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Litho- and biostratigraphy of a late Oligocene–Early Miocene succession in the Weber area, southern Hawke’s Bay, and implications for early Hikurangi subduction-margin evolution
New Zealand Journal of Geology and Geophysics ( IF 2.2 ) Pub Date : 2022-08-10 , DOI: 10.1080/00288306.2022.2108069
Kyle J. Bland, Hugh E. G. Morgans, Dominic P. Strogen, Hannah Harvey

ABSTRACT

A deep-marine sedimentary succession of Whaingaroan to Altonian age (Early Oligocene–Early Miocene), cropping out near Weber, southern Hawke’s Bay, records abrupt changes in depositional paleoenvironments and sedimentary lithofacies. Highly calcareous early Waitakian (latest Oligocene) Weber Formation (Mangatu Group/Waka Supergroup) is unconformably overlain by terrigenous-dominated late Waitakian–Otaian (Early Miocene) Coast Road or Whakataki formations (Tolaga Group/Māui Supergroup). Most notably, in some localities, lowermost parts of the Coast Road Formation (Mangapuku Mudstone Member) contain prominent matrix-supported extra-formational olistoliths of centimetre to decametre scale derived from the underlying Weber Formation. Deposition of these blocks is attributed to deep-water collapse of parts of rapidly growing, over-steepened, reverse-fault-controlled thrust ridge(s). The onset of Coast Road and Whakataki formation deposition and associated abrupt changes in sedimentary lithofacies correlate to prominent Early Miocene lithological, mineralogical, and paleoenvironmental changes elsewhere along the Hikurangi Margin. We attribute these bio- and lithostratigraphic changes as evidence for significant shortening and upper-plate reverse faulting marking the onset of subduction beneath eastern North Island during the mid-Waitakian (c. 23 Ma). Proposed lithostratigraphic revisions presented herein help clarify depositional events and correlative sedimentary packages within the Miocene Hikurangi margin.



中文翻译:

霍克斯湾南部韦伯地区晚渐新世-早中新世演替的岩石和生物地层学,以及对早期 Hikurangi 俯冲边缘演化的影响

摘要

在霍克斯湾南部韦伯附近出土的 Whaingaroan 到 Altonian 时代(早渐新世 - 早中新世)的深海沉积序列记录了沉积古环境和沉积岩相的突然变化。高度钙质的早期怀塔克纪(最新渐新世)韦伯组(Mangatu 组/Waka 超组)不整合地被陆源主导的晚期 Waitakian-Otaian(早中新世)海岸公路或 Whakataki 组(Tolaga 组/Māui 超组)覆盖。最值得注意的是,在某些地区,Coast Road 组(Mangapuku 泥岩段)的最下部包含显着的基质支撑的地层外石磨,其源自下伏 Weber 组的厘米至十米尺度。这些块体的沉积归因于快速生长、过度陡峭、反向故障控制的推力脊。Coast Road 和 Whakataki 地层沉积的开始以及沉积岩相的相关突变与 Hikurangi Margin 其他地方显着的早中新世岩性、矿物学和古环境变化相关。我们将这些生物和岩石地层变化作为显着缩短和上板块反向断层的证据,标志着怀塔基期中期(约 23 Ma)北岛东部下方开始俯冲。本文提出的拟议岩石地层修正有助于阐明中新世 Hikurangi 边缘内的沉积事件和相关沉积包。Coast Road 和 Whakataki 地层沉积的开始以及沉积岩相的相关突变与 Hikurangi Margin 其他地方显着的早中新世岩性、矿物学和古环境变化相关。我们将这些生物和岩石地层变化作为显着缩短和上板块反向断层的证据,标志着怀塔基期中期(约 23 Ma)北岛东部下方开始俯冲。本文提出的拟议岩石地层修正有助于阐明中新世 Hikurangi 边缘内的沉积事件和相关沉积包。Coast Road 和 Whakataki 地层沉积的开始以及沉积岩相的相关突变与 Hikurangi Margin 其他地方显着的早中新世岩性、矿物学和古环境变化相关。我们将这些生物和岩石地层变化作为显着缩短和上板块反向断层的证据,标志着怀塔基期中期(约 23 Ma)北岛东部下方开始俯冲。本文提出的拟议岩石地层修正有助于阐明中新世 Hikurangi 边缘内的沉积事件和相关沉积包。我们将这些生物和岩石地层变化作为显着缩短和上板块反向断层的证据,标志着怀塔基期中期(约 23 Ma)北岛东部下方开始俯冲。本文提出的拟议岩石地层修正有助于阐明中新世 Hikurangi 边缘内的沉积事件和相关沉积包。我们将这些生物和岩石地层变化作为显着缩短和上板块反向断层的证据,标志着怀塔基期中期(约 23 Ma)北岛东部下方开始俯冲。本文提出的拟议岩石地层修正有助于阐明中新世 Hikurangi 边缘内的沉积事件和相关沉积包。

更新日期:2022-08-11
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