SEDIMENTARY FACIES OF THE MIOCENE IN THE … Sup.5... · African Study Monographs, Supplementary Issue 5: 59-77, March 1987 SEDIMENTARY FACIES OF THE MIOCENE IN THE SAMBURU HILLS,

African Study Monographs, Supplementary Issue 5: 59-77, March 1987

SEDIMENTARY FACIES OF THE MIOCENE IN THE SAMBURU

HILLS, NORTHERN KENYA

Masaaki T A TEISHI

Faculty of Science, Niigata University

INTRODUCTION

Constituting of volcanic, volcanoclastic and clastic sedimentary rocks, the Tertiary in the

Samburu Hills west of Baragoi, northern Kenya, is divided into the Nachola, Aka Aiteputh,

Namurungule, Nanyangaten, Kongia, Nagubarat and Tir Tir Formation, in ascending order

(Sawada et a/., 1987; Makinouchi et a/., 1984). By the 1982 and 1984 Japan- Kenya Expedi

tion, a number of Miocene hominoid and mammal fossils was collected from the sediments of the

Nachola, Aka Aiteputh and Namurungule Formations. It is important to make clear the environ

mental background at the depositional stage of their formation. The paleoenvironment has been

investigated geologically and paleontologically. Very little, however, has been stated about the

sedimentary environment. Baker (1963) briefly described it only the lacustrine sediments.

Taking part in a fieldwork of the 1984 expedition, the author observed and described the

sedimentary facies of the three formations at some localities. This paper shows the sedimentary

columns of these formations, and briefly presents the tentative interpretation of depositional

environment.

NACHO LA FORMATION

The Nachola Formation, unconformably covering the Precambrian basement complex, is the

lowest formation of the Miocene in the Samburu Hills. It consists of clastic sediments, pyroclastic

sediments and lava flows of volcanic rocks. The clastic sediments composed the lower part of the

formation. Although they interbed with the thick lava flows of basalt and trachybasalt in the

south, the intercalations of lava flow thin northward (Sawada et a/., 1987- Fig. 6). Along the

westside of the Nanyangaten River, the intercalation is not observed.

Three columnar sections (Fig. 3-Locs. I, 2 & B5) present the sedimentary facies ans succession

of the Nachola Formation (Fig. 2). Loc. B5 is located in the southern part (Sawada eta!., 1987-

Fig. 6), and Locs. I and 2 are west of Nachola (Fig. !). Sediments are mainly composed of

thick-bedded, ill-sorted and massive sand. They are thicker-bedded and coarser in the south than

them in the north. Although cross lamination and crude grading are observed in a few sand beds

at Locs. I and 2, the massive texture is the characteristic of most of sand beds. Illsorted sands

contain frequently granule-sized, rarely pebblesized, grains. At Loc. B5, thick-bedded and distinct

59

NACHOLA

• M- X, 20-42; Fossi I Locality

0 1~7; Locality of Columnar Section

Fig. 1 Locality map

Numbers 1 - 7 of localities measured columnar sections

correspond to ones of columnar sections (fig. 3).

African Study Monographs, Supplementary Issue 5: 59-77, March 1987

~ 0 ::r-

100m 0 iii'

~ .., 3 Ill .... c· ::3

0

-~,

Sediments

Mud flow deposit

Tuff (partly welded)

Basalt

Phonolitic basalt

Trachyte

Sodalite trachyte

Basement rocks

4

·I 3 Kenyapithecua

1

I 2

I

61

Fig. 2 Stratigraphy and horizons of columnar sections Lines numbered show the horizon of each

section.

62 M. T A TEISHI

grading beds are observed. Massive silts bearing commonly pumice grains are intercalated with

the sand beds.

Clastic material is supplied from the south. The sediments are considered to have been

deposited mainly under the depositional environment of fluvial fan in the south and fluvial plain

in the north. In the latter environment, the sands were deposited in sheet floods.

AKA AITEPUTH FORMATION

The Aka Aiteputh Formation mainly consists of lava flows of basalt. Sediments are intercalated

with the lower part at the northern area (west of Nachola), and with the uppermost part at the

western area (Samburu Hills) (Fig. 2).

Facies and columnar sections of the lower sequence are shown in Fig. 3-Locs. I, 3 & 4. The

sediments mainly consist of massive silt, but contain some intercalated sand and thin siliceous

layers. The silts contain commonly pumice and granule-sized grains, and sometimes calcareous

nodules. Cross lamination is rarely observed in the silt. The sands, containing commonly pumice

grains, are generally massive, but rarely cross-laminated. The thin siliceous layers, mostly being

greyey white chert, are intercalated with the silts. The lower sequence includes characteristically

many fossils of silicified wood.

Lowermost part of columnar section (Fig. 3- Loc. 5) shows the uppermost part of the Aka

Aiteputh Formation. Sediments overly conformably on thick sequence composed of lava flows of

basalt (Fig. 2), and inter bed lava flows of basalt (Plate I-1 ). Sediments mainly consists of reddish

brown pebble- to cobble- sized gravel, sand and granular silt containing basalt breccia with

intercalated white chert, massive silt, and calcified Iapilli tuff. The gravel and granular silt

containing basalt breccia, called weathered basalt sediments by Makinouchi et a!. (1984), stratify

and show crude cross lamination (Plate 1-3). The chert is interbedded with greyey white silt, and

grades in lateral into siliceous or calcified silt. The lapilli tuff layers are stratified and calcified

(Plate 1-2). Thick cobble-sized gravel is observed in lower horizon than this section along the

Asanyanait and Nakaporatelado Rivers (Makino-uchi et a!., 1984).

