Petrogenesis of diachronous mixed siliciclastic-carbonate megafacies in the cool-water Oligocene Tikorangi Formation, Taranaki Basin, New Zealand

Hood, Steven D.; Nelson, Campbell S.; Kamp, Peter J.J.

Petrogenesis of diachronous mixed siliciclastic-carbonate megafacies in the cool-water Oligocene Tikorangi Formation, Taranaki Basin, New Zealand

dc.contributor.author	Hood, Steven D.
dc.contributor.author	Nelson, Campbell S.
dc.contributor.author	Kamp, Peter J.J.
dc.date.accessioned	2009-12-15T22:41:04Z
dc.date.available	2009-12-15T22:41:04Z
dc.date.issued	2003
dc.description.abstract	The Oligocene (Whaingaroan-Waitakian) Tikorangi Formation is a totally subsurface, lithostratigraphically complex, mixed siliciclastic-limestone-rich sequence forming an important fracture reservoir within Taranaki Basin, New Zealand. Petrographically the formation comprises a spectrum of interbedded rock types ranging from calcareous mudstone to wackestone to packstone to clean sparry grainstone. Skeletal and textural varieties within these rock types have aided in the identification of three environmentally distinctive megafacies for the Tikorangi Formation rocks-shelfal, foredeep, and basinal. Data from these megafacies have been used to detail previous conclusions on the petrogenesis and to further refine depositional paleoenvironmental models for the Tikorangi Formation in the central eastern Taranaki Basin margin.Shelfal Megafacies 1 rocks (reference well Hu Road-1A) are latest Oligocene (early Waitakian) in age and formed on or proximal to the Patea-Tongaporutu-Herangi basement high. They are characterised by coarse, skeletal-rich, pure sparry grainstone comprising shallow water, high energy taxa (bryozoans, barnacles, red algae) and admixtures of coarse well-rounded lithic sand derived from Mesozoic basement greywacke. This facies type has previously gone unrecorded in the Tikorangi Formation. Megafacies 2 is a latest Oligocene (early Waitakian) foredeep megafacies (formerly named shelfal facies) formed immediately basinward and west of the shelfal basement platform. It accumulated relatively rapidly (>20 cm/ka) from redeposition of shelfal megafacies biota that became intermixed with bathyal taxa to produce a spectrum of typically mudstone through to sparry grainstone. The resulting skeletal mix (bivalve, echinoderm, planktic and benthic foraminiferal, red algal, bryozoan, nannofossil) is unlike that in any of the age-equivalent limestone units in neighbouring onland King Country Basin. Megafacies 3 is an Oligocene (Whaingaroan-Waitakian) offshore basinal megafacies (formerly termed bathyal facies) of planktic foraminiferal-nannofossil-siliciclastic wackestone and mudstone formed away from redepositional influences. The siliciclastic input in this distal basinal setting (sedimentation rates <7 mm/ka) was probably sourced mainly from oceanic currents carrying suspended sediment from South Island provenances exposed at this time.Tikorangi Formation rocks record the Taranaki Basin’s only period of carbonate-dominated sedimentation across a full range of shelfal, foredeep, and basinal settings. Depositional controls on the three contrasting megafacies were fundamentally the interplay of an evolving and complex plate tectonic setting, including development of a carbonate foredeep, changes in relative sea level within an overall transgressive regime, and changing availability, sources, and modes of deposition of both bioclastic and siliciclastic sediments. The mixed siliciclastic-carbonate nature of the formation, and its skeletal assemblages, low-Mg calcite mineralogy, and delayed deep burial diagenetic history, are features consistent with formation in temperate-latitude cool waters.	en
dc.format.mimetype	application/pdf
dc.identifier.citation	Hood, S. D., Nelson, C. S., & Kamp, P. J. J. (2003). Petrogenesis of diachronous mixed siliciclastic-carbonate megafacies in the cool-water Oligocene Tikorangi Formation, Taranaki Basin, New Zealand. New Zealand Journal of Geology and Geophysics, 46, 387-405.	en
dc.identifier.doi	10.1080/00288306.2003.9515016	en_NZ
dc.identifier.uri	https://hdl.handle.net/10289/3497
dc.language.iso	en
dc.publisher	SIR Publishing	en_NZ
dc.relation.isPartOf	New Zealand Journal of Geology and Geophysics	en_NZ
dc.relation.uri	http://www.royalsociety.org.nz/Site/publish/Journals/nzjgg/2003/025.aspx	en
dc.rights	This article has been published in the New Zealand Journal of Geology and Geophysics. © The Royal Society of New Zealand 2003.	en
dc.subject	petrogenesis	en
dc.subject	limestone	en
dc.subject	shelf-to-basin facies	en
dc.subject	tikorangi formation	en
dc.subject	oligocene	en
dc.subject	taranaki basin	en
dc.subject	reservoir	en
dc.subject	cool-water carbonate	en
dc.title	Petrogenesis of diachronous mixed siliciclastic-carbonate megafacies in the cool-water Oligocene Tikorangi Formation, Taranaki Basin, New Zealand	en
dc.type	Journal Article	en
pubs.begin-page	387	en_NZ
pubs.edition	September	en_NZ
pubs.elements-id	29460
pubs.end-page	405	en_NZ
pubs.issue	3	en_NZ
pubs.volume	46	en_NZ