SOSNOWIEC, POLAND–It could not have been a better day for field work: warm with a light, cooling breeze and plenty of leafy green shade. Our team consisted of me and three Polish scientists: Michał Zatoń and Wojciech Krawczyński (I work hard to get those special Polish letters in there!) of the University of Silesia, and PhD student Tomasz Borszcz of the Institute of Oceanology in Sopot, Poland (near the famed city of Gdansk on the Polish Baltic coast). Our goal was to simply see some Jurassic rocks and fossils and talk geology. Mission accomplished.
The top image shows outcrops of remarkable lithistid sponge mounds from the Oxfordian (earliest Upper Jurassic) punching up through the forest cover a few kilometers northeast of Sosnowiec. They formed relatively deep on the Jurassic seafloor and supported an associated brachiopod community.
I was able to visit for the first time one of the localities from which large Middle Jurassic oncoids (cobbles and pebbles covered with the deposits of microbial biofilms) were found and became the basis for a paper co-authored with Michał and Wojciech. In the picture above of a broken cobble you will notice bivalve borings (Gastrochaenolites) penetrating from the outside.
Lunch was in a tavern near the town square of Sławków in the Silesian Highlands. The Polish custom of carving the date of the building on the central roof beam meant we could see right away it was constructed in 1701. (It seems to be preserved in a modern shell of some kind.) I had a typical Silesian meal of rolled beef and dumplings (I think).
A view of the Silesian Highlands from a street in Sławków. This small city is the western terminus of the Broad Gauge Metallurgy Line, a rail system designed “in communist times” to transport iron ore from Ukraine to iron smelters in Poland. The rail gauge in Ukraine and points east is wider than the standard gauge in western Europe.
Our last stop of the day was to a set of deep holes in the middle of a forest. Amateur fossil collectors dug through about two meters of soil and Pleistocene sediment to expose a layer of Callovian (latest Middle Jurassic) rock rich in ammonites, belemnites and other fossils. The three paleontologists, in typical paleontological poses, are from the right Wojciech, Michał and Tomasz.