Paleoenvironmental controls on mineral assemblages in a shelf sequence: Te Kuiti Group, South Auckland, New Zealand

Abstract

The Late Eocene--Oligocene sediments of the Te Kuiti Group represent a classical transgressive sequence from basal nonmarine coal measures to overlying shallow marine mudstones, sandstones, and limestones. Paleoenvironmental conditions in the South Auckland region during the Paleogene were such that basement Mesozoic sandstones and mudstones, the only local source rocks for terrigenous material, exerted a relatively subordinate role on the mineralogy of the Te Kuiti Group sediments accumulating in adjacent depocentres. Instead, the sediments include abundant transformed, authigenic, and biogenic mineral associations reflecting conditions pertaining in each of the pedogenetic, paludal, and temperate latitude, shallow marine environments. A kaolinite-quartz-siderite mineralogy dominates the nonmarine beds, and a low-Mg calcite-smectitequartz-sodic plagioclase-glauconite mineralogy characterises the bulk of the marine deposits. The mineralogy bears the imprint of a complex set of factors in which the influences of climate, soil provenance, depositional environment, and diagenesis greatly dominate over the influences of tectonics and source-rock provenance.

Paleogeography of Late Eocene to earliest Miocene Te Kuiti Group, central-western North Island, New Zealand

“…The subgroups are separated by a prominent unconformity marking a pronounced change in lithofacies character from dominantly mixed carbonate-siliciclastic sediment below to dominantly carbonate sediment above. For the Waitomo area, the Okoko Subgroup has 48% average calcium carbonate content, whereas the Castle Craig Subgroup has a carbonate content of 65-98% (Nelson 1978;Nelson & Hume 1987). The formations comprising the Okoko Subgroup show successively higher positions of coastal onlap onto basement, consistent with continuing regional subsidence during this interval.…”

“…6A. The fine-grained lithofacies dominating the Waikato Coal Measures were sourced from deeply weathered basement regolith (Nelson & Hume 1987), transported south to north via a fluvial system (Edbrooke et al 1994) and deposited in meandering river and floodplain environments in the northern Waikato region between basement ridges to the west and east.…”

A giant Oligocene fossil penguin from the North Island of New Zealand

“…The Dunphail Siltstone represents a mid-shelf environment and was deposited along the western continental shelf of Zealandia during a major marine transgression near peak continental submergence (Nelson and Hume, 1987;King, 2000;Kamp et al, 2014a;Strogen et al, 2014). At a larger scale, the Glen Massey Formation represents a broadly similar depositional setting to the Kokoamu Greensand in the South Island of New Zealand, which yielded the holotype specimens of Kairuku waitaki and Kairuku grebneffi (Fig.…”

Lithostratigraphy and depositional episodes of the Oligocene carbonate‐rich Tikorangi Formation, Taranaki Basin, New Zealand

“…The Otaraoa, Tikorangi, and Taimana Formations together form the Ngatoro Group, a name proposed by King (1988a,b) for this succession of generally calcareous Oligocene to early Miocene rocks, analogous to the age-equivalent Te Kuiti (Mahoenui) Group(s) onshore in King Country Basin (Fig. 1B) (Nelson 1978b;Nelson & Hume 1987).…”