Miocene wood from the LaTrobe Valley coal measures, . Victoria, Australia DAVID R. GREENWOOD GREENWOOD, DAVID R., 30.9.2005. Miocene wood from the LaTrobe Valley coal measures, Victoria, Australia. Alcheringa 29, 351-363. ISSN 0311 5518. An initial study of a collection of fossil conifer wood is reported from the late early Miocene Yallourn Clays, an interseam unit intergrading into the base of the early to middle Miocene Yallourn seam of the LaTrobe Valley, Victoria in southeastern Australia. The fossil wood shares characteristics with the modern genera Dacrycarpus and Dacrydium. On the basis of contiguous, uniseriate tracheid pitting and 1-2 podocarpoid cross field pits, it is placed in the form genus Podocarpoxylon, and the new species P. latrobensis. The wood is compared with extant Podocarpaceae and other Australian fossil woods. Its ring anatomy is consistent with low temperature or rainfall seasonality in the early Miocene. David R. Greenwood [Greenwoodd@brandonu.ca], Sustainability Group, Victoria University, St Albans campus, PO Box 14428, Melbourne City MC, VIC 8001, Australia; received 18.7.2003; revised 6.1.2005. Current address; Environmental Science, Brandon University, 270-18th Street, Brandon, MB, Canada, R7A 6A9. Key words: Miocene, wood, Podocarpaceae, coal, LaTrobe Valley, Australia MIOCENE vegetation in Australia is primarily known from fossil pollen and the macrofossil record of leaves or reproductive organs. Bishop & Bamber (1985), Leisman (1986), and Bamford & McLoughlin (2000), are the sole recent systematic accounts of Australian Cenozoic fossil wood, although early and more recent Australian workers noted the presence and quality of preservation of Cenozoic fossil wood in the brown coals of the LaTrobe Valley of Victoria and in South Australia, and in other sediments in these States and also in New South Wales, including silicified wood (Chapman 1918, Nobes 1922, Howchin 1923, Chapman 1926, Barnard 1927, Patton 1928, 1958; Gill 1952, Douglas 1983, Taylor et al. 1990). Sahni (1920) described two angiosperm species from Paleogene sediments near Brisbane in Queensland, and Rozefelds & Baar (1991) have described termite frass in Cenozoic wood from Queensland. Fossil wood with well-defined uniform growth rings has been reported from high palaeolatitudes sites in Paleocene floras from the Southern Highlands of 0311/5518/2005/02351-13 $3.00 © AAP Australia (Taylor et al. 1990), a wood character that is consistent with deciduous forests (Greenwood 2001). The paucity of systematic analysis of Australian Cenozoic wood is perplexing given the abundance of material readily available and the attention given to systematic analysis of modern taxa of Australian forest trees (e.g. Dadswell & Eckersley 1935, 1940, Dadswell 1972, Ilic 1991, see also Greguss 1955). In their account of the Australian fossil record for conifers, Hill & Scriven (1998) did not cite any fossil wood taxa. The brown coal deposits of the LaTrobe Valley of South Gippsland in Victoria (38° 05’S, 146° 05’E; Fig. 1) have been palaeobotanically investigated since early last century (Chapman 1925a, 1925b; Deane 1925, Greenwood et al. 2000, Holdgate 2003). They were also the subject of numerous investigations by Cookson and her coworkers (Cookson 1947, 1950, 1953; Cookson & Duigan 1950, 1951; Cookson & Pike 1953a, 1953b; Pike 1953), and others (e.g. Willis & Gill 1965), culminating in Duigan’s (1965) description of the Miocene palaeovegetation. Numerous palyno- 352 DAVID R. GREENWOOD ALCHERINGA Fig. 1. Location map showing site of the Morwell Open Cut brown coal mine and the Latrobe Valley, and other localities where Cenozoic fossil wood has been described from southeastern Australia (1 Moorlands, 2 Lachlan River, 3 Monaro Plains / Southern Highlands, 4 Yallourn mine, 5 Morwell mine, 6 Jungle Creek). Inset A, sketch map showing Early Miocene palaeolatitude of the study area, modified from a map provided by S.J. Gallagher. Inset B, detail of the LaTrobe Valley showing fossil collection site (5). logical studies (Luly et al. 