Regional structure and kinematic history of a large subduction back thrust: Taranaki Fault, New Zealand

Abstract

The Taranaki Fault is a back thrust antithetic to the Hikurangi margin subduction thrust. Subduction back thrusts, like the Taranaki Fault, accrue displacement transferred from the subducting plate, and growth analyses of these structures contribute to an improved understanding of subduction processes. The Taranaki Fault forms the eastern margin of the Taranaki Basin and is part of a system that extends for at least 600 km in continental crust of western New Zealand. The fault is preserved beneath young sedimentary cover and provides a rare opportunity to investigate the geometry and kinematic history of a large subduction back thrust. Two‐dimensional seismic reflection lines (2–5 km spacing), tied to recently drilled wells and outcrop, together with magnetotelluric and gravity models are used to examine the fault. These data indicate that the fault is thick skinned with dips of 25–45° to depths of at least 12 km. The fault accommodated at least 12–15 km of dip‐slip displacement since the middle Eocene (circa 40–43 Ma). The northern tip of the active section of the fault stepped southward at least three times between the middle Eocene and early Pliocene, producing a total tip retreat of 400–450 km. The history of displacements on the Taranaki Fault is consistent with initiation of Hikurangi margin subduction during the middle Eocene, up to 20 Ma earlier than some previous estimates. Fault tip retreat may have been generated by clockwise rotation of the subduction margin and associated progressive isolation of the fault from the driving downgoing Pacific Plate.

Integrated 3D facies modeling of the Mangahewa Formation, Maui Gas Field, Taranaki Basin, New Zealand

“…Most of the basin remained tectonically quiescent till the end of the Eocene. However, it is also observed that an overall pattern of asymmetric eastward thickening of Middle to Late Eocene strata suggests regional fault-controlled subsidence during this period (Stagpoole and Nicol 2008). Major formations within the field have low regional dip angle (~ 10°) in the north and (~ 15°) in the southern part of the field (Haque et al 2016).…”

“…Taranaki Basin is the largest basin of New Zealand which is overprinted by Neogene convergent margin-related tectonics (Stagpoole and Nicol 2008;King and Thrasher 1992;King 1990). The entire New Zealand subcontinent is characterized by a passive margin and subsidence followed by consecutive accumulation of Paleocene-Eocene sediments across the shelfal and coastal plains of the basin (King 1990).…”

“…1). This field is situated in the southern region of the Taranaki Basin and is bounded from both east and west by two regional faults, Cape Egmont Fault and Whitiki Fault (Stagpoole and Nicol 2008;Laird 1993). This gas field has been producing from three main reservoir sands, namely the Mangahewa, Kaimiro and Farewell formations of the Kapuni Group (King and Thrasher 1996;Bryant et al 1994;Voggenreiter 1993).…”

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“…Seismic-stratigraphic evidence shows that the New Caledonia Trough either formed or was substantially modified during this event, though Cretaceous sedimentary basins beneath the trough escaped Cenozoic convergent deformation in most places (Collot et al, 2008;Sutherland et al, 2010). Regional deformation and emplacement of allochthons in northern New Zealand occurred later than in New Caledonia or the Norfolk Ridge system, with the onset of tectonic activity during the late Oligocene and early Miocene (~30-20 Ma) (Bache et al, 2012;Herzer, 1995;Herzer et al, 1997;Rait et al, 1991;Stagpoole and Nicol, 2008).…”

Late Paleozoic low-angle southward-dipping thrust in the Züünharaa area, Mongolia: tectonic implications for the geological structures in the Sayan-Baikal and Hangai-Daur belts

“…For instance, the Taranaki Fault in the northern part of New Zealand is considered to be a back thrust antithetic to the Hikurangi margin subduction thrusts. The Taranaki Fault has accommodated at least 12-15 km of dip-slip displacement since the middle Eocene (~40-43 Ma) (e.g., Stern et al 2006;Nicol et al 2007;Stagpoole and Nicol 2008).…”