鳥取県日野川上流域における花崗岩斜面中のシーティング節理

Low angle sheeting joints，which lie sub-parallel to gentle mountainous slopes，are frequently observed in exposures of granitic rocks．They may develop depending not only on rock textures and weathering condition，but also topographic conditions including river dissection．An area in which sheeting joints were developed was found in the headwaters of the Hino River，Tottori，Japan．Micro sheeting，which is a zone of dense cracks concordant with the sheeting joints，was also observed．Low relief surfaces and deep river dissection charactedze the area topographically．
The dominant trends of the sheeting joints are almost same as the mountainous slopes facing the valley，whereas average dip is gentler than the slopes．However，the sheeting joints are not present in narrow and shallow valleys．Based on these geometrical relations，the sheeting joints are believed to have formed due to stress balance by release of steep valley slopes related to rapid dissection by rivers．This may support the model presented by Hashikawa for similar features
found in the Hiroshima area．