Geology of the Molo Area
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CONTENTS(.IOXTENTS PAGEP .x L.‘ [- Abstract.-'\3.‘.\.".1'1t£.‘i I-Introduction.l-—-1n‘.r0du::iia'm... II-PhysiographyH I"h}\fi'\1gl'ii1'!]'f}' 3 III-PreviousIll—Pz‘cx'imls GeologicalCicofogjcul Work 6 IV-Summaryl\-' SLJnn'nnr} of0:70:31)Geology 7 V-Details\J—Dutnilvt mof G's-3103'Geology. 8 1.1. Tertiary'I'CrliaLr} 9 (1)I' i) KerichoKcrlchu phonolitesgfiizmzuiéicx 9 1 '. -.\'-- -- —-.. .. i '-. ’...'n. l', _ (2)f._ JanBasalts:.u.. a intercalated.. HL‘LlIi.- . :: c x. inI’.u Kerichok-I1., .-.. lullm--. phonolites‘-. |\-:=.£.fll x. 10il] (3)f3] PhonoliticPIiL.)I“.O.|iI‘.L.‘ nephelinitesnephcli.’ .. 10in (4)l4].\c;\.‘.g.|r1:tu. Nephelinites‘Kl' '.\..and.111..... melanephelinites:.1c...:.cp.1;.1. '. I. ' of(11‘ Nyando\'_-..I.'.1.iu Valley\"'.;.E-.:'-. ] 1 (5)['5] Tuffs'I'Lfl‘S of02‘ thelite MauMam and3.11;: MountMOLIT‘L LondianiLomilam; ]2 (a)rm Tuffs12m} of theLhc south-west.50.1LI'1—xx . 13 (b)N}: Pink fineFm“ grainedgmirsd eutaxitic;-'..:.-.\|:j.‘. tuffs'..:.":k ]3 (c).‘H PalePatio greygm; cut-An:eutaxitic crystal tuffs[Lji'z'n I3 (6)m) Turrieir}Tertiary pyroclastic.§.'J'm:fastic rocks"0c 0:"of the UpperL j‘pcr MauHim 14 1 . (a){.11 GreyCir-C} and bleached‘ifiicaiuhcfi. agglomerates, tuffs"2} andan. sediments.s-cgiin‘cz‘w . 15 (b)"3"?! BlackB15»; ashes.mlics of E]burgon 17 (c)H'] Eutaxitici-.L.!l.L\i'.iu welded\Aclulcd tuffs-.-.. 18 (7).51 SedimentsSeaiirncr-H of LondianiLon. and Maji Mazuri ]9 (8)[BL-\IixA]kali basalts.‘nulzx'nf\Eu'-..~:..-.1-c.a.1of Molo plateau 20 (9)[‘)J BasaltsBit‘iklllx of01' MajiMLLji Mazuri.\-1.L/!;:'i .. 20 (10)IE{}|T1I‘.;5LIZ'(':Tinderet phonolitesphcwim‘dtux . 20 (1])-;I1_\'y..Nyando.n Valley\ l;i.C_\ phonolitesPin-1' 21 (12)_: TrachytesTrudiylm and quartzquw‘lz trachytesmac-:1}. !L‘.\' oful' Londiani!.-;1:1d'.:=.|‘.f and KilombeKiioltwim‘ .. 22 (a):.«.-IT:';=.L.-':1}t'c<Trachytes. 23 (b)!.r"‘-' Quartz(Juan?! trachytesJE'Z'JH" 23 2....r Pleistocenel’lcis'. murm- 24 (1)!. E II MaficMaui; basalts,5* basanites and limburgites of Londiani 24 (2)-:I Mau3!”... ashesLL with basal tuff 26 (3)I'FJ Tuffs'I‘LEI‘ZK' andsu‘. asheslI'IC-i ofUI‘ MogotioMngnié-fl 26 (4)=—+il Ashes.-\<':“.c< of;\"T'§:1\ici'=-"Tinderet . 27 (5)52 KilelwaKi':'.-.: Hill": phonolites.“ii-nan" . 28 (6) Trachytes of the north-east 28 (7) Eutaxitic welded tuffs of the north-east 28 . -- CONTENTS-( Con/d.) PAGE 29 3. Quaternary 29 (1) Black ashes of Rongai plain and Njoro 30 (2) Pyroclastics and sediments of Rongai plain and Mau slope 31 (3) Menengai pumice . 31 (4) Sediments of Rift Valley floor and Kilombe . 32 (5) Sediments of Mau Summit 32 VI-Structure 34 VII-Economic Geology 38 VIII-References. ILLUSTRATIONS 3 Fig. I-Physiography of the Molo area 5 Fig. 2-Average annual rainfall in the Molo Area MAP\1.\P at end '\ \.1’_'- Geological map of the Molo-.‘,L‘ area\L'L‘, (Degree'DJLJI'L‘C sheet\Ik‘L“. 