Journal of Geosciences, Osaka City University Vol. 37, A,l. 8, p. 213-242 March, 1994
Quaternary Geology and Hydrogeology of the Madiun Basin, Indonesia
Shigeru KUMAZAWA*
(With 19 Figures and 1 Table)
Abstract
The Madiun basin is located in the eastern part of Java Island, Indonesia. In the basin, a total thickness of more than 250 I'll of Quaternary sediments has been deposited after the Pucangan statge (Lower Pleistocene). After thick argillaceous sediments of the Pucangan Formation, the Kabuh Formation, the Notopuro Formation and the Setri Formation, consisting of thick Auviatile sediments, were deposited. The Kabuh, Notopuro and Setri Formations form good aquifers, so that various types of tubewells have be-;'n constructed since 1972 under the groundwater development projects in the basin. Tubewells constructed vary in depth, e.g., deep wells are between 80 I'll and 250 I'll, intermediate wells are-between 40 I'll and 80 I'll, and shallow wells are less than 40 I'll in depth respectively. The deep wells are generally pumping water from the aquifers of the Kabuh Formation and the lower half of the Notopuro Formation; the intermediate wells from the aquifers of the upper half of the Notopuro Formation and partly from the Setri Formation; and the shallow wells mostly from the aquifers of the Setri Formation. Transmissivity is larger in the Kabuh Formation and relatively smaller in the Setri Formation. The Madium basin is separated into the Madium sub-basin and the Ponorogo sub-basin topographically by projected Tertiary rocks and by a subsurface dyke of Tertiary rocks geologically as well as hydrogeologically. The aquifer system of the Madium basin is significantly related to the Quaternary geology of the basin. The aquifer of the Ponorogo sub-basin receives water from the eastern and western mountains, and water moves towards the center mainly through the Kabuh Formation and the otopuro Formation. Upward leakage takes place and water discharges into the Madium river near the main dyke between the sub-basins, and is then recharged again through the Setri Formation, entering the Madium sub-basin. In the Madium sub-basin, water entering and recharging the aquifer also moves mainly throught the Kabuh Formation and then the Notopuro Formation toward the center of the Madiun sub-basin. Near the Madiun river at the center of the Madiun sub-basin, water moves upward by vertical leakage, and is then discharged into the Madiun river. Lowering of the piezometric head has taken place in the Kabuh Formation in the area north of Caruban; this has probably been caused by abstraction of groundwater from the Kabuh Formation.
Key Words: Madiun Basin, Kabuh Formation, Notopuro Formation, Setro Formation, Groundwater Aow system in the Quaternary strata
1. Introduction
1.1. Background
The Madiun basin IS \cated in the eastern part of Java Island between longitude 111 °10'£ and 111°50'£ and latitude 7°20'S and 8°1O'S, as shown in Fig. 1. In "The
* Geotechnical and Hydrogeological Department, ippon Koei Co., Ltd. Research student of Department of Geoscience, Faculty of Science, Osaka City University during the priod from April 1992 to March 1993. Address; 2-6-2, Isogo, Kawasaki-ku, Kawasaki City, Kanagawa 210, Japan 214 Shigeru I{UMAZAWA
To Su boya
200
( 500 \ i ""·'AMI. Liman ,7 (2563) f-~~~if?!:l~-+-tln-~r~-t---\ ; ) ../ / -----'- Main Rood / -H+++++++++ Rai Iway 10 20km,
B·'~F,·L'O~'E------,,-C'·-"-20""'E------"'-:!-·30-''''''E-----'-'-;;''·40C-::O::'E,------,....": Fig. 1. General Location Map. Geology of Indonesia"(VAN BEl\1l\1ELEN, 1949), the geology of the northern part of the Madiun basin is described In some detail. This was because the area from Sangiran to Mojokerto, through the northern rim of the Madiun basin, i.e., along the southern foot of the Kendeng Hills, had been given special attention by many geologists and anthropologists since 1893, when E. Dubois announced the first discovery of a Homo erectus (Pithecanthropus erectus) skull on the left bank of the Solo river at Trinil, 11 km west of the conjunction with the Madiun river. A geological survey of hominid fossil-bearing formations in Central and East Java was commenced in 1976 as an Indonesia-Japan joint research project, and completed in 1979 (WATANABE & KADAR et al., 1985). The joint geological study covered the sites of Sangiran, Sambungmacan, TriniJ, Sonde, Ngandong, Kedungbrubus and Mojokerto. This joint geological study was followed by the next study project on the "Geology of Quaternary Environment", which started in 1988 and was completed in 1992, with expanded scope covering the area from Surakarta to Caruban, including the whole Quatemary Geology and Hydrogeology of the Madiun Basin, Indonesia 215 Bemmelen (1949) Joint Study Team (1992) Text Age Southern Kendeng Madiun Ponorogo Discussion Mts. Area Area Area Young Alluvium Alluvium Alluvium/ Holocene volca f------r----~Sambirejo F. / noes S.~!-,ireio F_~,on F. Maron F. of I----TI 1II IIIII -I 111I,'TITIhll''rl--"I:=..:....::"'----=-'------j Upper the High Pleistocene Solo terra Setri Setri Setri Formation -~~ .E...e~~lftrril?mT For-!!!ation Middle _ I;!~t.ol'.I;F9_.!l._ Upper Notopuro Pleistocene Notonuro F. Formation ------! Uplift __~K~a~bu~h~Be~d~Sjml1Jn-.l-ll<:.rU-rr-l-Cwrit-h~~~I~:;;---1 I-- Totokan F. Kabuh Pucangan Kabuh Formation Lower Beds Formation Tumpuk Bed Pleistocene Pucangan F. Pucangan F. Upper Young Kalibeng B. Ban- Dangean Tertiary Rocks Pliocene f------~ Kali- cak Formation (Kalibeng F. / beng Form. Bancak F. / Old Lower Form. Sanpumg Lst. / Pliocene Kalibeng Miocene Vol. ) Beds Upper lilllLSamp- ung F Mio- f-----+--.,-;-::-:::-::-;-,----;~;-::----- cene Kepek Beds Miocene Middle 1----- [la_l).:@k Bed~ Volcanics 1I11111111111 Hiatus 1, -'1 Not exposed Fig. 2. Stratigraphic correlation of the Madiun-Ponoogo Area. Madiun basin. The results of the latest Indonesia-Japan joint study were presented at the workshop on Quaternary geology held in February 1992 (Joint Study Team, 1992) at Bandung, Indonesia. On the other hand, a groundwater development project of the Indonesian government had been going on in East Java since 1972 and more than 280 tubewells have been drilled in the Madiun basin till early 1991. Drilling data of these tubewells, consisting of cutting samples and logs, enables an In depth study of the subsurface geology and hydrogeology of the basin to be made. The author joined the Indonesia-Japan joint study team in 1991/92 and reviewed the drilling data. In this paper, the subsurface geology and hydrogeology of the basin, as revealed by the drilling data, are discussed. 