New palynological data on the age of the Kiltorcan Flora of Co. Kilkenny, Ireland

The age of the fossil flora found in the Kiltorcan Formation of Co. Kilkenny has been disputed for many years, with no datable miospore assemblage ever being extracted from the plant beds due to the preservation. New exposure on Kiltorcan Hill, and experimentation with palynological techniques has allowed the extraction of two miospore assemblages. The palynological data studied shows that the strata on Kiltorcan Hill straddles the Devonian/Carboniferous Boundary; A Devonian LE Miospore Biozone assemblage has been examined from a plant bed with Cyclostigma kiltorkense whilst a Carboniferous VI Miospore Biozone date was determined for a plant bed with Lepidodendropsis sp., and? Rhacophyton. The topmost occurrence of Cyclostigma kiltorkense is unknown but it is certainly very near to the Devonian/ Carboniferous Boundary. The use of Cyclostigma kiltorkense as an index fossil for the uppermost Devonian is therefore not precluded.

. The Old Plant Quarry (the "Classic Quarry" of Colthurst 1978) measures only 20 m by 6 m at maximum and is situated towards the top of Kiltorcan Hill, approximately 1.5 km ESE of Ballyhale village which lies on the main Waterford-Thomastown road, County Kilkenny. A wealth of work has been undertaken on the palaeontology of this locality which is now unfortunately almost entirely fllled in. More extensive exposure now occurs 150 m to the north of the Old Plant Quarry in a network of disused Roadstone quarries, worked in the 1960's and 1970's. These cover a large area at thesummit of Kiltorcan Hill (the"CouncilQuany"ofCo1thurst 1978) and expose a seven to nine metre section of green and red siltstones and mudstones and yellow sandstones. A more recent exposureis to be found 100 metres to the south west of the Roadstone quarries. This has been termed the Kiltorcan New Quarry and was quarried during 1984-1985 where another short stratigraphic interval wasexposed.This sequence underlies the Roadstone quarries and the two can be related by a section of intermittent exposure along a track (Fig.1).

PREVIOUS WORK ON AREA
Most interest in this area was originally concerned with the well preserved examples of plant fossils collected in the mid 19th Century from a small quarry on Kiltorcan Hill (the "Old Plant Quarry"). The first published work on the Kiltorcan locality was that of Forbes (1853); He described the 1851 discovery of the quarry, which was seen to "abound in fossils of great beauty and apparently entirely new". The fossil fauna includes, Archanodon jukesii (Forbes) Howse (a freshwater bivalve), Groenlandaspis disjectus (Woodward) Ritchie (fish plates) and the arthropods Belinurus and eurypterids (Clayton et a/ 1980). More detailed work on the flora was carried out by Chaloner,who (in Holland 198 1) lists a floral assemblage including Archaeopferis hihernica (Forbes) Dawson, Cyclostigma kiltorkense Haughton, Ginkophyllum kiltorkense Johnson, Sphenopteris hookeri Baily and the seedSpermolithus devonicus Johnson. The fossil flora is very well preserved in chlorite and attracted much attention from palaeobotanists of the time [Baily ( 186 1,1869), Griffith and Brongniart (1 857, 1858) and Haughton (1 855,1859). Much argument ensued as to the age of the flora. Griffith (op. cit), Haughton (op. cit), and others regarded the deposits as Lower Carboniferous, Forbes concluded a Devonian age, whilst Brongniart found the specimens were not sufficiently distinctive to enable him to decide between the two views.
No good miospore assemblage has ever been extracted from the strata on Kiltorcan Hill prior to the present study as the chlorite preservation of plant material does not aid the extraction of miospores with standard palynological techniques. Johnson ( 19 13b) claims he observed miospores in material from the Old Plant Quarry. He experimented with some sporangia, treating them with schulze solution and ammonia, and obtained "many rounded bodies, some with triradiate mark"andconc1uded they weremiospores. Chaloner ( 1968) was, however, unconvinced by Johnson's miospores. He stated that '' none of his (Johnson's) preparations appear to have been preserved, and his photograph is rather unconvincing," and concluded that "that the body Johnson observed and regarded as a microspore was either an artifact of preparation or a contaminant". Chaloner (op.cit) examined megaspores on the surfaces of the sporangia of Cyclostigma kiltorkense concluding that mey were similar to the dispersed genera Lagnicula and Lagenoisporites. Yet he was unable to extract any miospore assemblages to indicate the the exact biostratigraphic level of the beds. described the discovery of seed Spermolifhus devonicus during the re-excavation; This seed is important in the understanding of early gymnosperm evolution. Clayton et ul (1977) examined three palynological assemblages from the Kiltorcan Formation elsewhere in County Kilkenny. In this paper John Colthurst concluded that the sampled horizons were 40 and 50 m above the highest exposed levels on Kiltorcan Hill. Clayton eta1 (1977) suggest that the samples come from Carboniferous strata with an absence of Retispora lepidophytu correlating with the VI Miospore Biozone; Moreover, one of the higher samples contains Spelaeotriletes balteaus (Playford) Higgs, which suggests to the present author that the higher assemblage belongs to the higher BP Miospore Biozone of Higgs et a1 (1988) (Fig.3).

