Definition card for: Bloods Range Formation

State(s): NT, WA,
Status of unit: Formal
Usage: Redefined
Stratno: 36765
Replaces: Bloods Range beds

Reserved by: C.J. Edgoose, D.F. Close on:
Approved: Y
Approved by: Kruse, P.D. on: 21-JAN-02

Parent: Tjauwata Group

Name source: Bloods Range, northeastern Hull and northwestern Bloods Range 1:100 000 mapsheets.

Unit history: Bloods Range beds, Bloods Range Beds (Forman 1966).

Constituents: Nil

Geomorphic expression: Footslopes below scarps of strike ridges of Dean Quartzite and Kulail Sandstone, rarely as isolated low hills.

Type section locality: Upper and lower stratigraphic contacts exposed on southern slope of Bloods Range, 11 km west of Mount Harris at location 24o 38' 15.96" S, 129o 24' 22" E (WGS 84).

Description at type locality: Lower contact is polymictic conglomerate with interlayered quartzose sandstone beds above weathered porphyritic rhyolite. Upper contact is interlayered red siltstone and quartz sandstone beds with a 50 cm top layer of leached clay below quartzofeldspathic sandstone beds. Thickness of section is approximately 80 m.

Extent: Mount Berteaux region (northwestern Petermann ranges 1:250 000 mapsheet), Manananna Range, Mount Skene Range, Mount Hastie area, Bloods Range, Rowley Range (Hull and Bloods Range 1:100 000 mapsheets).

Thickness range: Laterally variable, on average approximately 100 m.

Lithology: Polymict pebble conglomerate (possible debris flows), quartzite-cobble conglomerate, immature sandstone, red and dark fine grained sandstone and siltstone, epiclastic and volcaniclastic rocks, rare tuffs. Thickness and presence/absence of these lithologies varies from outcrop to outcrop. Sediments are very locally derived, therefore sequence vary considerably with composition of the substrate source.

Depositional environment: Fluvial and probably lacustrine environments contemporaneous with extrusive activity.

Relationships and boundaries: Unconformably overlain by Kulail Sandstone and overlies Puntitjata Rhyolite, Mount Harris Basalt and Musgrave Block granites.

Age reasons: Meso-Neoproterozoic. Older than Dean Quartzite (~850 Ma) and younger than Puntitjata Rhyolite (1075 +/- 2.5 Ma).

Correlations: Originally correlated with Dixon Range beds (WA) which are defined by Forman (1966) as conformable beneath the Dean Quartzite. However redefinition precludes this correlation as the contact between the Bloods Range Formation and the Kulail Sandstone/Dean Quartzite in the Bloods Range region is defined by an erosional disconformity.

Proposed publication: Close, D.F., Edgoose, C.J., Scrimgeour, I.R., 2002. Bloods Range and Hull 1:100 000 geological special, Northern Territory Geological Survey, Explanatory notes.

Comments: Former name Bloods Range beds included parts of newly defined Tjuninanta Formation and Kulail Sandstones. The Bloods Range Formation forms the uppermost unit of the Tjauwata Group. True thickness of sequence difficult to measure due to both upper and lower stratigraphic contact rarely exposed in same section, and strong foliation development during the 570-530 Ma Petermann Orogeny.

References: R087 - Forman, D.J., 1966. The geology of the south-western margin of the Amadeus Basin, central Australia. Bureau of Mineral Resources, Australia. Report, 87.