Solnhofen – Palaeoenvironment

This post is one in a series of posts which compares the depositional environment of the late Jurassic lithographic limestones at Solnhofen in Germany based on extracts from Solnhofen: A Study in Mesozoic Palaeontology with observations made at a modern inter-tidal mudflat at Ha Pak Nai, Deep Bay, New Territories, Hong Kong and proposes an inter-tidal mudflat origin for the examples cited.

This post covers details of the palaeoenvironment as documented in Solnhofen: A Study in Mesozoic Palaeontology. Comparisons with the inter-tidal mudflat at Ha Pak Nai, Deep Bay, New Territories, Hong Kong will be made in the following posts.

Extracts from: Solnhofen: A Study in Mesozoic Palaeontology

Early depositional model

“Early depositional models envisaged the Southern Franconian Alb as a vast mudflat where sediment was brought onshore by storms to consolidate and dry out under the sun” (Barthel et al - Page 56).

Comment: This model was rejected and the deposits at Solnhofen are currently interpreted to have formed in a “restricted basin” - see below.

The restricted basin model

“It is now generally agreed that the plattenkalk basins lay permanently submerged under a stable body of water” (Barthel et al - Page 56).

“The Solnhofen area may then be thought of, in a broad sense, as a lagoon bordered to the north by low-lying land and to the south by a chain of coral reefs which protected it from the Tethys Ocean. The base of the lagoon was covered by dome-shaped mounds, built by sponges and cyanobacteria (blue-green algae) in the Kimmeridgian stage of the Late Jurassic. The mounds shielded intervening hollows from the effects of currents and, in the quiet basinal waters, the plattenkalk sediment was deposited” (Barthel et al - Page 57).

Stagnation of the bottom waters

“The peculiar composition of the waters not only deterred normal marine organisms from living in this environment, but for any organism unfortunate to be washed over the reef and steeped in this solution, death followed very shortly afterwards. Hence the examples of mass mortality and sudden death seen in some of the fossils” (Barthel et al Page 58) 

References

Barthel, K.W., Swinburne, N.H.M., and Conway Morris, S. (1994). Solnhofen: A Study in Mesozoic Palaeontology. Cambridge University Press, Cambridge.