east african mid-holocene wet–dry transition recorded in laketurkana, northern kenya rift

Author's personal copy

East African mid-Holocene wet–dry transition recorded in palaeo-shorelines of LakeTurkana, northern Kenya Rift

Yannick Garcin a,⁎, Daniel Melnick a, Manfred R. Strecker a, Daniel Olago b, Jean-Jacques Tiercelin c

a Universität Potsdam, Institut für Erd- und Umweltwissenschaften and DFG Leibniz Center for Surface Process and Climate Studies, 14476 Potsdam, Germanyb University of Nairobi, Department of Geology, PO Box 30197-00100, Nairobi, Kenyac UMR CNRS 6118 Géosciences Rennes, Université de Rennes 1, Rennes, France

a b s t r a c ta r t i c l e i n f o

Article history:Accepted 2 March 2012Available online 1 April 2012

Editor: P. DeMenocal

Keywords:East African Rift SystemLake TurkanaPalaeo-shorelinesAfrican Humid PeriodHoloceneTectonic deformation

The ‘wet’ early to mid-Holocene of tropical Africa, with its enhanced monsoon, ended with an abrupt shift to-ward drier conditions and was ultimately replaced by a drier climate that has persisted until the present day.The forcing mechanisms, the timing, and the spatial extent of this major climatic transition are not well un-derstood and remain the subject of ongoing research. We have used a detailed palaeo-shoreline record fromLake Turkana (Kenya) to decipher and characterise this marked climatic transition in East Africa. We presenta high-precision survey of well-preserved palaeo-shorelines, new radiocarbon ages from shoreline deposits,and oxygen-isotope measurements on freshwater mollusk shells to elucidate the Holocene moisture historyfrom former lake water-levels in this climatically sensitive region. In combination with previously publisheddata our study shows that during the early Holocene the water-level in Lake Turkana was high and the lakeoverflowed temporarily into the White Nile drainage system. During the mid-Holocene (~5270±300 cal. yrBP), however, the lake water-level fell by ~50 m, coeval with major episodes of aridity on the African conti-nent. A comparison between palaeo-hydrological and archaeological data from the Turkana Basin suggeststhat the mid-Holocene climatic transition was associated with fundamental changes in prehistoric cultures,highlighting the significance of natural climate variability and associated periods of protracted drought asmajor environmental stress factors affecting human occupation in the East African Rift System.

© 2012 Elsevier B.V. All rights reserved.

1. Introduction

Deciphering the long-term climate history and accurately identi-fying the mechanisms underlying variations in hydrologic budgets isan important task in light of ongoing global change, water stress,and the associated environmental and socioeconomic impacts in theAfrican tropics (Boko et al., 2007). In this context climatic variability,climatic extremes, and the transitions between episodes with differ-ent environmental conditions, have become the focus of numerousinvestigations in tropical Africa (e.g., Shanahan et al., 2009; Tierneyet al., 2008).

A period of particular interest in the climatic history of Africa is theAfrican Humid Period or AHP (cf. deMenocal et al., 2000; Ritchie et al.,1985). The AHP occurred approximately between ~12,000 and ~5000calendar years before present (cal. yr BP) and resulted in a northwardexpansion of vegetation zones (e.g., Hoelzmann et al., 1998). Exten-sive parts of tropical Africa subsequently experienced pronouncedand rapid hydrologic changes associated with the termination of theAHP during the mid-Holocene, about 5000 years ago (e.g.,deMenocal et al., 2000). This transition toward drier conditions

fundamentally impacted ecosystems across northern Africa, prompt-ing a return to arid and semiarid vegetation in the Sahara and theSahel regions (Jolly et al., 1998). These environmental changes arealso believed to have led to important demographic shifts (Brooks,2006; Kuper and Kröpelin, 2006).

The origin of, and underlying mechanistic principles for, the AHPtermination are not yet fully understood and remain the subject ofongoing investigations. This episode, which may have lasted a fewcenturies, is considered to have been too rapid to be solely drivenby a linear response to gradual insolation changes (e.g., Claussen etal., 1999; Cole et al., 2009; deMenocal et al., 2000). On the otherhand, the existence of an abrupt and spatially synchronous AHP ter-mination has recently been called into question (e.g., Chase et al.,2010; Kröpelin et al., 2008; Marshall et al., 2011).

Here, we present a detailed study of multiple abandoned Holoceneshorelines from the Lake Turkana basin in the northern Kenya Rift ofthe East African Rift System (EARS, Fig. 1). These palaeo-shorelinesprovide a record of the East African moisture history that helps inunravelling the characteristics and environmental impacts of theAHP termination in a region that is located in the immediate vicinityof the equator. Preliminary studies of these palaeo-shorelines provid-ed an unprecedented insight into the environmental history of theHolocene (e.g., Butzer et al., 1972; Owen et al., 1982). However, the

Earth and Planetary Science Letters 331-332 (2012) 322–334

⁎ Corresponding author. Tel.: +49 331 977 5837; fax: +49 331 977 5700.E-mail address: [email protected] (Y. Garcin).

0012-821X/$ – see front matter © 2012 Elsevier B.V. All rights reserved.doi:10.1016/j.epsl.2012.03.016

Contents lists available at SciVerse ScienceDirect

Earth and Planetary Science Letters

j ourna l homepage: www.e lsev ie r .com/ locate /eps l

Juan

Cuadro de texto

http://www.researchgate.net/publication/256695135_East_African_mid-Holocene_wet-dry_transition_recorded_in_palaeo-shorelines_of_Lake_Turkana_northern_Kenya_Rift._Earth_Planet_Sc_Lett_331-332322-334


exact nature and timing of some inferred environmental changes de-rived from lake water-level fluctuations were subsequently found tobe equivocal and/or irreproducible (cf. Barton and Torgersen, 1988;Cerling, 1986; Halfman et al., 1992; Ricketts and Johnson, 1996). Inour study we have focused primarily on the largely unexplored south-ernmost margin of the Turkana Basin (Fig. 1B), where steep slopeshave helped preserve a unique staircase morphology of palaeo-shore-lines, between 0 and 80 m above the present-day lake water-level. Inorder to reconstruct lake water-level fluctuations in the Turkana

Basin and use them as indicators of past variations in the moisture re-gime, we mapped shoreline elevations with a high-precision differen-tial global positioning system (dGPS) and measured oxygen-isotoperatios of in situ fossil mollusk shells collected from shoreline deposits.By combining 21 new 14C ages obtained from these shells with otherpublished ages we have constrained the timing of past lake water-level changes and provided insights into the environmental historyof Lake Turkana, particularly during the mid-Holocene. We alsoused the abundantly available archaeological data from the Turkana

A B

Fig. 1. (A) Map of the Turkana Basin and adjacent basins (SRTM topography). Also shown are rivers (thin blue lines), catchment boundaries (thick and thin black lines), the maximumextent of Lake Turkana during the Holocene (MHS, thick blue line) approximated using a present-day surface elevation of 460 m, and the various overflow sills in the area (arrows linkedto white circles). The overflows were active during the early to mid-Holocene when the Turkana Basin received inflow from the Bogoria, Baringo, and Suguta basins to the south and theAbaya, Chamo, and Chew Bahir basins to the east; at that time Lake Turkana overflowed into the Nile Basin. Bathymetric map of Lake Turkana (below 360 m) from Johnson et al. (1987).Inset is a structural map of the EARS. (B) Location map for the radiocarbon sample sites and dGPS survey sites. Also shown are the Holocene shorelines, the approximate position of themaximum highstand shoreline, and the main recent (late Quaternary) faults; all were mapped using field observations, SPOT satellite imagery, and SRTM data, together with previouslypublished data (e.g., Baker et al., 1972; Dunkelman et al., 1989; Johnson et al., 1987; Morley et al., 1992).

