Year

2013

Degree Name

Bachelor of Science (Honours)

ANZSRC / FoR Code

04 EARTH SCIENCES, 0403 GEOLOGY, 040308 Palaeontology (incl. Palynology)

Department

School of Earth & Environmental Sciences

Advisor(s)

Dr Solomon Buckman

Abstract

Diverse and well-preserved radiolarian faunas are rare in the Early Paleozoic, but the importance of the result of the ages should suggest some idea on the provenance linkage and terrane amalgamation in the NEO. A moderately well-preserved radiolarian fauna consisting of 12 Devonian taxa was recovered from siliceous strata in both the Djungati and Gamilaroi terrane, in the southern New England Orogen, New South Wales. Fauna includes; Trilonche davidi(Hinde), Tr. hindea (Hinde), Tr. echinata (Hinde), Tr. minax (Hinde), Tr. vetusta (Hinde), Tr. elegan (Hinde), Tr. palimbola (Foreman), Tr. tanheensis (Luo, Aitchison & Wang), Palaeoscenidium cladophorus(Deflandre), Stigmosphaerostylus sp., Helenifore laticlavium (Nazarov) and Protoholoeciscus hindea (Aitchison) Results of radiolarian studies on each site provide reliable age constraints on the timing of sedimentation of each terrane. The Birpai sub-terrane recovered well radiolarian faunas that contained Helenifore laticlavium (Nazarov), which dates the terrane to a lower Famennian (Cheng, 1986) the upper Frasnian age. Protoholoeciscus hindea (Aitchison), recovered from the Djungati cherts at the Barnard River dated an age of Lower (Emsian) to Middle (Eifelian) Devonian age. The needle-like spines and spumellarians with three -bladed spines, from the Woolomin beds at Chaffey Dam, are indicative of Middle Devonian and younger radiolarians (Jones and Murchey, 1986). Indicative of fossils are scarce even though there was a thick exposure of cherts reflecting the extensive deformation at this site. The red ribbon-bedded cherts of the Djungati terrane were accreted in a sediment starved trench probably associated with an intra-oceanic island arc, but there is no evidence linking the red-ribbon cherts as an accretionary complex of the Gamilaroi terrane. The rarity of zircons and SHRIMP ages of the two zircons obtained from the coarse sandstones from the Upper Barnard River reflects events of much older origins than the sedimentary rocks themselves, and further support the distal environment for formation. These Devonian lithologies have inherited structural patterns as a result of processes of accretion and orogenesis throughout the Carboniferous. Three different types of structures are distinguished: (i) conjugate arrays of en echelon, quartz-filled tension gashes, showing extensional shear offsets. (ii) Fining directions on tuffs and overlay sequences, showing younging directions. (iii) Fold vergence. From these results geological model of the Chaffey Dam, Yarras district have been established in relation to the NEO. The structural data from this report supports the theory proposed by Aitchison (1992), about the collision of the Gamilaroi terrane giving rise to a subduction flip, causing another subduction zone developed east of accreted Gamilaroi terrane rocks in association with the east-dipping subduction.

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