Terrane affinities in the southern Blue Mountains

Stenhouse, Paul.

The basement of the southern Blue Mountains consists of a northwes(trending belt of sandstone and siltstone sequences, with a small area of Dun Mountain Ophiolite Belt (DMOB) volcanics at @southern end. The Livingstone Fault is a major terrane boundary that cuts through the southern /ID \)\p];J ; ) Blue Mountains al_o_n_g _a s.,. u_b_-p_a_r1 1-1lel -tr-end. Definition of the Livingstone Faults exact position is dependent on the determination of terrane affiliations within the sedimentary sequence. Mapping has identified 11 lithologies (9 sedimentary and 2 volcanic) on the basis of field criteria such as grain size, colour, composition and internal structure. Spatial associations of these lithologies has led to the description of 10 informal mapping units that imply an apparent stratigraphic continuity from the northern limit of the field area to the DMOB contact in the south. Modal analysis indicates the seqvence has affiliations with the Tuapeka Group (Caples terrane). Geochemical analyses also indicate a Caples terrane affiliation with most samples falling within ~ either the Tuapeka Group or Chrystalls Beach petrofacies fields.Q'_~ data disprovejthe presence of the Watties Sandstone in the Blue Mountains as mapped by Cawood ( 1987), and shif)i the location of the Livingstone Fault south to the DMOB contact. Field mapping and whole rock chemistry indicates that analyses with Chrystalls Beach block affiliations are interbedded with sediments of Tuapeka Group association. This strongly suggests that the Chrystalls Beach block may represent a more evolved variant of the Tuapeka Group, rather than a distinct entity as previously thought. Structur~ in the area is dominated by two reverse faults, a deformation zone that inverts younging direction across it, and the Livingstone Fault (that can now be defined as the contact between the structurally unbroken sedimentary sequence and DMOB). These structures all strike northwest and are inferred to dip northeast. A younger, subordinate northeast trend also occurs in the Blue Mountain Fault system and at discrete localities throughout the southern Blue Mountains.

118 leaves : ill. (some col.), maps (some folded) ; 30 cm.

2002Stenhouse

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