1.2. The Madiun Basin The Madiun basin is enclosed by Mt. Lawu (3,265 m) on the west, Mt. Wills (2,563 m)* on the east, the Sourthern Mountains on the south and the Kendeng Hills on the north. The Madiun river begins in Mt. Lawu and gathers tributaries from Mt. Wilis and the Southern Mountains near Ponorogo city. The river then flows north through Madiun city. After being joined by the Jeroan fiver and the Muneng rIver * Mt. Wilis is a volcanic complex, of which the highest peak is Mt. Liman (2,563 m). 216 Shigeru KUMAZAWA from the east, at about 10 km north of Madiun city, the river turns to the northeast. Finally, the Madiun river joins the Solo rIver (Bengawan Solo) at the northeast corner of the basin, and the Solo river then traverses the Kendeng Hills farther to the north. The basin has an elongated north-south shape and narrows at the middle by the projections of mountain slopes from both the west (Mt. Lawu) and the east (Mt. Wills). The southern (or upstream) half of the basin is centered on Ponorogo city and the northern (or downstream) half is centered on Madiun city; these are hereinafter called the Ponorogo sub-basin and the Madiun sub-basin, respectively. The altitude of Ponorogo city is 95 m above s.l. (sea level) and that ofMadlun city is 68 m above s.l. 1.3. General stratigraphy of the area VAN BEMMELEN (1949) divided the Quaternary geology of the area into four stratigraphic units, i.e., Pucangan Beds, Kabun Beds, Notopuro Beds and Yound volcanics of the Solo Zone/High terraces from the lower to the upper strata, as summarized in Fig. 2. The type locality of the Pucangan Beds is Mt. Pucangan, 20 km north of Jombang; that of the Kabuh Beds is in the Sumberingin river, 3.5 km east of the Kabuh village; and that of the Notopuro Beds is at the village of Notopuro, 35 km east-northeast of Madiun (P. MARKS, 1957). The series of strata is, however, well exposed and has been studied in the Sangiran dome, north of Surakarta, or 65 km east of Ngawi, by VAN Es (1931), VON KOENIGSWALD (1940) and VAN BEMMELEN (1937; 1947), and by the Indonesia-Japan Joint Research Project (WATANABE and KADAR et al., 1985) more recently. The Indonesia-Japan Joint Study Team (1992) divided the Upper Pleistocene and Holocene deposits in more detail and identified the Setri Formation of Upper Pleistocene age and the Sambirejo Formation and Maron Formation of Holocene age. The finding and identification of the Setri Formation which is widespread in the area, not only on the slopes of the mountains but also beneath the basin, are significant in the study of the Quaternary geology and hydrogeology of the area. The type locality of the Setri Formation is in the middle reaches of the Sawur river, which has dissected the gentle slope of the northern foot of Mt. Lawu. The type localities of the Sambirejo Formation and the Maron Formation are in the downstream parts of the Madiun and Ponorogo sub-basins of the Madiun river, respectively. In the Ponorogo area, the stratigraphic names of the Totokan Formation and the Tumpuk Bed are given to the lahar deposits on the western slope of Mt. Wilis by the Joint Study Team (1992). Thick and continuous sediments of Quaternary strata from the Pucangan Formation to the Setri Formation have, however, been confirmed below the Holocene sediments by tubewell drilling data in both the Madiun and Ponorogo sub-basins, and the Totokan Formation and the Tumpuk Bed are correlated with the members of the Kabuh Formation. Although the type localities of the Pucangan Formation, the Kabuh Formation and Quaternary Geology and Hydrogeology of the Madiun Basin, Indo11esia 217 the Setri Formation are located outside of the Madiun basin, the area of this report, these formations in the Madiun basin have been well correlated with the stratigraphic setting in the type localities (P. MARKS, 1957; WATANABE and KADAR et al., 1985; Joint Study Team, 1992). Hence these formation names have been generally applied to the strata of the Madiun area. Consequently, the stratigraphic units shown in the right-end column of Fig. 2 are used in this paper, following the formation names and chronological setting of the Joint Study Team (1992) in principle, except for the Totokan Formation and Tumpuk Bed. 2. Stratigraphy of The Madiun Basin 2.1. General The Quaternary geology of the lVIadiun basin consists of the Pucangan Formation, the Kabuh Formation, the Notopuro Formation, the Setri Formation and Holocene alluvial deposits from the lower to the upper strata, as shown in Fig. 3, "Stratigraphy of The Madiun Basin" and Fig. 4, "Geological Map of The Madiun Basin". The basement Tertiary rocks are exposed widely in the Southern Mountains and the Kendeng Hills, and sporadically on the slopes of Mt. Lawu and Mt. Wills. The Tertiary rocks consist of the Kalibeng Formation in the Kendeng Hills and of the Miocene Volcanics, the Sampung Limestone and the Banchak Formation 10 the Southern Mountains and on the slopes of Mt. Lawu and Mt. Wills. As summarized in Fig. 3, the Pucangan Formation, the Kabuh Formation, the Notopuro Formation and the Setri Formation are, chronologically, attributed to the early Lower Pleistocene, Lower Pleistocene to Middle Pleistocene, upper Middle Pleistocene and Upper Pleistocene, respectively. The Holocene alluvial deposits occupy much of the central parts of the Madiun and Ponorogo sub-basins, and are named, by the Indonesia-Japan Joint Study Team (1992), the Sambirejo Formation and the Maron Formation, respectively. 