常磐炭田における基盤の形態と炭層の発達状態との関係について

抄録

During the course of the present study, we have recognized the following three important facts : 1) In six areas where two workable coal seams are developed, the lower of about one meters thick and 20∼30 meters above the basement, and the upper about two meters thick and 15∼20 meters above the lower, and the whole about 200 meters distant from a buried hill, the following facts were confirmed., The strata underlying the lower coal seam, that between the lower and upper coal seems, the coal seams themselves and also the partings within the coal seams all tend to become thinner as the buried hill is approached where these strata abut against the buried hill they follow the general inclination of the hill, but thin out completely at the top of the hill., 2) From the fact that blocks of amphibolite and amphibole mica schist as large as 20×10×3cm in size are abundantly contained in the above mentioned sequence in areas neighboring the buried hill, it is inferred that they were derived from the basement which consists of similar rocks during sedimentation., It is noteworthy that the quantity and size of the blocks both diminish rapidly as the distance from the buried hill increases., The calcite crystals found embedded in the coal seams and shales above and below are considered to be recrystalized weathered products of the amrhibolite and amphibole mica schists above mentioned., 3) From the paleogeological map constructed from observations in coal pits, numerous bore-core data and seismic prospecting, it is confirmed that the basement in the present district consists of at least two buried hills, each trending in NW-SE-direction, and separated from one another at their broadest eastern extremity by 3 to more than 6 kilometers., The promontories of these hills at their eastern extremities measures from about or to more than 500 meters., The coal seams above referred to belong to the Hanakawa formation and were deposited in these inlets or small bays or embayments., The respective coal seams can be traced from one basin to another, and are actually being mined., The number of cycles within the Hanakawa formation developed in each district of the Joban coal-field have been studied in detail, and the relationship existing between number of cycles for each independent field with that of other fields has been worked out to an advantageous stage.,