323Y. Garcin et al. / Earth and Planetary Science Letters 331-332 (2012) 322–334


Basin to address the possible influence of the AHP termination on thecultural development of prehistoric populations.

2. General characteristics of the Turkana Basin

The fault-bounded Turkana Basin constitutes an area of~148,000 km2, while the lake (formerly Lake Rudolf) has a surfacearea of ~7000 km2. The Turkana Basin is internally drained and ispart of a low-lying area in the zone between the Kenya Rift to thesouth and the Ethiopian Rift to the north (Fig. 1). The Lake Turkanaarea comprises a series of halfgrabens with alternating polarity(Morley et al., 1992). The basin accommodates fluvio-lacustrine andvolcanoclastic deposits up to 7 km thick, accumulated between theLate Oligocene-Plio-Pleistocene and the present (Dunkelman et al.,1989; Morley et al., 1992). The faulted and tilted blocks are associatedwith several volcanic centres rising above the modern lake surface,forming three small islands (the North, Central, and South islands)(Brown and Carmichael, 1971; Karson and Curtis, 1994).

South Island, which is ~12 km long and ~5 km wide, forms themain focus of this study. Several distinct N–S striking faults and mag-matic fissures (Karson and Curtis, 1994) traverse the entire island. Ac-tive normal faulting has been documented in the recent sedimentssurrounding the island (Johnson et al., 1987). Terraces, beach ridges,and wave-cut platforms are particularly well developed in the west-ern part of South Island (Karson and Curtis, 1994).

Lake Turkana is elongated in a N–S direction, following the rift axis(Fig. 1). It is ~250 km long and ~30 km wide. The maximum lakedepth is 120 m, with an average depth of 35 m (Johnson et al.,1987). Lake Turkana is the most alkaline permanent lake in East Afri-ca, with an alkalinity of 20–23 meq/l (Cerling, 1979). The climate inthe southern and central part of the Turkana Basin, including themain depression accommodating the lake, is particularly arid, withthe mean annual rainfall reaching only ~200 mm/yr and a mean po-tential evaporation of ~3000 mm/yr. The mean annual minimumand maximum air temperatures are 23.6 and 34 °C, respectively

(East African Meteorological Department, 1975; Ferguson andHarbott, 1982). In contrast, the northern part of the Turkana Basin,which transitions into the Ethiopian Highlands, is significantly coolerand wetter and receives more than 1500 mm/yr of monsoonal rainfall(Halfman and Johnson, 1988). The Omo River (Fig. 1), which flowsinto Lake Turkana from the Ethiopian Highlands, consequently sup-plies 80–90% of the freshwater inflow and thus exerts a primary con-trol on lake water-level fluctuations today (Yuretich and Cerling,1983). The Kerio and Turkwel rivers to the south account for theremaining inflow to the lake, derived from westerly catchments.

3. Materials and methods

3.1. Kinematic dGPS survey of palaeo-shorelines

We surveyed palaeo-shorelines from the southernmost part of theTurkana Basin (Figs. 1–4) following the same approach as used in ourprevious investigations in the nearby Suguta Valley (Garcin et al.,2009). We carried out high-precision topographic surveys of theprominent palaeo-shorelines from this remote area using a dGPS(Leica GPS 1200) and helicopter support. We focused on the palaeo-shorelines on South Island as this area contains a well-preserved se-quence of beach ridges (Fig. 4) previously identified on SPOT satelliteimages, and surveyed their elevations along a down-slope traverse,perpendicular to the ridges (Fig. 4B, D). We also measured elevationprofiles by moving parallel to the shorelines (Fig. 4B). KinematicGPS data were collected continuously at a 1 Hz observation rate.The base-rover distance ranged from 47 to 75 km. The survey datawas post-processed using Leica GeoOffice (V6.0) software, whichonly provided coded solutions. The averaged height quality, whichcorresponds to the standard deviation of the height element of our21,000 post-processed field-measurements, was 22.1 cm. Note thatthe analytical errors of this measurement method are small comparedto the vertical range of surveyed shoreline elevations (~77 m forSouth Island, Fig. 4E), and to the natural variability in the elevations

South Island

Lake Turkana

Fault Faul

t

MHS

Lake Turkana: 360 m asl

440 m asl

Regressiveshorelines

N S

W E

Abili Agituk

Abili Agituk

Fig. 2. Aerial views of the maximum highstand shoreline (MHS: white arrows) cut into the Abili Agituk volcano (southernmost tip of Lake Turkana). Top photograph: view to theeast. Bottom photograph: view to the north, with South Island in the background. Several normal faults offset the MHS.

324 Y. Garcin et al. / Earth and Planetary Science Letters 331-332 (2012) 322–334


of lacustrine geomorphic markers (~0.3–1.5 m). In order to match ourmeasurements with the Shuttle Radar Topography Mission 3 arc sec-ond reference frame (SRTM V4; Farr et al., 2007) we added the com-puted height separations (EGM96 geoid–WGS84 ellipsoid) to thedGPS elevations.

Since differential elevations of coeval palaeo-shorelines may pro-vide clues on deformation patterns in the tectonically active settingsof the EARS (e.g., Stein et al., 1991), we also surveyed the elevationof the highest and most prominent shoreline at several sites (includ-ing South Island) along the southern edge of the Turkana Basin(Figs. 2 and 3). Detailed results from this complementary survey arepresented in a companion paper focusing on Holocene extensionalprocesses and hydro-isostasy in the Turkana and Suguta basins(Melnick et al., this volume).

In addition to the dGPS survey of the southernmost margin of LakeTurkana, we also surveyed palaeo-shoreline deposits from its westernmargin – a low-relief area – using a handheld GPS (Fig. 1B). As the el-evations obtained from this secondary survey were not precise weassigned an elevation derived from the SRTM dataset to each samplecollected.

3.2. Age control

In order to estimate the possible radiocarbon-age reservoir of LakeTurkana we obtained two accelerator mass spectrometry (AMS) 14C

dates on modern Melanoides tuberculata shells provided by Drs. H.Scholz and M. Glaubrecht from the Museum für Naturkunde at Hum-boldt University, Berlin. Modern samples (including a live snail) werecollected on August 4, 2006, along the northern shore of the KoobiFora spit (Fig. 1B).

