Abstract We evaluate whether outer shelf/upper slope settings preserve a record of astronomical forcing using gamma ray logs from the upper Oligocene (upper Chattian) Tikorangi Formation, onshore Taranaki Basin, North Island, New Zealand. The formation is a siliciclastic‑carbonate succession deposited in outer neritic to upper bathyal depths at paleolatitudes of c. 45oS. Gamma ray and sonic logs calibrated to core indicate four lithofacies based on percent carbonate. These are calcareous siliciclastic mudrock (highest gamma ray values), highly calcareous siltstones (high gamma ray values), very fine to fine siliciclastic muddy packstones (intermediate gamma), and winnowed very fine to medium grain-dominated packstones and grainstones (low gamma). Detrended gamma ray logs were tuned using minimal tuning methods (405 kyr long eccentricity cycle or, where this was poorly developed, the ~100 kyr short eccentricity cycle) with sedimentation rates tested statistically against astronomical forcing. The tuned data show well developed long- and short-term eccentricity, obliquity, and a weak precessional forcing. Obliquity modulation is observed at the 1.2 Myr scale (one well) and 175 kyr scale (two wells). The floating time scale was tied to the absolute time scale via published biostratigraphy, the La2004 eccentricity solution, the Atlantic ODP site 1264 δ18O record, and the Mi-1 isotope event at c.23 Ma. Sea-level fluctuations typically were moderate (20 to 40 m) estimated from the δ18O record. The high gamma siliciclastic-prone units formed during warmer and wetter phases (and possibly slightly higher sea levels), whereas the cleaner carbonates with abundant inner-shelf-derived fine carbonate developed during cooler, drier phases (and possibly slightly lower sea levels). Gamma ray logs from outer shelf/upper slope settings provide valuable data sets for documenting the effects of astronomical forcing on the sedimentary record. The study supports climate models for New Zealand which predict generally increased precipitation with warming over the next 100 years. The study appears to be the first to record astronomical forcing in the Oligocene marine record of New Zealand.

中文翻译：

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在外陆架/上斜坡、混合硅质碎屑-碳酸盐中测试循环和伽马射线信号的天文强迫：新西兰上渐新世

摘要 我们使用来自新西兰北岛陆上塔拉纳基盆地渐新世（上查蒂安）蒂科兰吉组的伽马射线测井来评估外大陆架/上斜坡设置是否保留了天文强迫的记录。该地层是沉积在外浅海至深海深部古纬度 c 的硅质碎屑-碳酸盐层序。45oS。校准到岩心的伽马射线和声波测井表明基于碳酸盐百分比的四种岩相。这些是钙质硅质碎屑泥岩（伽马射线值最高）、高钙质粉砂岩（伽马射线值高）、极细至细的硅质碎屑泥质泥岩（中伽玛）和风选的极细至中等颗粒为主的泥岩和颗粒岩（低伽玛） . 使用最小调谐方法（405 kyr 长偏心周期或，在这方面发展不佳的地方，~100 kyr 短偏心周期）与沉降率对天文强迫进行了统计测试。调整后的数据显示，长期和短期的偏心率、倾斜度和岁差强迫都得到了很好的发展。在 1.2 Myr 规模（一口井）和 175 kyr 规模（两口井）上观察到倾斜调制。浮动时间尺度通过已发表的生物地层学、La2004 偏心率解、大西洋 ODP 站点 1264 δ18O 记录和约 23 Ma 的 Mi-1 同位素事件与绝对时间尺度相关联。根据 δ18O 记录估计，海平面波动通常是中等的（20 至 40 m）。高伽马硅碎屑倾向单元形成于较暖和较湿的阶段（可能还有略高的海平面），而更清洁的碳酸盐具有丰富的内陆架衍生的细小碳酸盐，是在较冷、较干燥的阶段（可能还有略低的海平面）形成的。来自外大陆架/上坡设置的伽马射线测井为记录天文强迫对沉积记录的影响提供了有价值的数据集。该研究支持新西兰的气候模型，该模型预测未来 100 年随着气候变暖，降水量普遍增加。该研究似乎是第一个在新西兰渐新世海洋记录中记录天文强迫的研究。该研究支持新西兰的气候模型，该模型预测未来 100 年随着气候变暖，降水量普遍增加。该研究似乎是第一个在新西兰渐新世海洋记录中记录天文强迫的研究。该研究支持新西兰的气候模型，该模型预测未来 100 年随着气候变暖，降水量普遍增加。该研究似乎是第一个在新西兰渐新世海洋记录中记录天文强迫的研究。