A Cretaceous/Paleogene (K/Pg) boundary interval in the north flank of Alborz Mountains (Aboksar section), northern Iran, has been studied to investigate the biological and geochemical variations of this event in the eastern Tethys. Abathomphalus mayaroensis at the late Maastrichtian, Pα (Parvularugoglobigerina eugubina), P1a (Parasubbotina pseudobulloides) and P1b (Subbotina triloculinoides) at the early Danian are the recognized planktic foraminiferal biozones and subzones in the studied area. The Plummerita hantkeninoides subzone at the uppermost Maastrichtian and P0 Biozone at the base of Danian were not defined in the studied section. This proposes a short-term hiatus and sedimentary discontinuity at the base of Paleocene and probably uppermost Maastrichtian, which most likely caused by winnowing of sediments after a cooling phase and development of bottom current in the Albors Basin. The K–Pg transition in the Aboksar section is characterized by a bloom in the Guembelitria cretacea, evolution of first Danian species (Pv. eugubina, Pv. longiapertura), δ¹³C negative shift (about 0.5‰), and a gentle Ir anomaly (0.1 ppb). Planktic foraminifera were diverse and abundant during the late Maastrichtian of studied section in a warm (relatively lower δ¹⁸O contents) and well stratified environment. Bloom of the opportunist species, G. cretacea, and decrease of planktic foraminiferal abundance and diversity at the base of Paleocene interval propose an abnormal stressful environment in this time probably after the asteroid impact and its following temperature decline. The appearance of more complete species with more specialized shells and larger sizes, such as Globoconusa daubjergensis, Parasubbotina pseudobulloides, Eoglobigerina eobulloides and Subbotina triloculinoides in the P1a and P1b subzones and return of carbon isotope diagram into the pre-boundary values testify an environmental recovery and optimization of ecosystem conditions.

已经研究了伊朗北部 Alborz 山脉（Aboksar 部分）北侧的白垩纪/古近纪 (K/Pg) 边界区间，以调查该事件在东特提斯山脉的生物和地球化学变化。马斯特里赫特晚期的Abathomphalus mayaroensis、Pα( Parvularugoglobigerina eugubina )、P1a( Parasubbotina pseudobulloides )和P1b( Subbotina triloculinoides )是研究区公认的浮游有孔虫生物区和亚区。该Plummerita hantkeninoides马斯特里赫特最上部的亚带和大年底部的 P0 生物带在研究剖面中没有定义。这表明在古新世底部和可能在马斯特里赫特最上层存在短期中断和沉积不连续性，这很可能是由于奥尔伯斯盆地冷却阶段和底流发展后沉积物的风选造成的。Aboksar 剖面的 K-Pg 转变的特征是Guembelitria cretacea的水华，第一大年物种（Pv. eugubina，Pv. longiapertura）的演化，δ ¹³ C 负移（约 0.5‰），以及温和的 Ir (0.1 ppb)。在研究剖面的马斯特里赫特晚期，在温暖的（相对较低的 δ¹⁸ O 含量）和良好分层的环境。机会主义物种G. cretacea 的大量繁殖以及古新世区间底部浮游有孔虫丰度和多样性的减少表明，此时可能在小行星撞击及其随后的温度下降之后出现了异常的压力环境。在 P1a 和 P1b亚区出现具有更特殊外壳和更大尺寸的更完整物种，例如Globoconusa daubjergensis、Parasubbotina pseudobulloides、Eoglobigerina eobulloides和Subbotina triloculinoides，以及碳同位素图恢复到边界前值证明了环境恢复和优化生态系统条件。