An Inter-Arc Flysch Basin in Northern New Zealand: Waitemata Group (Upper Oligocene to Lower Miocene)

Thermal history of the early Miocene Waitemata Basin and adjacent Waipapa Group, North Island, New Zealand

“…Synchronous with this development was the formation of the Alpine Fault as a continuous transform through the New Zealand block, intersecting obliquely the earlier late Eocene to mid Oligocene rift system of western South Island (Kamp 1986b). The other tectonic events that are significant to this study and related to this change were: (1) obduction of nappes of the Northland Allochthon (the former passive margin wedge) between 24 and 22 Ma, along with the obduction of the Tangihua/Matakaoa ophiolites (Ballance ¿Í Sporli 1979;Hayward et al 1989); and (2) the development of the inter-arc Waitemata Basin (Ballance 1974;Hayward 1993;Isaac et al 1994).…”

“…To the northwest, and in the centre of the basin, strata rest unconformably on strongly deformed and displaced deep-marine rocks of the Northland Allochthon. The basin is flanked to the north and south by uplifted basement blocks, over which thinner sequences of sandstone, mudstone, and a few turbidite beds accumulated (Ballance 1974). Both blocks consist of autochthonous Oligocene Te Kuiti Group carbonate and sandstone overlying the Mesozoic Murihiku and Waipapa rocks.…”

“…The main part of the Waitemata Basin fill is an interbedded turbidite sandstone and pelagic siltstone sequence deposited at bathyal depths during the Otaian Stage c. 23-19 Ma (Ballance 1974;Hayward 1979). Interbedded with these sequences are thicker volcaniclastic mass-flow units of possibly lahar/debris avalanche origin (e.g., Parnell Grit beds; Ballance & Gregory 1991).…”

“…Interbedded with these sequences are thicker volcaniclastic mass-flow units of possibly lahar/debris avalanche origin (e.g., Parnell Grit beds; Ballance & Gregory 1991). Paleocurrent directions indicate that most of the sediment supply was from the northwest (Ballance 1974).…”

“…Internal stratigraphy and correlation within the basin is poorly established due to the lack of marker units and the complexity of the deformation (Ballance 1974;Sporli 1989a). However, there is a general regional tilt and younging towards the west (Ballance 1974;Hayward 1979).…”