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Overview

The Jurassic was characterized by a greenhouse climate and is generally thought to have been dominantly ice-free. This period in Earth history was punctuated by several episodes of major environmental change. Geochemical, stratigraphic, and palaeontological datasets indicate that some of these involved considerable increases in global temperature, but there is recent and growing evidence that the Jurassic was also marked by geologically brief interludes of climatic cooling [1]. The biotic effects of major intervals of global warming in the Jurassic, such as the Toarcian oceanic anoxic event, included widespread extinctions and faunal turnover among marine invertebrates [2]. However, the biotic effects of climatic cooling events in the Jurassic are less well understood. Land plants are tightly constrained by climate because they are relatively immobile and are dependent on light, soil water, and temperature. As such, they are an ideal group of organisms with which to investigate the complex interplay between climatic and biotic change.  

 

This project will investigate vegetation dynamics during the early Aalenian, an interval of climatic cooling in the Jurassic between ~174 and ~170 Ma. Palaeobotanical work indicates that plants such as ferns, cycads, bennettites, ginkgos and conifers were significant components of Jurassic vegetation [3], and this project will provide data on how these plants responded to an interval of ancient climatic change. This will contribute to the wider debate surrounding the response of Earth's vegetation to temperature changes, as well providing information on land cover for workers building numerical models of Jurassic climate.   

 

The specific aims of this project are to:

(1) Reconstruct early Aalenian vegetation dynamics by extracting and analysing fossil pollen and spores (Figure 1) from two European rock successions.

(2) Compare the diversity and composition of early Aalenian vegetation from these two different regions using multivariate statistical analyses.

(3) Integrate this palaeoecological data with published temperature and carbon cycle proxies for the late Toarcian and early Aalenian in order to understand the link between vegetation change and climatic change at this time. 

Examples of a Jurassic moss spore (A) and Jurassic pollen produced by seed-ferns and conifers (B & D) and cycads (C). Scale bars represent 20µm.

Methodology

A suite of 50 pilot samples from Toarcian–Aalenian rock successions on the Isles of Skye and Raasay (Hebrides Basin) are available for immediate study prior to going into the field. Two field trips will be required. The first will involve collecting a second suite of 125 samples from the Hebrides Basin. The second will involve collecting 125 samples from strata of the same age from southern Germany (Swabo–Franconian Basin) in order to generate comparative data. The field trips will involve graphic logging of the successions and taking samples. Fossil pollen and spores will be released from these rock samples using acid digestion techniques in the fully equipped laboratories at the Open University. Pollen and spores will be examined using a transmitted light microscope and will be classified with reference to the published literature. The datasets will be compared using multivariate statistical analyses, and will be stratigraphically correlated and statistically compared to published carbon isotope and palaeotemperature proxy data. 

Training and Skills

This project will provide specific training in:

  • Field-based recording and sampling of sedimentary rocks and acid digestion laboratory techniques.
  • Transmitted light microscopy, and scanning electron microscopy.
  • Taxonomic expertise in a microfossil group that is of biostratigraphic significance in the context of hydrocarbon exploration.
  • Multivariate statistics and integrated stratigraphy.

CENTA students will be provided with 45 days training from CENTA through their PhD which includes a 5-day residential and a 10-day work placement. In the first year, students will undertake training in general environmental science, research methods and core skills as a single cohort. Training in years 2 and 3 will progress from core skills to masterclasses specific to the project and overall scientific theme.  

Timeline

Year 1: Process pilot samples from the Hebrides Basin to release fossil pollen and spores. Develop a working classification for these fossil pollen and spores. Collect a second suite of samples from the Hebrides Basin and start to process them in the laboratory. Examine the residues under the microscope and start to generate palaeoecological counts of the constituent taxa. Collect a suite of samples from rock successions in the Swabo–Franconian Basin (southern Germany) and start to process them in the laboratory.

Year 2: Complete processing of the samples. Finish palaeoecological counting of the residues in order to generate data on the composition of Aalenian vegetation in the Hebrides Basin and the Swabo–Franconian Basin. Prepare a presentation detailing preliminary results for the Palaeontological Association Annual Meeting. Prepare a manuscript detailing the results from years 1 and 2 of the project.

Year 3: Analyse these palaeoecological data in order to compare the composition of Aalenian vegetation from the Hebrides Basin and the Swabo–Franconian Basin. Prepare a presentation for the European Geosciences Union General Assembly, and manuscripts detailing this comparison. Write up PhD

Partners and collaboration (including CASE)

This project will involve collaboration with Prof. Stephen P. Hesselbo, University of Exeter. Prof. Hesselbo has collected the suite of samples from Toarcian–Aalenian rock successions in the Hebrides Basin, which will provide the raw pilot material for the project. This project will also involve collaboration with Dr Christoph Korte (University of Copenhagen), who will provide expertise on Aalenian geochemistry. 

Further Details

Students should have a strong background either in biology or in Earth science and have a keen interest in plants. Students should be enthusiastic about fieldwork and enjoy working with microfossils. The successful student will need to hold a full UK driving license. The student will join a well-established team researching palaeoenvironmental change at the Open University (http://palaeoenvironmentalchange.org)

Please contact Luke Mander (Luke.Mander@open.ac.uk) for further information.