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Flora Fossil Site - Yea, Limestone Rd, Yea, VIC, Australia

Photographs None
List National Heritage List
Class Natural
Legal Status Listed place (11/01/2007)
Place ID 105851
Place File No 2/07/107/0002
Summary Statement of Significance
Yea Baragwanathia Flora Fossil Site has deposits containing pioneer vascular land-plant floras and ancient invertebrates of international significance. It is the oldest known Baragwanathia flora fossil site in the world, providing significant information about the evolution of early land plants. This site, with its Lower Plant Assemblage, includes many more members of the Baragwanathia flora and has a richer associated marine fauna than any other site, and importantly, the specimens are better preserved. Specimens of the primitive club moss, Baragwanathia longifolia, and other Baragwanathia flora occur as part of an extensive floral assemblage in graptolite-bearing beds dating to the Late Silurian age (about 415 million years ago). Barclays Cutting is one of only two Baragwanathia localities with graptolites (jellyfish-like colonial marine invertebrates) and an extensive floral fossil assemblage in close association, and is the site with the best and richest such fossils in Australia.
 
These plant fossils considerably predate club mosses (lycopods) found in the Northern Hemisphere fossil record. They provide evidence of the extensive evolution and development of early vascular plants, and most significantly, adaptations of plants from the sea to the land. Fossil evidence from the Yea site indicates that land plants may have developed first in the Southern Hemisphere.
 
The Yea Baragwanathia fossil site is the best example exposing the older Lower Plant Assemblage in Australia. It contains representatives of the Baragwanathia flora, including Baragwanathia longifolia and an unusually high number of other early vascular land plants such as Drepanophycus sp., Yarravia sp., Hedeia sp. and Salopella australis sp. nov.
 
The site has strong associations with the internationally renowned pioneer palaeobiologist Dr Isabel Cookson (1893-1973) who described the Yea Baragwanathia fossils in 1935. Cookson, a Research Fellow in Botany, University of Melbourne (1952-1959) was world renowned for her research on fossil plants. She created many international collaborations and associations that led to significant discoveries. The Cooksonia plant genus (containing the oldest known land plants) and the Isabel Cookson Award (Botanical Society of America) have been named in her honour.
 
Official Values
Criterion A Events, Processes
The Yea Baragwanathia Flora Fossil Site (Barclays Cutting) exposes well preserved specimens of Baragwanathia longifolia and a range of other plants occurring as part of a floral assemblage in graptolite-bearing beds dating from the late Silurian period. This rich fossil deposit of some of the earliest known vascular land plants is well recognised as being of international significance. The plant fossils considerably predate lycopsids (club mosses and their allies) found in the Northern Hemisphere fossil record. They provide evidence of the dramatic evolution and development of vascular plants that occurred during this time, particularly the adaptation of plants from the sea to the land. B. longifolia is almost exclusively found in the Southern Hemisphere and these fossils may indicate that land plants developed first in the Southern Hemisphere (Garratt 1978, Jaeger 1966, Joyce & King 1980, White 1988).
 
The lowermost assemblage at Barclays Cutting contains an unusually high number of early vascular land plants including Baragwanathia longifolia and another lycopsid, Yarravia sp. (Lycophytina), Salopella australis sp. nov., a new species of Hedeia (Rhyniophytina), members of the Trimerophytes (a related group of early plants from which all higher plants evolved) and at least one zosterophyll (Zosterophyllophytina). The assemblage at Barclays Cutting is considered to be of Late Silurian (Ludlow) age based on the presence of the grapolite species Bohemograptus bohemicus, known only from Ludlow strata elsewhere.  The presence of graptolites confirms the Late Silurian (Ludlow) age of about 415 million years. This makes Yea the oldest site for early vascular land plants in Australia, and one of the oldest such sites in the world (Garratt 1978, Tims & Chambers 1984, White 1988).
Criterion B Rarity
Localities with Silurian graptolites and an extensive Baragwanathia flora fossil assemblage in close association are restricted to two sites in Australia. The Barclays Cutting site has the best-preserved specimens and has yielded the widest array of fossil species. This site also provides the most conclusive evidence for the Silurian (Ludlow) date (Garratt 1978; Garratt & Rickards 1984, 1987).
Criterion C Research
The presence of Baragwanathia flora in association with graptolite fossils has attracted considerable research since the site’s discovery in 1875. Graptolites, such as Bohemograptus bohemicus which occur at the locality, are key faunal taxa used to stratigraphically age fossils and hence determine the relationships of Baragwanathia floras (Garratt 1978, Harris & Thomas 1942). The Yea site has played a central role in the long-running debate surrounding the evolution of the earliest land plants. Only relatively recently has the stratigraphy been conclusively confirmed as of Silurian age (Garratt & Rickards, 1984).
Criterion D Principal characteristics of a class of places
The site is regarded as providing the best example of an early land plant fossil flora in Australia because of its species richness and excellent state of preservation. It has yielded an unusually high number of early vascular land plants including Baragwanathia longifolia, other lycopsids and several other early plants from now extinct groups (Garratt 1978; Garratt & Rickards 1984, 1987).
Criterion H Significant people
Baragwanathia fossils were first discovered at Yea in 1875 and subsequently described by Australia’s eminent pioneer palaeobiologist Dr Isabel Cookson and Professor William Lang from Manchester University in 1935. Cookson (1893-1973) was world renowned for her fossil plant studies and is strongly associated with the Yea fossil site. Cookson’s description of the Baragwanathia fossil assemblage rates as one of her major achievements over a research career that spanned 58 years and produced great insight into the history and evolution of Australia’s flora (Australian Science and Technology Heritage Centre 2005).
 
