Summary:
Kulda and Garjanbahal coal mines are situated in north-western part of Gopalpur sector of Ib Valley coalfield, Sundargarh district, Odisha.
Ib Valley coalfield (also known as Ib River coalfield) located in the districts of Jharsuguda, Sambalpur and Sundergarh of Odisha is having latitudes 21°31' to 22°14' N and longitudes 83°32' to 84°10' E.
Ib valley coalfield which comprises southeastern most part of NW-SE trending SonMahanadi valley of Gondwana basin forms a half elliptical basin with a linear NW-SE trend. The trend of this synclinal Gondwana basin bears close parallelism to the structural configuration of the basement pre-cambrian rocks. The coalfield is connected with Talcher coalfield by a thin narrow strip of Talcher formation. The boundary between Mand-Raigarh and Ib Valley coalfield is administrative boundary of Orissa and Chhatisgarh states.
Barakar and Karharbari are the two potential coal bearing formations in Ib Valley coalfield, Barakar formation is the store house of majority of coal seams. The potential coal bearing area (excluding Kamthis, non-coal bearing Lower Karharbari Formation) of the coalfield is about 1000 sq. km stretching along the south, east and northern periphery of the coalfield. Based on exploration carried out in the coalfield, five coal horizons: Ib, Rampur, Lajkura, Parkhani and Belpahar have been identified in ascending order. Most of the coal seams are split into 2 to 7 sections.
The altitude of the coalfield varies widely from less than 200m to more than 600m above MSL (mean sea level). The general altitude however, varies between 200m and 350m. A series of low parallel ridges of sandstone interspaced with valleys of shales & coal seams are the characteristics of coal bearing Barakar formations.
Kulda opencast mine
Detailed exploration in this block has established the existence of Barakar and Karharbari Formations under thin blanket of soil, sub-soil and laterite. The geological structure of the area has been interpreted on the basis of surface and sub-surface data obtained from boreholes.
Strike of the strata is roughly NW-SE. The dip is generally 7° towards southwest. Dip is slightly higher in southern part and near faults compared to rest of the area.
There are three coal seams, namely Ib, Rampur and Lajkura seams at the Kulda mine. Ib and Rampur seams occur covering almost entire block, whereas occurrence of Lajkura seam is restricted to the western half of the block.
These three coal seams altogether occur in 12 split sections, leaving mergers and sub-splits.
Ib seam is the bottom most coal seam, with maximum depth upto floor is about 238 m. Ib seam is split in to 3 sections: Ib Top, Ib Middle and Ib Bottom. Ib Bottom seam, which is the lowest coal section, is not workable in the northern part of the block. Ib Middle section which overlies Ib Bottom section is also not workable in the northern part. These two sections are combined over major part of the block. Ib Top section is not workable over major part of the block and is not considered in quarriable reserves.
Rampur seam is split into five sections namely Rampur I, Rampur II, Rampur III Top, Rampur III bottom, Rampur IV and Rampur V. Rampur I seam which overlies Ib Middle section is not workable in the northern, southern and south-eastern parts. It is combined with overlying Rampur-II seam over a long narrow strip in the western half of the block. The workable section of Rampur I occurs at a minimum depth of about 34 m in the region of borehole CMHG-118 while Rampur II seam occurs in the entire block as workable coal section. Rampur III bottom is not workable in the northern half of the block whereas other split sections overlying Rampur III bottom are workable in the area of occurrence.
Lajkura is also a thick seam and split into 4 sections: Lajkura I, Lajkura II, Lajkura III and Lajkura IV. Out of these four sections Lajkura II seam is the thickest with a maximum thickness (including all bands) of 34.07 m.
The parting between Ib Middle seam and Rampur horizon varies from 3.79 m to 13.62 m. The parting is thicker where Rampur I is not workable. The parting between Rampur horizon and Lajkura horizon is thickest with thickness ranging from 31 m to 47 m. Except these two partings other intervening partings between split sections are generally thin.
Garjanbahal opencast mine
There are three coal seams, namely Ib, Rampur and Lajkura seams at the Garjanbahal mine. Ib seam, occurring in 2 splits is thin and impersistent and has got no potentiality in this block except for the northern part in a very small patch. The Rampur and Lajkura seams are split into six sections: Lajkura I, Lajkura II bottom, Rampur II, Rampur III, Rampur IV, Rampur V.
The thickness of the Lajkura seams: minimum 1.04 m, maximum 26.37 m. The thickness of the Rampur seams: minimum 1.15 m, maximum 15.56 m.