42,Jr: N.E.) .. '" ABSTRACfABSTRA Cl‘ The report describes an area of approximately 1,200 square miles in the Rift Valley region west of Nakuru, bounded by the eqmvtor and latitude OO30'S and longitudes 35°30'EL ;andm1 36°00'E. The greater part of the area to the west and south consists of forested highlandsahfl and farmland on the western shoulder of the rift, while the north- easterncan (gunkquadrant includes the Rongai Plain on the floor of the Rift Valley. This area in- cludesgum much:tmch of the1‘ highest ground to the west of the rift and can be considered as the U, r‘li a» m centreL C of0; themg, volcanicn? LJT‘HL‘activity for the region. ...\\ fl , ‘ w. r. ,, nv H ‘ ‘ The rocksTUghn- v'. encounteredLLkI LA, u are limited toA the Tertiary. A, 7‘ and\L‘ Quaternaryk A volcanicw suite, , , 1 V of centr:al Kenya and are largely pyroclastic in ori~in. A wide range‘ ¥ ofA lava11x; types have been recognized and described, ranging from mdilite and perovskite melanephelinites and basanites, through varieties of basalt, phonolite and trachyteKr to the‘g‘ .4quartz trachytes of the Londiani region. Many of the pyroclastic rocks are attributed to an ash-flow origin, and this concept js briefly described. The structure of the area is largely obscured by late-stage\L, pyroclastic‘ ‘, x ¥ activity‘L and little has been added to present knowJedge of Rift Valley tectonics. GEOLOGY OF THE MOLONIOLO AREA I-INTRODUcnONI—INTR()I)L'C.'1"I()N During the1111: ped'Odperiod February16131111113: 19621%: ta10. July11111 1962 a:1 gealagical‘ reconnaissance was carried:CL aut.1111 in1:1 an.111 areaawn ta:11 the1115 west11:5: 'Of1'15 Nakuru,.\'..111:‘ induding‘1L1L111'1 the westernWC. ' ‘11 scarp\C" 11P- 'Of the Rift VaHey,‘...1C1_1'_ Mount Londiani1011111111 and1111111115:the northernL1C‘1r‘111c1‘11. Mau.\‘1; The survey0.1111: coveredcmVcrcd same31011113 1,2001. square miles‘1“:r. boundedbuLdd by3 the:11: 1:C111;11111equator 1111::and latitude1113.11.11.11]? oo30'S11.1118 and longitudes.1.1.11;111111;~5 35'3.”35°30'E and 36°00'E.' ‘111‘ 1". The111: area111611 faUs1:111. within111111111 the111C RiftR111 Valley\'.111Cj. Pravince,P111111“: 1.1.1131with the greatergrc. 11:1 partp.11: administered1111111111516 Cd by1“-. the:11: District C'Ommissianer,C1’m11113i51111101‘. Nakuru.3111111111, A smaller51.11;? 1:1 part111.171 in111 the111C north-east,:1011117011x‘1. 11311111152111belanging ta the1‘11: Baringa113111131) District,1)1~‘.PC‘I. is1.1 administeredL111"'11f1‘1~.1C:‘:‘C1 fr'Om111'111‘1 Eldama1.11.1111; Ra'V'ine,RSL1.11‘.C. and..1‘C1 areas.11‘C‘gm in11 the5:11" north-“1171.11 west~51 and sauth-west~11uLh-WC51 are1.1'6 administered.11111‘111115131‘131'1 from11:11:11 Kerioh'O.c1C‘11o Land Utilization.-The1131111111. 11:: Mola\10111 a,rea can~ 1 be1 divided: 1' "1 int'O1.111 two11.111 major111.1jc1' parts,:.."‘1\. the:larger,111: 1:1":zer. same\1’1111; 56 per coo,t. 'Of1111111:the wh'Ole,11111:. being' ranch, plantation and farmland, while1:111:1C theL11: smaller,1111;111:1‘. same~111111C‘ 42 per cent,‘ ' . is1\ caveredC131 L‘“L.