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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >The 'Tortonian salinity crisis' of the eastern Betics (Spain)
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The 'Tortonian salinity crisis' of the eastern Betics (Spain)

机译：东部贝蒂奇（西班牙）的“托尔顿盐度危机”

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The late Miocene depositional history of the Lorca and Fortuna basins, both occupying an internal position in the eastern Betics of Spain, is marked by a regressive sequence from open marine marls, via diatomites and evaporites, to continental sediments. Based on facies similarities, these evaporites have often been correlated to the well-known Mediterranean evaporites of the Messinian salinity crisis, although this correlation was never substantiated by reliable chronological data. In this paper, we present an integrated stratigraphy of this regressive sequence which shows that the evaporites of the Lorca and Fortuna basins are entirely of late Tortonian age and as such have no relation with the Messinian salinity crisis. The main phase of basin restriction, resulting in deposition of diatomites and evaporites, took place at 7.8 Ma, while the last marine deposits (massive evaporites of the Lorca basin) are dated at 7.6 Ma. Consequently, this 'Tortonian salinity crisis' of the eastern Betics had a duration of approximately 200 kyr, while continental deposition prevailed throughout the entire Messinian as also revealed by the fossil mammal record. The 'Tortonian salinity crisis' of the eastern Betics is obviously related to a local phase of basin restriction caused by uplift of the metamorphic complexes at the basin margins, probably in concert with strike-slip activity along SW-NE trending fault systems. The development of a submarine sill is of crucial importance for the increase in salinity because it allows marine waters to continuously enter the basin at the surface while it restricts or prevents the outflow of dense saline waters at depth. Furthermore, we show that evaporite and diatomite cyclicity in these restricted basins is predominantly related to precession controlled circum-Mediterranean climate changes and that glacio-eustatic sea level changes only play a minor role. It is remarkable that the lithological sequence of the Tortonian salinity crisis mimics in many aspects that of Messinian salinity crisis. This suggests that the diatomaceous facies is an essential part of the lithological sequence associated with basin restriction.
机译：洛尔卡盆地和福图纳盆地的中新世晚期沉积历史都在西班牙东部的贝蒂克山脉中占据着内部位置，其特征是从开放的海洋泥灰岩，硅藻土和蒸发岩到大陆沉积物的回归序列。基于相相似性，这些蒸发物经常与墨西尼盐度危机的著名地中海蒸发物相关联，尽管这种相关性从未得到可靠的时间序列数据的证实。在本文中，我们给出了这种回归序列的综合地层，表明洛尔卡盆地和福尔图纳盆地的蒸发物完全处于托尔托期晚期，因此与墨西尼盐度危机无关。流域限制的主要阶段是硅藻土和蒸发岩的沉积，发生在7.8 Ma，而最后的海洋沉积物（洛尔卡盆地的大规模蒸发岩）的发生在7.6 Ma。因此，东部贝蒂奇斯的“托尔托尼亚盐度危机”持续了大约200年，而化石哺乳动物记录也显示出整个梅西尼亚大陆的沉积普遍存在。东部贝蒂奇斯的“托尔顿盐度危机”显然与盆地边缘变质岩体抬升引起的盆地约束的局部阶段有关，可能与西南偏北走向的断层带走滑活动有关。水下槛的发展对于增加盐度至关重要，因为它可以使海水连续进入地表，同时限制或防止浓盐水在深处流出。此外，我们表明这些受限制的盆地中的蒸发岩和硅藻土的循环性主要与旋进控制的环地中海气候变化有关，而冰川-欧拉海平面变化仅起较小作用。值得注意的是，Tortonian盐度危机的岩性序列在许多方面模仿了Messinian盐度危机。这表明硅藻相是与盆地限制有关的岩性层序的重要组成部分。

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