Description
The Yea Baragwanathia Flora Fossil site (Barclays Cutting) is the locality of the oldest known vascular land plants in Australia, and one of the oldest known localities for such a fossil assemblage in the world. Australia was very different during the Silurian and much closer to the equator. A large sea occupied central Victoria and there were volcanoes on the New South Wales / Victorian border. Most significantly, the remarkable evolution of vascular plants occurred during this time, with adaptations of lower plants from the sea to the land. The Baragwanathia flora assemblage contains the earliest vascular land plants, including a key member, Baragwanathia longifolia, after which the assemblage is named. B. longifolia was a primitive club moss (lycopod) with a stout stem covered with spirally arranged, long, simple needle-like leaves and reaching up to one metre in height. It is amongst the oldest land plants yet recognised in the world. Another species of Baragwanathia has been described from Ontario in Canada but in rocks of late Devonian age, at least 25 milion years younger than the Yea specimens. Other simple plants that occur as part of the Baragwanathia flora assemblage include species of the lycopsid Yarravia, the rhyniophyte Hedeia and various algae. These plants most probably occupied moist habitats such as coastal environments and river flats and were large enough to modify the landscape with thicket-forming vegetation.
 
Because the fossil site is comprised of marine sediments, it is theorised that an event such as a flood washed some of these plants into the sea, where they were preserved in shallow marine sediments. The group of plant fossils associated with the site is known from a range of other younger fossil sites in eastern Australia dating to the early Devonian. The Barclays Cutting site is the only site that can be definitively dated to the Silurian period (10 to 20 million years earlier) because of the presence of particular extinct marine invertebrate fossils known as graptolites. Graptolites were small, stick-like, colonial marine animals now long extinct which were widespread through the seas of the Palaeozoic.
 
Located in and immediately adjoining a road cutting on a barren hillside, the Yea Baragwanathia Flora Fossil Site occurs within an area of anticlines and synclines with clearly defined fold belts. An anticlinal belt passes through Yea township, exposing the oldest sediments of the area within its core. A number of distinct, ancient fauna and flora fossil assemblages occur in the Yea area, all of which include elements of the Baragwanathia flora. The more recent, Early Devonian (Praguian) assemblage is referred to as the Upper Plant Assemblage and the older Late Silurian (Ludlovian) assemblage is referred to as the Lower Plant Assemblage. They are separated stratigraphically by 1700m of unfossiliferous strata characterised by dark, grey green, siltstones. Steeply dipping Silurian sediments contain the oldest members of the Baragwanathia flora assemblage of the Late Silurian. This occurs in thin brown to grey claystones of the Yea Formation, beneath the Rice's Hill Sandstone Member comprising a 70m thick sequence of grits and interbedded sandstones and siltstones. Two principal plant bands are exhibited in a well-laminated, buff-grey, fine-grained sandstone which splits easily along laminae (each about 30 cm in width). A more restricted buff-orange band of slightly coarser sandstone forms the upper band, with a prominent marker bed containing marine fossils, principally orthoceratids (octopus-like nautiloids) and large pelecypods (benthic aquatic molluscs). Marine fauna identified include the pteropod Hyolithes, bivalve Necklania, brachiopod Maoristrophia banksi, and at a few sites, the graptolites Bohemograptus bohemicus, Pristiograptus dubius, Monograptus aff. uncinatus and Saetograptus. The lower plant band consists of beds containing small oval-round algae 1-4 cm in diameter and a prominent quartz vein 10 cm thick overlain by an indurated red-brown band 5-10 cm thick occasionally bearing plant remains. The beds separating the plant bands are less well laminated and contain a prominent siltstone band 10 cm thick that forms an uneven surface on splitting.
 
