当前位置: X-MOL 学术Precambrian. Res. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Paleolatitude estimation and premises for geomagnetic field instability from the Proterozoic drilling core material of the south-western part of the East European Craton
Precambrian Research ( IF 3.8 ) Pub Date : 2021-02-26 , DOI: 10.1016/j.precamres.2021.106135
K. Dudzisz , M. Lewandowski , T. Werner , G. Karasiński , A. Kędzior , M. Paszkowski , J. Środoń , M.J. Bojanowski

This study addresses new paleomagnetic, geochemical, mineralogical, and rock-magnetic data from four drill cores of the western part of the East European Craton, representing mainly siliciclastics supplemented by volcaniclastics and a few basaltic rock samples. The cores comprise Mesoproterozoic samples of 1400–1030 Ma and Neoproterozoic (Ediacaran) samples of 588–541 Ma. According to the magnetic data, the dominant magnetic carrier in basalts is magnetite, while two genetic types of hematite (detrital and syngenetic/early diagenetic) carry magnetization in sedimentary rocks. The characteristic components of the natural remanent magnetization (NRM), carried by the fine-grained hematite (intermediate temperature component [CM]) and the coarse-grained hematite (high-temperature component [CH]), were identified during thermal cleaning. Mineralogical and geochemical studies provided evidence for detrital and synsedimentary/early post-sedimentary origin of fine-grained hematite and suggested hot and humid environmental conditions on the western part of Baltica during Meso- and Neoproterozoic time. Because of a low-temperature diagenetic history, which affected the Mesoproterozoic and Ediacaran rocks of Pinsk 26, Ochrymy IG-1, and Šaškai 2 boreholes, no post-Ediacaran paleomagnetic overprint is expected there. On the basis of these findings, the CM component in these profiles was classified as nearly primary (synsedimentary/early post-sedimentary) in origin. The CH component in these profiles and the Ediacaran sandstones of the Kaplonosy IG-1 section is also considered primary and acquired as detrital NRM (DRM). Paleomagnetic results yielded a reliable record with the domination of shallow-to-moderate inclinations, showing both polarities. The calculated paleolatitudes for 550–541 Ma time span, regardless of correction for the inclination error, fall within the subequatorial zone. Steeper inclinations, suggesting subpolar paleolatitudes, were observed in the volcaniclastics and basalts interlayering with sedimentary rocks and, sporadically, in the Ediacaran sedimentary successions. The origin of this steep component, however, was attributed to the anomalous behavior of the geomagnetic field, as a consistently warm environmental facies pattern did not support a fast and far-distance, cross-latitudinal, poleward movement of Baltica during the Ediacaran time and then back to the equator. These results complement previous studies that sought to resolve uncertainty of the paleogeographic position of Baltica in the Proterozoic time.



中文翻译:

东欧克拉通西南部元古界钻探岩心材料的古纬度估计和地磁场不稳定性的前提

这项研究处理了来自东欧克拉通西部四个钻芯的新的古磁,地球化学,矿物学和岩磁数据,这些数据主要代表硅质碎屑岩,火山碎屑岩和一些玄武岩样品。岩心包括1400-1030 Ma的中元古生界样品和588-541 Ma的新元古代(Ediacaran)样品。根据磁数据,玄武岩中的主要磁性载体是磁铁矿,而赤铁矿的两种遗传类型(碎屑和同生/早成岩)在沉积岩中都具有磁化作用。在热清洗过程中,确定了细粒赤铁矿(中温成分[CM])和粗粒赤铁矿(高温成分[CH])所携带的自然剩磁强度(NRM)的特征成分。矿物学和地球化学研究为细粒赤铁矿的碎屑和沉积/沉积/沉积后早期证据提供了证据,并提出了中元古代和新元古代的波罗的海西部湿热的环境条件。由于低温成岩史,影响了Pinsk 26,Ochrymy IG-1和Šaškai2钻孔的中元古代和埃迪卡拉岩石,因此,预计那里不存在后埃迪卡拉岩石层的古磁性套印。根据这些发现,这些分布图中的CM成分被归类为起源近乎主要的(沉积的/沉积后的早期)。这些剖面中的CH成分和Kaplonosy IG-1部分的Ediacaran砂岩也被认为是主要的,并作为碎屑NRM(DRM)获得。古磁结果产生了可靠的记录,其中浅至中度的倾角占主导地位,显示了两种极性。无论校正倾斜度误差如何,计算出的550–541 Ma时间跨度的古纬度都位于赤道以下区域。在与沉积岩夹层的火山碎屑岩和玄武岩中以及零星的埃迪卡拉火山沉积演替中观察到更陡峭的倾斜,表明亚极古松散。但是,这种陡峭成分的起源是由于地磁场的异常行为所致,因为在Ediacaran时期,持续的温暖环境相图并不支持Baltica的快速和远距离,跨纬向极移。然后回到赤道。

更新日期:2021-02-28
down
wechat
bug