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

Lead Research Organisation: University of Cambridge
Department Name: Earth Sciences

Abstract

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.

Planned Impact

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.
 
Description The aim of the project is to resolve evolutionary changes associated with the radiation of animals from around 550 to 520 million years ago (the 'Cambrian explosion'). Having previously identified a promising new category of microfossil - Small Carbonaceous Fossils (SCFs) - we were keen to see if these might yield a coherent account of the transitional interval in the Baltic Basin - based on exceptionally well preserved sedimentary sequences in the Baltic States and Sweden. Rather than just look for fossils, however, we combined this work with a study of biomarkers (chemical fossils) and redox geochemistry. This multidisciplinary approach has proven to be very successful. In addition to discovering a rich assortment of SCFs from throughout the succession, we have recovered a unique biomarker record from the terminal Ediacaran (just prior to the Cambrian explosion) and an overall geochemical record that tracks the microfossil record with surprising fidelity. Taken together, these data offer an unprecedented view of the Edicaran-Cambrian transition, and the environmental circumstances under which animals first rose to ecological prominence.

March 2017 update:
- Paper on Baltic SCFs published in Palaeontology (Slater et al. 2017) - the first substantial record of Burgess Shale-type fossils on Baltica.
- ms on Cambrian oxygen minimum zones currently in review at Nature Geoscience - with important implications for reconstruction palaeo-redox signatures (Guilbaud et al.)
- ms about to be submitted on SCFs from the earliest Cambrian of the Baltic Basin (Slater et al.)
- ms in preparation, documenting the relationship between SCF preservation and redox geochemistry (Guilbaud et al.) March 2018 update: Paper on earliest Cambrian SCFs publishished in Palaeontology (Slater et al. 2018); paper on early Cambrian Oxygen Mimimum Zones published in Geochemistry Perspectives Letters (Guilbaud et al. 2018); ms about to be submitted on 'Redox taphonomy of Small Carbonaceous Fossils' (Guilbaud et al.)

March 2021 update - paper published on 'Cochleatina: an enigmatic Ediacaran-Cambrian survivor among small carbonaceous fossils (SCFs) (Slater et al. 2020, Palaeontology)
Exploitation Route This study is based on the use of a novel extraction technique for recovering delicate organic-walled microfossils. These techniques and data are now recognized internationally. Other groups are beginning to adopt a similar approach, though a number simply send their samples to us.

Our integration of microfossil data with associated geochemical signatures has identified a key control on the preservation of organic-walled fossils - and thereby a tool in the search for further fossil occurrences.
Sectors Education

Environment

Culture

Heritage

Museums and Collections

 
Description This work has established a valuable working relationship between Cambridge and the Tallinn University of Technology. They have also helped to develop the career of Dr. Ben Slater, now a post-doc at Uppsala University
First Year Of Impact 2014
Sector Education,Environment,Culture, Heritage, Museums and Collections
Impact Types Cultural

 
Title Data from: Small carbonaceous fossils (SCFs) from the Terreneuvian (lower Cambrian) of Baltica 
Description We describe a new assemblage of small carbonaceous fossils (SCFs) from diagenetically minimally altered clays and siltstones of Terreneuvian age from the Lontova and Voosi formations of Estonia, Lithuania and Russia. This is the first detailed account of an SCF assemblage from the Terreneuvian, and includes a number of previously undocumented Cambrian organisms. Recognisably bilaterian-derived SCFs include abundant protoconodonts (total-group Chaetognatha), and distinctive cuticular spines of scalidophoran worms. Alongside these metazoan remains are a range of protistan-grade fossils, including Retiranus balticus gen. et sp. nov., a distinctive funnel-shaped or sheet-like problematicum characterized by terminal or marginal vesicles, and Lontohystrichosphaera grandis gen. et sp. nov., a large (100-550 µm) ornamented vesicular microfossil. Together these data offer a fundamentally enriched view of Terreneuvian life in the epicratonic seas of Baltica, from an episode where records of non-biomineralized life are currently sparse. Even so, the recovered assemblages contain a lower diversity of metazoans than SCF biotas from younger (Stage 4) Baltic successions that represent broadly equivalent environments, echoing the diversification signal recorded in the coeval shelly and trace-fossil records. Close comparison to the biostratigraphic signal from Fortunian small shelly fossils (SSFs) supports a late Fortunian age for most of the Lontova/Voosi succession, rather than a younger (wholly Stage 2) range. 
Type Of Material Database/Collection of data 
Year Produced 2018 
Provided To Others? Yes  
URL https://datadryad.org/stash/dataset/doi:10.5061/dryad.8hn63
 
Description 10th New Phytologist Workshop, Natural History Museum, London 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact A small international research meeting met to investigate the early evolution of plants and their interactions with fungi
Year(s) Of Engagement Activity 2014
URL https://www.newphytologist.org/workshops/10
 
Description Invited departmental seminar, Geoforschungs Zentrum (GFZ-Potsdam, Germany) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Presentation of research seminar: 'Ocean redox chemistry at the dawn of animal radiation'. Follow-up questions and discussion.
Year(s) Of Engagement Activity 2016
 
Description Invited departmental seminar, Universite des Sciences et Technologies de Lille (Lille-1), Lille, France 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Presentation of an invited research seminar: Cambrian ecology and evolution: New insights from exceptionally preserved microfossils. Follow-up question and answers, with interest in new techniques and data
Year(s) Of Engagement Activity 2015
 
Description Invited departmental seminar, University of Portsmouth 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact Presentation of an invited research seminar: The Cambrian "explosion" under the microscope: exceptionally preserved "small carbonaceous fossils" (SCFs). Followed up with a question and answer session, including interest in novel techniques and data.
Year(s) Of Engagement Activity 2015
 
Description Presentation of research to colleagues at Tallin University of Technology, Estonia 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact A presentation to local stakeholders regarding our research interests in Estonian geology.
Year(s) Of Engagement Activity 2014
 
Description Presentation of research to colleagues at Tallin University of Technology, Estonia 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact Presentation of our research to interested parties at the Tallin University of Technology - primarily to communicate our research on Estonian geology to TUT staff and researchers
Year(s) Of Engagement Activity 2014
 
Description Public lecture to the Charnia Research Group, Leicester 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Public/other audiences
Results and Impact Presentation of public lecture: The Cambrian "explosion" under the microscope. Enthusiastic follow-up discussion session from a wide range of backgrounds.
Year(s) Of Engagement Activity 2015