ABSTRACT

This study investigates the spectacular geomorphological features of Jurassic (Younger) Granites in NE Nigeria by using field observations and some structural (i.e. joints) analyses. The study area is in the Sahel region of the Subsaharan of Africa as a transition zone between the Sahara Desert and Equatorial region, where many studies have focused on the loess deposits, ergs, climate change, and Saharan Desert boundary changes. Morphological features of rocks in the study area have not been widely discussed in the literature. However, inselbergs, ruwares, and pillar structures are the major landforms in this vast plain with an arid environment. Boulders, blocks, mushrooms, and corestones, tafoni, shelter caves, flared slopes, polygonal cracks, and weathering pits are minor features. Weathering products consisting of white-colored, granular quartz-bearing grus and red clayey laterite surround the granite masses. Subsurface weathering has favored the formation of major geomorphological features; however, subsequent superficial weathering leading to hydration and stripping occurred mostly under the humid climatic conditions with seasonal variation of dry and humid climatic conditions. Local paleoenvironmental – paleoclimatic conditions would have prevented excess weathering and erosion in the study area.

摘要

本研究通过现场观察和一些结构（即节理）分析，调查了尼日利亚东北部侏罗纪（年轻）花岗岩的壮观地貌特征。研究区位于非洲撒哈拉以南的萨赫勒地区，是撒哈拉沙漠和赤道地区之间的过渡地带，许多研究集中在黄土沉积、尔格、气候变化和撒哈拉沙漠边界变化。研究区岩石的形态特征尚未在文献中广泛讨论。然而，在这片干旱的广袤平原上，岛状、岩状和柱状结构是主要的地貌。巨石、块、蘑菇和核心石、塔福尼、避难所洞穴、喇叭形斜坡、多边形裂缝和风化坑是次要特征。耐候产品包括白色，粒状含石英的 grus 和红色粘土红土围绕着花岗岩块。地下风化有利于主要地貌特征的形成；然而，随后的表层风化导致水化和剥离，主要发生在潮湿的气候条件下，干湿气候条件有季节性变化。当地的古环境 - 古气候条件可以防止研究区域过度风化和侵蚀。