Late Middle Cambrian agnostid trilobites from the Gunns Plains area, north-western Tasmania

Ten species of agnostid trilobites, including a new species, Utagnostus(?) nevel, are described from two localities within the lower sedimentary succession of the Radfords Creek Group, Dial Range Trough, north-western Tasmania. The faunas from both localities (near Gunns Plains) are of late Middle Cambrian age; one is either of the Lejopyge laevigata II Zone or the L. laevigata III Zone and the other is either of the L. laevigata III Zone or the Damesella torosa-Acsionepea janitrix Zone

An abrupt Upper Middle Cambrian faunal change, Christmas Hills, Tasmania

Sediments containing two almost entirely different Upper Middle Cambrian faunas are in direct contact near Christmas Hills, Tasmania. Two reasons are advanced in explanation for this faunal change, (a) that there is a disconformity at the position of the faunal change, or (b) that the younger fauna replaced the older fauna due to a change in environment

Late Middle Cambrian fossils from Beaconsfield, Tasmania

The only known Cambrian fauna of the Beaconsfield Trough has a late Middle Cambrian (PtychQgnostus nathorsti or Lejopyge laevigata Zone) age; it occurs 4.5 km south-west of Beaconsfield, northern Tasmania. The poorly preserved fauna includes an orthid brachiopod, plus the trilobites Nepea sp., cf. Erediaspis sp., a probable member of the Damesellidae, a possible solenopleurid, agnostoids and some fragmentary material. The fauna occurs about 140m below the contact with the overlying Tremadocian or Arenigian Cabbage Tree Formation, which suggests that most, if not all, of the Late Cambrian is not represented in the Beaconsfield area

Geology of the Maydena Range

The oldest rocks of the area are the (?) Precambrian pyritic quartzites with interbedded conglometates. These are overlain by 60 m of pebbly siltstone, about 300 m of ferruginous sandstones and siltstone and 300 m of quartzitc and siltstone which represent a stable tectonic environment of pre-Ordovician age. The pre-Ordovician rocks were folded before deposition of the Ordovician sediments. The Arenigian Florentine Valley Mudstone is at least 140 m thick and is overlain by the lower 600m. of the Gordon Limestone, the upper parts of. Which are faulted out.The Lower•Upper Middle Devonian .Tabberabberan Orogeny resulted In the formation of north-westerly plunging folds. A complete flatly dipping Permian sequence begins with at least 220 m of Lower Sakmarian Wynyard Tillite, which was derived from a glacier With a north-westerly origin .This. is overlain by 137 m of Woody Island Siltstone, 9.2 m of fossiliferous siltstones, 3.7 m of Darlington Limestone, and 32 m of Bundella Mudstone all of which are marine. These are overlain by the freshwater sedimennts of the Mersey Group (with a maximum thickness of 52 m), followed] by a marine sequence composed of 80 m of the Cascades Group, 64 m of the Malbina Siltstone and Sandstone and about 150 m of the Ferntree Group. The terrestrial Cygnet Coal Measures 4.4 m thick, is the top Permian formation. The Permian rocks form a very shallow east plunging syncline. Three hundred and twenty metres of freshwater Triassic sediments disconformably overly the Permian rocks and are intruded by a Middle Jurassic dolerite sill. Normal faults, with down throw to the east -north-east and to t he northwest and probably associated with the formation of the Tertiary Derwent Graben, cut the older rocks. Dolerite talus slopes developed as periglacial material during the Pleistocene

A new Middle Cambrian polymerid trilobite from north-western Tasmania

A new species of trilobite, Pianaspis(?) leveni, is described from the Radfords Creek Group, Dial Range Trough, north-western Tasmania. Its age is late Middle Cambrian, either of the Lejopyge laevigata II Zone, or the L. laevigata III Zone

Late Cambrian fossils from the Climie Formation, western Tasmania

The Climie Formation, which is about 460 metres thick in the type section of the Dundas Group, contains the youngest known fossils within the Dundas Group. Just south of the Murchison Highway bridge over the Dundas Rivulet the Climie Formation is overturned, sheared and contains poorly preserved fossils in two main horizons, which are well exposed in road cuttings. The lower fauna occurs about 200 metres below the top of the formation, while the upper fauna occurs about 145 metres below the top of the formation. The lower fauna contains the inarticulate brachiopods Angulotreta(?) sp., and Lingulella(?) sp., plus the trilobites described herein as Olenus sp., Neoagnostus sp., Agnostus sp., and Ceratopygidae, gen et sp. indet. Five fragmentary trilobite specimens are left in open nomenclature. The upper fauna contains the inarticulate brachiopods described herein as Lingulella(?) sp., and Acrotretidae, incertae sedis plus the trilobites Agnostus sp., Lotagnostus(?) sp., Peltura(?) sp., and an unassigned member of the Olenidae. It is suggested that the lower fauna is probably of early post-Idamean age, with the higher fauna being slightly younger. Both faunas are of a cosmopolitan nature and indicate easy communication with the open ocean at the time of deposition

Late Cambrian brachiopods from the Denison Range, southwestern Tasmania

Eight unnamed species of brachiopods and one indetenninate hyolithid species are described and figured from three stratigraphic intervals within the early Late Cambrian Singing Creek Formation, Denison Range, southwestern Tasmania

An early Late Cambrian fauna from Tom Creek, western Tasmania

A small, poorly preserved, but stratigraphically significant fauna from Tom Creek in western Tasmania contains the trilobites Agnostardis and Aulacodigma which indicate correlation with the upper part of the Brewery Junction Formation in the Dundas area and an age of very early Late Cambrian Glyptagnostus stolidotus Zone

Late Middle Cambrian trilobites from Trial Ridge, southwestern Tasmania

The first Middle Cambrian trilobites to be described from southwestern Tasmania come from two localities within siltstone in the Trial Ridge area on the HUNTLEY 1:50 000 sheet. Sixteen trilobite taxa are described. The 11 agnostoid species include one new species, Hypagnostus trali. Lisogoragnostus is recorded for the first time in Tasmania. The faunas of both localities are of a very similar late Middle Cambrian age, probably high in the Lejopyge laevigata Zone on the northern Australian biostratigraphic scale. One fauna is dominated by complete specimens of Goniagnostus nathorsti but has very few polymeroids. In the other fauna, there are no complete agnostoids, G. nathorsti is absent, and the most common trilobite is a member of the Proasaphiscidae, thus suggesting that the former fauna is of deeper water origin than the latte

Early Idamean (Late Cambrian) agnostoid trilobites from the Huskisson River, Tasmania

Two trilobite taxa, Agnostus (Homagnostus) sp. and Pseudagnostus (Pseudagnostus) idalis huskissonensissubsp. nov. are described from the upper part of the Huskisson Group, western Tasmania. The only trilobite previously described from this level is the early Idamean (early Late Cambrian) zone fossil Glyptagnostus reticulatus. Palaeontological and stratigraphic evidence suggests that there may be a disconformity of very late Middle Cambrian age (about Lejopyge laevigata III Zone) within the Huskisson Group, which would correspond to a postulated disconformity of similar age from the Dundas Group at Dundas