At the depositional stag of lower part of the Aka Aiteputh Formation, the sediments was

accumulated around the coast of lake, appeared in the west to northwest of Nachola. After that,

the products of volcanic eruption overly widely and thickly. At the depositional stage of upper

most part, the sedimentary basin along the present Rift Valley begin to depress largely and deeply.

The sediments are considered to have been deposited in the fluvial environment. The volcanic

activity continued intermittently, and threw the lavas on lad. The lava flows were interbedded

with the sediments. The chert is considered to have been deposited as evaporate in the depression

part of flood plain.

Sedimentary Facies of the Miocene m the Samburu Hills, Northern Kenya

Loc. 1

y v v v v v

15

40 I;,;; ::;:i'' 50

60 ~

40~

porphyritic ol1vin basalt

f. peb. gravel {grey.white) lamin. & g:r:ading

granular sairl I pale yel. green I

ill-sorted m.-c. sand

I pale yel. green I p.mri.ceous ill-sorted silt

(grey.yei.- white) silicifia:i ill-sorted v.f. sand 1000 r---

100

15

55

7-15 25

220

130

(grey. white- pale yel. -~r silt

granular silt crtrlely stratified

1===~=: (green. grey) chert (green. grey) granular silt FOSSILE LAYER

r:~=~=~{grey. white) f. peb.-cob. gravel j:: (green. grey)phylit1c mas. silt

L L L

L L

L L L L

L L L L

p:>rous

phonolitic trachyte

(red. purple)

(grey. white) f. sam

grading

granular c. sand

50 > ~ (yel. green) puniC'eOUS silt intercalating lamin. f. sand

1~ !~.~~l~n;Jt sand 30 .·. 1 (white grey) f.sam

28~~~~ (~. ~- 'f."Y• white) 20 F 1~: grey~'mas. ~t& s>lt 20 I grey. white I f. sam

120

75

270

150

I green. grey I

mas. silt

(brown. grey)

granular m. sand, mas.

(yel. green)

ill-sorted granular c. sam

(brcMn in weathered surface)

grading

I yel. green I

granular c. san:i

. p.mticeous in lower part L..=.;,~e..c..::~~.:.L__/'

II I'' m • 0

90

160

150

L L L

L L L

L L L

L L L

L L L

L L L

L

L L

L L L

L L

(grey. white)

mas. f. sand f. p:b. - v.c. sand

(green.greyl

ill-sorted mas. f.sand

phonoli tic trachyte

(yel. green - grey. white)

mas. m. san:i with granule

(green. grey) m. sarrl

(green. grey) ~Ms. silt

(yel. green) m. sarrl with granule

(white grey! cross lamin. cob. bearing c. sa.rrl

(yel. green) peb. bearing c. sam

(yel. green) IMS. silt (green.grey) IMS. silt

with f. sarrl 10 an thick in mid::lle

(green. grey, re:i. brCMn in weatllered

(~.~e~mas. silt I green.grey I

f. sam

I grey. white I

(green. grey)

{:hylitic silt

(grey. white)

mas. f. sarrl

grading m.-c. sand

I yel. green I f. sam (grey. white)

surface)

cru:iely lamin. c. sand with peb.

(re:i & white)

rra.s. m. sarrl

grading

===::::;:l:;;lll~llmlurl-(grey. wtute) c. sarrl

m • o

63

Fig. 3 Columnar sections and sedimentary facies of the Miocene In the Samburu Hills and

Nachola area, northern Kenya (Locs. I ~ 7)

Section of Loc. 5 is shown throughout 5 pages.

64

Loc 2

L. 1-L.. _L phonolitic trachyte, 'w'So:lthered

so t-""""'"--=T-~-•yel.greenl

20 t-v-v--'----,. a~Yrf~ =1~ ~!~

200+

30 f---:-'-:---'1, 100

130

60

100

120

150

80

no outcrop

40c:r

no outcrop

60r---1

k3

11""1"' m • •

(yel. green)

mas. f. sand

grading

mas.c. sand (dark green grey 1 ill sorted

silty sand

( yel. green l

granule - fine peb.beal:ing c. sand

( yel. green)

granule-bearing mas. m.-c. sand

( yel. green I grading fran mas. f. sand to

sandy silt

(yel. white)

mas. m. sand

(green. grey I

P-lflye ~;redan~~. ~Eng I yel. brown I m. -c. sand

I green. grey I

puniceous mas. s i 1 t

I yel. green I mas. f.-m. sand

{yel. green) granular c. sand I yel. green I f. sand

(grey. white - yel.white)

well sorted m. sand

(grey.white)

granular sard

I yel. green I

mas. f. sand

I yel. green I

p.miceous v.c. silt to sandy silt

(grey. white)

f. sand

no outcrop atout several meters

al::x:Ne aP,yric basalt 2 m thick.

