No. 2.] 49 9. The Terra Rossa Type Bauxite and the Bando.. Ketsugan, or Redeposited Laterites. By Takao SAKAMOTO. Geological Institute, Faculty of Science, Tokyo University. (Comm. by S. TsuBol, M.J.A., Feb. 13, 1950.) Abstract. Stratigraphically, the bed of a redeposited laterite can be reckoned as an abnormal facies of a basal conglomerate. The types of coal ashes, represented by different evolutional stages of clay minerals, reflect different types of crustal movements to which the coal basins are due. Bando•Ketsugan and Terra Rossa Type Bauxite Deposits as an " Abnormal Facies of a Basal Conglomerate ". The bando-ketsugan is found in beds, " A "-and " G " beds in the Upper Paleozoic coal-bearing formations in N. China, S. Manchuria and Korea. The thickness of each seam reaches from 2.5 to over 10 m. Being strikingly constant laterally, they cover almost whole area of the Upper Paleozoic coal-bearing formations which are thought to represent remnants of a larger sedimentary basin and are scattered over an area of nearly 2,000 km EW and 700 km NS. Beside these " A "-and " G " beds, there are other beds of kaolinite and flint clay. The aggregate thickness of them all attains 20 m in most coal-fields, the largest thickness in the world as ore beds of aluminous hydroxide and kaolinite. It is a conspicuous feature of this sedimentary basin that the coal measure covers infallibly with disconformity the Lower Paleozoic group ; and that there is a big hiatus corresponding to the Upper Ordovician, Gotlandian, Devonian and Lower Carboni- ferous systems. It is true, however, that pebbles with Gotlandian fauna in a Mesozoic conglomerate (1) and a formation of ottrelite slate with Devonian fauna (2) were found near Heijo, N. Korea and, therefore, the gap is considerably shortened there. The "G" bed covers the plane of disconformity and is conformable with the coal measure in the hanging wall. The Middle Ordovician upon which the "G" bed was deposited consists chiefly of limestone, but occasionally of dolomite and an alternation of marl and gypsum. While in Ta-tung, Chin-hsi and Tung-pien-tao, it takes on a different aspect. In Ta-tung basin, the Lower Permian with a "G" bed covers Cambrian ; in Nan-piao basin in Chin-hsi, the Sakmarian with a "G" bed successively covers those systems of Lower 50 T. SAKAMOTO. [Vol. 20, Ordovician, Upper and Middle Cambrian in different places. In Nan-piao and Tung-pien-tao, the "G" beds become quite sandy and are mixed with well rounded quartz pebbles. That is, the footwall beds had been warped and eroded prior to the deposition of the "G" bed and the hanging wall beds lack in the Middle Carboni- ferous (3) or in some cases, in both the Middle Carboniferous and the Sakmarian, thus bringing forth the Sakmarian or even the Lower Permian as a hanging wall with a "G" bed at the base (4). There are observed local transgressions of the sea. As has been stated above, the "G" bed itself is sandy and often contains quartz pebbles in these regions. These observations point to the fact that the "G" bed is a basal conglomerate. Therefore, a "G" bed, consisting of pure flint clay and bando-ketsugan in the central part of the sedimentary basin is nothing but an abnormal f acies of a basal conglomerate (Fig. 1). F. 1, Sfrd[l~rdrkccal 4BrpaKS oceLJ zec.'d~ I. TkeTerr~Aos7"eB~uy'/ ca Soufkern F'ranc'e. No. 2.] The Terra Rossa Type Bauxite. 51 The " A " bed bando-ketsugan is interbedded with white quartzose sandstone and variegated shale at the base of the thick formation of the Upper Permian "variegated shales ". Geomor- phologically, this sedimentary basin had already been changed into a limnic basin after the time of the deposition of the Lower Permian " coal measure " . While, climatologically, an increasing dryness brought forth the deposition of the " variegated shales " first in the Upper Permian. But occasional gray shales are still present which produce the Gigantopteris flora. This flora is characteristic of Asia and is a relict of the Paleozoic or an intermediate type between the Paleozoic and Mesozoic flora. First in the Triassic, a " red bed" proper (The Shih-chien-f eng Series) was deposited. The climatological changes were not only delayed but also very slow and gradual when compared with other continents, such as Europe, N. America, etc. The approach of the sign of dryness after a period of high temperature and humidity during the deposition of the Lower Permian " coal measure'' was so slow that there seems to have obtained, at least temporarily, a climatic condition of a monsoon. The incomplete laterite profiles, i.e., kaolinite profiles, had so ex- tensively been formed during the time of deposition of the "coal measure ". Whereas, under the new climatic condition, the later- itization was