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首页> 外文期刊>ICES Journal of Marine Science >Luminescence age estimates of Pleistocene marine terrace and alluvial fan sediments associated with tectonic activity along coastal Otago, New Zealand
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Luminescence age estimates of Pleistocene marine terrace and alluvial fan sediments associated with tectonic activity along coastal Otago, New Zealand

机译：新西兰奥塔哥沿岸与构造活动相关的更新世海洋阶地和冲积扇沉积物的发光年龄估计

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摘要

Six luminescence age estimates have been obtained from raised beach sands and loess, and alluvialfan sediments in the outboard zone of the active Otago reverse fault province, coastal Otago, New Zealand. These age estimates constrain the timing of movement of the Akatore Fault and the Titri Fault System. Five of the samples were dated by optical dating of K-feldspar in the polymineral fine silt fraction; the remaining sample was dated using thermoluminescence (TL) emitted from quartz (fine sand fraction). Raised beach sands from the lowest Pleistocene marine terrace on the upthrown side of the reverse faults (Taieri Beach) yielded ages of 117 +- 13 ka (optical dating, K-feldspar) and 117 +- 12 ka (TL dating, quartz), indicating terrace formation during the peak sea-level highstand of the last interglacial, marine oxygen isotope substage (MISS) 5e (c. 125 ka). The K-feldspar optical age has not been corrected for anomalous fading, but its consistency with the quartz TL age indicates that anomalous fading is insignificant in this sample. Samples from a raised beach sand unit and an underlying loess unit that bracket a marine terrace that has previously been associated with the c. 125 ka sea-level highstand, situated 10 km northeast of the effects of faulting (Warrington), yielded optical age (K-feldspar) estimates of 91 +- 11 and 96 +- 5 ka, respectively. These ages have not been corrected for anomalous fading and therefore the true ages might be slightly older. Two loess units within alluvial fans along the Titri Fault System in the Waihola region yielded optical age estimates of 92 +- 5 and 151 +- 5 ka (both K-feldspar), which bracket the last period of faulting along the Titri Fault System; the latter age result is consistent with geomorphic evidence that suggests fan formation during the glacial period MIS 6 (186-128 ka); this consistency also implies that there was no significant anomalous fading in these samples. Together with published radiocarbon ages, our results imply that no activity has occurred on the Akatore Fault in the period c. 125-3.8 ka and only localised activity (at Moneymore) on the Titri Fault System post-150 ka.
机译：从活跃的奥塔哥反向断裂省，新西兰奥塔哥沿海地区，从凸起的沙滩和黄土以及冲积扇沉积物中获得了六个发光年龄估计。这些年龄估计值限制了Akatore断层和Titri断层系统的运动时间。五个样品通过多矿物细粉砂质中钾长石的光学测年法测定。剩余的样品使用石英（细砂级分）发出的热致发光（TL）标定日期。从反向断层上升侧最低的更新世海洋阶地（太里海滩）上抬起的沙滩沙的年龄为117 +-13 ka（光学测年，钾长石）和117 +-12 ka（TL测年，石英），表示在最后一个冰间期，海洋氧同位素子阶段（MISS）5e（约125 ka）的高峰海平面高位形成阶地。钾长石的光学年龄尚未针对异常衰落进行校正，但其与石英TL年龄的一致性表明该样本中的异常衰落无关紧要。来自凸起的沙滩沙单元和下面的黄土单元的样本，这些样本包围了以前与c相关联的海洋阶地。位于断层效应（沃灵顿）东北10公里处的125 ka海平面高位估计的光学年龄（K-长石）估计分别为91 +-11和96 +-5 ka。这些年龄尚未针对异常衰落进行校正，因此实际年龄可能会稍大一些。怀霍拉地区沿Titri断层系统的冲积扇内有两个黄土单元，得出的光学年龄估计为92 +-5和151 +-5 ka（均为K-长石），将Titri断层系统沿断层的最后一个时期包括在内；后者的年龄结果与表明冰川期MIS 6（186-128 ka）形成扇形的地貌证据一致；这种一致性还意味着这些样本中没有明显的异常褪色。连同已公布的放射性碳年龄，我们的结果表明，在c时段内的Akatore断层没有活动。 125-3.8 ka，只有150 ka之后在Titri Fault System上的局部活动（在Moneymore）。

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