Nine AMS 14C dates were obtained from fossil carbonate shells offreshwater organisms collected on South Island: these were mostlysnails but also included an oyster and a bivalve (Table 1). The shellssampled were from the most distinctive beach ridges (Fig. 4D). Toavoid any sampling bias such as that introduced by the presenceof reworked shells derived from higher-elevation shorelines remo-bilized during sheetwash erosion/deposition events, the shellswere collected from pits excavated to ~40 cm depth in the beachgravels (Fig. 4F). In nearly all of the sites sampled a distinct layerof rounded gravels (~10–20 cm thick), identical to deposits in thepresent-day lakeshore environment and intercalated with pyroclas-tic-fallout deposits, testified to the existence of a former lake shore-line. A snail and an encrusting oyster were also collected from smallcavities (10–20 cm deep) on the surface of a bedrock abrasion plat-form associated with the highest palaeo-shoreline elevation(Fig. 4B).

A further 12 ‘conventional’ 14C dates were obtained from oystersand snails, as well as one from a stromatolite, collected along thewestern margin of Lake Turkana including, from south to north, theLothagam, Eliye Springs, Kataboi, and Nachukui areas (Fig. 1B).

C

D

A

B

Fig. 3. Differential elevations for the maximum highstand shoreline (MHS) across the southern Turkana Basin. (A) SRTM shaded-relief digital topography of the surveyed area. Alsoshown is the 460 m contour (dark blue line) corresponding to the present-day maximum elevation of the overflow sill. Red dots are the MHS sites surveyed with dGPS (cf. Melnicket al., this volume). (B) Same area as shown in A: map of the recent (late Quaternary) active faults. Offshore faults were extrapolated from Dunkelman et al. (1989) and Johnsonet al. (1987). (C) W–E swath profile. Green line indicates mean elevation values from the swath profile shown in A; grey lines with area shaded between are minimum andmaximum elevation values. Also shown are the projected main faults (cf. map B) as well as the measured elevations of the MHS sites (red dots). Red lines show interpreteddeformed MHS. (D) Schematic structural cross-section (W–E) of the Turkana Basin between the overflow sill area and the eastern half of the rift axis area, showing the deformationpattern affecting the elevation of the MHS. Approximate fault locations delineating horst and graben geometries are fromMorley et al. (1992). Note the strong vertical exaggeration(×800).



These lacustrine carbonate shells were buried in coarse deposits suchas sands, gravels, and pebbles, characteristic of high-energy shorelineto nearshore environments.

Since the sampled fossil shells were composed of aragonite, whichis a metastable mineral, they were investigated by X-ray diffraction toensure that recrystallisation to diagenetic calcite had not occurred:the shells used in our analysis were all pure aragonite. AMS ageswere measured at the Leibniz Laboratory for Radiometric Datingand Isotope Research in Kiel (Germany), while ‘conventional’ ageswere determined by liquid scintillation at the LODYC in Paris (France)(Table 1). Specimens with no dissolution or local abrasion were se-lected for dating. The specimens were first cleaned using 30% H2O2

in an ultrasonic bath, rinsed with distilled water, and dried, in orderto remove adhering dust and detrital carbonate as well as any organicsurface coating. This was followed by a second cleaning step using15% H2O2 in an ultrasonic bath. Dates were calibrated using the

OxCal 4.1 programme (Bronk Ramsey, 2001) with the IntCal09curve (Reimer et al., 2009).

3.3. Stable isotope analysis (δ18O and δ13C) of mollusk shells

A small part (150–500 μg) of each shell used for AMS radiocarbondating was further processed for stable isotope analysis. The sampleswere cleaned with deionised water, dried at 40 °C, and then crushed.Oxygen and carbon isotope ratios were measured with a FinniganMAT 251 mass spectrometer at the Leibniz Laboratory of Kiel Univer-sity. The system is coupled online with a Carbo-Kiel Device (Type I).Samples were reacted by individual acid addition (99% H3PO4 at73 °C). Standard external error was better than ±0.07‰ and±0.05‰ for δ18O and δ13C, respectively, according to the perfor-mance of international and laboratory internal carbonate standardmaterials. Results were calibrated against the carbonate isotope

A B

C D

E F G

Fig. 4. South Island survey area. (A) Field view to the south of the maximum highstand shoreline (MHS), which is marked by a distinctive wave-cut notch. (B) SPOT satellite imageof the area surveyed in A. Also shown are dGPS tracks, sampling sites, faults, and the position of the MHS (yellow line). (C) Oblique aerial view to the southwest of one of the mainsurvey areas, showing prominent fossil beach ridges. (D) SPOT satellite image of the area surveyed in C. (E) Composite topographic profile of the surveyed shorelines with projectedposition of the dated samples. (F) Representative profile of sample pit in fossil beach ridges. (G) Simplified map of South Island.



standard NBS 19 and are reported on the Vienna PeeDee Belemnite(VPDB) scale.

4. Results: the palaeo-shoreline record of Lake Turkana

Series of palaeo-shorelines are ubiquitous on the flanks of the Tur-kana Basin (Fig. 1B). They form a staircase morphology of successiveformer lake water-levels, well exposed over a vertical range of~100 m, from the present-day lake water-level at ~360 m to an eleva-tion of ~455 m.

4.1. Definition of the maximum highstand shoreline

Observations from our field survey, complemented by the analysisof SPOT satellite images and SRTM data, indicated that the highestshoreline is a continuous geomorphic marker spanning the entirelake basin. Importantly, this distinct shoreline is always much widerand better developed than the lower-elevation shorelines (Fig. 2).We related this shoreline to the maximum highstand shoreline(MHS) of Lake Turkana. The MHS either forms wave-cut notchessculpted into steep-sided cinder cones (Fig. 2), or marked, gently in-clined wave-cut platforms. At the northern margin of Lake Turkanathe MHS is characterised by prominent beach ridges up to 50 kmlong and 700 m wide (cf. Harvey and Grove, 1982) (Fig. 1B). Theridges there occur up to about 450 or 455 m (SRTM data), only afew metres below the present-day elevation of the overflow sill,50 km to the southwest. This overflow sill, which controlled lakehighstands in the past, has an elevation between ~457 and ~460 m(SRTM data); it is an integral part of the barrier that separates theTurkana and Nile basins (cf. Brown and Fuller, 2008). The virtuallyidentical elevations of the sill and the MHS along the northern marginof the lake suggest that the MHS developed when Lake Turkana was

overflowing (cf. Butzer et al., 1972; Harvey and Grove, 1982; Owenet al., 1982), with this overflow resulting in the stabilisation of thelake's water-level over a protracted period of time.