Baragwanathia fossils were first discovered at Yea in 1875 and subsequently jointly described by Australia’s eminent pioneer palaeobiologist Dr Isabel Cookson and Professor William Lang from Manchester University in 1935. Cookson (1893-1973) lectured in Botany at the University of Melbourne 1930-1951 and was a Research Fellow from 1959. Cookson developed a keen interest in fossil plants during the first of many research trips to the University of Manchester in 1926. She created many international collaborations and associations that led to significant discoveries. World-renowned for her research on fossil plants spanning a career of 58 years, Cookson published over 80 papers, produced many botanical illustrations and was recognised as a Doctor of Science. The Cooksonia plant genus (containing the oldest known land plants) was named in her honour and the Botanical Society of America commemorate her with an annual award for the best paper on palaeobotany. The Isabel C Cookson Research Laboratory for Palaeobotany and Plant Morphology at the School of Botany, Melbourne University, is named after her.
 
The name Baragwanathia was given to these particular plant fossils in recognition of the collection of the first specimens by Mr William Baragwanath (1878-1966), a geologist who was Director of Geological Survey in Victoria from 1922 to 1924 and Chief Mining Surveyor from 1924 to 1932.
 
History
Fragmentary Baragwanathia noted nearby, 1941.
Fragmentary Baragwanathia noted, 1960s and 70s.
Council widens cutting, exposing richest Baragwanathia bed known, 1979.
Council demolishes portion of bed above road level, 1979.
Council excavates below road level for international conference to provide new access to fossil beds, 1982.
Condition and Integrity
Barclays Cutting was subject to disturbance from quarrying and road construction in 1979, but the Local Council has been actively managing the fossil site since then. Although the surface material was damaged, the huge pile of resultant rubble yielded many fine specimens of Baragwanathia and other fossils. Access to further in situ fossils would require bulldozing of subsurface material (Douglas and Holmes 2006).
 
Location
About 13ha, 1.5km east-south-east of Yea, comprising the area within a circle of radius 200m centred on AMG point: 7923 Yea 362300mE 5879330mN (MGA point 362420mE 5879480mN).
Bibliography
Australian Science and Technology Heritage Centre 2005. Bright Sparcs biography entry for Isabel Cookson. At http://www.asap.unimelb.edu.au/bsparcs/bsparcshome.htm, accessed 31 October 2005.
 
Birch, W.D. (editor) 2003. Geology of Victoria, 3rd edition. Special publication 23, Geological Society of Australia, 842 pp.
 
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Cookson, I.C. 1935. On plant remains from the Silurian of Victoria, Australia, that extend and connect floras hitherto described. Phil. Trans. Roy. Soc. Lond. 225;127-148.
 
Cookson, I.C. 1949. Yeringian (Lower Devonian) plant remains from Lilydale, Victoria, with notes on a collection from a new locality in the Siluro-Devonian sequence. Mem. Nat. Mus. Vic. 16;117-131.
 
Couper, J. 1965. Late Silurian to Early Devonian stratigraphy of the Yea-Molesworth district, Victoria. Proc. R. Soc. Vict., 79; 1-9.
 
Douglas, J.G. 1976. Some additions to the Baragwanathia flora. Unpub. Rep. Geol. Surv. Vict., 1976/81.
 
Douglas, J.G. 1976. Baragwanathia flora from Yea. Unpub. Rept. 1976/81 Mines Dept. Vic.
 
Douglas, J.G. & Ferguson, J.A. (eds) 1988. Geology of Victoria. Geological Society of Australia, Victoria Division, Melbourne.
 
Douglas, J. & Holmes, F. (2006). The Baragwanathia story: an update. The Fossil Collector, 77, 9-26, January 2006.
 
Garratt, M.J. 1976. On the probable Silurian Age for the earliest Baragwanathia flora. Unpubl. Rept. 1976/80 Mines Dept.
 
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Garratt, M.J., Tims,J.D., Rickards, R.B., Chambers, T.C. & Douglas, J.G. 1984. The appearance of Baragwanathia (Lycophytina) in the Silurian. Botanical Journal of the Linnean Society 80;355-8.
 
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Jaeger, H. 1966. Two late Monograptus species from Victoria, Australia and their significance for dating the Baragwanathia flora. Proc. R. Soc. Vict. 79;393-413.
 
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Joyce, E.B. and R. L. King (eds) 1980. Geological features of the National Estate in Victoria. Geological Society of Australia Inc. Victorian Division, Melbourne.
 
Lang, W.H. & Cookson, I.C., 1927. On some early Palaeozoic plants from Victoria, Australia. Mem. Proc. Manch. Lit. Phil. Soc. 71;41-51.
 
Lang, W.H. & Cookson, I.C. 1935. On a flora, including vascular land plants, associated with Monograptus in rocks of Silurian age, from Victoria, Australia. Phil. Trans. Roy. Soc. Lond. 224;421-449.
 
Lang, W.H. 1930. Some fossil plants of Early Devonian type from the Walhalla Series, Victoria, Australia. Phil. Trans. Roy. Soc. Lond. 219;133-161.
 
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Tims, I.D. & Chambers, T.C. 1984. Rhyniophytina and Trimerophytina from the early land flora of Victoria, Australia. Palaeontology 27;265-279.
 
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Report Produced  Wed Sep 3 09:05:28 2014