Preservation of Permian Fishes from the Marl Slate of County Durham

DEPARTMENT OF EARTH SCIENCES- DURHAM UNIVERSITY

Prof. David Harper: [email protected] Dr Stuart Jones: [email protected]

Preservation of Permian fishes from the Marl Slate of County Durham

1. Background The fossil fishes from the Permian Marl Slate (Fig.1) display superb preservation of palaeonis- A large fauna of beautifully-preserved fishes from coid fish from scales scattered sparingly to com- the Marl Slate was first described by William King plete whole specimens with extraordinary detail. in his landmark monograph on the Permian fossils of England, in 1850. The Marl Slate was deposited over large areas in middle Europe (extending from England to Russia) in a restricted, almost la- goonal environment; the setting is virtually unique in the stratigraphical record. Neverthe- less, we know little of the modes of preservation of the fishes, many of their life styles and their contribution to late Permian food webs. The po- tential too that soft parts may have been preserved offers a unique opportunity to study the anatomy and decay processes of these Palaeozoic fishes. Outside Britain, the most closely compara- ble fish-bearing formation to the Marl Slate is the Kupferschiefer of Germany. This is a similar fine- grained, flaggy rock in which specimens are well preserved, flattened on individual laminae. The Kupferschiefer extends across north-west Europe (Lower Zechstein), and is regarded as marking a series of anoxic events prior to the main flooding of the Zechstein Basin in the first of five cycles Figure 1: Two examples of Palaeoniscus freislebenen- sis, Marl Slate, County Durham, UK The soft-part preservation remains because of se- lective preservation and subsequent diagenesis Key questions to study: to more resistant biopolymers. Permineralization, • the permeation of tissues by mineralizing fluids, What are the key preservational modes for the Permian Marl slate fish? may preserve remarkable detail particularly of plants. However, evidence of more labile tissues, • How can detailed quantitative mineral mapping e.g., muscle, normally requires the replication of assist with understanding the fish ecology oc- their morphology by rapid in situ growth of min- currence prior to the P-T Mass Extinction event. erals, i.e., authigenic mineralization. This process relies on the steep geochemical gradients gener- The project will involve some fieldwork, locally, ated by decay microbes. The minerals involved, but principally a study of selected fishes from the and the level of detail preserved (which may be large collections held in the Earth Sciences de- subcellular), depend on a number of factors, in- partment. Detailed SEM, SEM-EDX, Quantitative cluding the nature of microbial activity and mineral mapping and cathodoluminescence stud- amount of decay, availability of ions, and the type ies will enhance studies of fish anatomy and help of organism that is fossilized. Understanding establish what material is actually preserved, in- these controls is essential to determining the con- cluding its preservational pathways, its signifi- ditions that favour exceptional preservation. cance and contribution to understanding the ecology and phylogeny of major groups of fishes just prior to the end Permian mass extinc tion event. MSc-by-Research in Earth Sciences PROPOSAL — 2019 http://www.dur.ac.uk/earth.sciences/postgraduate/ DEPARTMENT OF EARTH SCIENCES- DURHAM UNIVERSITY Strang, K.M., Armstrong, H.A., Harper, D.A.T. & Trabucho-Alexandre, João P. (2016). The Sirius Passet Lagerstatte: silica death masking opens the 2.Methodology window on the earliest matground community of High-performance scanning electron microscopy the Cambrian explosion. Lethaia 49(4): 631-643. (SEM) with a Zeiss Evo ESEM and Sigma 300 SEM and full quantitative mineralogy will be used in this study. Quantitative Mineralogic suite is a dedicated automated mineralogy designed to map mineral types in samples and provide re- peatable mineral and elemental maps using the Sigma 300 ZEISS SEM with the use of multiple in- tegrated EDX detectors. Detailed SEM work will be combined with pe- trography, geochemistry and micro-CT analysis of suitable samples to determine the preservation of the samples. For suitable samples XRF will be undertaken to further constrain the geochemistry of the fossil fish and Marl slate mineralogy.

3. Training

The student will become part of a vibrant research culture in the department of Earth Sci- ences, in which ~80 postgraduate students work on a wide range of Earth Science research pro- jects. In particular, the student will closely collab- orate with the academic staff, postdoctoral re- searchers and fellows, and postgraduate students in the sedimentology and palaeontology research groups.

Support and training will be provided in all of the analytical techniques and specifically in using the Durham University based Zeiss quantitative Min- eralogy Zeiss Microsystems, UK, will offer full support for this project.

References & reading Hammarlund, Emma U., Smith, M. Paul, Rasmus- sen, Jan A., Nielsen, Arne T., Canfield, Donald E. & Harper, David A. T. (2019). The Sirius Passet La- gerstätte of North Greenland—A geochemical window on early Cambrian low-oxygen environ- ments and ecosystems. Geobiology 17, 12-26.

Strang, K.M., Armstrong, H.A. & Harper, D.A.T. (2016). Minerals in the gut: scoping a Cam- brian digestive system. Royal Society Open Sci- ence 3(11): 160420.

MSc-by-Research in Earth Sciences PROPOSAL — 2019 http://www.dur.ac.uk/earth.sciences/postgraduate/