Loc 85 (see Fig. s in SAWADA et al. 1986)

500

300

350

40

100

15

400

500

__:__": -=-\ "'

~ ..:;

~

1'--=-;..

. o. 0. 0

0 0

:J•D

0. o:o • 0 D

0 o· ·o. 0

11'"'1"1 ..

( yel. white)

lapilli tuff pumiceous

(grey. white)

lapilli t:ea.ring tuffaceous silt

grading

(yel. green)

f. peb. l:earing

tuffa~ silt peb. l:earing

tuffaceous sand

peb. gravel

lyel. green)

mas. silt

I yel. green I

cob. gravel

I red. brown I

welded lapilli tuff

M. TATEISHI

Sedimentary Facies of the Miocene in the Samburu Hills, Northern Kenya

Loc 3

aphyric basalt

No outcrop

:-:--- -50 :. : ·l (dark grey)

501-'--'-~·.;..·-'· ~~~:-=_cp.~ green. grey)

- mas. hard silt

50

700

Loc 4 v

1-'--"'---""---aphyric basalt

I red. purple I welded tuff

I yel. brown I

mas. granular silt

70 (greyey white, brown. yel. in ~ur~~&e<f

mas. hard silt with

20 y :. ~ (whi~tt~~:e~ ~c~~ part

30 ~ (greyey white) mas. hard silt 50 I green. grey I

mas. silt, small blocky

,;~t:=:=:::::::i'=~r~~i~~~ ~; phylitic silt

80

100

-I dark green. grey - yel. green I

ma.s. phylitic silt

I dark green. grey I

20=·

mas. silt, small blocky

phy li tic in the la.r.~er part (yel. bra.ml cr. lam.in. f.-m. sarrl

250 lye!. green - yel. white)

mas. f. sarrl

inte;~~~t~~~ thick

lamin. c. sand with granule

(green. grey - yel. green)

mas. silt with white p!.Dri.ces & granule

~:::t~~::::;.;::•:::J (green. grey) peb. gravel

(green. grey - yel. green)

mas. hard silt

with white calcite ncxiule

an:! partially phylitic

L. LL pllonoli tic trachyte

L L L t. LL L

1 pmi"l m ' 0

400

'>.i .. ~.: ~:

m. sand in the upper

(grey. white)

grading

mas. v.c. puniceous sand

250 .

(blu. grey - grey. white) mas. m. sand

puniceous in the 1~

1.:::!!::: .:f!!.=!! pun.iceous in the upper 70 ~ (grey. white) ~ cr. lamin. silt

27 Lf-----==:!===i'lyel. white - yel. green) silt 12/ r (yeL green) mas. silt 3- 1y<ey-grey. white) chert

80 (pale green. grey) mas. silt

5 ~ (yel. green) silic. silt

FUSSll. IAYm 93 (yel. green) mas. silt

with granule

v v APHYRIC BASALT

11""1"1 m ' 0

65

66

Loc 5-1

70 =

100

84

t (red. brown l cob. bearing ~- gravel

! imbricated f. t=eb· gravel

t (red. brown)

mas. silt 1ntercalated gran. c. sand

!M.s. gran. silt

fyel. brt:lWI1) intercalated gran. s1lt

peb. gravel in lense

( yel. brown l crudely lamin. peb. sard

(red. brown)

crudely stratified

peb. gravel

(yel. green)

mas ~n~lWing calc. ncx:iule

{red. brown) gran. v.c. sand (red. brc:lwn) f. sand & gran. silt (red. br) gran. silt with m. sd (red. brl gran.v.c. sarrl

~~~~~~ 1aXti~ ~- Z!f.l~. sd

~~~: ~l ~~~~ I~: f. sand (grey. white)

alt. gran. v.f. sd & mas. silt

cross lamin. f. sand (grey. white)

mas. silt

(red. brl cross lamin. m. sd

(red. br) mas. silt

(red. br)

graded bed fran pe.b.gravel to gran. c. sd

cross laminated

~;~: ~~~ ~It silt

(yel. br.-yel. white) alt. croo lamin. gran. sd &

silt

fyel. white)

mas. silt

(yel. white) crco lamin. v.f. sd intercalating silt

(yel. white)

silt partially cross laminated

(yel. white - yel. br) alt. mas. silt & ripple cross

lamin. f. sd (yel. white)

mas. silt (yel. br) gran. c. san::l (yel. white)

silt intercalated gran. m. sd (yel. ocher) rip. lamin. c. sd

~~:c. b;J linguoid r~~~ Ehe ~op_ (yel. br - grey white)

cross lamin. gran. gravel lamin. c.-f. sd with silt trough cross lamin.

gran. gravel

15

"' r--s 50

15 20

50

15 30

35 15

60

100

·o·:··.

