Stratigraphy and bibliography of the waitemata group of auckland, new zealand

Abstract

The Waitemata Group comists of flysch and related strata, of uppermost Oligocene to Lower Miocene age, outcropping widely around Auckland. It is redefined to exclude the Manukau Breccias, which are included with the Waipoua Basalt and Omapere Conglomerate of Hokianga in Hayward's new Waitakere Group. Also excluded are the co-eval marine strata of Hokianga (Hay's Otaua Group) and North Cape (Leitch's ParengarengD Group), The group includes a central body of flysch extending from Papakura to Brynderwyn (Warkworth Subgroup), It is flanked to the north by a shelf facies (Bream Subgroup); to the west by a distal-volcanic deep shelf facies (Kaipara Subgroup); and to the south by a shelf facies (Meremere Subgroup), To the east, the group overlaps an uneven surface on Torlesse metagreywackes. Both upper and lower contacts of the group are unconformable. There is a substantial volcaniclastic content in some formations, but no in-situ volcanics occur.The existing formations are defined, and the following new formations are proposed. The basal Cape Rodney Formation (much enlarged from Park's original usage); East Coast Bays Formation, non-volcanic flysch centred on Auckland; Pakiri Formation, strongly volcanic flysch occurring northwards from Waiwera; Blockhouse Bay Formation, mixed volcanic and non-volcanic flysch and non-flysch lithologies, occurring west of Auckland and in the Manukau lowlands; Ruarangi Formation, tuff-bearing mudstones and minor flysch; Ngatoka Formation, massive calcareous sandstone; Puriri Formation, calcareous siltstones with volcanic turbidites. The proximal-volcanic Waitakere Group and the Waitemata Group are co-eval and interdigitate. The Waitakere Group oversteps eastwards across the Waitemata Group. The boundary between the two groups west of Auckland is taken at the conformable iunction of the Blockhouse Bay Formation with the overlying Cornwallis Formation. The boundary in the Kaipara Harbour is taken at the unconformable junction of the Timber Bav Formation with the overlying Okahukura Formation.The oldest formations in the Warkworth, Kaipara, and Bream Subgroups are probably Waitakian. The remainder of the group is Otaian. A bibliography of the revised Waitemata Group is included. © 1976 Taylor and Francis Group, LLC.