2.2. Tertiary Rocks The Kalibeng Formation, consisting of marine lcays, argillaceous sands, marls and limestones, extends widly east-west in the Kendeng Hills. The top of the Kalibeng Formation is formed by the Balanus-linestone in the Sangiran area. In the Madiun area, however, white foraminiferous marls and limestones are in contact with the Pucangan Formation without typical Balanus-limestone. On the other hand, the Miocene Volcanics (frequently called "Old Andesite"), consisting of vocanic rocks and breccias, are exposed in the Southern Mountains. The Southern Mountains were elevated and tilted southward, forming the south flank of the Java-geanticline, during the Middle Pleistocene (VAN BEMMELEN, 1949). The other Tertiary formations, namely the Banchak Formation, consisting of volcanic breccias, conglomerates, sandstones and siltstones, and the Sampng Limestone, are exposed 218 Shigeru KUMAZAWA Geologic Formation Harks Description of Li tho-facies Thick- Age Name ness ------Fine sand and a Iternat ion of fine Sambi rejo/ ...... sand and si It (Samb irejo Formation), Holocene Maron ------...... and fine to medium sand, si Ity clay IS. Formations and si It with basal gravel (Maron ------~ 000000000000 Formation)...... : .. -...... ,...... Black clay, tuffaceous sand, silty ...... sand, Pumice graye I, white/pink tuff Upper Setri and a Iternat ion of gravel and sand. ------...... 1'010 .. ,...... Pleistocene Formation @@~ @ @ @ 35m 000000000000 ~ ...... Grave I, sand, si It, tuff and lahar ------beds with pumice and andes ite frag- Notopuro ------ments. lJ.-lJ.-lJ.-lJ.-lJ."lJ.- 13011I Middle Formation ------(9()a) IJ.-IJ.-lJ.-lJ."lJ.-IJ." Pleistocene ------...... 000000000000 Fine to coarse sand, gravel and 2;;;;222'~.. @fi@ tuffaceous s i It. Pumice flow and Kabuh lahar beds with andes i te fragments ~~~~~~~~--- on the slope of Mt.wi Iis. Formation ...... 12~ 000000000000 ------...... 000000000000 Lower ~ Silty clay, sand, tuffaceous fine Pleistocene !J. At,: f.:!J. - t,:!J.- sand and lahar beds. Pucangan ------...... ·0· .... Formation ~ lOO1tt ------~ ~ LLLLLLLLLLLL Kal ibeng Formation (alternation of. ------Ii mes~one and marl, si Itstones and lJ."lJ.-lJ.-lJ.-IJ.-IJ.- tuffaceous si Itstones), Banchak For- Tertiary Basement ...... mation (cong Iomerates, lahar beds, 1001I+ 000000000000 000000000000 sandstones, s i Itstones), Sampung LLLLLLLLLLLL Limestone, and Miocene Volcanics. wvvvvvvvvvv wvvwvwvvv Fig. 3. Stratigraphy of the lVIadiun Basin sporadically on the southwestern slope of Mt. Lawu and the southeastern slope of Mt. Wills. They seem to enclose the Ponorogo sub-basin together with the Tertiary rocks of the Soutern Mountains, except for the northern drainage toward the Madiun sub-basin. Planktonic foraminifera, Globorotalia tosaensis, were found in the sediments below the Balanus-limestone layer, indicating Late Pliocene age, but have not been found above the limestone layeL This suggests that the Plio-Pleistocene boundary is in or just above Quaternary Geology and Hydrogeology of the Madiun Basin, Indonesia 219 1 ~~2 11I 3 4 5 6 7 10 I Fig. 4. Geological Map of the Madiun Basin. ·'-Holocene alluvial deposits (Sambirejo Formtion, Maron Formation and river terrance deposits along the Solo river); 2-Setri Formation (Upper Pleistocent); 3-Notopuro Formation (Middle Pleistocene); 4-Kabuh Formation (Lower to Middle Pleistocene); 5-Pucangan Formation (Lower Pleistocene); 6,7-Tertiary Rocks (6-Kalibeng Formation exposed in the Kendeng Hills; 7-Tertiary rocks exposed in the Sourthern Mountains and on the slopes of Mt. Lawu and Mt. Wills). 220 Shigeru KUMAZAWA the layer (KADAR, 1985). Concordantly, HVODO et al. (1993) reported that the normal zone, with intermediate directions around the Balanus-limestone in the Kalibeng Formation, can be correlated with the Olduvai event between 1.67 and 1.87 m.y., based on the magnetostratigraphy. 2.3. Pucangan Formation The type loclity of the Pucangan Formation is Mt. Pucangan (112°17'7"E, 7°23'10"S), 20 km north of Jombang, East Java. In this formation two facies may be distinguished: a marine clayey facies and a volcanic, tuffaceous to sandy facies. The latter is rich in vertebrate fossils. The volcanic facies is developed in the western part of the Kendeng Hills, whereas to the east more and more marine intercalations occur, so that near Surabaya the formation consists entirely of clays and volcanic tuffs, with marine mollusks (P. MARKS, 1957). In the Madiun area, the Pucangan Formation is exposed only along the southern foot of the Kendeng Hills, extending east-west narrowly and dipping gently beneath the Madiun basin. The Pucangan Formation is characterized, in the typical Sangiran area, by thick, black clay layers with fresh water mollusks, indicating that the sea in which the Kalibeng Formation had been deposited was closed. In the Madiun area, however, the formation is composed mainly of lahar layers with thin interbeds of balck clays. At the junction between the Solo river and the Madiun river, the Pucangan Formation, consisting of three lahar beds, is well exposed, overlying the Kalibeng Formation conformably. Magnetostratigraphy (HVODO et al., 1992; 1993) indicates that the Jaramillo event, in age between 0.90 and 0.97 m.y., is corelated with the normal zone, mixed with intermediate magnetic vectors, between the Grenzbank zero, the lowermost horizon of the Kabuh Formation, and the tuff layer TIl, the uppermost tuff layer of the Pucangan Formation; this is concordant with fission-track dating (SUZUKI et al., 1985). 