One of the most impressive insect fossil localities is the Eckfeld Maar. The Eckfeld locality is actually a fossilised maar of the Eifel Mountains, Germany. Beneath the lake sediments lies a breccia layer, including basaltic fragments, meaning an easy argon dating opportunity: the bottom, i.e. oldest age of the sediments is 44.3 ± 0.4 Ma (Mertz et al., 2000).
The crater itself was 900 m in diameter and the lake’s depth between 110 and 150 m (Pirrung et al., 2001). The lake was meromictic, i.e. had clear layers of differing salinity, chemistry and temperature. Critically, the deepest part of the lake, the monimolimnion (this term applies only to meromictic lakes!), was anoxic and highly-alkaline (Mingram, 1998), meaning there were no organisms living there. This is the key to the impeccable fossil preservation in Eckfeld: there weren’t any scavengers feasting on dead bodies, bacterial activity was not too high, and there were no infaunal burrowing animals that messed up the layering of the sediment, meaning carcasses and other biotic bits that floated down to the bottom were left relatively undisturbed, until some palaeontologist hammered them out. The rock type is a very characteristic oil shale. It is very black, and knocking it with a hammer releases a very charcoalish smell, because of the very high carbon content of the rock.
Refer to Lutz & Kaulfuß (2006) for a general review of the locality.
This taphonomy also means that these fossils require special preservation methods: leaving them out in the open air would oxidise the rock and it will crumble, along with your fossil. So all specimens from Eckfeld are kept under glycerine; the same applies for Messel, among other localities.
And what are these specimens? Much like in the present-day Eifel, there was a forest around the lake, and many of the organisms that lived there ended up dying in the lake – both terrestrial and aquatic ones. We have the remains of plants (leaves blown into the lake, for example) and many, many insects – there are over 30000 fossil known from Eckfeld (and that’s a conservative estimate), and over 80% of them are beetles. Below are pictures of my favourite fossils from there.
Electrapis prolata: a bee. From: Wappler T & Engel MS. 2003. The Middle Eocene bee faunas of Eckfeld and Messel, Germany (Hymenoptera: Apoidea). Journal of Paleontology 77, 908-921.
Megamenopon rasnitsyi and a Recent relative, Holomenopon brevithoracicum: bird lice. Very, very cool – if only for being an example of parasitism from the fossil record! From: Wappler T, Smith VS & Dalgleish RC. 2004. Scratching an ancient itch: an Eocene bird louse fossil. Proc. R. Soc. B 271 (Suppl. 5), S255-S258.
Mastotermes krishnorum: a termite from the Mastotermitidae family, and thus important for understanding the early evolution of termites from cockroaches. Source: Wappler T & Engel MS. 2006. A new record of Mastotermes from the Eocene of Germany (Isoptera: Mastotermitidae). Journal of Paleontology 80, 380-385.
Oecophylla eckfeldiana: a weaver ant; A and B are gynes, C is a major worker, D is a minor worker. From: Dlussky GM, Wappler T & Wedmann S. 2008. New Middle Eocene Formicid Species from Germany and the Evolution of Weaver Ants. Acta Palaeontologica Polonica 53, 615-626.
The importance of Eckfeld cannot be understated: along with Messel, it is arguably the most significant non-amber fossil locality we have in the Eocene of Europe; while Messel has a much more diverse fauna, the palaeoentomological holdings of Eckfeld shouldn’t be underestimated: while it’s mostly beetles, as you can see above, there’s all sorts of stuff to be found, preserved in good detail, from an important time in insect evolution when many of the families we know today were diversifying. (And there’s also plant-insect interactions preserved there, such as scale insects in situ on leaves!)
Lutz H & Kaulfuß U. 2006. A dynamic model for the meromictic lake Eckfeld Maar (Middle Eocene, Germany). Zeitschrift der Deutschen Gesellschaft für Geowissenschaften 157, 433-450.
Mertz DF, Swisher CC, Franzen JL, Neuffer F-O & Lutz H. 2000. Numerical dating of the Eckfeld maar fossil site, Eifel, Germany: a calibration mark for the Eocene time scale. Naturwissenschaften 87, 270-274.
Mingram J. 1998. Laminated Eocene maar-like sediments from Eckfeld (Eifel region, Germany) and their short-term periodicities. Palaeo3 140, 289-305.
Pirrung BM, Bochel G & Jacoby W. 2001. The Tertiary volcanic basins of Eckfeld, Enspel and Messel (Germany). Zeitschrift der Deutschen Geologischen Gesellschaft 152, 27-59.
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Lutz, H., & Kaulfuß, U. (2006). A dynamic model for the meromictic lake Eckfeld Maar (Middle Eocene, Germany) Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 157 (3), 433-450 DOI: 10.1127/1860-1804/2006/0157-0433