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首页> 外文期刊>Stratigraphy >Stratigraphy and sedimentology of the lower Black Bear Ridge section, British Columbia:candidate for the base-Norian GSSP
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Stratigraphy and sedimentology of the lower Black Bear Ridge section, British Columbia:candidate for the base-Norian GSSP

机译：卑诗省黑熊山下段的地层学和沉积学：诺里安GSSP基地的候选人

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摘要

The upper Ludington and lower Pardonet formations at Black Bear Ridge, northeastern British Columbia, Canada repre-sent a continuously exposed succession through the upper Carnian and lower Norian (medial Upper Triassic). These strata were depos-ited in a deep marine setting (distally steepened carbonate ramp / medial to distal slope) on the northwestern margin of Pangaea. The Black Bear Ridge section is apparently continuous, with no evidence for either subaerial exposure or submarine erosion. The absence of erosional scours in the study interval confirms emplacement of these strata below both fair-weather and storm wave base. Event beds, particularly those resulting from sediment gravity flows, dominate the Carnian-Norian boundary interval at Black Bear Ridge. Upper Carnian strata, primarily assigned to the Ludington Formation at Black Bear Ridge, record an upward transition from moderate-scale, olistolith-bearing debris flow deposits (debrites) to medium / thin-bedded turbidites remobilised as small-scale sediment slump /slides. The Carnian-Norian boundary interval and the lower Norian succession is dominated by medium- to thin-bed-ded calcareous turbidites and lesser hemipelagic suspension deposits. Diverse and abundant fossil assemblages, particularly conodonts and bivalves, occur within the study interval. Despite evidence of post-depositional sediment remobilisation (i.e debrites and turbidites) conodont faunal successions indicate that the Black Bear Ridge section represents a complete and continuously exposed Carnian-Norian boundary succession. Rapid and relatively continuous sedi-mentation is attested to by the thickness of the section, the abundance of calcareous turbidites and the thin nature of intercalated hemipelagic beds. Abundant well-preserved fossils, evidence of continuous and rapid sedimentation and minimal alteration by tectonic disturbances, metamorphism or diagenesis make Black Bear Ridge an excellent candidate Global Stratotype Section and Point (GSSP) for the Carnian-Norian boundary.
机译：位于加拿大不列颠哥伦比亚省东北部的黑熊岭的上部卢丁顿岩层和下部的帕多内岩层表现为通过上卡尼期和下部诺里安（中上三叠统）不断暴露的演替。这些地层沉积在Pangaea西北边缘的深海环境中（碳酸盐岩坡度陡峭/中至远端斜坡）。黑熊山脊部分显然是连续的，没有证据表明有暴露于地下或潜艇受到侵蚀。在研究间隔中没有冲刷冲刷，证实了这些地层在晴天和风暴波基下方均已安放。事件床，特别是由泥沙重力流产生的事件床，在黑熊岭的Carnian-Norian边界区间占主导地位。上Carnian地层主要分配给黑熊岭的Ludington地层，记录了从中等规模的含橄榄石的泥石流沉积物（碎屑）向以小规模沉积物坍落度/滑坡移动的中/薄层浊积岩的向上过渡。 Carnian-Norian边界区间和较低的Norian演替以中层至薄层的钙质浊质和较少的半悬浮悬浮物为主。在研究间隔内，发生了多种多样的化石组合，尤其是牙形石和双壳类动物。尽管有沉积后沉积物迁移的证据（即碎屑和浊质），牙形石动物区系演替表明黑熊岭剖面代表了一个完整且连续暴露的Carnian-Norian边界演替。断面的厚度，钙质浊质的丰富性和夹层的半流化床的薄性证明了沉积的快速和相对连续。大量保存完好的化石，连续不断的快速沉积以及构造扰动，变质作用或成岩作用造成的最小变化的证据，使黑熊岭成为了卡尼诺-诺里安边界的最佳全球地层剖面和断面（GSSP）候选者。

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