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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
Sedimentary Facies of the Miocene in the Samburu Hills, Northern Kenya
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
Sedimentary Facies of the Miocene in the Samburu Hills, Northern Kenya
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
Sedimentary Facies of the Miocene in the Samburu Hills, Northern Kenya
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
(pale green. grey) mas. 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
(pale green. grey) mas. silt
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
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.
Sedimentary Facies of the Miocene in the Samburu Hills, Northern Kenya 77
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.
Recommended