‘\1 by3‘). natural and planted farests. The remaining 2 per cent in the :narth falls[71.11% within11111.1 the Lembus land unit and is grazed by the cattle and gaats 'Of the Tugen and“111011 Njemps\I‘C‘f1‘1m tribesmen. TheT11C‘ extremeC1111: 11c n{)!fth-east1111 1.1-c.15 'Ofof the111: area,.11C.1_ consisting0111111111115 'Of111 11111.:that partD1111. at:11 lawest11.1'1VGSi altitude:1 111C111C (belQw13:11.1“ 5,500$51111 ft.):11 and11111 with1.1.111 IQwest111‘.‘\':"\I rainfall15111111 (avemging:1u.cr:11111ig: ,less15.. 17.1111.than 35715 inches1.1111161 per11:" annum)1;:111L1111'1 is-. cxtcnexten- sively.21 used1:11:11 far11:11 sisal9;.11 plantatians.111.;7111111’1m. A»\ factary15.111111. far1111‘ extracting31.11.1111” ,the‘11: fibre1'1b is‘11 sited~1tC‘L1 anon the M11111M'OI'O RiverRi‘uC‘r‘ 'One1.111: mile111.1: south\11LL'."1 1.1.1'Of Mogatia,\11.’1_1C1..'1T‘1.1. and411.1 411.1111:anather 7111‘just 'Outside the:31c aTea.1:‘C.. ta111 the111.“ 11111i1'1—‘C‘1'LR‘L.naDth-east. TheT1: RangaiRangu Plain,.1111. whioh111c11 extendsemcmk fram1:11:11. Kampi1\.1:1'111. yaj. .1. Mata.\1111.1 in{11 the131: narth11111111 (5,500 ft.) tQ south 'Of the Nakuru-Mau11:11 .\1‘.'LL1 Summit31111111111: RaadR11.1L1 (6,500111.5111 .£.t.),11.1. and.11111 ,is11 flanked11.1:‘111511 ta1C1 the:11: west by the rising land at the faat1111-1 'Of111‘ the1111; Rift Valley 'sc'arp, is~1. utilizedL:1:112C‘C1 mainly1111111113 for11:11:11C111‘1T11L1C‘13the productian 'Of maize,11.111; beef1)::1 and dairy11.11“}. cattle.C;LLL1C. At311 a:1 slightly higher altitude‘1.11.11i: (6,500-7,50011151111351111 ft.)111.1 theT113 rolling hills.1111. and.1;1C1 plains111:1111~ in511 the111C Njara\111.“1.1 area‘.."C:. carry maize and C1111.cattle, alsa.11\1\ wheat,111113.11. market1111mm g;1711Cf1garden produce11:1 .11.:.';‘ and111111 peas.11111» L A belt 'Of1'1.1‘ highly1111:1111 praductive1‘ 1111L1‘C‘Y1‘.C‘ smallx.‘ mixed farms..11"’1’\ extendsC‘\1L'1111\ alang.: the. well-watered‘1‘1C11:‘~'1.11.C': 1'11 lawer1.51‘1'x‘C'" slapes\ 11:13. 'Of1.17111131111f1h»1:.1\1the north-east Mau.\11L11.’1:C‘1.1:‘:11(be.tween 7,500.5111111‘10.and 8,50031.51111 £t.)111 frDm111.1111 Njoro\f1.\'1.1 through111111111511 ElburganElburg 'and. .. Turi. .. 1 ta:11 Mala.311111: Mixed\ \CC1 farming1‘11" is1. alsa.111 carried11:11 aut1.111 an1.111 the111: plain$1.111". narth[11.17111 'Of Londiami1: C1 . (7,500-8,000‘.<1‘111-5_1’11'111 ft.).f:_1. On0:1 the111: 111211high gr'Ound sauth>.1.1L1‘.11 'Of1.11 Turi,111.1. in111 the'regiDn111: of Mau\Igu Summit911:111:111 1111and particularly.‘L:CL11.111\ within11:111111 the:hC‘ large1.11.91;- arable.1..1:1.C enclave811C1(L\L‘ in1:1 theThe Mau311.11 Forest1111\1 which11111.11 acoupies1VJCLJP1C< the111C 51.1111.sauth- 1 'west quadrant1'1C1111. 'Of1.1 the area, cultivation is carried aut1.11 ta1.1.1 altitudes12111111CLW 'Of11. 9,00011.111111 ft.11 Wheat and pyrethrum,:‘1 '..-.r11’.11‘1.. cattle.111: and.111C1 sheep01:1:11 are.1 the majar'1‘ .111." praducts.:11‘11L11C‘m. SmallV1 specialist\p‘C‘C‘11111\1 prajects11:01:?“ have beensec-11 develaped1EC\C11111C‘-51 in111 cannexianC‘1’11111e\31'1;1 with,1.11111. 'Or1.1“ as11‘ part1111.1: 'Of1'11 the1.1:: lacal agricultural'.C‘L11‘1.L.1‘..