Field trip to Holderbank and Lenzburg
Excursion leaders: Christian Klug, Kristína Kocáková
Excursion date: 1st of August 2025
Minimum/Maximum number of participants: 10/40
Estimated duration of the field trip: ~ 7 hours
Program:
- 08:00 - Meeting at Platform 32 at Zurich HB (Main station)
- 08:10 – 08:49 - Transport by train to Holderbank AG
- 09:00 – 11:45 - Holderbank fossil collection
- 12:15 – 12:37 - Transport to Lenzburg
- 13:00 – Onwards - Lunch at Hotel Krone
- Optional: Visit of the Lenzburg Castle
- Transport by train to Zurich
Transport (train): We recommend buying a Z-Pass A-Welle day train ticket or using the “Easy-ride” function in the SBB application. Detailed instructions will be provided for the participants.
Description: The former Schümel Quarry near Holderbank, nested in the Jura mountains of Aargau canton, offers a unique insight into the geological history of this mountain range and is often described as a geological open-air museum. The site exposes a well-preserved sequence of Jurassic marine sediments, deposited in an epicontinental marine basin of moderate depth probably ranging from fair weather wave base to 300 meters depth. These strata, ranging from the Bajocian to the Oxfordian, show clear temporal facies changes, from cross-bedded condensed limestones with ooids to marl-rich limestones, reflecting shifting depositional environments over time. Bathonian and Callovian marl layers are particularly rich in ammonites, while the Oxfordian marls and limestones contain diverse assemblages of cephalopods, including both ammonites and belemnites, along with other macrofossils. The Birmensdorf Member particularly contains abundant calcareous sponges, brachiopods, and ammonites. Sea urchins and shark teeth may also be found. This site provides an excellent opportunity to study Jurassic sponge meadow development, faunal diversity, and sedimentary facies variation in a relatively small geographic area.
What to bring: Snack for the morning, water or other drink, Sturdy shoes, hat, sunglasses, sunscreen. This trip will include a lot of walking, including walking uphill for long periods of time, potentially in quite hot weather! Please make sure you have adequate clothing and bring plenty of fluids! Optional: Hand lense, geologic hammer, materials to store collected fossils (zip-lock bags, newspaper, tissue paper)
Predicted cost per person: 100 CHF (covered by participants individually)
