A reinterpretation of two chertbreccias from the Proterozoic basins of India

Several horizons of a unique lithotype called “chertbreccia” are interbedded within the Proterozoic platform sediments of the Peninsular India. These cherty rocks with brecciated texture appearing as blocky masses were earlier diversely interpreted as being products of disparate processes such as fault-zone breccias, collapse breccias, and so on. Two of these horizons, one from the Kaladgi Basin (Dharwar Craton) and the other from the Dhar Forest Inlier of the Vindhyanchal Basin (Bundelkhand — Aravalli Craton) are compared in context of their geological setting, field relations and petrological constitution. A model of the mode of development of these peculiar rocks is reconstructed, taking into account their characters and limitations of previous interpretations. They are interpreted as transported debris deposits of syntectonogenic material released during the episodic activity of the growth faults of the Kaladgi and Vindhyanchal Basins that was diagenetically silicified.     

Dinoflagellate cyst stratigraphy and depositional history of Miocene and Lower Pliocene formations in northern Belgium (southern North Sea Basin)

The occurrence of organic-walled dinoflagellate cysts (dinocysts) in the Diest Formation, a largely decalcified succession with a poor fossil content, and in the adjacent strata of Lower Miocene and Lower Pliocene formations, allowed a biostratigraphic evaluation of these deposits and an assessment of the hiatus between the lithostratigraphic units. The Diest Formation was deposited during Tortonian – Messinian times. Dinocyst biozones defined in the North Sea region and the U.S.A. East Coast are recognised within the Diest Formation, although environmental factors seem to have influenced the presence of some key zonal species in the shallow-marine deposits of northern Belgium. The two members of the Diest Formation studied, i.e., the Dessel Sands and the Diest Sands, appear to be strongly diachronous. The depocentre was located in the Campine area during the early Tortonian and shifted to the area north of Antwerp during late Tortonian to Messinian times. The age assessment provides a correlation of the sequence boundaries of Haq et al. (1987) at the top of the Diest Formation with SB 5.5.     

冕洞演化与太阳活动周的关系及在日地预报中的应用

冕洞的研究在近二十多年里取得了丰硕的成果。本文回顾了冕洞的发现及观测历史,系统阐述了冕洞的结构特征、形成及演化规律,讨论了冕洞对日地空间产生的影响,冕洞与超级活动区的关系以及冕洞在太阳活动预报中所起的作用,在此基础上利用１９７０—１９９５年的冕洞资料对冕洞的时空分布和磁极性演化规律与太阳活动周的关系,以及冕洞与太阳风速度、地磁扰动等方面进行分析研究,得出以下结论：（１）冕洞在南北半球的分布在形态上基本是对称的,但在冕洞数量上北半球稍占优势;（２）冕洞的盛衰演化呈周期性,表现为赤道冕洞周期与黑子周期是完全一致的,极冕洞周期与黑子周期相位相差１８０°;（３）赤道冕洞的纬度分布随太阳活动周上升而上升,当太阳活动周达到极大值时,它也达到极大,然后再随太阳活动周下降而下降,极冕洞的纬度延伸方向演化与赤道冕洞相反;（４）极冕洞的极场呈１１年周期性,并且极场反转出现在太阳活动峰年期间;（５）太阳风和地磁扰动与冕洞的演化有着密切的关系