Abstract This paper investigates the magnetostratigraphy of the ~750 m-thick Costa Grande Member (lower Miocene) from the Castagnola Basin of NW Italy, which represents the turbidite fill of a structurally confined basin where flow ponding resulted in a complete record of deposition from diverse sediment gravity flow types. The magnetostratigraphic profile of the Costa Grande Mb was correlated to the Geomagnetic Polarity Timescale using a well-established statistical method devised to be applied to sedimentary successions with steady accumulation rate. The results of the correlation exercise, validated with the available biostratigraphy, indicate an early Miocene age (from Chron C6AAr.3r to C6Bn.2n) between 21.7 and 22.3 Ma. The obtained age model was then used to calculate accumulation rates and frequencies of small volume and low-density vs. large volume and high-density gravity flows over an estimated 650 kyr time span. Results show that low-density flows contributed at a constant pace of 545 m Myr−1 to sediment accumulation, depositing relatively thin-bedded turbidites with a minimum recurrence time of 1.7 kyr, whereas the high-density flows, which are at least four times less frequent, are clustered in the stratigraphy, and become more abundant up-section. We also show that the minimum sediment volumes discharged by high-density flows suggest triggering by submarine failures whose recurrence and magnitude were probably not random. Lastly, we propose that the statistical method used in this study to correlate the Costa Grande Mb magnetostratigraphy to the GPTS provides best results when the products of episodic but voluminous depositional events are carefully identified and removed.

中文翻译：

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应用磁年代学评估浊积岩沉积速度：以亚平宁山脉北部中新世下部积水片状浊积岩为例（意大利）

摘要 本文研究了意大利西北部 Castagnola 盆地约 750 m 厚的 Costa Grande 段（下中新世）的磁地层学，该段代表了结构受限盆地的浊积充填，在该盆地中，水流积聚导致了来自不同地区的完整沉积记录。沉积物重力流类型。Costa Grande Mb 的磁地层剖面与地磁极性时标相关联，使用了一种完善的统计方法，该方法旨在应用于具有稳定积累率的沉积层序。相关练习的结果，用现有的生物地层学进行了验证，表明中新世早期（从 Chron C6AAr.3r 到 C6Bn.2n）在 21.7 到 22.3 Ma 之间。然后使用获得的年龄模型来计算小体积和低密度与低密度的积累率和频率。在估计 650 kyr 的时间跨度内，大体积和高密度的重力流。结果表明，低密度流以 545 m Myr-1 的恒定速度对沉积物积累做出贡献，沉积相对薄的浊流，最小重现时间为 1.7 kyr，而高密度流至少为 4 倍频率较低，在地层中聚集，并且在剖面上变得更加丰富。我们还表明，高密度水流排放的最小沉积物体积表明由潜艇故障触发，其复发和规模可能不是随机的。最后，我们建议本研究中使用的统计方法将 Costa Grande Mb 磁地层与 GPTS 相关联，当仔细识别和去除偶发性但大量沉积事件的产物时，可提供最佳结果。