The oldest ‘millipede’-plant association? Age, paleoenvironments and sources of the Silurian lake sediments at Kerrera, Argyll and Bute, Scotland

ABSTRACT

On Kerrera island, poorly dated braided stream conglomerates and sandstones are interbedded with finer lake siltstones and shales, with land plants, fish and arthropods, including ‘millipedes’. Crystallization dates for minerals in the overlying Lorne Plateau Lave are older than 425 Ma (Upper Silurian Ludfordian), yet palynological data are supposed to give an early Devonian (419 Ma) age. Detrital zircon U/Pb dates of sediments enclosing the fish beds give two clusters of dates, one Proterozoic and the other Silurian. The most concordant youngest single grain date of 427.0 ± 4.5 Ma (0% discordance) gives the maximum age of the Fish beds and is consistent that the radiometric dates of the overlying rapidly erupted lavas. This maximum age is slightly older than that of the ‘millipede’-bearing Cowie fish bed with maximum age of 414.3 ± 7.1 Ma, which make the Kerrera ‘millipedes’ the oldest so far dated.

KEYWORDS:

• U-Pb
• age
• Silurian
• Kerrera
• millipede-bearing
• lake

Acknowledgments

We appreciate the help of Gabriel Villeseñor with the analyses and Daniel Stöckli for use of his U/Pb dating laboratory.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was support by a University of Texas at Austin grant to E. Catlos.