4.2. Influence of tectonic deformation on shoreline elevation

Our detailed dGPS survey of the MHS in the southernmost part ofthe Turkana Basin (Melnick et al., this volume), which included SouthIsland as well as seven additional sites distributed both on the riftmargins and along the rift axis (Fig. 3), reveals variations of up to~9 m in the absolute elevation of the MHS. The measured elevationsranged from ~10 to ~20 m below the present-day elevation of theoverflow sill (Fig. 3C). The difference in elevation between these geo-morphic features, which would originally have been located at thesame elevation, is a result of subsequent tectonic deformation of thelake basin (Melnick et al., this volume). Field observations and map-ping using satellite images and digital elevation models show furtherevidence for recent tectonic deformation in the area, such as the pres-ence of numerous fault scarps (Fig. 3B) affecting Holocene lacustrinesediments, alluvial fans, shorelines, and river channels. Offshore andonshore seismic reflection profiles in the area also indicate ubiquitousrecent normal faulting (Dunkelman et al., 1989; Johnson et al., 1987;Vétel et al., 2004).

The Turkana Basin has thus remained tectonically active up to thepresent, whichmay be the most viable explanation for the basin-widedisparities in surveyed elevations of coeval palaeo-shorelines.According to the regional structural model developed by Morley etal. (1992), extension has led to subsidence along the inner rift and si-multaneous flexural uplift of the footwall (Fig. 3D). Such a model rec-onciles inconsistencies in the elevation of the overflow sill withrespect to the MHS elsewhere.

Table 1Radiocarbon ages of lacustrine carbonates from Lake Turkana.

Sample ID Sitea Elevation(m asl)

Corrected elevation(m asl)b

Lat.(°N)

Lon.(°E)

Materialc 14C age(yr BP)

Cal. age(cal. yr BP)d

Cal. age range BP(95.4%)d

Cal. age range BP(99.7%)d

KIA 36856e SI 431.1f ~454 2.6611 36.5879 M 8180±45 9085 9015/9270 8998/9399KIA 36857e SI 431.1f ~459 2.6611 36.5879 E 9740±50 11,190 10,884/11,247 10,787/11,275KIA 36858e SI 425.8f ~438 2.6272 36.572 M 4645±35 5420 5306/5469 5288/5580KIA 36859e SI 415.6f ~427 2.6261 36.5712 M 4330±30 4865 4843/4969 4831/5039KIA 36860e SI 406f ~418 2.6255 36.5716 M 4680±35 5385 5316/5576 5310/5583KIA 36861e SI 398.1f ~410 2.6247 36.5715 M 4370±35 4925 4855/5040 4838/5265KIA 36862e SI 392.6f ~405 2.6237 36.5713 B 4910±35 5625 5590/5715 5582/5747KIA 36864e SI 385f ~414 2.6221 36.5708 M 10,025±55 11,500 11,275/11,764 11,249/11,966KIA 36865e SI 381.3f ~393 2.6192 36.5711 M 4695±35 5375 5319/5579 5313/5584KIA 38214e KF 363g – 3.9516 36.187 mM 111.2%Mh AD 1996 – –

KIA 38215e KF 363g – 3.9516 36.187 mM 109.1%Mh AD 2001 – –

Pa 2226i LO 440g – 2.9316 36.0627 M 9795±100 11,215 10,788/11,606 10,716/11,760Pa 2227i ES 422g – 3.2185 36.0032 B 6285±50 7255 7024/7318 7000/7418Pa 2224i ES 422g – 3.2185 36.0032 S 6630±45 7550 7438/7576 7426/7611Pa 2223i KA 444g – 3.7477 35.7848 B 9515±80 10,765 10,585/11,125 10,509/11,195TOP 02/11i KA 434g – 3.8450 35.7720 O 5810±70 6650 6446/6780 6399/6886LAPS 02/14i NK 433g – 4.2838 35.8629 O 5225±80 5950 5754/6263 5725/6284Pa 2230i NK 439g – 4.1183 35.8508 O 4810±30 5500 5474/5601 5333/5645Pa 2231i NK 439g – 4.1183 35.8508 St 4790±30 5500 5470/5594 5330/5605Pa 2225i NK 443g – 4.1513 35.8521 O 5320±35 6070 5992/6208 5941/6276Pa 2228i NK 443g – 4.1513 35.8521 M 4965±40 5710 5601/5875 5592/5893Pa 2229i NK 429g – 4.0864 35.8382 O 5260±40 6000 5927/6180 5911/6204Pa 2232i NK 429g – 4.0864 35.8382 O 5255±30 5995 5929/6178 5920/6183

a SI = South Island; KF = Koobi Fora; LO = Lothagam; ES = Eliye Springs; KA = Kataboi; NK = Nachukui.b Elevations have been corrected for local tectonic subsidence (see main text).c M = Melanoides tuberculata; E = Etheria elliptica; B = bivalve; mM = modern Melanoides tuberculata; O = oyster; S = snail; St = stromatolite.d Calibrated radiocarbon ages given before 1950, except for the modern samples given in year Anno Domini (AD); 14C calibration method: programme OxCal 4.1 (Bronk Ramsey,2001) with the IntCal09 curve (Reimer et al., 2009).e AMS ages.f Measured using dGPS.g Estimated from SRTM V4 data.h Expressed as % modern (%M).i ‘Conventional’ ages.



4.3. Reliability of the radiocarbon ages on lacustrine carbonates

Charcoal and other organic material is generally not preserved inthe palaeo-shorelines of Lake Turkana and radiocarbon dating ofthese geomorphic features relies on lacustrine carbonates. In orderto assess the reliability of the radiocarbon ages obtained from thesedeposits we dated two modern mollusk shells collected from the pre-sent-day lake shore and estimated the potential radiocarbon agereservoir.

The two samples contained 14C originating from post-secondWorld War atomic-bomb tests and thus carbon younger than yearAD 1954 (Table 1). The 14C concentration of 111.2% modern carbon(%M) measured in KIA 38214 (live snail in AD 2006) correspondedto that in the atmosphere in AD 1996, while the 14C concentrationof 109.1%Mmeasured in KIA 38215 corresponded to that in the atmo-sphere in AD 2001 (Levin and Kromer, 2004). The 14C concentrationin the living snail does not correspond exactly to that of the atmo-sphere when it was collected (~10-year difference). As Melanoideshas a short life span, ranging from a few months to a few years(Leng et al., 1999), the slightly higher 14C concentrations in the livingsnail may indicate that this organism was feeding on older organicmatter (i.e., with a higher 14C concentration).

Overall, our new data unambiguously document that the radiocar-bon age reservoir in present-day Lake Turkana is negligible. These ob-servations are consistent with radiocarbon dating of sediment-coresobtained from the southern part of the lake. Indeed, Halfman et al.(1994) found that coarse Holocene ostracod shells, which wereformed in situ, probably provide a true age for the deep sedimentsof Lake Turkana. On the basis of our own observations we have as-sumed that all the dated fossil shells collected on palaeo-shorelineshad not been affected by the uptake of old carbon, although a radio-carbon age reservoir may have existed in the past.