1980, Sluiter & Kershaw 1982, 1996; Kershaw et al. 1991, 1994; Sluiter et al. 1995, Kershaw 1996), and the macrofossil work of Blackburn (1980, 1985) and Blackburn & Sluiter ALCHERINGA MIOCENE WOOD FROM VICTORIA 353 Fig. 2. Annotated lithological log of site of fossil wood collection (April, 1981) from a vertical exposure of the Yallourn Clays in the Morwell Open Cut Mine. Bulk samples macerated from the 1-5 m interval yielded leafy shoots of Dacrycarpus latrobensis and other Podocarpaceae. Fossil wood samples were collected at ‘A’ from one in situ log. (1994) provided insight into the palaeoecology of the middle Miocene Yallourn Coal seam and the early Miocene Morwell coal vegetation. As noted above, surprisingly little has been published on the fossil wood from the LaTrobe Valley brown coals and associated sediments 354 ALCHERINGA DAVID R. GREENWOOD (e.g. Patton 1958), and the palaeobotany of the interseam sediments in general, despite an apparent abundance of material (Greenwood et al. 2000). This report is an initial attempt to redress this situation. Geological setting The LaTrobe Valley of southeastern Australia is a major area of brown coal extraction (Hocking 1972, Holdgate & Clarke 2000, Holdgate 2003). Three open cut mines in the vicinity of the towns of Morwell and Traralgon (Fig. 1) provide access to extensive lateral and vertical stratigraphic sequences of both the brown coal seams and the inter- and intraseam clays, sands and gravels. Major interseam clastic sediments are laterally extensive, and generally extend across the whole basin (Holdgate 2003, Holdgate et al. 1995). The Yallourn Clays constitute an interseam clastic unit between the Morwell 1A Coal Seam (M1A), and the Yallourn Coal Seam. According to Luly et al. (1980), the Yallourn Clays are basal to the Triporopollenites bellus Zone of Stover and Partridge (1973), and are thus middle Miocene. However, more recent stratigraphic analyses place the Yallourn Clays (Interseam Influence Zone 12 [IIZ 12]) as spanning the boundary of the Upper Proteacidites tuberculatus and Triporopollenites bellus Zones, and thus late early Miocene (Holdgate & Sluiter 1991, Blackburn & Sluiter 1994, Holdgate et al. 1995, Holdgate 2003; Holdgate & Gallagher 2003). The fossil material described herein was collected by the author and David T. Blackburn in April 1981 from an exposure of the Yallourn Clays in the north-west corner of the Morwell Open Cut Coal Mine operated by the then State Electricity Commission of Victoria (see also Blackburn & Sluiter 1994, p. 350). A 10 m vertical sequence overlying the Morwell 1A seam was sampled through basal coarse white sands interbedded with carbonaceous seams, gradually replaced by very fine silty clays barren of leaf fossils (Fig. 2). Analysis of macrofossils extracted from the lower 5 m of this sequence (Fig. 2) is reported elsewhere (Greenwood 1981, 1994; Greenwood et al. 2000, Greenwood & Christophel 2005). The topmost fine silty clays were progressively more carbonaceous upsection and graded into a thin exposure of the overlying Yallourn Coal seam. Blackburn & Sluiter (1994) considered the Yallourn Clays intergradational with the Yallourn Coal seam. Palynological analysis of samples from the upper 2 m of the section containing the fossil wood yielded 10.833.0% Nothofagidites (6.3-20.8% subgen. Brassospora & 0.5-12.5% subgen. Lophozonia), 7.0-23.5% Myrtaceae (incl. 0-0.3% Eucalyptus simplex & 4.5-17.0% Syzygium complex), 0-3.5% Proteaceae, and 10-32.5% conifer pollen (incl. 7.028.8% Podocarpaceae) (I.R.K. Sluiter, pers. comm. 1981 in Greenwood 1981; see also Blackburn & Sluiter 1994). This assemblage is typical for early Miocene sediments in southeastern Australia, and is indicative of a mixed Nothofagus-Syzygiumconifer closed forest, although sclerophyllous forest may also have been present based on the low counts of Eucalyptus simplex pollen. Occasional large pieces of conifer wood were encountered in the topmost unit, including in situ stumps with associated Dacrycarpus latrobensis leafy shoots (Blackburn & Sluiter 1994). One sample of this wood is dealt with systematically here. Materials and methods Histology of the fossil material was analysed using standard histological sectioning techniques with wood pretreated in 80% ethanol prior to sectioning. Transverse, radial and tangential sections were made using a sledge microtome and the sections placed in an alcohol dehydration series (80%, 90% and 100% ethanol), remaining in each bath for at least 5 minutes. The dehydrated sections were immersed in xylene for 5-10 minutes and mounted in xam neutral mounting medium on glass microscope slides, and photographed using black and white film at 50 ASA in the former Botany Department, University of Adelaide. Terminology of wood histology follows Greguss (1955), but using the ALCHERINGA MIOCENE WOOD FROM VICTORIA pit descriptions and types from Philippe (1995). Data on modern wood anatomy are principally based on Greguss (1955), but using the systematic treatment of the Podocarpaceae from Page (1988). The fossil wood xylotomy slides are lodged in the University of Adelaide Palaeobotany Collection, Department of Environmental Biology. The original fossil wood specimens were destroyed in a fire at the University of Adelaide’s Thebarton campus facility in 1998. Systematic palaeobotany Phylum CONIFEROPHYTA Order CONIFERALES Family PODOCARPACEAE Podocarpoxylon Gothan, 1908 Type species. Podocarpoxylon juniperoides Gothan, 1908. Podocarpoxylon latrobensis sp. nov. (Figs 3 - 5) Holotype. Xylotomy slides; YC-wood 001. Type locality. Yallourn Clays, late Early Miocene, Morwell Open Cut coal mine, Victoria. Etymology. Named for the LaTrobe Group sediments and the LaTrobe Valley from which it was collected. Diagnosis. Wood with simple tracheids with circular pits. Growth rings indistinct, tracheids squarish in transverse view, and parenchyma rare. Rays 1-2 cells high in tangential view, and lacking pits. Pits in 1-2 rows on tracheids in radial view; ray cells with smooth horizontal and tangential walls. Cross field with one Figs 3-5. Histological sections of fossil Podocarpaceae wood. Fig. 3, transverse section showing indistinct growth rings and general appearance of tracheids in transverse section; scale bar = 100 µm. Fig. 4, radial longitudinal section showing tracheids in long section with prominent podocarpoid pits; scale bar = 25 µm. Fig. 5, detail of cross-field pits showing ray cells (L to R across vertically oriented tracheids); scale bar = 25 µm. Inset in Fig. 5, sketch of cross field podocarpoid pit, traced from pit in central view. 355 DAVID R. GREENWOOD ALCHERINGA podocarpoid pit, or rarely none or 2 pits. resin ducts indicates that the fossil wood represents the extant family Podocarpaceae (Greguss 1955; Table 1). Podocarpoxylon latrobensis shares a number of characteristics with extant taxa in the Podocarpaceae (Table 2). The tracheids are squarish in transverse section in P. latrobensis (Fig. 3) and a majority of the extant taxa surveyed, including both species of Dacrycarpus and Dacrydium cupressinum Solander ex G. Forst., but may also be roundish in Dacrydium elatum (Roxb.) Wallich ex Hook., Podocarpus elatus R.Br. ex Endl. and Prumnopitys ferruginoides (RH Compton) de Laubenfels. Wood parenchyma in transverse section was rare in the fossil and in Microcachrys tetragona (Hook.) Hook.f., and was absent in Phyllocladus trichomanoides D. Don, but was common in all of the other species surveyed. Medullary rays in tangential section were uniseriate in Podocarpoxylon latrobensis, and in the majority of extant species surveyed (rarely biseriate in Dacrycarpus). Rays varied in height significantly between the extant taxa, but were of a similar number of cells high in both P. latrobensis (2-18 cells), Dacrycarpus imbricatus (Blume) de Laub. (1-15 cells), both Dacrydium species, (1-10 cells), Retrophyllum minor (Carrière) Page and Phyllocladus trichomanoides (1-12 cells). The size ranges of ray cells in tangential section overlaps in many of the species, but on average Podocarpoxylon latrobensis has