2.4. Kabuh Formation The formation is named after the village Kabuh, 18 km nOT-th of the small town of Jombang. The type locality is at 112°14'47"E and 7°23'45"S in the Sumberingin river, 3.5 km east of the Kabuh village, East Java (P. MARKS, 1957). Within the Madiun basin, the Kabuh Formation is distributed along the northern margin of the basin and on the western slope of Mt. Wills. The typical Kabuh Formation is characterized by fluviatile deposits with cross bedding. It is remarkable that coarse debris of older stages were suddenly deposited in the Kabuh stage, after the relatively quiet conditions of sedimentation in the Pucangan stage. The Kabuh Formation extends east-west on the south of the Pucangan Formation. It consists of thick, gravel layers and tuffaceous and/or pumiceous sand layers with cross bedding in the northern marginal area of the basin. Gravel layers are well exposed there, showing that they are more resistive to erosion than sand layers_ In places, cliffs Qualemary Geology alld Hydrogeology of lhe Madiu1I Basill, Jlldollesia 221 of gravel layers have been formed by excavation for con truction materials. The formation dips south concordantly with the Pucangan Formation, though more gently, e.g., less than 3° in inclination. The Kabuh formation on the slope of Mt. Wills consi ts of old lahar deposits occupying the area which has been well dissected. This sedimentation is attributed to the Kabuh Formation in age. Although the other name, Totokan Formation, has been given to these lahar layers by the Indonesia-Japan Study Team (1992) in their surface geologic map, the name of the Kabuh Formation is used not only for the fluviatile sediments in the northern area but also for lahar facies on the mountain slope in this paper. Magnetostratigraphic study (HYODO et al., 1992; 1993) has revealed that the polarity change at just below the Upper Tuff, the upper horizon of the Kabuh Formation, is attributed to the Brunhesll\1atuyama boundary at age 0.73 m.y., which is concordant with the discovery of a tektite by excavation from the horizon between the Upper Tuff and the Middle Tuff (WATANABE and KADAR, 1985). 2.5. Notopuro Formation The type locality of the Notopuro Formation is in the village of Notopuro, 35 km east-northeast of Maddiun, East Java (P. MARKS, 1957). The Notopuro Formation also has a fluviatile sediment facies exposed along the northern margin of the Madiun basin and a lahar facies deposited on the mountain slopes. Along the road from Ngawi to Caruban, passing through the northern marginal zone of the Madiun basin, where there are some undulations in topography, the otopuro Formation occupies the areas which are relatively higher and the lower flat areas are buried by the Setri Formation. The otopuro Formation in this area consists mainly of laharic layers, including gravels, lapilli and pumice fragments, with interbeds of tuffaceous and/or pumiceous silt and sand layers. The thickness of the Notopuro Formation is rather thin in this area, compared with its thickness in the Sangiran area and in the Solo river north of Mt. Lawu. In the Sangiran area, the Notopuro Formation (or the Pohjajar Formation in the Sangiran area) consists of two layers of lahar deposits and tuffaceous silt, sand and gravel layers. The contact with the underliving Kabuh Formation (or the Bapang Formation in the Sangiran area) is unconformable. The Notopuro Formation on the slope of Mt. Lawu consists of lahar deposits, silt, sand and gravels. Reddish paleo-soil layers, interbedded in the upper horizon and at the top of the otopuro Formation, are seen at 35 km west of Ngawi in the Sawur river and at 15 km southwest of gawi in the Widodaren river. Paleo-soils and trace fossils found in this formation suggest that the formation has been deposited under shallow sub-aqueous and/or subaerial conditions in this area. This formation is attributed to the upper Middle Pleistocene (Joint Study Team, 1992). 2.6. Setri Formation 222 Shigeru KUMAZAWA The Setri Formation was first reported in "Stratigraphic Correlation of the Quaternary System in the Sangiran Area and Its Surroundings, Central Java" (Joint Study Team, 1989). The type locality of the Setri Formation is located in the Sawur river, near the Setri village, 35 km west of gawi. There, the Plumutan Formation (correlated to the Notopuro Formation in the stratigrtaphy along the Sawur river) IS unconformably overlain by the Setri Formation. The Setri Formation consists of a humic, black clay layer covered by tuff and tuffaceous silt layers in the lower part, cross-laminated arenaceous layers with pumice gravels and pinkish tuff in the middle part, and poorly sorted gravel and sand layers In the upper part. The Setri Formation spreads widely in the Mdiun basin below 100 m above s.l., except on the western slope of Mt. 'iVills, where a young lahal- layer, rich in pumice fragments and correlated to the Setri stage, covers the slope thickly; and on the marginal area of the Ponorogo sub-basin, where the Setri Formation decorates the fringe of the flat flood plain, forming very gentle slopes on the foot of the hills composed of Tertiary rocks. Thick, black clay layers in the lower horizon of the formation indicate an event of wide inundation which covered the whole Madiun basin in the early Upper Pleistocene. 2.7. Holocene Alluvial Deposits Holocene flood plains are widespread in the central part of the Madiun and Ponorogo sub-basins, and their sediments are called the Sambirejo Formation and the Maron Formation, respectively. They form very flat, fertile lands which are well cultivated with paddy and sugarcane. The flood plains are less than a few meters higher than the latest deposits on the river terraces along the rivers, and the formations consist of well cross-bedded sand and gravel layers overrlain by poorly sorted silt to very fine sand layers and dark gray clay layers, frequently rich in caliche. The thickness of the formations is not more than 15 m. 3. Subsurface Geology 3.1. Drilling Data The Madiun basin has been known to be rich in groundwater resources, so that groundwater has been utilized not only for domestic use but also for irrigation since more than a century ago. In 1972, a groundwater development project was started by the Indonesian Government, systematically by means of modern drilling rigs. Since then more than 280 tubewells have been drilled in the basin. The depth of the drilled tubewells ranges from about 30 m to more than 300 m from the ground surface. The location of the tubewells that have been drilled is shown in Fig. 5, "Location Map of Tubewells in The Madiun Basin". Geologic logs of the tubewells along the profile lenes (see Fig. 5) are shown in Quatemary Geology and Hydrogeology of the Madilln Basin, Indonesia 223 x ... 