considers that this basalt is of the same age as the porphyries discovered in a former season by Dr. Heron in some of the outer islands (see Records Geol. Surv. Ind., LIV, p. 52). A cap of laterite covers the central portion of the basalt outcrop. Minbu and Thayetmyo districts. 8514 Mr. E. L. G. Clegg continued the geological survey of the Minbu and Thayetmyo districts, over portions of sheets 84, 84, 84, 84, 85, 85, 85, 85 and 85 An interesting synclinal basin was mapped near Sidoktaya in sheet 84, which is faulted down on the west of the great axial strike-fault of the Nwamataung range. This brings Pegu beds into juxtaposition with Pondaung sandstones near Handauk village. Further south-west of the same strikefault in sheet 84, there is a small cuvette or synclinal basin near Sabagyidan, where lower Pegus (Padaung Clay horizon) are faulted against Pondaung sandstones. The age of the Pegus is well fixed by the presence of Lepidocyclina elephantina Tourn, Lepidocyclina sp. and Heterostegina sp., which is the same association found in the main outcrop of the Padaung Clay to the east. In sheet 89, a third cuvette west of the Nwamataung strike-fault exposes lower Pegu beds (Shwezetaw Sandstones) with a well-marked fossiliferous limestone band beneath, containing the same fauna as is found in the Kyet-u-bok band (see Records Geol. Surv. Ind., XLI, p. 226). The Kyet-u-bok band is characterised, both here and in its main outcrop, by Orthophragmina omphalus Fritsch, while molluscan species of the Yaw stage are also found, such as Volutoconus birmanicus Dalton, Tellina (Arcopagia), Tazuocusis Cotter and Cardium thetkegyinense Cotter. The fossil species and the lithological characters of the limestone make it quite clear that the band surrounding this cuvette is the same as that of Kyet-u-bok. An examination of these two cuvettes, and the fixture of their ages by means of their fossil contents, lead to the very interesting conclusion that the Pegu series and Kyet-u-bok band in these areas strongly overlap the Pondaung Sandstones. The Kyet-u-bok band has been traced from Kyet-u-bok as far south as latitude 19° 45'. Southwards it dies out, but small discontinuous bands are met with. Mr. Clegg regards the Kyet-ubok fauna as typically Yaw stage, and has taken the band as the upper limit of the Eocene. Southwards in sheets 85 and, there is no well-marked band or horizon whereby to separate the 14 Pegu series from the Eocene, which is here conformable. The boundary mapped has been fixed mainly on palæontological evidence. Lithologically the upper Eocene may be described as shales grading down into more arenaceous beds, without sharp transitions. A few lenticular seams of coal are found in the shales. The lower Pegus are sandy in sheet 85, but to the south of this sheet, these sandy beds are underlain by shales in the Tiyo-Pungyi valley. The lower Pegu shales in this area may be distinguished from the Eocene by the absence of coal seams, and by their different appearance. A collection of fossils from the Eocene includes two new species of Ampullina, and various specimens of Orthophragmina which have not yet been worked out. In this area the Pegu series contained no new points of interest. The divisions adopted in north Minbu and Pakokku of the Pegu and Eocene series could not be maintained in this southern area, owing to the rapid changes in the character and facies of the beds, which were no longer sharply marked zones of alternating sandstones and shales. In mapping the Eocene, the Yaw stage and the Pondaung sandstone have been grouped as one unit, while the lower Eocene has been divided into a group consisting of the Tabyin Clays, Tilin Sandstones and Laungshe Shales, and another group equivalent to the basal Paunggyi conglomerates. This is due to the disappearance of the Tilin Sandstones as a continuous horizon. Certain sandstones occur at the horizon of the Tilins near Sidoktaya in sheet 84 but they are discontinuous and fade into shales. along their strike. Similarly south of sheet 84, the Padaung Clay horizon of the Pegu series is no longer mappable, since the Shwezetaw stage and the middle Pegus above develop argillaceous beds, through which the Padaung Clay boundaries are obliterated. In sheets 84 and 84 the Eocene-Axial boundary was mapped for a distance of about 20 miles. Wherever the boundary was examined basal Eocene conglomerates were found to be present. Mr. Clegg is of the opinion that the boundary is unconformable. Amygdaloidal trachitic lavas were found at several points along the boundary between Hpa-aing and Sidoktaya. L L יד Captain F. W. Walker was engaged in mapping parts of the Pakokku and Lower Chindwin districts, in sheets 84, and The formations mapped were Pegu series (undivided), Yaw stage, Pakokku and Lower Chindwin districts, Burma. K 3 Pondaung Sandstones, Tabyin Clays, Tilin Sandstones, and Laungshe Shales. The outstanding structural features are the Kyaw syncline and the Pondaung anticline which roughly follow a N.-S. direction through and The Kyaw syncline occupies the valley between the mountain ranges of the Pondaung and the Ponyadaung, both lofty hills, the former attaining a height of 4,000 and the latter of 3,000 feet. The centre of the Kyaw syncline is occupied by Yaw Shales, and to the north in sheet still higher beds-basal Pegus—are exposed in a small basin. 