'r'·~II'VJ' ......,) ,.,..,-tu stlr:

M. TATEISHI

c.sd linguoid ripple, sd volca.n:::l

(yel.br) gran. gravel, /¢ 1 an h<l

(grey.whl silt leb:nssp..1ren (yel.greyl gran~·m~mu~ted by calc.:.te (yel.greyl mas. sdy silt

t:~:i: :~y~!dectsd~~:n ~an~·m. sd to (yel.grey) gran. sdy silt Lgran. sdy s1lt

( yel. br J graded bed fran pe.b. gr.J.vel to gran. c. sd, trough cross

(yel.wh) silt to sdy silt

brl gran. v.c. sd br J graded bed fran pe.b. gravel to

wh) gr:~il~· sd, trough cross

br) graded bed fran pe.b. gravel to gran. c. sd, trough cross

{green. grey) mas. gran. c. sd to m. sd

f~~!i. ~e~j ~ad. OOd fran gran gravel to

i( ~~· c. sd, trocg!poss f':;::;:;j:::;i::;:t~ 1'Fe'C"9rey1 graded bed fran f. sd to silt 1-' (yel. br) pebbly c. sd

t (yel. br) c. sd to gran. silt

{yel. wh) phyli tic silt l;,;~:g:t:p .fdyel. br) gran. gravel to m sd, trough

r{grey. wh) grad. bed fran gran. c. sd to v. f. sd, crucle cross

(yel. green)phylitic silt

(yel. whl mas. silt

35 ··t· . . ·:·:~.·;_._ t(yel. grey) grad. bed fran f. ~· gravel ......... •· • to c. sd, cross 1n the top

48 (yel. grey) phylitic silt

. .. :. i(yel.br)f sd 78 .::~~·;:£~:~;.o .. f.pe.b. gra~l crude stratified

180

160 180

:!:Q;~'·.~~.-;··.·i-·6·. t f. peb. gravel to gran. gravel

(yel. green-yel. wht: phylitic silt

f (yel. wh)grad. OOd of c. to m. sd

(yel. ~;'f~~~~i~'; ~v6lute lamina. silt(?)

{yel. wh) lamina. silt, calci.f.:".cated

(yel. wh) laminated silt

-f. sdfyel. green> mas. silt . . . gran. gravel

............ z.~~-.;_.~ .. ·.:·:·~~-.·~ {yel. green) clast SUpp:lrted gran. gravel ...... ·· .. ..... • .. . ..... ; -~: ... ;. . ......... ~-~ ·-~--~·.

. ·. ~ .. (yel. whl

cn.de stratified suba.ngular f. pe.b. gravel

{ yel. green) gran. mas. silt in the top

{yel. brl gran. c. sd tom. sd, lanu.na. l (yel. gree-yel. wh) crude stratified

graded bed fran m. sd to silt

w. calcareous no::iule

~:;;;;;;:;:::i) :~~:r.~~35 ~~:c~i=tm. sd

11'"'1"1 m • 0


Loc 5-2 about 20m t.mder the base of 5-1 section

200

(yel.gr""'RAu~f· silt, calcified (yel. cx:herJ mas. silt

~~E$:81 (yel. ocher) gran. gravel )-: : '¥91n."8!!!!MJ~~aeilr~lfmn gran.

lyeL w11 - ,.W~wnf!sr~t..u..t... (yel. green) lamina. silt

gran. silt (pale p.Jiple grey) (yel. ocher) cru:le stratified

f-"--"-"-'-'-''-":.UL, graded gravel fran f. peb. to gran.

~ 0

"'' <:) ()' c '.'

''('<: 0 ''.._.! \J

..:...-.·

.0. 0 ......

'0 ,'

0. 0

;()','!'' . 0 .0.

-o: 1.·

0' ',, r.:,:>'or ... ·; ,',D,

,, 0,

lyel. green) tm.rl flow dep::>sit with OOulder-sized volcanic breccia

(red. brl

rrn..d flo..' dep::>.sit

massive

with large blccks in the m.id:ile part

with c.peb. sized breccia in the basal part

(yel. grey) ~~!~~~t~i:l~~fied the lower

(yel. whl ,as. silt calc. spit ( le.t::ensspuren) &

no:iule (yel. br) gran. c. sd, calcified

crude stratified (yel. wh) mas. silt,calcified

(yel. whl lamina. silt (yel. grey) mas. silt, calcified spits (yel. whl lamina. silt

mas. silt,calcified

(red. br) gran. v.c. sd, crude strati

(red. br - yel. wh) silt fied.

lamina ted in the lower

fyel. green, red. br in ~the.red surface) alternating bed of mas. silt &

lamina. silt

{yel. green) alternating bed of mas. silt & phylitic silt

(yel. green)cru:::ie lamina. silt

(red. brl silt (rOO. br) mas. silt, calcified

(yel. green-yel. whl mas. silt

(re::i. br & greyey wh) sd.y silt & silt cross-lamina. part & mas. part

(grey. wh) lamina. f. sd. to silt

(yel. green) a~~=-~ ~ii~ ( yel. green - greyey wh)

crude lamina. silt -

(-pale green. wh) crude lamina. v.f. sd

(yel. grey)lamina. silt,calcified (yel. green) mas. v.f. sd

(yel. green) v.f.sd w. p!.mticeous barrls (yel. green) lamina. silt, spits

(pale green. wh) partially red. br

lamina. silt, alt. c.silt & f. silt calcified spits

I green. grey I crude stratified mas. silt

I yel. wh -yel. green) calcified lamina. silt

(yel. green) mas. silt, calcified spits

(yel. green) lamina. silt

(yel. wh) calcified in the lCf.Aier

,.~----',1 fyel. wh) calcified silt

(yel. green) silt

:F===:;, iyel. grey1fficrtWH~ layer (yel. green) mas. silt

15~~:;;;:=:;;:=;5ffyel. brl calc. lamina. silt 5 (yel. grey) mas. silt w. calc. layer

