Late Cenozoic thrust tectonics, Picton, New Zealand

Abstract

In the Marlborough Sounds area near Picton. multiple deformation during the Miocene produced early (D 1 ) north-northeast-trending folds, and north-and east-striking thrusts. Later folding (D0 about east-west axes led to the formation of basin and dome interference structures. During D 1 • Mesozoic rocks of the Marlborough Schist and PermianTriassic Pelorus Group were thrust over an Oligocene sedimentary sequence. which is now exposed as erosional inliers.Thrust transport from west to east is inferred from fibre striations. Striation-derived M-axis data, calcite grain fabric studies, and the maximwn shortening direction of northnortheast-trending folds suggest that thrusting developed in association with approximate west-east compression. Thrust motion resulted in progressive late Cenozoic stacking of the basement sequence in this area, with considerable shortening and thickening of the Marlborough Sounds region.

Metamorphic zones, terranes, and Cenozoic faults in the Marlborough Schist, New Zealand

“…2). A major structural and metamorphic break on the southeast side of the low-grade schists (Mackay 1879;Morgan 1921;Henderson 1935;Branch & Bartrum 1939;Beck 1964;Vitaliano 1968;Nicol & Campbell 1990) is confirmed by the present work and is here called the Picton Fault Zone. For convenience, rocks northwest and southeast of the Picton Fault Zone are referred to in this paper as belonging to the Kaituna and Arapawa blocks, respectively (Fig.…”

“…One well-documented feature of the Picton Fault Zone near Picton is a sequence of three, stacked, post-Oligocene (probably Miocene), east-verging thrusts (Nicol & Campbell 1990). During the present study, a fault plane in the Picton Fault Zone 8 km southwest of Picton (P27/873848) was observed; it was oriented 066/66NW with northeast-trending mesoscopic kink fold axes in the pelitic schist of the hanging wall.…”

“…IIIB-IV Kaituna block and t.z. I-IIA Arapawa block rocks (Nicol & Campbell 1990 Mackay (1879) and depicted on maps by Henderson (1935), Beck (1964), andVitaliano (1968). They seem to have been postulated solely on the basis of the linearity of the Sounds, without demonstrated offset of any geological features.…”

“…IIIB-IV rocks (e.g., Fig. 4C) are extensively exposed southwest of Picton (Watters & Challis 1985;Nicol & Campbell 1990). 6.…”

An episodic Cretaceous cooling model for the Otago‐Marlborough Schist, New Zealand, based on40Ar/39Ar white mica ages

“…Another difference between the two regions is that the Marlborough Schist (particularly the Waikakaho block) has a greater density of postmetamorphic folds and faults, is closer to the Alpine Fault, and lies at the northern margin of the Marlborough strike-slip fault system. The Marlborough study region also straddles the Picton Fault, a major post-Oligocene reverse fault zone (Nicol & Campbell 1990;Mortimer 1993c). The Picton Fault is upthrown on the northwest, and duplicates the metamorphic and textural zonation in the Marlborough Schist across its plexus of northeast-striking splays.…”