Paleoecologic and Paleoclimatic Reconstruction During Mid-Cretaceous to Quaternary, Khartoum Basin: Geochemical and Clay Mineralogy Implication

Abstract

This study documents the paleoecology and paleoclimatic development during the mid-Cretaceous to Quaternary times in the northern part of the Khartoum Basin. Eighty four (84) samples were selected from the Omdurman and the Gezira Formations and analysed through Philips X-Ray diffractometer (45 samples for clay minerals) and X-Ray Fluorescence (39 samples for geochemistry). The high content of kaolinite noted in the sediments of the Umm Badda Member (Albian–Cenomanian) suggests the prevalence of warm and humid condition. However, the presence of minor amount of smectite in the same interval indicates the occurrence of dry seasons, at least, toward the end of the Cenomanian. Simultaneous increase in kaolinite and smectite in the sediments of the lower part of the Gezira Formation (Oligocene – Miocene) reflects the prevalence of tropical humid climate with very long dry seasons directed toward total aridity with very short humid seasons at the end of the Miocene. The Miocene–Quaternary period was characterized by total arid conditions as indicated by the dominance of smectite in the sediments of the upper member of the Gezira Formation. The arid conditions became relatively wet during Holocene as indicated by the relative increase of kaolinite through the black cotton soil that covers the upper most unit in the Khartoum Basin.