similar size ray cells to Dacrycarpus dacrydioides (A. Rich.) de Laub., the two Dacrydium species, Phyllocladus trichomanioides, Microcachrys tetragona, and Podocarpus elatus (Table 2). In common with only Dacrycarpus dacrydioides, Podocarpoxylon latrobensis lacks pits on the tangential walls of the tracheids. In radial section, P. latrobensis and the following extant taxa have 1-2 pit rows on the tracheids; both species of Dacrycarpus, Dacrydium elatum, Retrophyllum minor, and Prumnopitys ferruginoides. The pits on the tracheids were of similar diameter in all species. In the cross field, Podocarpoxylon latrobensis had a similar number of pits to Dacrycarpus dacrydioides and D. imbricatus. However, the pits in the cross field were of greater 356 Description. Transverse section: growth rings generally indistinct, the transition from early to late wood poorly defined; tracheids 25-75 x 4075 µm (40 cells); rays 3-10, rarely 1-14 tracheids apart; horizontal walls generally unpitted; parenchyma cells rare to absent; tracheids square to rarely rectangular in cross section. Tangential longitudinal section: rays 2-18 cells high but typically 5-12 cells high and invariably uniseriate; tracheid walls smooth, tangential walls typically smooth and unpitted; the walls of some tracheids irregular through the presence of crassulae; ray cells in cross section from square-circular to circular, with marginal cells slightly tapered to rarely triangular and their walls usually thin, pitting not seen; height commonly 12-17 µm, width 12-15 µm (20 pits). Radial longitudinal section: pits common to scarce on radial walls of tracheids, occurring singly or in a single row, sometimes staggered, rarely in two rows, 15 µm in diameter (15 pits), rarely occupying the full width of the tracheid, generally circular though flattened when crowded, never touching, and usually in groups of 2 to 4; apertures of pits ellipsoid to eye-shaped, rarely circular, 4-7 µm in length, generally or nearly so oblique, forming an X-shape with aperture of adjacent pit; cross field commonly with one podocarpoid pit, occasionally none, rarely two; pit aperture eye-shaped, almost touching sides but within a wide circular border 10-15 µm in diameter, aperture oblique to rarely vertical, 9-14 µm in length; marginal cells of rays indistinct from other ray cells, thin walled; some tracheids with crassulae; rays homogeneous and lacking transverse tracheids. Comparison with modern and fossil wood The absence of vessels and the predominance of simple tracheids with circular pits indicates that the fossil wood is coniferous. The presence of podocarpoid pits (or ‘Podocarpoïde’, of Philippe 1995) and homogeneous uniseriate rays, angular tracheids in cross section, and the absence of Tangential surface Families and genera Tracheid shape Wood parenchyma Growth rings distinct Araucariaceae: Rounded X no 1-10 (40) 1 (2) Rounded X no 1-16 (20) Usually square, rarely rounded + yes Dacrydium s.l. Angular to rounded + Microcachrys Square Phyllocladus Ray height in cells Ray width in cells Radial surface Bordered pits on tangential tracheid walls Cross field pit type Number of pits on tracheids Number of pits on ray cells + 1-5 1-16 Araucarioid 1 (2) X 1-4 1-12 Araucarioid 1-6 1 + 1-2 1-2 Podocarpoid yes & no 1-16 (22) 1 X 1-2 (0) 1-4 Podocarpoid or Dacrydioid X yes 1-6 (12) 1-2 + 1-2 1 (2-3) Rarely Podocarpoid, usually Dacrydioid Square - yes 1-22 1-2 X 1 1 (2) " Podocarpus s.l. Square to rounded + Some species 1-40 (60) 1 X 1-2 0-4 Either Podocarpoid or Dacrydioid Prumnopitys Rounded + no 1-8 (10) 1-2 X 1-2 2-3 Usually Podocarpoid, rarely Dacrydioid Cupressaceae: Rounded + Some species 1-36 1 (2) X 1-2 1-3 Rarely Podocarpoid, usually Cupressoid ALCHERINGA Transverse surface Agathis Araucaria Podocarpaceae: Acmopyle MIOCENE WOOD FROM VICTORIA Callitris Table 1. Wood structure (main characters only) contrasting the major genera (as per Greguss 1955; systematics from Page 1988) of the principal Australian conifer families. X present rarely or occasionally; + always present; - absent. 