Orbital control on carbonate-lignite cycles on sediment core KAP-107 in the Ptolemais Basin, northern Greece

Time control is essential for the reconstruction of geological processes. We use a combination of relative and absolute methods to establish the chronology and related paleoclimatic processes for Late Neogene lacustrine sediment from the Ptolemais Basin, northern Greece. We determined changes in magnetic polarity and correlated them to the global magnetic polarity time scale, which again is calibrated by radiometric methods, to provide a low-resolution age model for the Upper Miocene to Lower Pliocene (7 - 3 Ma). Sedimentary successions show rhythmic alterations of lignites, clays, and marls. Using photospetrometry we measured this variability at 1-cm resolution, and correlated the pattern to known changes in earth's orbital parameters, namely to eccentricity and precession. For 230-m long borehole KAP-107 from the Amynteon Sub-Basin we obtained a high-resolution age model that spans 2 myr from 5.1 to 3.1 Ma, with age control points at insolation maxima (20-kyr resolution). We recommend using photospectrometry as reliable tool to establish orbital-based chronologies and to reconstruct paleoclimate variability at high resolution.

年代学控制对于地质过程重建而言至关重要。本研究结合相对定年与绝对定年方法，为希腊北部托勒迈斯盆地（Ptolemais Basin）的新近纪晚期湖相沉积物构建了年代序列及相关古气候过程记录。本研究测定了沉积物的磁极性变化，并将其与经放射定年法校准的全球磁极性年表进行对比，从而为上中新统至下上新统（7~3 Ma）建立了低分辨率年代模型。该沉积序列呈现出褐煤、黏土与泥灰岩的韵律性互层特征。本研究采用分光光度法（photospetrometry）以1厘米的分辨率测定了该沉积序列的变化特征，并将其变化模式与已知的地球轨道参数变化——即偏心率与岁差——进行了对比关联。针对阿米尼翁次盆地（Amynteon Sub-Basin）内总长230米的KAP-107钻孔，本研究建立了覆盖5.1~3.1 Ma、时长2百万年的高分辨率年代模型，其年代控制点基于日照峰值，分辨率为20 kyr。本研究推荐将分光光度法作为可靠工具，用于构建基于轨道参数的年代序列，并实现高分辨率的古气候变化重建。