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Survival of early Viséan foraminifers in the Western Meseta of Morocco
Palaeoworld ( IF 1.7 ) Pub Date : 2019-06-13 , DOI: 10.1016/j.palwor.2019.06.001
Pedro Cózar , Daniel Vachard , Alain Izart , Ismael Coronado

Typical early Viséan foraminiferal assemblages documented in outcrops of the Western Meseta of Morocco led to the erroneous biostratigraphic dating of areas that later, after much effort, have been demonstrated to correspond to the mid and late Viséan. These sections are analyzed to decipher if they are formed by reworked specimens or if this fauna really survived into younger rocks. Key sections are located in vast areas of the Western Meseta, in the north of the Azrou-Khenifra basin, Fourhal area, El Hammam Ridge, Oulmès area, Sidi Bettache basin (all on the north of the Western Meseta), and the Skoura region (on the southern border). The environmental settings as well as the taphonomical stage of preservation of the foraminifers suggest that most of the assemblages are composed of autochthonous or parautochthonous foraminifers and, thus, that the fauna really survived into the middle and even upper Viséan carbonate platforms of the Western Meseta. In some sections, the early Viséan foraminifers share the same levels with mid Viséan foraminifers; in others, they share the same levels with mid and late Viséan foraminifers, and in a third group, the early Viséan foraminifers occur in the same stratigraphic sections with mid and late Viséan assemblages, although never in exactly the same stratigraphic levels but alternating. These distributions exemplify the three patterns of interaction between the stratigraphic and biogeographic ranges of the assemblages.

The absence of similar patterns is noteworthy in the surrounding regions of the Palaeotethys, and thus, this anomalous distribution can be discarded as a matter of dispersal from neighbouring regions. The absence of similar patterns in basins situated far from the Western Meseta allows abiotic factors to be discarded, such as tectonic/environmental setting, palaeolatitude or isolation. The most plausible hypothesis to explain the survival of these fauna is related to biotic factors, such as species interaction and competition, and they can be compared to some similar modern ecological patterns. However, the primary triggering factor allowing these biotic factors to interact is considered to be the late arrival of the mid Viséan foraminifers to the Western Meseta, allowing them to occupy niches completely different from the rest of the Palaeotethys.



中文翻译:

早期的维森人有孔虫在摩洛哥西梅塔的生存

在摩洛哥西梅塞塔地区的露头上记录的典型的早期维森有孔虫组合导致了该地区生物地层年代的错误,后来经过大量的努力,这些地区已被证明与维森中后期相对应。将对这些部分进行分析,以判断它们是否是经过重新加工的标本形成的,或者该动物群是否真的存活到了较年轻的岩石中。关键部分位于西梅塞塔的广阔地区,在阿兹鲁-克涅夫拉盆地的北部,傅哈尔地区,埃尔哈马姆岭,乌尔梅斯地区,西迪贝塔奇盆地(均在西梅塞塔的北部)和斯科拉地区(在南部边界)。环境条件以及有孔虫的保存的分光阶段表明,大多数组合都是由自生或旁生有孔虫组成的,因此,该动物群真正幸存到了西部梅塞塔的中乃至上维森碳酸盐台地。在某些部分中,早期的Viséan有孔虫与中等的Viséan有孔虫具有相同的水平。在其他组中,它们与维森有孔虫和中孔有孔虫的水平相同,而在第三组中,维森有孔虫的早期和中孔虫组合在相同的地层剖面中,尽管从未在完全相同的地层中发生而是交替出现。这些分布示例了组合物的地层和生物地理范围之间相互作用的三种模式。它们与维森有孔虫和中孔有孔虫的水平相同,在第三组中,维森有孔虫的早期和中孔虫组合在相同的地层剖面中,尽管从未在完全相同的地层中发生,而是交替出现。这些分布示例了组合物的地层和生物地理范围之间相互作用的三种模式。它们与维森有孔虫和中孔有孔虫的水平相同,在第三组中,维森有孔虫的早期和中孔虫组合在相同的地层剖面中,尽管从未在完全相同的地层中发生而是交替出现。这些分布示例了组合物的地层和生物地理范围之间相互作用的三种模式。

值得注意的是,在Paleotethys的周围区域中没有类似的模式,因此,这种异常分布可以从邻近区域中分散出去而被丢弃。在距西梅塞塔较远的盆地中缺乏相似的模式,这使得非生物因素可以被丢弃,例如构造/环境,古环境或孤立环境。解释这些动物生存的最合理的假设与生物因素有关,例如物种相互作用和竞争,可以将它们与某些类似的现代生态模式进行比较。但是,使这些生物因子相互作用的主要触发因素被认为是中维森有孔虫到达西梅塞塔的时间较晚,从而使它们能够占据与古猿其他地方完全不同的生态位。

更新日期:2019-06-13
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