A detailed biostratigraphic, chemostratigraphic, and chronostratigraphic study was carried out in the South‐Western margin of the Neo‐Tethys ocean (Tunisia) covering the Eocene‐Oligocene interval to report potential paleoenvironmental and paleoclimatic changes associated with the growth of the Antarctic ice sheet (AIS). The studied section consists of marls and limestones extending from the Helicosphaera compacta nannofossil Zone (CNE21) to the Reticulofenestra umbilicus Zone (CNO2). The Bc of Clausicoccus subdistichus coincides in northeastern Tunisia with the extinction of hantkeninids and is thus used here to define the Eocene/Oligocene boundary (EOB) at 34.03 Ma. Calcareous nannofossil assemblages suggest a significant change from oligotrophic/warm surface waters during the late Eocene to eutrophic/cool waters during the early Oligocene. The observed changes in trophic conditions are synchronous with a shallowing trend testified by an increase in nearshore species and enhanced terrigenous input. Major environmental changes occurred at the EOB and across glaciation event Oi‐1a whereas we record a poor imprint of glaciation event Oi‐1. Three orbital configurations have been distinguished: (1) The late Eocene is characterized by a prominent 405‐kyr cycle and a weak obliquity component; (2) the onset of cooling at 34.35 Ma coincides with the rosette‐shaped discoaster extinction and is reflected by a shift toward enhanced obliquity and short‐eccentricity cycles. The installation of a fully developed AIS (event Oi‐1a, 32.75 Ma) shows the most pronounced obliquity imprint reflecting an increased influence of high‐latitude climate processes; (3) after 31.75 Ma, the obliquity decreases in coincidence with the return to a dominant long‐eccentricity cycle.

中文翻译：

---

西南新特提斯（突尼斯）的始新世-渐新世过渡：天文校准和古环境变化

在新特提斯洋（突尼斯）的西南边缘开展了详细的生物地层，化学地层学和年代地层研究，报告了始新世-渐新世间隔，报告了与南极冰盖生长相关的潜在古环境和古气候变化（ AIS）。所研究的部分由泥灰岩和石灰岩组成，从泥质螺旋藻纳米化石区（CNE21）延伸至网状脐橙（CNO2）。的BC Clausicoccus subdistichus在突尼斯东北部与hantkeninids的灭绝相吻合，因此在这里用于定义34.03 Ma的始新世/渐新世边界（EOB）。钙质纳米化石组合表明，从始新世晚期的富营养/温水到渐新世早期的富营养/冷水，发生了显着变化。观测到的营养条件变化与近岸物种增加和陆生输入增加证明的浅化趋势同步。在EOB和整个冰川事件Oi-1a期间发生了重大的环境变化，而我们记录到冰川事件Oi-1的痕迹不佳。区分了三个轨道构型：（1）始新世晚期的特征是一个明显的405-kyr旋回和一个弱的倾角分量；（2）在34.35 Ma处开始冷却与玫瑰形Discoaster的灭绝，并通过向倾斜度和偏心率短周期的转变而反映出来。完全发展的AIS（事件Oi-1a，32.75 Ma）的安装显示出最明显的倾斜印记，反映了高纬度气候过程的影响增加；（3）在31.75 Ma之后，倾角减小，同时返回到主导的长离心率周期。