~::':::::=~~-;t_~m. sd in the base

l'";'l"~ continue to next page

67

68

Loc 5-3

62

15f-:==-1 80

(red. brl lamina. calc. silt

tl'i\~Y. %!\'Fiali!I~! i~.H~. w5,'ftanule

(yel. green) mas. silt

(yel. wh) calc. silt

(yel. green) rre.s. silt w. granule

23i----+ (yel. br) silt, calcified Ln the top 7~==Q (yel. wh) calc. f. sd, siltfru.grrents

350 (green. grey. whl

mas. silt w. granule

(yel. wh) mas. silt w. calcified fragrrents

{green - green. grey) mas. silt w. granule

(yel.greenl calc. silt

, zone of silt fragrrents

{yel. green) tuffaceous silt, laminate:l

•~~;iid(yel. br)cross lamina. silt, calcified green. grey) mas. silt

(green. gr) lamina. silt, v.c. sd in the base grey. wh) mas. silt

lamina ted parts

(br. grey) calcified silt, spits (~1. green) f. sd, w. silt fragments (pale green. grey) mas. siltw. calc. c. sd

with calcified layers

(pale green. grey - grey) mas. silt, partially phylitic

(red. br - grey) alt. calc. silt & mas. silt

t (yel. green) grad. bed, rn. sd to silt (yel. green) punice zone, cru:::le lamina

{yel. green) lamina. silt, punice, calc. ncdule

~"'"""'""=~""-" f (green. br)c.-m. sd, lamina silt, calcite rx:::dule

{green. grey) gran. gravel to gran. sd

grey)s~~uk-!~s ptmice 170

• --====

M. TATEISHI

(yel. green) granular f. tuff calcareous ncdule

calcified layer

(yel. green)granular s.:lt calcifiOO layers

a lot of gran~.,;.le in the base P,ylitic in the top

r (yel. green)

11""1"' m • •

fine tuff partially laminated

calcareous ncrlule

(dark gree.•1) ptml.ice

(green. grey) f. peb.- gran. gravel

(green. grey) phyL.tic silt calcified irregular lens gran. - to f. peb. - tearing

(dark grey - red. br) clast suPiXJrted f. peb. gravel

with l:oulder gravels

( yel. green - green. grey) matrix supp:>rted

(red. br)

rratrix su~rted cob. gravel with l:oulder gravels

rratrix gran. v. f. sd to silt angular - subangular

(red. br) mas. c. sd. w. granule

(wh) calcified layer

(red. br) clast SUI={X)rted cob. gravel

with sd layer

subroun:jed to rourrled

(yel. green) laminated granular silt with pumice & basalt brecc:a grains

crude stratified

granular f. sd, ill-sorted

(yel. wh - yel. grey) ill-sorted granular f. -m. sd

intercalating latn1nated sllt

continue to next page


Loc 5-4

.. ·• :,·.:.:·;:. (rerl. brl

.().

·o • A ~

Q . . -0

.. 90 ~ -~·4}j: ... ~ 4_ ....

·:·: ·•· .. 120 ....&..._-:-

·.·.· ·.·

{p3.le br. grey) crude laminated f. sd

(red. brl cru::ie stratified fine pebble gravel

(red. br) rras. gran. silt w. calc. ncx:iule

(grey. wh) mas. gran. v.f. sd

{yel. br) basaltic lapilli matrix silt to sdy silt

calcareous nodule green punice grains in the lower

(yel. wh) cnx:)e laminated v,f. sd

(yel. wh) crude laminated gran. f. to v.f. sd intercalating ~3ilt layers

(grey. wh) gran. to f. pe.b. silt

(pale yel. whl laminated silt

(grey. wh - bro.m) matrix suRX~rted f. pe.b gravel with tx:ulder gravels matrix, f .sd to sdy silt

{wh) granular f. sd, calcified ncdule

(red. br) granular silt

including basalt block

a lot of basalt breccia

ill-sorted sdy silt Ired. br)granular sd

f. peb. sized basalt breccia

(red. br) crude stratified f. pe.b. to granule bearing silt

(red. br)

silt to ill-sorte::i m. sd including a lot of basalt breccia

25

40

partially stratifiOO

(red. brl ill-sorted silt to m. sd inclu::iing d lot of basalt breccia

partially clast supp:::lrted

lrerl. brl ill-srorte:3 silt to m. sd

inclu::Hng basaltic breccia arx:l calcified layer

(yeL wh) calcified silt

I red. br - yel. ocher) weathered basalt

(dark grey - broom. grey) p:>rphylitic basalt columnar joint

(grey. wh) chert

(red. br) granular silt ~thered

lwh - yel. ocher I chert including calcite layer irregular layering

(grey. wh)-phylitic silt

(wh) irregular layering chert

partially calcified granular silt

continue to next page

69

70

Loc 5-5

115

(yel.ocher) tuffaceous silt

silt inchx:ling tuff balls

(red. br) cnxie stratified c. to f. sd

f. peb. layer

1 graded bed fran granular c. sd to silt

mas. silt

including f. sd layer

(whJcalcifie:l gran. silt with volcanic cobble

(red. br) silt with tuffaceous laminated part

irregular layering ( wh) granular f. tuff

calcified

(red. br) granular silt (wh) lapilli tuff, calcified

(red. br) mas. silt

( (wh) calcified lapilli tuff

silt and lapilli tuff

(red. br) laminated sdy silt

(red & wh, SI;Otted) tuff & silt

195 ·. ·, · (red. br) granular v.f. sd

. ~ .