06> -."'""" , ~ "" tN o Shallow Well: nol deeper Thon 40m • InTermediate Well: 40m 10 BOrn D. Deep Wei r : deeper !hon 80m o TUbu Well drilled before 1972 (nonself - f1owln9) • Tube Well drilled before 1972 (seH- flowinq I 10 20km I======:I'======:=;[ Fig. 5. Location Map of TubeweJls in the Madiun Basin. Fig. 6, "Geological Logs along the Profile Line X-X'" and Fig. 7, "Geological Logs along the Profile Line Y-Y'''. Towards the center of the Madiun and Ponorogo sub-basins, the Quaternary strata have been deposited thickly, much thicker than observed from the surface exposures. IV IV .j:. Alluvium Depth 1m) SNg98 SNg 100 SNgll1 SNg112 OWII TW22 SMdll SMd7 SMdS SMdS2 SMd94 o ~E'" ~~~ --- ... - ~~~ /'/ ~~. ~.~~ ·n;": i,:;:; --- .::,::.: ~ ;~ §~~ ~~ 50 .~~~ Notopuro Formation i~~f----111~----t ~~.~ ------~~.-: ~~:~~: 00-·7" --~ ,;",:::.;: 5;:;,-, oo:~, E~ ::'~'J. 100 f__----l-';:.;;.~"i.;f------i w1 Kobuh Formo1ion ~K~ en ::r aQ' ~ C ISO ",c __--- - _ ~~~I- ;;:: c ~~ _- =c l: .~..::~ ~;; .~.:.. ..: » .i~~ ~~; ~~~ • Pucongon Formation ~ ::.j= ... .. !o::: » 200 ~t~ ~~~ ~H~ ~+~~ ::B .!.i:: ...;:+!-' ~ ii';~ 2so1 1"m..:011------I~m.....1 .J •;~. Fig. 6. Geological Logs along the Profile Line X-X'. (the profile line is shown in Fig. 5.) Oep h Iml o r-1r-=1-f'--r"=1--:::-=--r--,----== - ", '---- SE~~o..!....m~~ -' ...... 50 NOlopuro Formation No'opuro Formation •• I ~:.~ --- I" __ .. I Bosemenl Kobuh Forma Ion ~.~.. 1501-----1 -:g,-" '" I I J I J I Pucongon Formotlon 2501------+-~[j------_{§§------ 300'------t:zl------ Fig. 7. Geological Logs along the Profile Line Y-Y'. (the profile line is shown in Fig. 5.) N N VI 226 Shigeru KUMAZAWA "" N + o Shallow Well: nOI deeper than 40m • InTermediate Well: QOm 10 80m 6 Deep Well: deeper thon 80m o Tubu Well drilled before 1972 (nonself - flowinQl • Tube Well drilled before 1972 (self- flowinO) 10 20km k======l'======:;j' Fig. 8. Isodepth Map of the Contact between the Pucanan Formation and the Kabuh Formation. (Isodepth: unit in meter above 5.1. and minus figures show below s.l.) 3.2. Distribution of Quaternary Strata As shown in Fig. 8, 'Isodepth Map of the Contact between the Pucangan Forma tion and the Kabuh Formation', which was drawn based on the geological logs of the tubewells, the base of the Kabuh Formation is deepest northeast of Ponorogo Quaternary Geology and Hydrogeology of the Madiun Basin, /udonesia 227 city In the Ponorogo sub-basin, where the depth is 140 m below s.l., and at about 5 km south of Madiun city in the Madiun sub-basin, where the depth is deeper than 160 m below s.!. The deepest points of the base of the otopuro Formation are at 40 m below s.!., located east of Ponorogo city in the Ponorogo sub-basin, and 80 m below s.!., located west of Madiun city in the Madiun sub-basin. This is shown in Fig. 9, "Isodepth Map of the Contact between the Kabuh Formation and the Notopuro Formation". The next upper stratum, the Setri Formation, has also been deposited deeper In the central area of the basin. The deepest points are 40 m above s.l., located northeast of Ponorogo city in the Ponorogo sub-basin, and 20 m above s.!., located at 3 km southwest of Ngawi in the Madiun sub-basin, as shown in Fig. 10, "Isodepth Map of the Contact between the Notopuro Formation and the Setri Formation". 3.3. Structue of The Madiun Basin A thick series of Quaternary sediments, more than 200 m since the beginning of the Kabuh stage, the middle of the Lower Pleistocene, has been deposited in the Madiun basin. The base of the Pucangan Formation under the Madiun basin is unknown. Apparently, these thick sediments have been deposited in a sedimentary basin which has been subjected to continuous depression. As seen in the isodepth maps, there are at least two depression centers, one at Ponorogo city and the other south of Madiun city, separated by the projection of the Tertiary basement. These sedimentary basins had and are ellipsoidal in shape, elongated in a north-south direction. In more detail, however, the sedimentary basin of the northern half, i.e., the Madiun sub-basin, is complex, being composed of two depressions. One is an ellipsoidal depression, centered south of Madiun city, and the other is a zonal depression, the axis of which extends WNW-ESE through the south of Ngawi and Caruban. The ellipsoidal depression was dominant in the otopuro stage, as seen in the isodepth map of the base of the Notopuro Formation, and the zonal depression was dominant in the Setri stage, as seen in the isodepth map of the base of the Setri Formation. The shape of the base of the Kabuh Formation has resulted from superimposition of one trend of depression on the other. The ellipsoidal depressions were probably caused by block subsidence due to collapsing of the basement after volcanic ejections of huge volume; the zonal depression of the northern side stemmed from the tectogenesis which uplifted the Kendeng Hills. This hypothesis on the mechanism of the development of the Madiun basin is supported by the regional stratigraphy. Vigorous volcanisms in both Mt. Wills and Mt. Lawu, as well as rapid uplift of the Kendeng Hills occurred in the Kabuh stage, resulting in deep sedimengary depositions in the basin, superimposed by the zonal sedimentary basin and ellipsoidal sedimentary basins,. In the Notopuro stage, violent volcanisms ejected huge amounts of volcanic materials, and the sedimentary basin was buried rapidly by 228 Shigeru KUMAZAWA tN t o Shallow Well: nol deeper than 40m • InTermediate Well: 4Qm fa 80m 1:1 Deep Well: deeper thon 80m o Tubu Well drilled before 1972 (nonsel, - flowim;j I • Tube Wei I drilled before 1972 (sel'-flowinol 10 20km 1======1'======' Fig. 9. Isodepth Map of the Contact between the Kabuh Formation and the Notopuro Formation. (Isodepth: unit in meter