EXPOSURE DESCRIPTION AND SAMPLED HORIZONS
The Kiltorcan Formation is the highest division of the Old RedSandstonefacies (O.R.S.) in S. E. Ireland.The sediments of the Kiltorcan Formation exposed on Kiltorcan Hill consist mainly of siltstone and fine sandstone with laterally extensive coarse sandstone bodies occurring at two horizons. Fine grained arenaceous rocks show both vertical and lateral gradation between red and green colouration. Plant material is found in most of the green coloured sediment; there are, however, a number of horizons where plant material is especially common. These are: (1). at the base of the succession in the New Quarry, ( 2 ) , the Old Plant Quarry and (3), in the northern part of the Roadstone Quarry. The Plant Quarry horizon contained both Archaeopteris hibernica and Cyclostigma kiltorkense whilst only C . kiltorkense is present at the New Quarry horizon. The floral assemblage collected from the Roadstone Quarry includes Lepidodendropsis spp. aff. L. hirmeri, cf. Rhacophyton spp. and the alga Bythotrephis spp. (pers. comm. W. S. Lacey 1989). Preservation in the Roadstone and Old Plant Quarries is by chloritisation whilst the New Quarry horizon shows coalified preservation. Palynology samples were collected from the New Quarry plant bed (sample 88/11 which is estimated to be some 20m below the floor of the Old Plant Quarry, and from the Roadstone Quarry (sample CQI) an estimated 4 or 5m above the topmost strata in the Old Plant Quarry.

PREPARATION TECHNIQUES
Numerous attempts were made by the author to extract a productive palynological sample from the plant beds in the Roadstone Quarry. Best results were obtained by collecting large amounts of thinly laminated dark grey mudstone found within green siltstone. These were thencrushed andchemically broken down by hydroflouric acid. The resulting residue was then subjected to prolonged boiling in hydrochloric acid to remove the large amounts of flourides present. The organic residue obtained was small but contained a diverse and well preserved palynoflora. Samples from Kiltorcan New Quarry only required standard palynological techniques to produce a very rich residue. The palynological assemblages studied from both samples display lower levels of organic maturity than samples observed from similar horizons in the Kiltorcan Formation elsewhere in Southern Ireland. Thermal alteration index (TAI) values ( S t a p h 1982) in the order of 3, with a spore colour of dark yellow to orange brown (of Pearson 1984) were noted in unoxidised material. Oxidation times with Schulze Solution were limited to 1 hour for the New Quarry and 30 minutes for the Roadstone Quarry samples. Permanent scatter mounts were made using Cellusize as a dispersing agent and Elvacite as a cold mounting medium. These slides are housed in the Micropalaeontological collection of the Department of Geology, U.C.C.