4.4. South Island: a detailed record of Holocene shorelines

The palaeo-shorelines on South Island are well developed geo-morphic features (Fig. 4). They form a set of 10 major beach ridges(up to 60 m wide and 80 cm high), each containing additional smal-ler-scale and lower-amplitude ridges (Fig. 4C–E). The palaeo-shore-line elevations range from 360 m (the present-day lake shoreline)to 437.5 m (Fig. 4E). The highest palaeo-shoreline, which correspondsto the MHS, forms a distinctive wave-cut notch sculpted into volcanicbedrock (Fig. 4A). This shoreline can be confidently traced around theentire island, although on the eastern side it is covered by extensivelava flows.

In order to account for the effect of tectonic subsidence on SouthIsland (see Section 4.2), which has affected the palaeo-shoreline ele-vations, we translated upward the elevation of the oldest dated sam-ple associated with the formation of the MHS (sample KIA36857=11,190 cal. yr BP) to the present-day elevation of the over-flow sill (~459 m). We obtained a subsidence rate of ~2.5 mm/yr(Fig. 5A) and, assuming a steady subsidence rate during the Holocene,we then applied this rate to the other dated shorelines to correct theirelevations (Table 1 and Fig. 5B). The shoreline elevations at South Is-land, corrected for tectonic subsidence, are systematically reportedbelow.

The oldest shoreline deposits on South Island (11,500 cal. yr BP)occur at an elevation of ~414 m (Fig. 5B). Although the subsequentfluctuating lake water-levels (see below) and the associated waveerosional processes should have obliterated this relatively low-eleva-tion shoreline, its particular location at the edge of a closed depres-sion (cf. sample KIA 36864 in Fig. 4D), isolated from the mainpalaeo-lake, may have contributed to its preservation. The highestand most distinctive shoreline (the MHS) developed between11,190 and 9085 cal. yr BP. The absence of data between ~9000 and~6000 cal. yr BP precludes any inference concerning the palaeo-lake

water-level during this period of time. Subsequently, within a shorttime interval between 5625 and 4865 cal. yr BP, we identified asuite of distinct shorelines covering a vertical elevation range of~50 m (from ~438 to ~393 m). These shorelines record the lastmajor lake regression. Shoreline radiocarbon ages associated withthis regression scatter significantly and include several age reversals(Fig. 5B), which may suggest reworking by wave-action of oldershells from former shorelines in a high-energy lakeshore environ-ment (cf. McGlue et al., 2010). However, the δ18O values from thesedated shells argue against substantial reworking (Table 2 andFig. 6). The δ18O values of lacustrine carbonates are generally con-trolled by changes in lake-water isotope composition, which maysometimes be related to lake water-level fluctuations, especially for

390

400

410

420

430

440

450

460

KIA 36864

KIA 36862

KIA 36865

KIA 36860

KIA 36858

KIA 36861

KIA 36859

KIA 36857

KIA 36856

Overflow sill

4000 6000 8000 10,000 12,000Age (cal. yr BP)

4000 6000 8000 10,000 12,000

Age (cal. yr BP)

Cor

rect

ed e

leva

tion

(m a

sl)

Sample

?

10

20

30

Subsidence rate: ~2.5 mm/yr

Sub

side

nce

(m)

B

A

Fig. 5. Dated palaeo-shorelines from South Island. (A) Estimated local tectonic subsi-dence rate on South Island. To correct for the effect of tectonic subsidence affectingpalaeo-shoreline elevations, the oldest sample related to the MHS (i.e., KIA 36857:white star) was translated upward to the level of the overflow sill. The obtained subsi-dence rate (~2.5 mm/yr) was assumed to have been constant and was used to correctthe elevation of the other samples. (B) Radiocarbon ages of shorelines shown withprobability curves and with corrected elevations. Age error bars represent the 99% con-fidence interval. Solid green line represents inferred main lake water-levels. Dashedgreen line represents uncertain lake water-levels.



closed-lake basins (e.g., Leng et al., 2006; Ricketts and Johnson, 1996).The observed changes in δ18O values from freshwater shells, whichranged from −0.56 to +3.85‰ (including the modern shell data),follow the changes in lake water-level reasonably well (Fig. 6), withlighter δ18O values associated with the higher water-levels (largerlake volumes), and heavier δ18O values associated with the lowerwater-levels (smaller lake volumes). Moreover, since the largest ac-cumulations of shells on South Island were found to be closely associat-edwith theMHS, older shells with lighter δ18O values should be presentin the lower elevation shorelines if significant reworking had occurred.Fromour observationswe estimate a ~50 m fall in the lake'swater-levelat ~5270±300 cal. yr BP, which probably lasted for a few centuries.Finally, since the beach ridges on South Island are in pristine conditionthe lake water-level must have remained lower than ~380 m after~4800 cal. yr BP, since subsequent lake transgressions would have sig-nificantly overprinted or obliterated the earlier ridges.

4.5. Synthesis of Holocene lake water-level fluctuations in the TurkanaBasin

4.5.1. Age control and elevation uncertainties across the Turkana BasinBy combining our new palaeo-shoreline ages from South Island

with 12 ages from the western margin of Lake Turkana (Table 1)and previously published ages from the greater Turkana Basin, weare able to re-evaluate and improve the lake water-level curve at abasin scale over the Holocene period. A total of 102 radiocarbonages have been obtained for this lake basin (Fig. 7) during a variety

of palaeo-environmental and archaeological investigations (e.g.,Hildebrand et al., 2011; Owen et al., 1982; Robbins, 1972), whichare referenced in the Supplementary materials.

In order to relate those previously reported ages from the TurkanaBasin to our new ages we re-calculated several of the published ages(cf. Brown and Fuller, 2008). This was necessary because Butzer et al.(1969) had assumed that the CO2 in Lake Turkana was not completelyequilibrated with the atmosphere, leading to erroneous, older ages.Butzer and Thurber (1969), Butzer et al. (1969, 1972), and Owen etal. (1982) consequently applied an arbitrary correction of−400 years to all of their shell ages in order to correct for this effect.However, since there is no significant radiocarbon-age reservoir atLake Turkana, we added back the 400 years to each of the radiocarbonages published by these authors (exclusively on mollusk shells) andcalibrated them, as well as the other available radiocarbon ages,using the same method as described in Section 3.2.