above 5.1. and minus figures show below 5.1.) lahar deposits and coarse volcanic materials. This resulted in the emergence of land on which reddish paleo-soil was formed, as seen in the upper horizons of the formation. In the early Setri stage, less volcanism and uplift of the Kendeng Hills resulted in wide inundation of the area and the deposition of black clay layers at the bottom of the formation. Quaternary Geology and Hydrogeology of the Madiun Basin, Indonesia 229 N + o Shallow Well; nol deeper Thon 40m • InTermediaTe Well: 40m 10 80m 6 Deep Well: deeper !han BOrn o Tubu Well drilled before 1972 (nonself - flowinQ) • Tube Well drilled before 1972 (self-flowinQ' ~======'"O======dzpkm Fig. 10. Isodepth Map of the Contact between the Notopuro and the Setri Formation. (Isodepth: unit in meter above s.l.) In the isodepth map of the Setri Formation base, ellipsoidal depression south of Madiun city is no more clear, though there are branches of depressions extending to the northwest on both the sides of Mt. Bancak. The trent of this branching of the depression is already seen in the isodepth map of the Notopuro stage. 230 Shigeru KUMAZAWA 4. Hydrogeology of The Basin 4.1. Project Tubewells Tubewells drilled by the groundwater development project have been classified into shallow wells, intermediate wells and deep wells. The shallow wells and the intermediate wells were designed as follows; Table 1. Shallow Well and Intermediate ';Veil. Design Diameter Design Well type Depth Chamber Screen Discharge Shallow Well 30 m 4" 2" 4lit/sec Intermediate Well 50 to 60m 6" 3" 100it/sec The shallow wells and intermediate wells were constructed recently, after 1988. The depths actually drilled varied, depending on the actual aquifer conditions; they ranged between 18 m and 40 m in the shallow wells and between 55 m and 60 m in the intermediate wells. Before 1988, tubewells constructed were much deeper in well depth and larger in diameter as well as in well yield. Mostly, they were deeper than 150 m, and were called deep wells. In this paper, the project tubewells constrcted after 1972 are, therefore, classifed into the shallow wells of not deeper than 40 m, intermediate wells of 40 m to 80 m, and deep wells of deeper than 80 m depth from the ground surface, respectively. 4.2. Aquifer Generally, the shallow wells were located on the flat lowland underlain by the Holocene alluvial deposits and/or the Setri Formation, and hardly penetrated below the Setri Formation. Almost all their well screens have been installed in the Setri Formation. Although the intermediate wells were also located on the flat lowland, the wells were drilled to penetrate deep into the Notopuro Formation, so that water 1S drawn mostly from the Notopuro Formation. The deep wells mosly range between 150 m and 200 m or somewhat deeper in depth, so that they penetrate the Setri Formation, the Notopuro Formation and then, the Kabuh Formation. Their screen sections generally cover the lower half of the Notopuro Formation and the entire Kabuh Formation; the screens sometimes extend even deeper, to the upper part of the Pacangan Formation. Screen positions correlated to the stratigraphic formations of 28 wells* are shown in Fig. II, together with their apparent transmissivity**. •. ';Veils of which geologic logs are shown in Figs. 6 and 7, except the wells of which transmissivity is not found in the well record file. ••. "Apparent transmissivity (T')" was calculated by the solution for a non-leaky aquifer system disregarding a possibility of leakage effects, so that the values might be more or less larger than the real transmissivity (T) which could be calculated by the solution for leaky aquifer system. Quaternary Geology and Hydrogeology of the Madiun Basil!, Indonesia 231 Stratigraphic Units (upper) ..4...------i.~ (lower) Well Well No. Setri F. Notopuro F. Kabuh F. Pucangan F. Depth SMd-94 205m SMd-52 1 ..•.. 68~ ·il 200m SMd-5 I i991 .1 201.5 m SMd-7 I ... ···730 ... 180 m SMd-11 1 : 696<1 180 m SNg-112 1 ...... J 180 m SNg-lll 164 m SNg-IOO 200m SNg-98 197 m SPNG-119 32m SPNG-124 30m SNg-63 180m SNg-67 1 •. 205.8 m ... SNg-70 I 215 m SNg-71 < .• ..16cy.....\.....<1 225m SMg-101 .{. 188 m SPPO-291 210 ····1 55 m SPPO-292 I ...{)',J I . ... I 55 m SPPO-153 18 m SPPO-151 30m SPPO-152 30m SPPO-148 30m SPo-19 125 m SPo-16 130m SPo-15 151 m SPo-14 129.2 m SPo-13 160m SMPO-295 60m T' in Average 249 m2/day 358 m2/day I 765 m2/day Notes; : Screen section; figures in the screen sections are apparent transmissivity in m2/day Fig. 11. Well Screen Sections Correlated to the Stratigraphic Unit. It appears that transmissivity is larger in the Kabuh Formation and smaller in the Setri Formation. In summary, apparent transmissivity ranges, mainly between 500 m 2/day and 1,000 m 2/day in the Kabuh Formation, between 200 m 2/day and 700 m 2/day 232 Shigeru KUMAZAWA Sc ... / / {:, DEPTH OF WELL / 1000 o - 40 m • 40 - BOm {:, eO-150m 500 f------1---t------7(.""- ~~+.c: --=---+__---1 ... 150 - 200m o 200m+ I 00 ~ ------1---1 o 50 1------+7/""0"'" o 2 10 10 50 100 500 1000 5000 T' m /D Fig. 12. Relation between Apparent Transmissivity (T') and Specific Capacity (Sc) in the Madiun Basin. in the Notopuro Formation, and between 100 m 2/day and 400 m 2/day in the Setri Formation. The Pucangan Formation is not a good aquifer, so that a screen has not been installed, except in the uppermost section consisting of sandy silt and/or lahar layers. The difference in transmissivity is apparently well correlated with the litho-facies of each formation. The Kabuh Formation, especially, forms a good aquifer, containing many gravel layers. In Fig. 12, the relation between apparent transmissIvIty (T') and specific capacity (Sc) is plotted. Specific capacity of the shallow wells ranges between 20 m 3/day/m and 300 m 3/day/m, which is smaller than that of deeper wells; this is apparently due mainly to the thinner aquifer thickness of the Setri Form~tion. However, transmissivity of the shallow wells ranges widely, from 30 m 2/day to 2,000 m 2/day, with