PALY NOLOGY RESULTS
The palynological slides produced were carefully scanned for important stratigraphic forms and new species, systematic counts of 500 specimens were made for both samples. Undescribed species will be examined in a later paper. The preliminary results are shown below. The range of each species within the Miospore Biozones of the Tournaisian of Ireland is givenafter Higgs era1 1988. See Fig. 3

PALAEOENVIRONMENTAL IMPLICATIONS
Van der Zwan and Van Veen (1 978) and Van Veen (1 98 1) working on sections of uppermost 0.R.S in West Cork and Hook Head (Fig. 1) made palaeogeographical reconstructions from the distribution of selected miospore taxa. Van Veen (1982) concluded that Diducites was related to an alluvial plain environment whilst Retispora lepidophyta was related to acoastal area environment in LN and LE Biozone times. He does, however,go on to state that "the regional and interregional implications of such environmentally controlled dominances can only be estimated when comparable data from other sections are available" Comparison of Van Veen's model with data from the present study is unfavorable. Palaeoenvironmental conditions for the New Quarry strata are interpretated as humid alluvial plain, however, Retispora lepidophyta is found in great amounts comprising 66.3% of the total palynological assemblage, whilst Diducites only makes up 1.9% of the same. Van Veen's (op. cit.) model would suggest the high percentage of R.lepidophyta was due to deposition on a coastal plain environment, this is not so in the case in hand.
However, the presence of RJepidophyta in large percentages does appear to be related to a palaeoenvironmental factor. Sedimentological analysis of the Kiltorcan Formation at this locality suggest that the sediments were laid down on a humid, wet floodplain. These conditions may have been much more water saturated than the conditions under which the O.R.S. alluvial plain sediments elsewhere in Southern Ireland were deposited. Moreover, humidity and water saturation levels in the coastal plain O.R.S. environments Van Veen (op.cit.) studied may have been much closer to those of the Kiltorcan Formation. Thus the high percentages of R.lepidophyta in the uppermost O.R.S. could represent conditions of high humidity and Yater saturation at the time of deposition. The relative percentages of Diducites and R.lepidophyta in late Devonian palynological assemblages may therefore prove to be an indicator of humidity and water saturation of environment rather than a palaeogeographical indicator.

BIOSTRATIGRAPHICAL IMPORTANCE OF THE MEGAFLORA
In terms of dating the macroplant beds the palynological

-+ S p e l a e o t r i l e t e s o b t u s u s V e r r u c o s i s i s p o r i t e s n i t i d u s V a l l a t i s p o r i t e s v e r r u c o s u s -NEW QUARRY 8811 c H y m e n o r o n o t r i l e t e s e x p l a n a t u s R e t i s p o r a l e p i d o p h y t ;
t SELECTED SPECIES RANGE TOPS c   Kaiser's (1970) assemblage list suggests the flora at Bear Island is preserved in Devonian strata from the LE Miospore Biozone. Palynological dates from these sections, therefore, suggest that C. kiltorkense could be restricted to the Strunian. Fairon-Demaret (op. cit) suggested that the stratigraphically restricted record of C. kiltorkense is indicative of it's index value for an upper subzone in Bank's floral assemblage VII (Banks 1980). However, Fairon-Demaret (op. cit) also notes that precise dating of the Kiltorcan Hill horizon is needed before absolute conclusions are to be drawn. The palynological evidence from the present study adds support to the suggestion that Cyclostigma kiltorkense on Kiltorcan Hill could possibly be restricted to the Strunian. Fairon-Demaret (op. cit) also notes that the range top of the genus Archueopteris is unknown "with it's persistance in the

Explanation of Plate 1
All Magnifications x 420          H312 P34 Jarvis Lower Carboniferous still depending on precise dating of critical localities as in the New Albany Shale and in the Kiltorcan Formation". From the present study it appears that the occurrence of Archaeopteris hihernica on Kiltorcan Hill could also be restricted to the Devonian. Chaloner et al. (1977) described a seed Sperrnolithus devonicus from the Kiltorcan Old Quarry. This seed was suggested to be the first Devonian platyspermic seed. It should be noted that a Devonian age for this seed is not precluded.