Abstract Cenomanian/Turonian boundary (upper Sarvak Formation) benthic foraminiferal assemblages were analyzed to reconstruct oxygen level, primary productivity, and water turbulence in the Izeh Zone, Zagros Basin. The interplay between environmental perturbations during the Oceanic Anoxic Event 2 (OAE2) and regional tectonic activities in the Zagros Basin resulted in formation of various benthic foraminiferal assemblages in the study section. The OAE2 interval at the region of study starts with extinction of rotaliporids at the onset of δ13C positive excursion (peak “a”), which is associated with population of infaunal benthic foraminifera (especially Bolivina alata). The following interval at the onset of Whiteinella archaeocretacea Biozone is characterized by the total absence of benthic taxa and dominance of planoheterohelicids (“Heterohelix shift”) in the black shale strata, indicating expansion of oxygen minimum zone and unhospitable conditions for both benthic and planktic foraminifera. The upper part of OAE2 interval (including δ13C peaks “b” and “c”) coincides with harbinger of Neo-Tethys closure in the Arabian Plate, causing a compressional tectonic regime, and creation of uplifted terrains in the basin. The relative sea level started to locally fall in this succession, which was accompanied by a better ventilation of seafloor, lower TOC contents, and reappearance of benthic foraminifera.

中文翻译：

---

扎格罗斯盆地（伊朗西南部）OAE2 区间的氧气水平、初级生产力和水湍流：碳酸盐微相中的底栖有孔虫变异

摘要 对 Cenomanian/Turonian 边界（上 Sarvak 组）底栖有孔虫组合进行了分析，以重建 Zagros 盆地 Izeh 带的氧气水平、初级生产力和水湍流。大洋缺氧事件 2 (OAE2) 期间的环境扰动与扎格罗斯盆地区域构造活动之间的相互作用导致研究部分形成了各种底栖有孔虫组合。研究区域的 OAE2 间隔始于 δ13C 正偏移（峰值“a”）开始时轮虫的灭绝，这与底栖有孔虫种群（尤其是玻利维亚藻）有关。Whiteinella archaeocretacea Biozone 开始的以下间隔的特征是在黑色页岩地层中完全没有底栖类群和平面异螺旋体的优势（“异螺旋位移”），这表明底栖有孔虫和浮游有孔虫的最低氧区和不利条件. OAE2 层段的上部（包括 δ13C 峰“b”和“c”）恰逢阿拉伯板块新特提斯闭合的先兆，造成挤压构造体制，并在盆地中形成隆起的地形。在此序列中，相对海平面开始局部下降，伴随着海底通风更好，TOC 含量降低，底栖有孔虫重新出现。表明底栖有孔虫和浮游有孔虫的最低氧区扩大和不适宜居住的条件。OAE2 层段的上部（包括 δ13C 峰“b”和“c”）恰逢阿拉伯板块新特提斯闭合的先兆，造成挤压构造体制，并在盆地中形成隆起的地形。在此序列中，相对海平面开始局部下降，伴随着海底通风更好，TOC 含量降低，底栖有孔虫重新出现。表明底栖有孔虫和浮游有孔虫的最低氧区扩大和不适宜居住的条件。OAE2 层段的上部（包括 δ13C 峰“b”和“c”）恰逢阿拉伯板块新特提斯闭合的先兆，造成挤压构造体制，并在盆地中形成隆起的地形。在此序列中，相对海平面开始局部下降，伴随着海底通风更好、TOC 含量降低和底栖有孔虫重新出现。