已使用X射线衍射和扫描电子显微镜支持的传统岩石学和相分析评估了伊拉克西北部和东北部两个露头剖面的古新世-始新世Sinjar组的沉积环境重建,重点是古新世-始新世(P-E)过渡边界。为此,进行了主要和痕量元素地球化学,并对古生物进行了各种古环境代理,古气候,确定了古盐度和古生产力,以评估广泛认可的环境和气候指标的变化以及跨P-E边界的元素富集/耗尽。氧化还原敏感的微量元素富集和红外比(V/V+Ni,V/Cr,和U/Th)表明在古新世晚期沉积期间普遍存在正常的含氧情况,在始新世早期沉积期间发生了缺氧条件和逐渐开始的氧气消耗。随着P2O5含量的增加,P/Ti,始新世沉积物中的P/Al比表明,由于始新世早期上升流的影响,养分和初级生产力增加。通过观察整个P-E边界的盐度水平从低到高的微小变化,可以验证这些条件。这可以用Sr/Ba比表示。此外,某些矿物,如镁方解石,白云石,和坡缕石是常见的,在从干旱到半干旱再到潮湿条件的P-E过渡过程中,可以观察到古气候的变化,可以从C值记录,Sr-Cu,Rb/Sr比值,和粘土矿物学。这些条件在辛贾尔地层中被注意到,它由许多微相组成,如石灰泥岩,wackstone,packstone,晶粒石和边界石。这些微相沉积在从潮滩延伸到礁坡的浅海环境中,有一个发达的珊瑚礁环境,包括背礁,珊瑚礁核心,和前礁环境。
Reconstruction of the depositional environment of the Paleocene-Eocene Sinjar Formation from two outcrop sections in northwestern and northeastern Iraq has been evaluated using the traditional petrographic and facies analysis supported by X-ray diffraction and scanning electron microscopy with a focus on the Paleocene-Eocene (P-E) transition boundary. To this end, major and trace elemental geochemistry was conducted and various paleoenvironmental proxies for the
paleoredox, paleoclimate, paleosalinity and paleoproductivity were determined in order to evaluate the changes in widely acknowledged environmental and climatic indicators and the elemental enrichment/depletion across the P-E boundary. The redox-sensitive trace element enrichment and the ir ratios (V/V + Ni, V/Cr, and U/Th) indicate that normal oxygenated circumstances prevailed during the late Paleocene deposition, and that anoxic conditions and a gradual commencement of oxygen depletion occurred during the early Eocene deposition. The coeval increase in the P2O5 content, P/Ti, and P/Al ratios in the Eocene sediments suggests an increase in nutrients and primary productivity due to the effect of upwelling currents during early Eocene. The conditions can be verified by observing a small change in salinity levels from low to high across the P-E boundary, which can be indicated by the Sr/Ba ratios. In addition, certain minerals such as Mg-calcite, dolomite, and palygorskite are commonly present, and paleoclimatic changes can be observed across the P-E transition from arid to semiarid and then to humid conditions, which can be recorded from C-values, Sr-Cu, Rb/Sr ratios, and clay mineralogy. These conditions were noted in the Sinjar Formation, which is made up of many microfacies such as lime mudstone, wackstone, packstone, grainstone and boundstone. These microfacies were deposited in a shallow marine environment that extended from tidal flats to reef slopes, with a developed reef environment that included back reef, reef core, and fore reef environments.