1000

(wh) layered silicified lapilli tuff

M. TATEISHI

(red. br) layere::l tuffaceous silt

(whl layered silicified lapilli tuff

(red. br) laminated silt (yeL ocherl lapilli tuff, irregular

layering

.. .d .... ,Q.

"'..,'"'v .. ": 4> "..,"

, ., ltl II "'

..... ..a. .., ........

11""1"' m s 0

(red. br)

clinker

porphylitic basalt lava

colUJmar anJ. platy joint


Loc. 6 (Site SH 22!

47

108

10

102

125

80

silt, larrunated graulS

(pale green. grey) silt w. pumice grains tyel. grey) m. sd (yel. whl mas. silt lyel. whl flaky silt

1 grading v.c. sd to silt, crude p;ra. (pale yel. green) lamina. silt

w. p.mti.ceous f. sd lo:1yer (pale yel. green)lamina. silt

w. white silic. discont. seam p..uniceous mas. silt

(pale green. grey) laminated silt including wh. rock

fri1gments

l~!ai~"'fllan'Jff;:'YkJ"til"~;fil to c. sct

grading fran c. sd w. gran. to mas. silt cnrle cross stratified

(pale green. grey) lamina. silt

(red. grey) mas. silt w. calc. no::iule

::i: =-~~r' s~i~t m.-f. sd

r grading fran granular sd to m sd " m. sd w. granule [FOSSIL]

