Precise biostratigraphic dating of the Tojeira Formation (Late Jurassic, Early Kimmeridgian) of the Montejunto section of west-central Portugal, which has yielded important planktonic foraminiferal assemblages, is hindered by poor preservation in the upper part of the section as the lithology shifts from shale to coarser clastics. Assignment was previously made to the Idoceras planula and Sutneria platynota zones based on ammonites. Coccolith and dinoflagellate assemblages described here concur with the Early Kimmeridgian, yet, a finer age constraint is proposed by cyclo- and chemostratigraphical correlation. Peaks in δ 13Corg and TOC, if equivalent to maxima in the envelope of clay/carbonate cycles in SE France, imply that the c. 50 m-thick section spans a 0.8-myr interval of the S. platynota through upper Ataxioceras hypselocyclum ammonite zones, with the approximate base of the A. hypselocyclum Zone at c. 15.4 m (level 13). Such stratigraphy provides new insights into the upper part of the formation by interbasinal correlation with other Tethyan records. An extended first occurrence of the dinoflagellate species Dichadogonyaulax? pannea in the S. platynota Zone is also proposed.

中文翻译：

---

葡萄牙中西部蒙特junto的Tojeira组（侏罗纪晚期，侏罗纪晚期）的年龄

葡萄牙中西部蒙特琼托剖面的Tojeira组（侏罗纪晚期，侏罗纪晚期）的精确生物地层测年，由于岩性从页岩转移，该区的上部保存不善，阻碍了重要浮游有孔虫组合的形成。碎屑。以前已根据炸药将其分配给Idoceras planula和Sutneria platynota区。这里描述的球墨石和鞭毛藻的组合与早期的Kimmeridgian一致，但是，通过环地热关系和化学地层学关系提出了更好的年龄限制。δ13​​Corg和TOC的峰值，如果等于东南法国的粘土/碳酸盐循环圈的最大值，则表明c。50 m厚的断面通过上层的共济失调子hypselocyclumammonite区跨越了白僵菌的0.8 myr区间，与c。的a。hypselocyclum区的近似基。15.4 m（第13级）。这种地层学通过与其他特提斯记录之间的基底间相关性提供了对地层上部的新见解。鞭毛藻物种Dichadogonyaulax的首次扩展出现？还提出了在S. platynota区中的pannea。