357 Radial surface distinct indistinct Height (µm) Width (µm) Horizontal walls of wood parenchyma smooth Horizontal walls smooth Tangential walls smooth + x + + - 1-6 1 20-28 10-12 + 11-12 x 13-14 1 + + + 1 (2) 8-11 Dacrycarpus dacrydioides + x + x + 1-60 1(2) 15-17 9-10 - - + 14-16 1-2 + + + 0-2 6-7 D. imbricatus + - + - + 1-15 1-2 8-12 11-12 x 8-10 + 12-14 1(2) + + + 1-2 (3) 7-8 Podocarpoxylon latrobensisF + - x - + 2-18 1 12-17 12-15 - - x 10-15 1(2) x + + 0-1 (2) 10-15 P. australeF + + x - x 1-12 1(2) 12-33 10-30 x 10-12 ? 12-18 1 + + + 1 (23) 4-12 P. minorF - + x - + 1-3(7) 1 8-20 5-13 x 8-13 ? 8-13 1 + + + 1 (23) 3-8 P. yallournensisF - + + - + 1-2(6) 1 15-40 10-35 x 10 ? 12-18 2 + + + 1-3 (5) 3-10 Dacrydium cupressinum + x + - + 1-10 1 14-16 10-16 x 14-15 + 16-18 1 + + + 1 10-13 D. elatum x + + - + 1-10 1 12-18 8-10 x 11-12 + 16-17 1-2 + + + 0-2 10-11 Retrophyllum minor + - + + - 1-20 1 18-20 12-16 + 13-14 + 13-14 1-2 + + + 2-3 (6) 10-12 Falcatifolium taxoides + - + - + 1-8 1 10-14 7-9 ? ? + 14-18 1 + + + 1 (2) 10-14 Lagarostrobos franklinii + - + + - 1-8 1 17-20 7-11 x 7-8 + 18-20 1 + + + 1 (2) 16-20 Microcachrys tetragona + - x + - 1-80 1 14-17 6-8 + 7-8 x 12-14 1 + + + 1 (34) 7-14 Phyllocladus trichomanoides + - - + - 1-12 1 12-16 7-8 + 8-10 ? 13-18 1 ? + + 1-2 14-18 (20-22) Phyllocladoxylon annulatusF + - - + - 1-3(7) 1 8-28 5-15 + 10-13 ? 12-18 1(2) ? + + 1 (2) 8-20 Podocarpus elatus x + + - + 1-9 1 11-13 8-10 + 11-12 + 16-18 1 + + + 1 (2) 9-14 Prumnopitys ferruginoides x + + - + 1-6 1 18-22 8-9 x 7-8 + 16-22 1-2 + + + 0-1 (2) 10-12 Cross field Pit diam. (µm) Ray cells Number of pits No. of pit rows Tracheids Pit diam. (µm) pits Ray cells Width in cells Height in cells rounded squarish Rays DAVID R. GREENWOOD Species Growth rings Pit diam. (µm) Wood parenchyma Tangential walls of tracheids Acmopyle pancheri Tracheids Horizontal walls of wood parenchyma smooth Tangential surface 358 Transverse surface ALCHERINGA ALCHERINGA MIOCENE WOOD FROM VICTORIA diameter for P. latrobensis than recorded for these two extant species of Dacrycarpus, but were of similar diameter to those observed in Dacrydium cupressinum, D. elatum and Falcatifolium taxoides (Brongniart et Grisebach) de Laubenfels (Table 2). The most likely extant genus for this material is Dacrycarpus, on the basis that the specimen keys out to Podocarpus dacrydioides (syn. Dacrycarpus dacrydioides) in Greguss (1955), and based on tabulating the principal wood characters (Table 2), the wood anatomy of Podocarpoxylon latrobensis most closely matches that of Dacrycarpus imbricatus. However, it is difficult in many instances to place Podocarpaceae wood into a modern genus (e.g. Table 2). As this specimen lacks any definitive generic characters, and shares almost as many similarities with Dacrydium as it does with Dacrycarpus, the material is referred to Podocarpoxylon. Patton (1958) considered Podocarpoxylon to represent Podocarpus s.l., so including such segregate genera as Dacrycarpus and Retrophyllum. The cooccurrence with this wood in the sediments with abundant leafy shoots of Dacrycarpus latrobensis suggests that this wood represents the trunk of the Dacrycapus latrobensis plant. However, other podocarpaceous genera are known from the same sediments (e.g. Dacrydium; Blackburn & Sluiter 1994), and also in the absence of attached woody stems and leafy shoots, this proposition must remain speculative. Conifer wood is notoriously nondescript, so placement below familial status is often not possible. Nobes (1922) described species of Mesembrioxylon, Cupressinoxylon (Cupressaceae, gen. indet.) and Dadoxylon (Araucariaceae, gen. indet.) from Moorlands in South Australia and from Yallourn in the LaTrobe Valley. Patton (1958) described five species of fossil conifer wood from coal deposits in Victoria, including four species of Podocarpaceae as three species of Podocarpoxylon and one species of Table 2. Wood structure of selected extant and fossil Podocarpaceae (data from Nobes 1922, Greguss 1955, Patton 1958). Key: + = present; - = absent; x = occasional to rare; ? = no data; F = fossil species. Measurements are ranges (extremes). 