the result that the slope of the relation line between transmissivity and specific capacity is !'ather gentle. This suggests that the quifer of the Setri FOI'mation is a leaky aquifer, so that vertical leakage from the underlying NotopUl'o Formation through a black clay layer at the bottom of the Setri Formation must take place when a shallow well is under pumping. As specific capacity data are obtained by dividing the pumping rate by the drawdown and are available in all wells which were pump-tested, the distribution of specific capacity value is drawn in Fig. 13 in order to examine the aquifer productivity. In general, specific capacity is larger in the Madiun sub-basin than in the Ponorogo sub-basin. In Qllatemary Geology and Hydrogeology of the Madilln Basin, Indonesia 233 N o Shallow Well: no! deeper rho" 40m • InTermediaTe Well: 40m 10 80m =i~~~~~~~ A Deep Well: deeper thon 80m J 0 Tubu Well drilled before 1972 (nonself - flowing I • Tube Well drilled before 1972 (self- flowin91 k======dl ?======d2fkm 3 Fig. 13. Distribution of Specific Capacity (m /day/m) In the Madiun Basin. the Madiun sub-basin, specific capacity is larger in the marginal areas than in the central area of the basin. On the other hand, specific capacity is larger in the central area than 111 the marginal areas in the Ponorogo sub-basin. This could be explained by the geological conditions and the well disign. The 234 Shigeru KUMAZAWA tN o Shallow Well: not deeper thon 4Qm • Infermediate Well: 40m 10 80m .0. Deep Well: deeper Than BOrn o Tubu Well drilled before 1972 (nonsel! - flowing) • Tube Well drilled before 1972 (self- flowing) b======'~?======::i20'm Fig. 14. Distribution of "Permeability" (rn/day) m the Madiun Basin. Ponorogo sub-basin IS surrounded by the Tertiary basement, which is not an aquifer. In the marginal areas of the Ponorogo sub-basin, of which the quifer is the smallest In specific capacity, recharging of groundwater from the surrounding mountains is limited and the thickness of the aquifer is thin. As a matter of fact, the number of tubewells Quaternary Geology and Hydrogeology of the Madiull Basin, Indonesia 235 IS less in this area. In the Madiun sub-basin, the surrounding hilly areas, except the northern side, comprise the Quaternary formations, favourable for groundwater storage and flowing, and the aquifer is thick. The difference of specific capacities between the marginal area and the central area of the Madiun sub-basin is due, most probably, to the well disign. The tubewells of the marginal area are generally deeper and longer in the screen length than those of the central area of the Madiun sub-basin. In the central area of the sub-basin, water level is shallow and groundwater resources are plenty, so that tubewells are not necessarily too deep. Apparent permeability (P in m/day) is computed by dividing the specific capacity by the total length of the screen section, and the distribution of P is shown in Fig. 14. Permeability is higher in the central area in both the sub-basins, though much higher in the Madiun sub-basin than in the Ponorogo sub-basin. 4.3. Water Level and Groundwater Flow System Contour maps of the peizometric surface of the aquifer In the Madiun basin under the initial conditions, before the start of the groundwater developmem project in 1972, and the conditions in September 1979 and March 1980, are shown together with their flow-net systems in Figs. 15, 16 and 17, respectively. The aqufer of the Ponorogo sub-basin receives water from the surrounding mountains, much of it from the east, where the mountain slope is made up mostly of Jahar layers of the Kabuh Formation. The other areas comprise the Tertiary basement, except a narrow channel from the west, which is filled with tuffaceous and laharic layers of the Notopuro Formation. Rechargs is derived from much precipitation, which is more than 3 m/year on both Mt. Lawu and Mt. Wilis. Fig. 16 indicates that water entering and recharging the aquifer is gathered at the spot, rounded by the piezometric surface contour line of 90 m, where the water is probably disdcharged into the Madiun rIver with vertical leakage upward. In the Madiun sub-basin, the aquifer received water from the southwest (i.e., northeastern slope of Mt. Lawu), from the southeast (i.e., northwestern slope of Mt. Wilis) and from the low hills at the northeastern corner of the Madiun basin. Fig. 15 indicates that water entering or recharging the aquifer gathered at the center of the Madiun sub-basin, near the confluence of the Madiun river and the Jeroan river from the east. The water of the aquifer was then discharged to the Madiun river by vertical leakage in the initial conditions before 1972. Fig. 16 shows that in 1979, water entering the aquifer from the northeast hills became Jess and that the piezometric surface was lower in the north of Caruban, compared with the initial conditions (Fig. 15). In the 1980 conditions (Fig. 17), lowering of the piezometric surface took place in the center of the groundwater basin, from the confluence of the Madiun river and the J eroan river to gawi. Schematic profiles of the groundwater flow system of the Madiun basin is shown 236 Shigeru KUMAZAWA tN o Shollow Well: nol deeper Than 4Qm • IntermediaTe Well: 40m 10 80m t:. Deep Wet I: deeper thon 80m o Tubu Well drilled before 1972 (nonself - flowinQl • Tube Well drilled before 1972 (self- flowing) b======';±O======~2fkm Fig. 15. Piezometric Surface (in m above s.l.) and Flow-net System under the Initial Condition in the Madiun Groundwater Basin (drawn based on the records before 1972: the areas with dotted marks are overflowing areas.) in Figs. 18 and 19, which could explain the system in more detail. Fig. 18 indicates that the aquifer receives water from the east and west and moves towards the center, mainly through the Kabuh Formation and the Notopuro Formation. Then, upward Quatemary Geology alld Hydrogeology of the Madiun Basin, Indonesia 237 tN o Shallow Well: nol deeper rhon 40m • Infermediate Wet I: 40m 10 80m 6 Deep