Hayburn Wyke

[TA 011 969]

Introduction

The Hayburn Wyke plant beds have long been known to yield a diverse and well-preserved fossil flora of Aalenian age. It is a key Yorkshire Jurassic plant fossil locality with unique floral elements, especially of cycads. The marchantialean liverwort Hepaticites haiburnensis is known only from this locality.

Hayburn (or 'Haiburn') Wyke is a small bay near Cloughton (Figure 3.29) and (Figure 3.30), and is an important source of plant fossils from the Saltwick Formation (the 'Lower Deltaic Series' of earlier authors). The earliest records seem to be by Phillips (1829) and Lindley and Hutton (1837). Leckenby (1864) also collected from here and some of his specimens were mentioned by Phillips (1875) (Leckenby's specimens are stored in the Sedgwick Museum, Cambridge). The 19th century records were summarized by Seward (1900a). Hamshaw Thomas collected extensively from the section in the early 20th century, although does not appear to have published descriptions of this material. Harris (1944a, 1945a, 1948, 1949a,b, 1950, 1951, 1952a, 1953) and Bose (1955) have described various species of bennettite, ginkgophyte, czekanowskialean and conifer foliage. However, the full spectrum of the flora at Hayburn Wyke was not revealed until the publication of Harris' monograph on the Yorkshire Jurassic floras (1961a, 1964, 1969, 1979a; Harris et al., 1974).

Description

Stratigraphy

The section exposed at Hayburn Wyke includes parts of the Saltwick and Eller Beck Formations (Figure 3.31). The plant beds are in the argillaceous floodplain sediments exposed in the centre of the small bay. The succession dips gently southwards, the Eller Beck Formation reaching beach level at lion Scar. The exposure is scattered over the rocky beach and often covered by landslip. The sandy units contain fragmentary plant remains, many of which are charcoalified. The finer-grained beds contain much abundant, more diverse, and better-preserved plants. Van Konijnenburg-van Cittert and Morgans (1999) have provided details of the field geology of this site.

Harris' unpublished notebooks refer to 12 separate plant beds in the vicinity of Hayburn Wyke (see (Table 3.3)), although some of these lie in the Cloughton Formation and are beyond the boundaries of the GCR site. The principle source of plant fossils is the main Hayburn Wyke Plant Bed, which probably corresponds to the Hayburn Beck and Zamites Beds of Harris.

(Table 3.3) The locations of the 'plant beds identified by T. M. Harris (in manuscript) along the coast at Hayburn Wyke

Palaeobotany

The complete list of about 60 plant species that have been found at Hayburn Wyke is given in (Table 3.1). It includes the marchantialean liverwort Hepaticites haiburnensis for which this is the type locality. The 12 ferns include Cladophlebis haiburnensis, which was first described from here by Lindley and Hutton. There are relatively few cycads and pteridosperms, although there are 11 bennettites, of which Bucklandia gigas, Otozamites leckenbyi, O. mimetes, O. parallelus, O. tenuatus (see also (Figure 3.32)), and Weltrichia sol were first described from here. The site is also the locality of the ginkgoalean Baiera furcata.

Van Konijnenburg-van Cittert (1978, 1989) used specimens of Coniopteris hymenophylloides (Figure 333), C. murrayana, C. simplex and Todites princeps from Hayburn Wyke in her studies of in-situ spores of these species. Morgans (1999) has described charcoalified conifer wood from floodplain mudstone and crevasse-splay sandstones at the site as Cedroxylon spp., Cupressinoxylon spp., Taxodioxylon spp. and Xenoxylon phyllocladoides Gothan, 1906.

Interpretation

There are several horizons at Hayburn Wyke that yield different assemblages. The Zamites Bed is the richest and most important although it shows intense localization, both vertically and horizontally. Ferns are frequently common with Clathropteris obovata, Coniopteris bella, C. hymenophylloides, C. murrayana, C. simplex, Matonidium goeppertii and Phlebopteris woodwardii. The pteridosperm Pachypteris lanceolata is also common in places. At one point the only gymnosperms found by Harris (1969) were great numbers of Zamites gigas leaves (Figure 3.34), a few pieces of Williamsonia (Bucklandia) stem, a few Williamsonia gigas flowers and a few good specimens of Weltrichia sol, suggesting that these three organs were parts of a single plant species.

In contrast, the Equisetum bed, which is just above the Iron Scar (Figure 3.29), is only rich in Coniopteris simplex, possibly reflecting a very local plant community immediately surrounding a small lagoon.

Conclusion

The Hayburn Wyke plant beds contain an important and rich flora including several species that were first described from here and the only known occurrence of the liverwort Hepaticites haiburnensis. A reassessment of the species content of the various horizons should reveal valuable ecological information.

References