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Definition card for: Purni Formation
State(s): NT, SA,
Status of unit: Formal
Usage: Defined
Stratno: 15684

Reserved by: Youngs B.C. on: 03-DEC-74
Approved: Y
Approved by: on: 09-DEC-74
Age and Evidence: Early Permian. Palynological evidence suggests it is restricted to Stage 3, but it could extend down to Stage 2 (Harris, 1972).
Comments: The Purni Formation is divisable into three members, these are defined briefly below: Upper Member - F.P.C.(A). Purni No. 1 well between 1417 and 1536 m. Fine, white, kaolinitic sandstones; silts; grey shales; carbonaceous shales. Middle Member - F.P.C.(A) Purni No. 1 well between 1536 and 1603 m. Fine to medium, grey-brown, well sorted, kaolinitic sandstone. Occasional thin interbeds of silts and carbonaceous shales. Lower Member - F.P.C.(A). Purni No. 1 well between 1603 and 1698 m. Thinly bedded, grey shales with lenses of fine to medium, grey, kaolinitic sandstones and occasional conglomerates. Rare coal bands. *The Purni Formation is also known from Mokari No. 1, McDills No. 1 and Hale River No. 1.
Distribution/extent: The formation is not known in outcrop. Its subcrop is believed to extend over the thicker parts of the Pedirka Basin (Youngs, in press)*.
Lithology: Beds of white kaolinitic sandstone; occasional thin conglomerates; thinly bedded grey shales, frequently carbonaceous; siltstones; thin coals and very carbonaceous shales.

Deriviation of name: French Petroleum Co. (Australia) Ltd. Purni No. 1 well. Dalhousie 1:250 000 sheeet area. Grid Ref. 412736.
Relationships and boundary criteria: It disconformably overlies the Crown Point Formation (except in Amerada Hale River No. 1) and is unconformably overlain by Mesozoic strata. The base is defined by a conglomeratic, silty, grey to black shale with minor coal lenses. The top of the formation at the type section, is marked by beds of black coal, interbedded with thin silty shales.
Thickness: 3-350 m.
Type-section locality: F.P.C.(A) Purni No. 1 well between 1417 m and 1698 m.

http://dbforms.ga.gov.au/pls/www/geodx.strat_units.def?strno=15684&stratname=Purni Formation