Reconstructing the Cambrian explosion using Small Carbonaceous Fossils: Ediacaran to Cambrian SCFs in the Baltic Basin

The Cambrian 'explosion' of early animal life was one of the most transformative events in Earth history, but the underlying patterns and players are difficult to resolve. The conventional shelly fossil record represents only a fraction of ancient diversity, while contemporaneous 'Burgess Shale-type' fossils are too rare and unrepresentative to track evolutionary trajectories. We have, however, identified a new and largely overlooked source of palaeontological data that promises to fill in many of the gaps. 'Small Carbonaceous Fossils' (SCFs) are organic-walled fossils that are too small to be identified on bedding surfaces, but too large and delicate to be recovered by conventional micropalaeontological techniques. Although mostly represented by disarticulated sclerites and cuticle fragments, SCFs are fundamentally more common and widely distributed than their articulated counterparts. Most significantly, the SCF record from shallow marine environments is revealing an unprecedented, and surprisingly modern, diversity of early animals,

Our recent SCF work has been extraordinarily successful, but limited to 'post-explosion' phases of the Cambrian record. Here we propose to extend the study of SCFs back in time, with an eye to tracking evolutionary patterns through the Cambrian explosion and into the preceding Ediacaran Period. By far the most promising place to carry out such a study is in well-documented Precambrian-Cambrian boundary sections of the Baltic Basin. These shallow water successions are exceptionally well preserved, richly fossiliferous and easy to access - primarily through drillcore archives at the geological surveys of Estonia, Latvia, Lithuania and Sweden, along with a unique research collection at the Tallinn University.

Our primary focus in the Baltic Basin will be in documenting the diversity and distribution of SCFs from the late Ediacaran through to the late Cambrian. We are particularly interested in using the SCF record to test macroevolutionary patterns derived from alternative datasets, including 'small shelly fossils' and execeptionally preseved arthropod biotas in the late Cambrian of Sweden. Microstructural analysis of problematic SCFs have the potential to identify unambiguous bilaterian animals in the Ediacaran, with major phylogenetic and macroevolutionary implications. Combined with geochemical analysis of associated palaeoenvironments, and a search for fossil biomarker molecules, these novel paleontological data will shed fundamental new light on the origin of the modern biosphere.

There are two non-academic constituencies that will benefit in particular from our proposed research - and that we will target in our Pathways to Impact plan.

Industry, Especially Petroleum Exploration:
The unexpectedly abundant and diverse range of Small Carbonaceous Fossils (SCFs) that we are discovering provides a valuable new source of biostratigraphic resolution in Proterozoic and early Palaeozoic sedimentary sequences. The potential of these fossils to correlate and date otherwise poorly resolved strata will be of particular interest to the Petroleum exploration industry, as well as companies involved more generally in geological mapping and engineering.

The Interested Public:
There is enormous public interest in both palaeontology and understanding how the Earth works as a biological planet. The Cambrian 'explosion' and accompanying origin of the modern biosphere figure significantly in this public awareness, and provide ready avenues for further engagement. The links are particularly strong in Cambridge where much of the formative work on the Burgess Shale was carried out in the 1970s and 1980s (and carries on with our diverse research expertise in Precambrian-Cambrian palaeobiology). Our Department also has the advantage of a major in-house palaeontological museum. With 100,000 visitors annually, the Sedgwick Museum offers a unique opportunity to communicate the excitement of this science to a wider audience.