Paleostress axes from mineral striations in faulted Mesozoic basement, Auckland, New Zealand

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Abstract
Conjugate systems of quartz-chlorite fibre striations in Mesozoic metagreywackes at Whitford and Halliwells quarries, Auckland, indicate a paleostress regime with ENE-directed, subhorizontal compression, accompanied by dilatant movement within the rock mass. The striations were formed at a yet unspecified time in the interval between Lower Cretaceous and lowest Miocene. Striations have a planar spacial distribution at Whitford and mostly record strike-slip movement, whereas the distribution at Halliwells is more complex and reverse dip-slip predominates. Quartz-chlorite striations at a number of other localities in the Auckland area record ENE or ESE compressions. In a few instances, however, the compression is at right angles to this trend, or compression has been exchanged with extension. Post-striation structures include scratch striations, clayey gouge zones, and various faults which displace the Miocene sediments overlying the greywackes.