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Stratigraphy and palaeogeography of the Cretaceous Blue Spur Conglomerate, Otago, New Zealand
New Zealand Journal of Geology and Geophysics ( IF 2.2 ) Pub Date : 2022-02-23 , DOI: 10.1080/00288306.2022.2039223
Dave Craw 1 , Nick Mortimer 2
Affiliation  

ABSTRACT

The non-marine Blue Spur Conglomerate in southeast Otago hosts the largest gold paleoplacer in New Zealand, but its formal stratigraphic relationships have thus far not been clear. The name reflects the extensive formation of ferrous iron-bearing diagenetic clay. We present a reference section for the unit, which is in part late Haumurian in age (c. 81–66 Ma). The unit is defined as a formal Member of the nearby, but not contiguous, Late Cretaceous Taratu Formation, Onekakara Group, Haerenga Supergroup. The Blue Spur Conglomerate contains three principal clast types: proximal schist debris, quartz pebbles and recycled distal greywacke cobbles, whereas the wider Taratu Formation is dominated by quartz pebble conglomerate with subordinate lithic clasts. Rare clasts of silicified quartz pebble conglomerate (silcrete) in both units attest to the recycling of older mature quartz sediments. The Blue Spur Conglomerate formed locally at the base of active normal fault scarps that controlled a broad valley in which the regionally extensive Taratu Formation accumulated. Detrital gold in the Blue Spur Conglomerate had both proximal and distal sources, whereas the Taratu Formation elsewhere received only distal gold.



中文翻译:

新西兰奥塔哥白垩纪蓝刺砾岩的地层学和古地理

摘要

奥塔哥东南部的非海洋 Blue Spur 砾岩拥有新西兰最大的黄金古砂矿,但其正式的地层关系迄今尚不清楚。该名称反映了亚铁含铁成岩粘土的广泛形成。我们提供了该单元的参考部分,该单元的部分年龄为晚 Haumurian(约 81-66 Ma)。该单元被定义为附近但不相邻的晚白垩世 Taratu 地层、Onekakara 群、Haerenga 超群的正式成员。Blue Spur 砾岩包含三种主要的碎屑类型:近端片岩碎片、石英卵石和回收的远端杂砂岩卵石,而更广泛的 Taratu 地层主要是石英卵石砾岩和次级岩屑。两个单元中罕见的硅化石英卵石砾岩(硅质混凝土)碎屑证明了较旧的成熟石英沉积物的循环利用。Blue Spur 砾岩在活动的正断层峭壁底部局部形成,正断层峭壁控制着一个宽阔的山谷,区域范围广泛的 Taratu 地层在其中堆积。Blue Spur Conglomerate 中的碎屑金既有近端来源也有远端来源,而其他地方的 Taratu 地层则只有远端黄金来源。

更新日期:2022-02-23
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