carried further into the formation of fully developed profiles, i, e., with free aluminum hydroxide on top. The redeposi- tion of these laterite materials resulted in the formation of the "A" bed bando-ketsugan . The terra rossa bauxite on the coast of southern France was formed during the Albian stage of the Middle Cretaceous. It was then deposited as a basal conglomerate in the following trans- gression from the Albian to Eocene (5, 6) (Fig. 1). The bauxite deposits along the Gulf embayment and in the Appalachian Valley in US were formed in the Wilcox stage of the Eocene epoch (7, S). These facts testify to the possibility of the formation of a bauxite deposit in a comparatively short period of time when climatological and morphological conditions are favorable. Accordingly, the gap of "A" bed may not be so large as it appears. But, it is significant from the stratigraphical point of view that the topography of the sedimentary basin of the coal-bearing formations continued to exist, and new elements were introduced only climatologically. Coal Seams, Bando-Ketsugan and Flint Clay Beds. The environment of the kaolinite formation is that of an in- complete laterite profile, i.e., high temperature, high humidity 52 T. SAKAMOTO. [Vol. 2s, and constant acidity, or entirely the same as that for coal genesis. While, the bando-ketsugan needs a fully developed laterite profile, i.e., high temperature, intermittent dry and wet seasons or an alternation of acidic and alkaline environments. Therefore, they no more coincide with the optimum for the coal genesis. Thus, the relation between coal seams and kaolinitic clay beds is extremely intimate in that both have their environment of formation in common. However, there seems to be very little influence of a coal seam, after the deposition, upon a clay bed. The idea of an epigenetic enrichment of alumina within a flint clay bed into the formation of a bando-ketsugan, as has been entertained in some quarters, seems to be untenable. Lenticular Rich Ore Bodies of "A" Bed Bando•Ketsugan and U, V and Cu.bearing Clay Lenses in the "Red Beds" in Western US as Channel Deposits on a Lake Bottom. The " A " bed, when fully developed, exceeds 10 m in thickness and shows a regular and more or less symmetrical color bands from bottom to top : red, bright yellow, greenish brown, dark green, greenish brown, cream yellow and pink. These colors are due to the presence of iron minerals such as hematite or turgite (red), limonite (yellow), nontronite (brown) and chamosite (green). These variations in color of sediments show the characteristic features of deposition under and conditions. The rich ores of bando-ketsugan is found in lenticular beds, from a fraction of 1 m to 3 m in thickness, being intimately accompanied by chamosite and nontronite, and enclosed within a thick flint clay bed which is usually ferruginous but sometimes very pure. These are, the writer believes, channel deposits on a lake bottom, like the sand and clay lenses containing uranium, vanadium and copper in the "Red beds" in the western US (9). Types of Coal Basins and the Composition of Coal Ashes or Clay Colloids. Do all the Upper Paleozoic coal bearing formations contain beds of such lateritic materials? The Upper Paleozoic coalfields in the world are compared with one another in Table I. The paralic coal-fields (1-3) along the northern margin, and the limnic or intermontane coal-fields (4) within the folded Varisciden in Europe are all of an orogenic type. The fields of this type are characterized by a large amount of clastic sediments and both the coal-bearing formations and coal seams reach a tremendous No. 2.] The Terra Rossa Type Bauxite. 53 Table I. The Upper Paleozoic coal-fields in the world. thickness in aggregate. While those coal-fields in US (~6, 7) are of an epeirogenic type. Kaolinite and aluminum hydroxide beds are 54 T. SAKAMOTO. [Vol. 26, abundant in the epeirogenic type and scanty in the orgenic type of the coal-fields, in other words, they are inversely proportional to the total thickness of the coal bearing formations. The Mesozoic coal-fields in N. China--S. Manchuria-Korea are all of an orogenic type, being formed in the period of deformation both in the forerunners (Lower Jurassic) and in the height of con- vulsion (Jura-Cretaceous) of the so called Yen-shan movements. The ashes in the Mesozoic coal are bentonitic. While, those in ,the Paleozoic coal are kaolinitic (Fig. 2). The former represents the juvenile stage and the latter the mature stage of the clay evolu- tion. The laterite materials in which the bando-ketsugan in . the latter basin consists are clay minerals in the senile stage, or the ones which have the least chance both of formation and preserva- tion in the region of an orogenic movement.