359 Phyllocladoxylon (Table 2). Krausel (1949) synonymised some of Nobe’s (1922) fossil wood taxa, including Mesembrioxylon sp. ‘Yallourn A’ in Podocarpoxylon australe. However, Patton (1958) argued that Krausel’s treatment was in error. The primary wood characters for the fossil species are shown in Table 2. Comparisons here will be based primarily on Patton (1958). Podocarpoxylon latrobensis shares a number of features with Patton’s (1958) fossil taxa, but is distinct from all these species and so is recognised as a separate species (Table 2). The tracheids are squarish in transverse section in both P. latrobensis and P. australe, but may also be roundish in the latter species, and are rounded in each of P. minor and P. yallournensis. Wood parenchyma is rare in P. latrobensis, P. australe and P. minor, but is common in transverse section in P. yallournensis. All four Podocarpoxylon species have indistinct growth rings (Table 2). Medullary rays in tangential section are generally uniseriate (rarely biseriate in P. australe) in all four species, and are a similar number of cells high in both P. latrobensis (2-18 cells) and P. australe (1-12 cells). Rays are much shorter in the other two species (1-7 cells high). The size ranges of ray cells overlaps in all four species, but on average Podocarpoxylon latrobensis has smaller ray cells than the other species. In contrast to all three previously described Australian Podocarpoxylon species (Patton 1958), P. latrobensis lacks pits on the tangential walls of the tracheids, a pattern seen also in the extant Dacrycarpus species (Table 2). In radial section, P. latrobensis and P. yallournensis have 1-2 pit rows on the tracheids, whereas P. australe and P. minor have one pit row. The pits on tracheids in radial section were of similar diameter in all four Podocarpoxylon species. However, cross field pits were generally of greater diameter for P. latrobensis (10-15 µm) than for P. australe (4-12 µm), P. minor (3-8 µm), or P. yallournensis (3-10 µm). Palaeoecological implications of the wood A number of wood characteristics are climatically indicative (Woodcock & Ignas 1994, Greenwood 360 DAVID R. GREENWOOD 2001). Annual growth rings indicate seasonality of temperature or precipitation; annual variation of ring widths (or the size of xylem cells within rings, i.e. wood density) is correlated with precipitation; and the degree of transition to late wood displayed at the termination of seasonal growth is correlated with the rapidity and severity of the transition to unfavourable conditions. The prevalence of homocellular and storied rays varies with temperature. Patton (1958) noted that Podocarpoxylon australe, P. minor and P. yallournensis all lacked distinct growth rings, whereas Phyllocladoxylon annulatus had distinct growth rings. The Paleocene fossil wood reported by Taylor et al. (1990) from the Monaro Plains had well-defined uniform growth rings. Of the temperate species shown in Table 2, Dacrycarpus dacrydioides, Lagarostrobos franklinii, Microcachrys tetragona and Phyllocladus trichomanioides possess distinct growth rings consistent with a winter cessation of growth. The majority of the tropical to subtropical species, i.e. Dacrycarpus imbricatus, Dacrydium elatum, Falcatifoilum taxoides and Podocarpus elatus, lack distinct growth rings (Table 2), consistent with growth in a low seasonality environment (either temperature or rainfall). Both species of Dacrydium for which data were available (Table 2) lacked distinct growth rings, including the temperate species, D. cupressinum, although the latter species occurs in the warmest areas of New Zealand. The lack of rings in the two extant Dacrydium species may therefore suggest a genetic predisposition to indistinct rings in the genus. However, the temperate species of Dacrycarpus had distinct rings, whereas the tropical species, D. imbricatus, lacked distinct rings, suggesting an environmental