Our new age compilation (Fig. 7A) exhibits substantial variabilityin the corresponding elevations for the dated samples. While lacus-trine deposits may provide a precise position for the former lakeshore, archaeological data from settlements or temporary shorelineoccupations can only furnish approximations for the maximumwater-level of the palaeo-lake. Considering only those ages associatedwith lacustrine deposits, the large range of estimated elevations forone particular time could have a variety of different explanations.For example, the fossil mollusks sampled from lake sediments mayderive from different water-depths, ranging from shallower near-shore to deeper offshore environments (Cohen, 1986), and maytherefore not be able to constrain water-depth estimates. In addition,wave action in exposed areas may have prevented the deposition ofsediments above a certain water depth (Johnson et al., 1987) and/ormay have resulted in the redistribution of shells from shallow to dee-per water (McGlue et al., 2010), thus adding noise to the originalwater-level signal. Field and analytical methods used to estimatesample elevations (e.g., handheld GPS, aneroid barometer, dumpylevel, and dGPS) may have also introduced vertical uncertainties inthe dataset since the precision and accuracy of each of these methodsvary significantly. The ongoing tectonic deformation of the TurkanaBasin may also be responsible for a significant part of the observedage scatter (see Section 4.2). In view of the lack of precise dGPS mea-surements for the previously dated samples from the Turkana Basin,an elevation correction for vertical tectonic displacements is not pos-sible. Thus, in order to account for all of the issues discussed abovethat may have affected the bathymetric information for the publishedage data points, we assigned an arbitrary vertical uncertainty of±10 m to each of these dated samples (Fig. 7A).

4.5.2. Lake-level historyDuring the Last Glacial Period the lake water-level in the Turkana

Basin was probably lower than at present (Johnson, 1996). Following

Table 2Stable isotope values (δ18O and δ13C) of freshwater mollusk shells from Lake Turkana.

Sample ID Sitea Elevation (m asl) Corrected elevation (m asl)b δ18O (‰)c δ13C (‰)c

KIA 36856 SI 431.1 ~454 0.21±0.03 0.02±0.01KIA 36857 SI 431.1 ~459 −0.56±0.02 −4.89±0.01KIA 36858 SI 425.8 ~438 2.70±0.03 −3.13±0.01KIA 36859 SI 415.6 ~427 3.03±0.02 −1.19±0.01KIA 36860 SI 406 ~418 2.39±0.02 −2.07±0.01KIA 36861 SI 398.1 ~410 1.89±0.02 −4.21±0.01KIA 36862 SI 392.6 ~405 3.02±0.01 −5.55±0.00KIA 36864 SI 385 ~414 2.15±0.01 −4.75±0.01KIA 36865 SI 381.3 ~393 2.91±0.01 −2.4±0.01KIA 38214 KF 363 – 3.67±0.01 −2.75±0.01KIA 38215 KF 363 – 3.85±0.02 −1.1±0.01

a SI = South Island, KF = Koobi Fora.b Elevations have been corrected for local tectonic subsidence.c Values are reported on the VPDB scale as measured (aragonite), not corrected to calcite values.

-0.5 0.5 1.5 2.5 3.5 4.5

Lake volume (km3)

440

360

380

400

420

Cor

rect

ed e

leva

tion

(m a

sl)

460

040080012001600

δ 18O (‰)

Overflow: early Holocene

Modernconditions

Regression:mid-Holocene

MHS

Fig. 6. δ18O values from freshwater mollusk shells vs. corrected elevations. Error barsrepresent the 95% confidence interval. Also shown is the depth-volume curve forLake Turkana (thick grey line).



this dry period, rare dated lacustrine deposits indicate a lake water-level reaching elevations of ~440 to ~410 m between 13,000 and11,500 cal. yr BP. However, the lake water-level curve remains poorlyconstrained for this period.

From ~11,500 cal. yr BP palaeo-shoreline deposits indicate thatthe lake's water-level rose rapidly to its overflow level, and thenremained relatively stable until ~8500 cal. yr BP. This lake highstandwas possibly interrupted by a brief water-level fall of ~15 m thatprobably occurred at ~10,200 cal. yr BP, if evidence from prehistoricnear-shore settlements is taken into account. The protracted high-stand period between ~11,500 and ~8500 cal. yr BP corresponds tothe ‘Phase I’ described by Owen et al. (1982) (Fig. 7A). During this pe-riod there was fluvial connectivity between Lake Turkana and the NileBasin, and the MHS was formed.

From 8500 cal. yr BP lacustrine deposits indicate a significant butshort-lived lake regression (Owen et al., 1982), which may havetaken place over a few centuries. The magnitude of this regressionmay have reached between ~50 and ~100 m. The subsequent trans-gression was equally abrupt, with the lake water-level rising againto high levels (i.e.,~445 m) at ~7500 cal. yr BP.

From ~7500 to ~5300 cal. yr BP the presence of lacustrine depositsindicates that the lake remained relatively stable at high levels. Thishighstand period corresponds to the ‘Phase II’ of Owen et al. (1982).While Lake Turkana may have again overflowed during this period,the available data are too scarce to be certain.

From ~5300 cal. yr BP the lake's water-level fell to an elevation of~390 m. Shoreline data from South Island suggest that this regressionmay have occurred abruptly, possibly within a few centuries. Addi-tional support for a rapid regression comes from the ages derivedfrom archaeological sites (Fig. 7A). It is interesting to note that duringthis period the ages obtained from abandoned occupation sites followour inferred fall in the lake's water-level, indicating that humans ad-justed their settlement locations to keep pace with the recedingshoreline.

Following this final regression the lake's water-level must haveremained low, particularly between ~4000 and 2000 cal. yr BPwhen the absence of any exposed lacustrine deposits may indicatethat the water-level was even lower than at present.

Owen et al. (1982) tentatively inferred a lake highstand periodfrom ~4500 to ~3000 cal. yr BP (Phase III). However, this last high-stand phase was poorly constrained as it relied on a single shelldated at 3870 cal. yr BP (cf. Butzer et al., 1969). Analyses of sedimentcores collected across Lake Turkana, including downcore changes insedimentation and accumulation rate (Barton and Torgersen, 1988;Cerling, 1986), diatom assemblages (Halfman et al., 1992), and iso-topic composition of fine-grained calcite (Ricketts and Johnson,1996), have subsequently called into question the existence of alate Holocene lake highstand. Our new palaeo-shoreline dataset alsoappears to rule out a return to a higher lake water-level duringPhase III.

Archaeologicalexcavation

Lacustrinedeposit

Radiocarbon ages

36°E

5°N

430

440

450

460

470

360

370

380

390

400

410

420

Ele

vatio

n (m

asl

)

AD 2008 lake-level

Age (cal. yr BP)20000 4000 6000 8000 10,000 12,000 14,000

Overflow sill

Ph

ase

I

Ph

ase

II

Ph

ase

III

?

?

4°N

6°N

5°N

3°N

36°E 37°E

0 25 50 km

360 m

390 m

460 m

n = 102

No. of radiocarbon ages0 10 20 30Age (cal. yr BP)

0

5000

15,000

10,000

0

5000

10,0

00

15,0

00

Lake Turkana

Om

o R

.K

erio

R.

Turkwel R.

Form

er la

ke-le

vel r

econ

stru

ctio

n (B

utze

r an

d T

hurb

er, 1

969;

Ow

en e

t al.,

198

2)

South Island

A B

Exposed land after the mid-Holocene lake regression

?

