Early Palaeozoic of southern Sweden: An up-to-date view
Leaders: Lennart Jeppsson, Birger Schmitz, Per Ahlberg, Mats Eriksson (Lund University, Sweden)
Västergötland (Per Ahlberg and Birger Schmitz)
The Lower Palaeozoic of Västergötland has a long history of palaeontological and stratigraphical research, extending well back into the eighteenth century. The sedimentary succession occurs as erosional outliers resting on a Proterozoic crystalline basement. These outliers constitute the geologically famous table mountains of Västergötland. The last decades have witnessed major efforts to increase the knowledge of the stratigraphy, sedimentologi, palaeontology, and geochemistry of the Lower Palaeozoic in Västergötland. This extensive research has, for instance, resulted in the establishment of a GSSP for the upper stage (Floian Stage) of the Lower Ordovician Series at Hunneberg in Västergötland, and in the identification of several Ordovician and Silurian K-bentonites with considerable event-stratigraphic and tectonomagmatic significance. Furthermore, the Ordovician of Mount Kinnekulle is now world-famous because of its abundance of fossil meteorites. More than fifty fossil meteorites (1-20 cm in diameter) have been found during quarrying of Orthoceratite Limestone at a level close to the Volkhov-Kunda (or British Arenig-Llanvirn) boundary at Österplana at Kinnekulle. The meteorites originate from the disruption of the L chondrite parent body in the asteroid belt at this time. This is the largest documented disruption event in the asteroid belt for the ca. past 3 billion years. About 20 % of the meteorites that strike Earth today originate from this event. In connection with the disruption event in the mid-Ordovician the flux of meteorites and larger asteroids increased substantially, as indicated by the abundant fossil meteorites but also by many craters of this age on Earth (in Sweden: the Lockne, Tvären, and Granby craters). The increased flux of asteroids may have spurred the ongoing Great Ordovician Biodiversification Event.
Gotland (Lennart Jeppsson and Mats Eriksson)
This island is famous for its world-class palaeontology and its cultural heritage, e.g. the world heritage city of Visby. The strata represent a series of stacked carbonate platforms that evolved in a shallow sea at tropical latitudes during the Silurian Period.
Research progress on the world-famous Silurian strata during the last 20 years has resulted in that Gotland has become the reference area for the sequence of latest Llandovery through the Ludlow oceanic events, associated mass extinctions, anachronistic facies, evidence of sea level changes, major d13C excursions, and the Wenlock standard conodont zonation. In addition, most of the strata are richly fossiliferous with fossils showing pristine state of preservation. During this field trip we will study a wide variety of localities spanning the entire stratigraphic interval, and including classical key sections as well as fossil collecting localities. We will see the sparsely graptolitic strata formed in offshore settings, exposed on the western part of the island, and the contrasting proximal reefs and associated strata exposed chiefly on eastern Gotland. We will also see some of the rich cultural heritage from the oldest time to the recent.
The locality lists below are preliminary. Furthermore, the approximate number of participants will influence what kind of bus we use – some roads are not suitable for a large bus. The level of the Baltic Sea fluctuates from day to day; if above normal, one or more costal localities may have to be exchanged at the last minute. We will visit localities with a wide array of biofacies and lithofacies. Some sections expose thin-bedded, argillaceous limestone and marls deposited in relatively deep and calm waters seaward of the reef barriers. These strata are in places exceptionally rich in free-weathered and very well preserved fossil assemblages, with vagrant and sessile benthos. We will also see reef-proximal strata and shallow-water facies with markedly different faunas. Several of the successions at these localities include unconformities, since long important for the stratigraphy of Gotland. However, high-resolution studies using isotopes, conodonts and other major clades, increasingly show that these unconformities reflect global sea level changes. Similarly, much of the other lithological changes are now being found to reflect a global pattern. Many of the visited sections are such key localities for global Silurian event stratigraphy. In addition to the geology, we plan to show you some of the rich Medieval and older heritage near the geological localities or the road (e.g. Bronze Age monuments, Romanesque and early Gothic churches). Similarly, accompanying persons may find that even if five days in Visby may be too little, the countryside will also compete for their attention.
This is the third field guide to Gotland produced by us during the last four years; hence, large parts are improved and updated from earlier versions.