale Formation and the Komstad Limestone. Thus, there is a hiatus, including the T⊘yen Shale and probably also the Bj⊘rkåsholmen Formation, in the Lyby area of central Scania. This provides new evidence of differential movements and periods of local uplifts. The boring at Tängelsås reveals a previously unknown occurrence of Lower-Middle Cambrian strata along the Fyledalen Fault Zone. Below the Quaternary overburden, the boring entered a sequence of alum shale (53-110 m) resting on a Lower Cambrian quartzarenitic sandstone. The boring was stopped within the sandstone sequence at 140 m depth. Well preserved specimens of an agnostid trilobite, Ptychagnostus punctuosus (Angelin, 1851), from the depth interval 70-90 m, are indicative of a medial Middle Cambrian age.

Keywords:

• Cambrian
• Ordovician
• stratigraphy
• conodonts
• trilobites
• Lyby
• Tängelsås
• Scania
• Sweden