8 The Pondaung Range shows anticlinal structure, the crest of the anticline running parallel to and about 1 mile east of the watershed. The crest shows exposures of Tabyin Clays in which are several seepages of oil and gas. Thin seams of coal (a few inches thick) are characteristic of the Tabyin Clays in this area. On the borders of sheet 84 and another syncline occurs, pitching gently to the north from the southern margin of sheet near the village of Mayin. This last syncline is on the same axis as the syncline which has been mapped north of Pauk, and the two synclines are to be regarded as the result of the same folding movement. Both in sheets 84 and 84 a considerable number of transverse faults were mapped. Besides these a few strike-faults have also been detected. Captain Walker has made collections of fossils from the Tilin Sandstones, which he is at present studying. Besides these a few mammalian teeth were collected from the Pondaungs, including Anthracohyus rubricae Pilg. & Cotter, and Metamynodon sp. In the Yaw stage a good collection of previously known species was made. Pakokku, Burma. K 5 Sub-Assistant Bankim Bihari Gupta was engaged in mapping sheets 84 and 84, part of the Gangaw subGangaw sub-division; division of the Pakokku district. The valley of the Maw and Myittha rivers is occupied by deposits of Maw Gravels (see Records, Geol. Surv. Ind., vol. XLVII, p. 32). The Maw Gravels had previously been tentatively correlated with the Irrawaddy Series owing to the discovery of a Rhinocerotid tooth doubtfully assigned to R. sivalensis. Further collecting by Mr. Gupta has indicated that the Maw Gravels are as a whole older than the Irrawaddy Series, and must be assigned in part at least to a lower Siwalik age, owing to the occurrence of the following mammals :-Diceratherium naricum Pilg., Acera.herium perimense F. and C., A. gajense Pilg., Tetrabelodon falconeri, Hemimeryx blanfordi Lyd., Anthracotherium silistrense Pent., and Dinotherium pentapotamia Pilg. This fauna is clearly a Lower Siwalik fauna. It must not be assumed however that the Maw Gravels are entirely Lower Siwalik in age. In the preceding field-season Mr. Gupta found near Ondwe in sheet 84, Sus titan Lyd., Mastodon hasnoti? Pilg. and Rhinoceros sivalensis F. and C. This is indicative of a Middle Siwalik (possibly Dhok Pathan) age. The Maw Gravels may possibly therefore as a series, lie astride of the Pegu-Irrawaddy boundary of the Irrawaddy valley. It is however premature to discuss this at present, and it may merely be noted that an undoubted Lower Siwalik fauna has been discovered in them. The localities from which the Lower Siwalik fauna come are: (1)mile west-south-west of Wekchiba (22° 4′; 94° 5'′). (22° 9′; 94° 9′). The eastern boundary of the Maw Gravels is strike-faulted, the Laungshe Shales being in juxtaposition on the east, except in a portion of sheet, where the following curious structure occurs. Along the eastern margin of the Maw Gravels near Shwekondaing and Semindaw villages is a series of shales with subordinate sandstones, which resemble very closely the Laungshe Shales. These shales were regarded as of Laungshe age and as part of the Laungshe outcrop, until on return to office a careful study of the fauna was made. During Dr. Cotter's visit to Mr. Gupta's camp in December 1922, some nummulites were discovered in the shales at the eastern boundary of the Maw Gravels. These nummulites proved to be Nummulites yawensis Cotter. Subsequently Mr. Gupta found Operculina canalifera (also a very common species of the Yaw Stage, although not confined to it), Volutoconus birmanicus Dalt. and a species of Genotia. The last two mollusca seem to indicate that the Yaw Stage is present here. If this be the case, it is necessary to suppose that there is in sheet a strip of Yaw Shales underlying the Maw Gravels, and west of the strike fault which elsewhere separates the Maw Gravels from the Laungshe Shales. The similarity of the Yaw Shales to the Laungshe Shales rendered it impossible to detect this occurrence in the field. The fauna of the Laungshe Shales, and in general the fossil horizons in these shales, bear a resemblance to the Des Valley section in Baluchistan (described in Rec., Geol. Surv. Ind., XXXVI, p. 172 et seq.) in that we find a downward transition from the Nummulites atacicus horizon (equivalent to the Laki stage) to what may possibly be the Cardita (Venericardia) beaumonti horizon (Upper Cretaceous). Nummulites atacicus has been found at five localities (two in sheet 84 and three in 84), all at a fairly high horizon in the Laungshe stage. Lower down in the Laungshes, a fauna of distinctly Ranikot type, which was discovered in the preceding field season, has yielded the following species : Strepsidura indica C. & P. Athleta burtoni Vred. Athleta noetlingi C. & P. Drillia inirakensis C. & P. Murex lyalli D. Arch. Volutilithes cf. cithara Lmk. besides others not yet identified. Only about 180 feet below this Ranikot fauna, a horizon containing Orbitoides apiculata, Cinulia sp., Roudairia sp., and Orbitolina sp. was discovered in the preceding season. Another species collected this year from the same horizon is Cyprimeria sp. possibly identical with C. analoga Forb. from the Cretaceous of South India. The fauna of this Orbitoides bed may possibly be Cretaceous, as has been suggested by Mr. Vredenburg (Rec., Geol. Surv. Ind., vol. LV, p. 53). Owing to the presence of Nummulites in an apparently lower horizon of the Laungshes, Dr. Cotter was at first inclined to regard this bed as Eocene, but since a further study of the nummulitebearing beds seems to point to their being a strip of Yaw Shales brought into juxtaposition with the Laungshes by strike faulting, it is no longer necessary to assume an Eocene age, and we may regard them as possibly upper Cretaceous. Mr. Gupta spent the latter part of the season in making some minor corrections in sheets |