sensitivity to temperature seasonality in Dacrycarpus. The lack of distinct growth rings in the wood described here from the Yallourn Clays matches the observations made by Patton (1958), and suggests low seasonality of both temperature and rainfall, and strongly indicates a lack of significant frost. Conclusions ALCHERINGA Miocene brown coals are relatively common in southeastern Australia, with significant economic and sub-economic reserves in Victoria and southern South Australia (Holdgate & Clarke 2000). The coal-forming vegetation reflected in these coals appears to have been dominated throughout the Cenozoic by conifers and keytaxa of woody angiosperms, such as Banksieae and other Proteaceae, based on dispersed cuticle analysis (Rowett 1991, 1992; Blackburn & Sluiter 1994, Greenwood et al. 2000, Greenwood & Christophel 2005). Macrofossil analysis of the Yallourn Coal seam has demonstrated a high diversity of both conifers and woody angiosperms, based on leaf and fruit remains, and also pollen (Blackburn & Sluiter 1994). Macroscopic remains of Podocarpaceae, chiefly leaves and leafy shoots, are relatively common from the interseam sediments, as well as from other southeastern Australian Cenozoic mudstone macrofloras (Cookson & Pike 1953a, 1953b; Greenwood 1981, 1987, 1994; Rowett 1991, 1992; Blackburn & Sluiter, 1994, Hill & Scriven 1998, Greenwood et al. 2000, Greenwood & Christophel 2005). That much of the wood preserved in the Morwell and Yallourn Coal seams was coniferous, and that Podocarpaceae were prominent, is well established in the literature (Patton 1958) and is consistent with other evidence for the presence of Podocarpaceae in the palaeovegetation (Duigan 1965, Luly et al. 1981, Blackburn & Sluiter 1994). However, only Nobes (1922) and Patton (1958) have dealt with fossil wood from the coals systematically. This present paper then serves to demonstrate that Podocarpaceae trees were also elements of the vegetation growing around the lakes and other water bodies that formed the interseam mudstone sediments found in association with the LaTrobe Valley Coals. The lack of distinct growth rings in all described conifer species from the coal and interseam floras (e.g. Patton 1958; this work) indicates that the local vegetation did not experience seasonal interruptions to growth. The fossil wood is therefore consistent with other evidence (e.g. Kershaw 1996) for the lack of seasonal extremes in temperature (i.e. no ALCHERINGA MIOCENE WOOD FROM VICTORIA sustained cold period) and the absence of marked seasonality of rainfall in the late Early Miocene of south-eastern Australia. Acknowledgements The collection and original analysis of the fossil wood was made while based (1981) in the former Botany Department, University of Adelaide, and was funded under a State Electricity Commission of Victoria research grant to D.T. Blackburn and D.C. Christophel. I would like to acknowledge the support afforded to me by the Botany Department, and by my parents John W. Greenwood (
1988) and C. Roxley Greenwood during this research. Completion of the manuscript was facilitated by an ARC research grant (A39802019) and the provision of facilities by the Department of Geological Sciences at the University of Saskatchewan (Canada) during my sabbatical there in 2001. I also thank Guy Holdgate and Stephen Gallagher for advice on LaTrobe Valley coal stratigraphy, and for assistance with the illustrations. The work greatly benefited from the reviews by Marion Bamford and Mike Pole. References ABELE, C., GLOE, C.S., HOCKING, J.B., HOLDGATE, G., KENLEY, P.R., LAWRENCE, C.R., RIPPER, D. & THRELFALL, W.F., 1976. In The Geology of Victoria, 251-350. Geological Society of Australia Special Publication 5, J.G. DOUGLAS & J.A. FERGUSON, eds. B AMFORD , M. & M C L OUGHLIN , S., 2000. Cainozoic euphorbiacean wood from the Canning Basin, Western Australia. Alcheringa 24, 243-256. BARNARD, C., 1927. A note on a fossil dicotyledonous fossil wood from Ulladulla, New South Wales. 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