(pale green. grey) mas. silt

partially laminated

~~~y';"'.lm'J"b?t. sMtto silt Iorey ~ .. <;al<;, ~na. silt

~gtl!e!\."'gl'~y11"C [FOSSIL] f9J:teen· grey) mas. silt, tuffaceous in the

·:._- +(grey. whJ gran. c. sd - f. sd ~ (yel. green) pumice. sllt, gran. silt in

.·.~mas. silt ~

(yel. green) f. sd ,puniceous zone

phylitic (pale green. grey) mas. silt

p..uniceous, intercalating f. sd

30 f (grey. wh) v.c.-c. sd, cross lamina

41 (pale green. grey) cross lamina. c. sd

19 (grey wh) cross lamina. c. sd [FOSSIL]

258~~~~ lyUlc?"!'®B!~lmu:l, 25 ~ (grey. wh) calc. silt, laminating 21 (grey. wh) gran. silt

15.5 ·· {grey. wh) silt, calcified in the upper 24 -. -.~. -- (grey. whlcalc. sd to silt laminated

21 {grey. whlcalc. silt, gran.in the upper

170

~ i; ~-~~~·E, -~:..._~, ,·~::~.~ 25 ..... ;·,;:-:4::_.·::s.• ....

1 1;5 c.c"'CC.'.'CCCC.'·

( acasia spin] (green. grey)

mas. granular silt

(grey. wh) calc. mas. gran. sd silt

{pale grey. wh)calc. lamina. silt {pale green grey) gran. silt l (grey. wh) calc. grading sd

f {grey wh)gran. c. sd to silt

l~y.1l!\)~f'i't, fp.Jillially calcified calc. lamina. silt

t, , Hh) stratified c. sd .,..q..-e. • w. granule

r 14 (pale green grey) mas. silt ~~~

2•o I .. " c

: ;; ~·C) (green. grey)

tuffaceous sllt

50

190

- ~-C).:·;;

with calc. ncdde & puru.ce gra~ns

cross lamina. in the top (green. grey) f. !_)eb. gravel

crude stratified

( re:::i. br) c. !_)eb to CCib gravel intercalating 2 sd. layers

matrix suPfX)rted !_)eb. gravel •..,ri th l:oulder

I green. grey) intercalating clast supp:>rted

c. peb. gravel zone

l (green. grey) graded bed fran 1'!'!::¥.'\l'it~l':if !_)eb. gravel to c. sd

t (yel. br - green. grey) 1 alternating bed of f. j;::et; - granule i gravel and v.c. - c. sd

I 20 r-~'?'=9" r v.c. sd

50 (br) c.p. gravel, crude stratified

300

15-25

1111111111 m • 0

I green. grey I mas. !_)eb. gravel matrix supp::lrt layering in the middle

(red. br, in weathered surface)

ITW< r/J 20an

;green. grey) (red. br, in weathered surface)

mas. c. sd w. granule

(whl calc. silt, laminate;j (green. grey, red. br-weat.hered surface)

c. sd w. granule

mas. silt inclu:iing plagioclase grains (whl

71

72 M. TATEISHI

Loc 7

27 .-' • • ~~ · ·: (yel. grey) f.-m. sd, bioturbated f 36 · 20+ ~(yel. grey) mas. silt /28

12 4 .. ~· . ~ .. : "~~ _t trough-type cross, f. sd sdt 30

(pale green. grey) para. lamina. silt ((pale green. grey - grey. whl lamina. silt

32 ~:;~·~=-- l (grey. whl cross stratified, v.c.-f.

300+~ sd, 5 graded beds

-------50 -... . _ .·. {pale greenish greyey white) E=5 alt. lamina. f. sd & mas. silt

(pale green grey) tTas. Hlt

(grey. whl mas. silt,calc. spits (pale green. grey) mas. silt, pseud.gr~vel

(grey~~~~ ~-l~!,l'l·~~c~dP~ (grey. whJ para. lamina. calc. silt

;~~~~ i (grey. whl para. lamina. calc. silt


(grey. wh) para. lamina. silt .., (pale green. grey - grey. whlalt .. nas.s~lt & _

58 ·::.::.L·~;:~·~·:·;: ~~~-: t (yel grey) calcified f. sd (grey. wh) para. lamina. calc. silt ]lamina s~lt ! parallel lamina. bioturbated

45 ~-~:_.;;. ... :.::-,:;'_-. ! (yel. grey) calcified graded sd 92 l (pale green. grey)grade:3 bed fran c. sd to 6 ·.:cc·,;:~:c:-:: : parallel ~~: silt silty sd

2~5 :~n...:.· ·..5- (green. grey)c sd in the base (br.grey) with granule

s, . (y:;r~~=yr~~: silt 41 .s . . ... i (pale green. grey)graded bed fr~ c. sd to

s, r .. (br. grey) graded bed fran c.v:;~ 10 : • .• •. • .• silty sd w.gran~~- silt, with peb ~n the lc::J'oEr

25{ .,. .. (yel. grey - green. grey) ~~ c:n_c:::,lr (pale green. grey)mas. silt 28 ··.:::·""~"~~r (green. grey) mas. silt,para. ~ 85 w. lamina. part including granule 16 .c"·-··········· ·· (yel. grey) alt. f.sd & sdy silt

83 (pale green. grey) 17 ~Zib~~ crude stratified granule gravel 1 ·::~:;::~~~;:~-~~·;,~-;:-1 trough-type cross lamina. f. sd 1- 1 sdy silt, w. pseudo. gravel of 7ilt :::::::;~;:;:.::,::;~.: .-·:::.1 para. lamina. f. sd so grading fran f. sd, para. lamJ.na.

40 (pale green. grey) mas. silt trough-type cross lamina, v. c. sd l " .... ,.,. t. inclu:Ung pumice grains in the lO>Jer stratified

28 ~ (pale green. grey) mas silt (pale green. grey)

2~ ·~i-~~,~~~,:, .. ~~,:-;,~t·E~7;e~ wh- green. grey) granule gravel slumping silt 28 · .... · · (yel. wh) mas. silt, cross lamina 28 0 ~ (pale green. grey) mas silt in the upper

49 20 lyel. grey) lamina. calcareous sd {grey. wh) calc. silt, lebensspuren

intercalating calc. f. sd 20 (yel. wh) mas. silt

55 ;.•.··· •. ·~-:.-..J l(pale green. grey) :~: ~:l~ sd 6 ·· .--:r~.if ... "!<:k~"\ (pale green. grey) mas. silt

2 ~4 laminat!!il,lilt1pale green. grey) 1 • 11 mas. r."M 22 ~~~ grey) mas silt

172 ~-_;-:--,pa§fa~egt~s§d~"m~sd 29. mas. silt-sdy silt

170


I pale green. grey l mas. silt

201~""'E:~t:o~~· (pale br. grey) calcareous silt

75 I pale green. grey l mas. silt

25 ~ : (br. grey) alt. cal. sd & silt

40 (pale green. grey) mas. silt

481 ......!.·~· (pale green. grey) para. lamina. silt 3_1 --:::::::L_-.L=~- calc. spits.

3_21a ~ {yel. wh) mas. ~ilt grading sd

28(~- • (grey. whl calc. silt 21 ,.! (green. grey - grey wh) mas •. silt

14.5 ___ ...,_,, " t (grey. -">l para. lanuna. S>lt

23b:r:l.lpale green. grey) mas. silt ~ ~ • silt

32 ·_.._,_·.;;;·.- -. .-•. _ t (pale green. gre~)m. r. sd ~- - .

!1"!11'1

0"' . 69 0 0

w. calc. nodule & granule {pale green. grey) mas. sdy silt