Fig. 7. (A) Proposed lake water-level reconstruction for Lake Turkana, based on original and previously published data. Raw data and references are available in the Supplementarymaterials. The lake water-level curve is a compilation of dated lacustrine deposits (radiocarbon ages mostly on mollusk shells) complemented by dated archaeological excavations(radiocarbon ages mostly on bones, ostrich egg beads, and charcoal). Age error bars represent the 99% confidence interval. All elevation uncertainties were arbitrarily fixed to±10 m, except for the South Island samples which were further corrected for tectonic subsidence. Green curve represents inferred lake water-levels. Curve is dashed where un-certainties are greater. Lake highstand periods (Phases I–III) were defined by Owen et al. (1982). (B) Location map for the dated lake water-level markers used in A. The lowerand right side subplots show the distribution of the radiocarbon ages (calibrated) corresponding to longitude and latitude, respectively. Colour coding refers to the sampled ma-terial (see A). Histogram of radiocarbon age distribution is shown in the lower-right corner; n is the total number of radiocarbon ages.



From ~2000 to ~750 cal. yr BP, large accumulations of bones ofaquatic fauna (fishes, crocodiles, and turtles) recovered from prehis-toric settlements located at elevations between 370 and 380 m sug-gest that the water in Lake Turkana rose to slightly higher levels(Lynch and Robbins, 1979) before falling back to its present level(i.e., ~360 m).

5. Discussion

5.1. Mid-Holocene hydrology of the Turkana Basin and its relationship toother sites in tropical Africa

The mid-Holocene ~50 m fall in the lake's water-level (Fig. 7), to-gether with the 18O-enrichment (+4‰) of the δ18O values of lacus-trine carbonates from the early Holocene to the present-day (Fig. 6),suggests that Lake Turkana experienced a major decrease in thelocal hydrological balance (lower precipitation/higher evaporation)as well as possible changes in the air-mass source areas, which affect-ed the isotopic composition of water input into the lake from bothrivers and precipitation (cf. Levin et al., 2009).

The contribution of environmental/climatic variables (i.e., evapo-ration and precipitation) responsible for the mid-Holocene lakewater-level fall and resultant changes in the δ18O values of lacustrinecarbonates can be derived from isotope-hydrology modelling ap-proaches (cf. Ricketts and Anderson, 1998; Ricketts and Johnson,1996). However, during the early Holocene the water flow both inand out of Lake Turkana differed greatly from today. As mentionedabove, Lake Turkana overflowed toward the Nile Basin during theAHP (Butzer, 1980; Butzer et al., 1972; Harvey and Grove, 1982;Owen and Renaut, 1986; Owen et al., 1982) and in turn received in-flow from the linked Bogoria, Baringo, and Suguta basins to thesouth through the overtopping of the sill on the western margin ofthe Suguta trough (Fig. 1) (Garcin et al., 2009; Renaut and Owen,1980; Tiercelin and Vincens, 1987; Truckle, 1976), as well as fromthe Abaya, Chamo, and Chew Bahir basins to the east (Grove et al.,1975). These two drainage systems, which are today structurally iso-lated to form closed basins (Owen and Renaut, 1986), increased thesize of the Turkana Basin by ~40% during times of fluvial connectivity(Fig. 1). The accurate parameterisation of any isotope-based water-balance model therefore remains elusive.

Since the catchment area of Lake Turkana covers a latitudinalrange of ~9°, the hydrological/climatic changes recorded during theHolocene and earlier periods must have been of regional significance.Our previous study of the adjacent Suguta Valley (Garcin et al., 2009)revealed a much earlier lake highstand period (from ~17 to ~8.5 cal.yr BP) than that for Lake Turkana. Although differences in local inso-lation could possibly be responsible for the observed temporal varia-tions of lake highstands within the EARS, a radiocarbon age reservoirmight also have existed for the Suguta Valley and other lakes (e.g.,Junginger, 2011). However, based on our analysis of present-day mol-lusk material we do not consider this to be a problem for the LakeTurkana record.

The lake water-level curve for Lake Turkana exhibits marked sim-ilarities with other local and regional proxy-data from tropical Africa,both in terms of the magnitude and timing of the observed changes(Fig. 8). For example, the lake water-level curve for Lake Turkana cov-aries with leaf wax δD data – a proxy for terrestrial hydrologic condi-tions – from Lake Tanganyika which is located ~1000 km to thesouthwest (Fig. 8B, C). The isotopic record from this site suggests aperiod of high precipitation during the early Holocene, which endedabruptly at ~4700 cal. yr BP (Tierney et al., 2008). Virtually identicalchanges in local hydrology have been recorded in other lakes in theEARS, such as the Ziway–Shalla (Ethiopia) and Abhé (Djibouti)lakes, where a major Holocene highstand lasting until ~5000 cal. yrBP has been documented (Gasse, 1977; Gasse and Street, 1978;Gillespie et al., 1983). A marine record of eolian dust off Cap Blanc

(Mauritania, Fig. 8D) also shares analogous patterns with the LakeTurkana record, despite being situated ~6000 km to the west. Lowdust flux into the Atlantic Ocean during the early Holocene was in-ferred from this site, at which time the Sahara experienced a relative-ly wet climate (Cole et al., 2009; deMenocal et al., 2000). Dust influxincreased abruptly, however, at ~5500 cal. yr BP following the estab-lishment of arid conditions and a reduction in vegetation cover in theSahara and Sahel, which is compatible with our observations and maysuggest a climatic teleconnection between the two regions.

According to our lake water-level reconstruction the AHP termina-tion recorded in the Turkana Basin was probably abrupt, although ageuncertainties preclude any precise estimation of its duration. In trop-ical Africa the exact nature of the transition from the wet early Holo-cene conditions during an enhanced monsoon toward a drier climateafter the mid-Holocene remains ambiguous. Palaeo-climate recordsfrom the whole of Africa, as well as marine records, have providedcontrasting results concerning the AHP termination, ranging fromabrupt (e.g., Cole et al., 2009; deMenocal et al., 2000; Shanahan etal., 2006; Tierney et al., 2008) to gradual and/or stepwise (e.g.,Chase et al., 2010; Jung et al., 2004; Kröpelin et al., 2008; Marshallet al., 2011; Vincens et al., 2010). Climate-modelling experimentshave related an abrupt termination of the AHP to a nonlinear re-sponse of the African monsoon to changing insolation, possiblycaused by a strong positive vegetation–climate feedback (e.g.,Claussen et al., 1999; Renssen et al., 2003). In contrast, Liu et al.(2007) simulated a minimal vegetation–climate feedback and insteadproposed that the collapse of the northern African vegetation attrib-uted to the AHP termination was in fact the nonlinear response ofthe vegetation to the crossing of a precipitation threshold. Thus, de-spite recent advances and the increasing size of the database forthis important event, the available data are still ambiguous. Furtherstudies involving new climate-proxies are therefore required inorder to resolve the mechanisms responsible for the AHP termination.