Well: deeper thon 80m Tubu Well drilled before 1972 (nonself - flowing 1 Tube Well drilled before 1972 (self - flowing) k======~19~======d20km Fig. 16. Piezometric Surface (in m above s.l.) and Flow-net System In September, 1979, in the Madiun Groundwater Basin. leakage takes place near the Madiun nver, and water discharges into the Madiun river which has dissected the plain so as to reach the upper surface of the Notopuro Formation. It is remarkable that a low piezometric head area has been formed in the Kabuh Formation near Caruban, which is one of the areas where deep tubewells have been 238 Shigeru KUMAZAWA tN o Shallow Well: no! deeper than 40m • Intermediate Well: 40m 10 80m ::e~~~~~~~ t:. Deep Well; deeper thon 80m J 0 Tubu Well drilled before 1972 (nanself - flowing) • Tube Well drilled before 1972 Iself- f1o ..... ing) 10 20km 'b====±======l! Fig. 17. Piezometric Surface (in m above s.!.) and Flow-net System 111 March, 1980, In the Madiun Groundwater Basin. constructed by the project most densely during the period from 1976 to 1979. It appears that the lowering of the piezometric head in the area north of Caruban and the decrease of recharging from the northeast hills which have taken place from the initial condi tions (Fig. 15) to the 1979 conditions (Fig. 16) have been caused by abstraction of X(West) (East) X' 2001..------,------,------,------,------=::.:.;.::.....:., ~'" Self-flowmg well I Ngowl heOd(mete{a~ Piezometric /Groundsudoce r:: ~ r-. ,., 100 --- - -"'-"'---- __ Top 01 ,he uroermos! screen IoD ...... Permeobilily(m/doy) Screen sec"onn. M'ddle po'n' 01 'he soeen sect,on 'L Bollomo!lhe loweS! soeen ~B0I1c:mo1IhebOrehOle o AllUVium and l-lolocene Formotions(Holocene) o Setn Formof1on(lJpper PlelstoceneJ fIB]] Nol0puro Formollon (Middle Pleistocene) D Kobuh ~ormo'ion(Lower-MldcJle PlelsTocenel ~ Pucongon Formation (Lower Ple,stocene) _ Bosement Rocks (Mlocene-PHocene) - ...... _..... Boundary of fo(motions 10 20 50 '-6~~d ~~u~~~e;'iOI line in kilometer--- ~FIOW\lne Fig. 18. Schematic Profile of the Groundwater Flow System of the Madium Basin along Section X-X' (the section line is shown in Fig. 5) 200Yr(_SOU_h_I --, ,..- -. --, .- ~------(::.:N:.::or:...:.lh~)Y' Oero l1J ~ c: l1J "0 :J -2((, ------~\I__-----4~~;;:~g -3 0 10 20 30 40 50 ffJ 70 Distance in kilometer ---- Fig. 19. Schematic Profile of the Groundwater Flow System of the Madium Basin along Section Y-V' (the section line is shown in Fig. 5.) 240 Shigeru KUMAZAWA groundwater from the Kabuh Formation. The N-S profile (Fig. 19) indicates that upward leakage from the Kabuh Formation to the Notopuro Formation frequently occurs in the Ponorogo sub-basin, and is controJled by the shape of the groundwater basin which is characterized by sporadic projections of Tertiary rocks. Among them, a dyke between the Ponorogo sub-basin and the Madiun sub-basin is most significant, as iJlustrated in Figs. 15, 16 and 17 as a "Hydrogeologic Barrier". Water movement rather than stagnant conditions from the Kabuh Formation to the Notopuro Formation in the sub-divided blocks indicates that the main recharge of water into the aquifer of the Ponorogo sub-basin comes from the east and west. That is, recharge comes from Mt. Wilis and Mt. Lawu, on which lahar layers of the Kabuh Formation and the Notopuro Formation have been deposited, and not from the Southern Mounains, which comprises Tertiary rocks. At the main dyke between both the sub-basins, water moves upward and is discharged into the Madiun river to some extent on the southern side of the dyke; it is then recharged again through the Setri Formation on the northern side of the main dyke, entering the Madiun sub-basin. In the Madiun sub-basin, water moves mainly through the Kabuh Formation and then through the Notopuro Formation towards the center of the basin. Near the Madiun river, water moves upward by vertical leakage and is then discharged into the Madiun river. 5. Conclusions 1) Study of the subsurface geology of the basin revealed that a total thickness of more than 200 m of Quaternary sediments have been deposited after the Kabuh stage. The axis of the sediment basin is elongated N-S in the Ponorogo sub-basin; the sediment basin of the Madiun sub-basin is a complex, made up of the N-S axis of the southern half and the WNW-ESE axis in the northern half. 2) The Madiun basin is separated topogrtaphicaJly into the sub-basins by projected Tertiary rocks, and by a subsurface dyke of Tertiary rocks, geologically as weJl as hydrogeologically. 3) The aquifer system of the Madiun basin is significantly related to the Quaternary geology of the basin. The aquifer of the Ponorogo sbu-basin receives water from the eastern and western mountains, and water moves toward the center, mainly through the Kabuh and the Notopuro Formations. Upward leakage takes place and water discharges into the Madiun river near the main dyke between the two sub-basins. The water is then recharged again through the Setri Formation, entering the Madiun sub-basin. In the Madiun sub-basin, water entering and recharging the aquifer also moves mainly through the Kabuh Formation and then through the Notopuro Formation toward the center of the Madiun sub-basin. Near the Madiun river, at the center of the Madiun sub-basin, water moves upward by vertical leakage and is then discharged into the Quatemary Geology and Hydrogeology of the Madiun Basin, Tndonesia 241 Madiun river. 4) Lowering of the piezometric head has taken place in the Kabuh Formation in the area north of Caruban. This was probably caused by abstraction of groundwater from the Kabuh Formation. Acknowledgments This paper is based on the study which has been carried out In Bandung, Indonesia, as a member of the Indonesia-Japan Joint Study from 1991 to 1992. Without the fruitful conclusions of the team, this work could not be completed. The author wishes to express his sincere thanks to all the members of the Joint Study Team, and partaicularly to the team leader, Professor T. 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