Seasonality and interannual climate variability during the Late Miocene: Testing and tuning climate models using oxygen isotope stratigraphy, growth increment analysis and new ground data

在古气候分析中，中新世浅水碳酸盐岩通常被认为是次要的，因为它们的地层记录被大量的空白打断。然而，珊瑚的年代学记录证明了大气的可变性--这是中新世古气候学迄今未知的一种SPECT。在与有节奏地分层的深水粘土和泥灰岩夹层的碎屑岩中发现了保持原始保存状态的骨骼，这些碎屑岩具有韵律分层的深水粘土和泥灰岩(托托尼亚/梅西尼亚时代，克鲁索纳斯地区，中央克里特岛；BR 1153/7)。因此，基于这些台地周围沉积物的多尺度氧同位素分析有可能跟踪年度、十年和千年时间尺度上的气候变化，以响应地中海地区在晚中新世过程中的日照强迫和干旱。将在克里特岛中部(菲斯托斯地区)勘探更多的露头。基于先前项目(BR 1153/7)期间获得的单一岩石年代学记录(10 Ma，中克里特岛)运行的气候模型非常好地反映了真实的生物相分布：比地中海目前的温度更温暖，而在东大西洋的温度更低。预测的晚中新世温度和变异性将使用马克罗涅斯横断面(亚速尔群岛、马德拉群岛、加那利群岛和佛得角群岛)沿线的经典生物相方法对大西洋东部进行测试。仔细的古生物分析将提供有关长期气候变化和地中海地区生态扰动期间热带生物群潜在避难所位置的信息。

Miocene shallow water carbonates are generally considered indaequate for palaeoclimatic analyses, because their stratigraphic record is punctuated by abundant gaps. However, sclerochronological records of corals document atmospheric variability - an spect hitherto unknown to Miocene palaeoclimatology. Skeletons in a pristine state of preservation required for sclerochronology have been detected in debrites intercalated with rhythmically stratified deep-water clay and marl (Tortonian/Messinian age, Krousonas area, Central Crete; Br 1153/7). A multi scale oxygen isotope analysis of based on these periplatform sediments therfore has the potential to track climate variability on annual, decadal and millennial timescale in response to insolation forcing and aridisation of the Mediterranean area over the course of the Late Miocene. Additional outcrops will be explored in Central Crete (Phaistos area). A climate model run based on a single sclerochronological record (for 10 Ma, Central Crete) obtained during a previous project (BR 1153/7) reflects real biofacies distributions superisingly well: warmer than present temperatures in the Mediterranean, and colder temperatures in the E Atlantic. Predicted Late Miocene temperatures and variability ion the E Atlantic will be tested using the classical biofacies approach along the Macronesian transsect (Azores, Madeira, Canary and Cape Verde Islands). Careful palaeontological analysis will provide information regarding long-term climate changes and the location of potential refugia for tropical biota during times of ecological perturbatins in the Mediterranean area.