Late Miocene stratigraphy, palaeoclimate and evolution of the Sandanski Basin (Bulgaria) and the chronology of the Pikermian faunal changes
Late Miocene stratigraphy, palaeoclimate and evolution of the Sandanski Basin (Bulgaria) and the chronology of the Pikermian faunal changes
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DOI：
10.1016/j.gloplacha.2018.07.019
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发表时间：
2018-11-01
影响因子：
3.9
通讯作者：
Spassov, Nikolai
中科院分区：
文献类型：
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作者：
Boehme, Madelaine;Van Baak, Christiaan G. C.;Spassov, Nikolai
我们研究的沉积学，古生物学和古地磁的500米厚的沉积序列中Gorna Sushitsa峡谷在Sandanski盆地（保加利亚西南部），这是非常丰富的Pikermian型哺乳动物化石。磁性地层学表明，这一部分是在2百万年内，8.5 Ma和6.5 Ma（晚托托尼亚到早墨西拿）之间沉积的。我们的调查表明，Sandanski盆地填充物代表两个堆叠的同裂谷阶段（德尔切沃和Kalimantsi形成），与一个中间的构造静止包（Sandanski形成）。Kalimantsi组沉积结束于6.9 Ma时盆地边界断层停止滑动，这可能是由7 - 6.5 Ma之间区域东西向向南北延伸的转换造成的。高滑动速率相比，上盘沉积速率引起的发展，大型角砾岩为主的重大断层陡崖在年轻的同生裂谷阶段（8.2至6.9马）。构造变化是由几种气候变化叠加而成的。8.5-8.2 Ma为中等湿润期，8.2~7.8 Ma为相对干燥期。7.74 - 7.56 Ma的第二个湿润期可能是造成东副特提斯湖Maeotian海侵的原因，7.42 Ma时轨道驱动的风尘沉积开始表明，随后出现了局部和超区域干旱化的显著趋势。我们的新数据扩大了北方地中海撒哈拉出生的尘埃记录在托托尼亚-梅西尼亚过渡到至少600 kyrs（7.42至6.85 - 6.8 Ma）。同时代的尘埃沉积的发生，我们观察到大型哺乳动物记录的进化变化，导致经典的Pikermian协会可追溯到7.42和7.27马之间。我们解释动物群的变化，在东地中海的托托尼亚-梅西尼亚过渡驱动的全球变冷和中纬度荒漠化。
We study the sedimentology, palaeontology and palaeomagnetism of the 500 m thick sedimentary sequence in the Gorna Sushitsa gorge in the Sandanski Basin (southwest Bulgaria), which is exceptionally rich in fossil mammals of Pikermian type. Magnetostratigraphy indicates that this section was deposited within 2 myrs, between 8.5 Ma and 6.5 Ma (late Tortonian to early Messinian). Our investigations reveal that the Sandanski Basin infill represents two stacking synrift phases (Delcevo and Kalimantsi formations), with an intervening tectonic quiescence package (Sandanski Formation). Kalimantsi Formation deposition ends with the cessation of slip on basin-bounding faults at 6.9 Ma, probably caused by a switch from regional E-W to N-S extension between 7 and 6.5 Ma. High slip rates compared to hanging wall sedimentation rates induced the development of mega-breccia dominated substantial fault scarps during the younger synrift phase (8.2 to 6.9 Ma). Tectonic changes are superimposed by several climatic changes. Moderately humid conditions prevail from 8.5-8.2 Ma, followed by relatively dry period from 8.2 to 7.8 Ma. A second humid interval from 7.74-7.56 Ma, which may be responsible for the Maeotian transgression in the Eastern Paratethys lake, is followed by a significant trend in local and supra-regional aridization, indicated by the onset of orbital driven aeolian dust deposition at 7.42 Ma. Our new data expand the Northern Mediterranean Sahara-born dust record at the Tortonian-Messinian transition to at least 600 kyrs (7.42 to 6.85-6.8 Ma). Coeval with the onset of dust deposition we observed evolutionary changes in the large mammal record, leading to the classical Pikermian association dated to between 7.42 and 7.27 Ma. We interpret faunal changes at the Tortonian-Messinian transition in the Eastern Mediterranean as driven by global cooling and mid-latitudinal desertification.