Stratigraphic and structural evidence for an accretionary precursor to the Northland Allochthon: Mt Camel Terrane, northernmost New Zealand

Abstract

Key tectonic events at the southern rim of the South Fiji Basin‐Three Kings Ridge‐Norfolk Basin region of the Southwest Pacific are revealed by analysis of the extremely complex structural sequence in a coastal section of Mt Camel Terrane units (Houhora Complex). The Cretaceous to early Tertiary clastic sedimentary and igneous lithologies of the terrane were deposited in an oblique‐slip extensional back‐arc basin. All units were deformed at relatively shallow levels (zeolite facies). Pervasive shearing to broken formation, and at least two phases of early folding, occurred during Tertiary accretion tectonics in a nascent subduction zone along the margin of the New Zealand micro‐continent. Accretionary processes were followed by pervasive sinistral shearing and associated folding and movement on low‐angle faults during overthrusting of the Northland Allochthon. Deformation was postdated by intrusion of dikes of intermediate composition, associated with establishment of the subduction‐related Miocene Northland volcanic arc.

Keywords:

• Southwest Pacific
• Mt Camel Terrane
• broken formation
• accretion tectonics
• thrust faulting
• excision
• obduction
• Northland Allochthon
• dike intrusion
• volcanic arc
• structural complexity