Definition, age, and correlation of the Clarence series stages in New Zealand (late early to early late Cretaceous)

Abstract

The New Zealand local Clarence Series spans the Lower/Upper Cretaceous boundary and includes three stages, in ascending order, the Urutawan, Motuan, and Ngaterian. All three were defined originally from a type section at Motu Falls, Raukumara Peninsula. To address problems with their original definitions and to improve correlations between the New Zealand time-scale and Global Chronostratigraphic Scale, four key sections have been restudied: the Motu Falls and adjacent Te Waka sections, and the Coverham and Seymour sections in the Clarence valley, Marlborough. The sections contain locally abundant macrofossils and have been sampled at a reconnaissance level for dinoflagellates. In addition, a middle Motuan tuff bed in the Motu Falls section has yielded a zircon U-Pb age of 101.6 ± 0.2 Ma, and an upper Ngaterian basalt flow in the Seymour section has yielded a plagioclase Ar/Ar age of 96.1 ± 0.6 Ma. The older of these dates allows, for the first time, direct age correlation of Clarence Series stages that are based on marine strata in eastern New Zealand, with non-marine rocks in the west. Thus, the Stitts Tuff, at the base of the Pororari Group in the western South Island, is shown to be middle Motuan. the Motuan is defined using the lowest occurrence of the bivalve Aucellina euglypha in the same section. The base of the Ngaterian is defined using the lowest occurrence of the inoceramid "I." tawhanus in the Te Waka section. In all three cases, the placements of the lowest occurrence datums are subject to uncertainties that can only be resolved by further biostratigraphic and/or taxonomic study. Based on biostratigraphic data and the new radiometric dates, the following international correlations are proposed: Urutawan Stage = lower-middle Albian (108-103 Ma); Motuan Stage = middle-upper Albian (103-100 Ma); Ngaterian Stage = upper Albian to middle Cenomanian (100-95 Ma).

Cretaceous felsic volcanism in New Zealand and Lord Howe Rise (Zealandia) as a precursor to final Gondwana break-up

“…It occurs in the lower part of the Matawai Group in Raukumara Peninsula of the North Island. Motu River is the type locality for the Motuan Stage (100 -103 Ma) of the New Zealand Cretaceous (Crampton et al 2004). The unit includes three 1.5-5 m thick pale weathering tuff beds.…”

Geochronological constraints on Cretaceous‐Paleocene volcanism in South Westland, New Zealand

“…Alkaline rocks from this time period include: alkaline basalt lavas of the Gridiron Formation, Marlborough, with an 40 Ar/ 39 Ar age of 96.1 ± 0.6 Ma (Crampton et al 2004); the Tapuaenuku Plutonic Complex in Marlborough, northeast South Island, which has concordant Rb-Sr, K-Ar, and titanite/zircon fission track cooling ages of c. 105-93 Ma (Baker & Seward 1996); and the Mandamus Igneous Complex in North Canterbury, which has a Rb/Sr isochron age of 97.0 ± 0.5 Ma (Weaver & Pankhurst 1991). The Mount Somers Volcanics Group of the central South Island, while not strictly alkaline, were erupted in an extensional environment from mantle wedge sources that had been metasomatised during previous subduction cycles.…”

Cretaceous sedimentation and metamorphism of the western Alpine Schist protoliths associated with the Pounamu Ultramafic Belt, Westland, New Zealand

“…The youngest detrital zircon populations determined by Adams et al (2013b) in Omaio facies rocks range from 10092 to 11291 Ma. These basement ages overlap with a UÁPb age of 101.690.2 Ma from tuff bed T2 in the unconformably overlying Karekare Formation cover sequence at Motu Falls, Raukumara Peninsula (Crampton et al 2004).…”