22. sf--=-· .,·--:1?'--'-1 (pale green. grey) silty sd w. v.c. grains

(pale green. grey) mas. sdy silt 86

65 0 0

w. calc. ncxlule & granule

{yel. wh) ma.s. sdy silt w. calc. nc:xiule & c. sci-sized grains

.. 0.

~i~~~~l:pale green. greyJ mas silt t; (grey. wh) c.-f. sd, double grading

f~t':~ l1fa~, c:rucle stratifi<rl

f'-C"-""=""f"-> f (pale green. grey) gr~~~.f::;;~- 1~:. (pale green. grey) mas. silt

1====!--------- silt

(pale green. grey)silt

Sedimentary Facies of the Miocene in the Samburu Hills, Northern Kenya 73

Plate

.... ('I)

74 M. TATEISHI

Plate II


Plate Ill

76 M. TATEISHI

NAMURUNGULE FORMATION

The Namurungule Formation is distributed widely in the west of the Samburu Hills (Makinouchi

et al., 1984; Sawada et al., 1987). It is composed mainly of the clastic sediments with intercalated

mud flow deposits and tuff layer (Fig. 3 ~ Locs. 5, 6, & 7). The lower mud flow deposit, observed

along the Namurungule and Nakaporatelado Rivers (Makinouchi et al., 1984), grades into

cobbleto pebble-sized gravel southward (Fig. 3 - Locs. 5, 6, & 7) (Plate 1-4). Thick-bedded tuff

layer overlies on the gravel layer correlated to the lower mud flow deposit (Plate 11-4). The

sediments under this gravel layer consists of the reddish brown pebble-sized gravel and ill-sorted

Explanation of Plate I

Fig. 1 Columnar joint of basaltic lava flow and overlying calcified lapilli tuff observed in the

uppermost part of the Aka Aiteputh Formation along the Nakaporatelado River (Loc. 5).

Fig. 2 White layers in the upper are chert. Horizon is more or less upper than one of No. I.

Fig. 3 Crude cross-laminated pebble-sized breccia in the uppermost of the Aka Aiteputh

Formation along the Nakaporatelado River (Loc. 5). It was called the weathered basalt

sediment by Makinouchi et al. (1984)

Fig. 4 Cobble gravel including boulder correlated with the lower mud flow deposit, in the lowest

part of the Namurungule Formation along the Nakaporatelado River (Loc. 5).

Explanation of Plate II

Middle horizon of the Namurungule Formation

Fig. 1 Alternation bed of dominant silt and sand along the Nakaporatelado River at Loc. 5.

Upper mud flow deposit containing large blocks is observed in the upper left.

Fig. 2 Alternating bed of dominant silt and sand at Loc. 7.

Fig. 3 Laminated silt above the horizon occurred Samburu Hominoid at Loc. 6 (SH 22).

Fig. 4 Massive tuff layer containg plagioclase phenocrysts and pumice grains at Loc. 7.

Explanation of Plate III

Upper horizon of the Namurungule Formation at Loc. 5

Fig. 1 Alternating bed of dominant sand and silt. Sands shows ripple cross lamination.

Fig. 2 Linguoid ripple mark observed on the upper bedding plane of sand.

Fig. 3 Alternating bed of dominant sand and silt. Lower surface of sand are erosive. Silt is very

illsorted, and contains pebble- to granule-sized basalt breccia.

Fig. 4 Cross laminated very coarse to granular sand.


sand. The sediments between two mud flow deposits mainly consist of purple greenish grey or

yellow green alternating bed of dominant silt and sand (Plate 11-1 & 2). Characteristically they are

calcified and contain small calcified spits, probably being trace fossils. The silts are generally

massive, but sometimes shows fine lamination (Plate 11-3) and slumping structure. The interbed

ded sands shows frequently cross lamination and are generally graded beds. The upper mud flow

deposit is very thick and contains the large blocks up to 4 meters in diameter of alternating bed of

sand and silt, and volcanic rocks (Plate 11-1). The sediments above the mud flow deposit consist

of alternating bed of dominant sand to gravel and silt (Fig. 3 - Loc. 5). Sand and gravel show

graded and cross laminated bedding (Plate III-4). Their basal planes are commonly erosive on

lower sediments (Plate III-3). Thin sand layers shows frequently ripple cross lamination (Plate

III-I and 2).

The sedimentary environment of the N amurungule Formation became firstly to the lake from the

fluvial ones at the depositional stage of the uppermost part of the Aka Aiteputh Formation to the

lowermost part of the Namurungule Formation. After that, it was turned again into the fluvial

ones at the depositional stage of sediments above of the upper mud flow deposit. The volcanic

activity around the Samburu Hills became weakly at that time, except of mud flows and tuff.

ACKNOWLEDGEMENTS I would like to express thanks to the Japanese Ministry of Education,

supported our research with its Grant-in Aid for Overseas Scientific Survey. Many thanks are due

to Profs. H. Ishida, Chief of the Japan - Kenya Expedition, of Osaka University, and other

members of the 1984 expedition for their encouragement and support.

REFERENCES

Baker, B. H. (1963) Geology of the Baragoi Area. Report No. 53, Geol. Surv., Kenya.

Makinouch, T., Koyaguchi, T., Matsuda, T., Mitsushio, H. and Ishida, S. (1984) Geology of the

Nachola Area and the Samburu Hills, West of Baragoi, Northern Kenya. African Study

Monographs, Suppl. Issue, no. 2, 15-44.

Sawada, Y., Tateishi, M. and Ishida, S. (1987) Geology of the Neogene System in and around

Samburu Hills, Northern Kenya. African Study Monographs, Suppl. Issue, no. 5, 7-26.

Documents

SEDIMENTARY FACIES OF THE MIOCENE IN THE … Sup.5... · African Study Monographs, Supplementary Issue 5: 59-77, March 1987 SEDIMENTARY FACIES OF THE MIOCENE IN THE SAMBURU HILLS,