5.2. Possible link between hydrological changes during the Holocene andprehistoric occupation in the Turkana Basin

Archaeological excavations within the Turkana Basin have provid-ed a rich, but complex history of human occupation, with major cul-tural steps during the Holocene (Fig. 8A). Abundant bone harpoonheads have been recovered from dated sections spanning ~10,600to ~5000 cal. yr BP in the immediate vicinity of the inferred palaeo-lake, generally in association with wavy-line or undecorated pottery(e.g., Beyin, 2011; Brown, 1975; Butzer et al., 1969; Phillipson,1977; Robbins, 1972, 1984, 2006; Sutton, 1977). At the time of theprotracted lake highstand this region was populated by hunter–gath-erers who relied mainly on fishing in their subsistence lifestyle (e.g.,Phillipson, 1977; Robbins, 1972).

The bones of domestic cattle, sheep, and goats, often in associationwith Nderit Ware pottery and occasionally with stone bowls, havebeen found in deposits younger than ~5000 cal. yr BP within the Tur-kana Basin (e.g., Ashley et al., 2011; Barthelme, 1977, 1984; Marshallet al., 1984; Owen et al., 1982). The cumulative probability distribu-tion of the radiocarbon ages related to human occupation alsoshows a marked maximum between ~5000 and ~4000 cal. yr BP(Fig. 8A). Although foraging persisted and fish still formed an impor-tant part of their diet, this particular period highlights the emergenceof pastoral groups in the area (Ashley et al., 2011; Barthelme, 1984;Hildebrand et al., 2011; Marshall et al., 1984; Ndiema et al., 2011).The first manifestations of herding around the palaeo-lake were ap-parently coeval with the construction of megalithic pillar sites in theTurkana Basin (Hildebrand and Grillo, 2012; Hildebrand et al., 2011;Lynch and Robbins, 1978; Lynch and Robbins, 1979; Nelson, 1995;Soper and Lynch, 1977). Possible support for this cultural changemay come from linguistic evidence suggesting that southern



Cushitic-speakers, herders of domestic livestock, entered northernKenya ~5000 years ago (Ehret, 1974).

It is interesting to note that the main mid-Holocene cultural tran-sition appears to be closely related to the timing of the documented

~50 m fall in lake water-level in the Turkana Basin. A possible link be-tween the lake regression and the emergence/expansion of pastoral-ism in the Turkana Basin may have been the exposure of ~10,000 km2

of fertile silty-clay lacustrine sediments (Fig. 7B). The vast majority ofthese newly exposed areas, which are characterised by relatively low-relief topography, correspond to the palaeo-deltas of the Omo, Turk-wel, and Kerio rivers. In this context Robbins (2006) hypothesisedthat any significant fall in lake water-level in the area would resultin the opening up of new pastures/browsing resources in a regionsuspected to have been relatively free of tsetse flies and the trypano-somiasis disease that they carry (cf. Gifford-Gonzalez, 1998). The lat-ter is a virulent infection affecting livestock, wild game, and humans,and is typical of regions south of the Sahara and Sahel. It is more like-ly, however, that the establishment of a drier and drought-prone cli-mate in northeast Africa after ~5300 cal. yr BP may have forced localherders and their domesticated livestock to converge on Lake Tur-kana, which was probably one of the last permanent water bodiesin the region and would have provided sufficient water and pastureto foster the settlement of pastoralists, ultimately leading to newforms of social and economic organisations (e.g., Marshall et al.,2011; Wright, 2011).

The changes in landscape and environmental conditions withinthe greater Turkana Basin associated with the mid-Holocene climaticchange, and the associated fall in lake water-level, may thus have en-couraged the regional expansion of pastoralist cultures.

6. Conclusions

Our survey of palaeo-shorelines from the Turkana Basin revealsnew insights into past hydrological changes in the EARS. We havedocumented a prolonged lake highstand with episodes of fluvial con-nectivity to the Nile Basin during the early to mid-Holocene, support-ing previous regional hydrological reconstructions. The lake water-level subsequently fell rapidly by ~50 m at ~5270±300 cal. yr BP,probably in response to a major climatic transition characterised bya rapid change in environmental conditions. This episode correspondsto the termination of the African Humid Period, which has often beeninferred to have occurred abruptly right across tropical Africa.

Our observations indicate that ongoing tectonic segmentation ofthe Turkana rift-basin has resulted in the vertical displacement ofthe maximum highstand shoreline (overflow stage) by up to ~20 m,relative to the present-day position of the overflow sill of the Turkanapalaeo-lake. When using palaeo-shorelines for high-resolution lakewater-level reconstructions and palaeoclimate assessments in activetectonic settings it is therefore important to decipher the imprint oftectonic deformation at various spatial and temporal scales.

Finally, since the emergence/expansion of pastoralism in the Tur-kana Basin was coeval with the mid-Holocene lake water-level fall,we propose that hydrological changes – such as long-term droughts

?

?

?

Harpoon:fishingsettlements

TurkwelPottery tradition

Pillar sites

Cushitic

Bone

Nilotic

Nderit

Linguisticevidence

Megalitharchitecture

Pastoralism

Occupation phases

?

?

Early Afro-Asiatic and Nilo-Saharan speakers?

?

Wavy line

Iron

??

n = 50

?

-130

-120

-110

-100

440

460

360

380

400

420

Ele

vatio

n (m

asl

)

45

50

55

60Ter

rigen

ous

(%)

δD

leaf

wax

(‰

VS

MO

W)

65

0

0.05

Dry

Dry

Age (cal. yr BP)20000 4000 6000 8000 10,000 12,000

Overflow

Lake Turkana water-level

Turkana Basin cultural record

L. Tanganyika

East Atlantic

A

B

C

D

Cal

ibra

ted

14 C

age

s (C

PD

)

Fig. 8. Comparison of the Turkana Basin environmental and archaeological history duringthe Holocene with reconstructed climate-proxy data from other African sites. (A) TurkanaBasin cultural record. Compilation derived from various archaeological sources: linguisticevidence (Ehret, 1974); harpoon distribution and pottery tradition (Ashley et al., 2011;Barthelme, 1977, 1984; Beyin, 2011; Brown, 1975; Butzer et al., 1969; Hildebrand et al.,2011; Lynch and Robbins, 1979; Nelson, 1991; Owen et al., 1982; Phillipson, 1977;Robbins, 1972, 1984, 2006); pillar sites (Hildebrand and Grillo, 2012; Hildebrand et al.,2011; Lynch and Robbins, 1978, 1979; Nelson, 1995; Soper and Lynch, 1977); pastoralismevidence (Ashley et al., 2011; Barthelme, 1977, 1984; Marshall et al., 1984; Owen et al.,1982). Also shown is the cumulative probability distribution (CPD) of the calibrated radio-carbon ages related to human occupation, which includes the ages derived from archaeo-logical excavations as well as those from lacustrine deposits associated with culturalremains (e.g., bone harpoons). (B) Lake Turkana water-level curve. (C) Variations in δD-leafwax from Lake Tanganyika recording past changes in humidity (Tierney et al., 2008).(D) Variations in terrigenous (eolian) sediment import off Cap Blanc (Mauritania)recording past changes in aridity over the Saharan region (deMenocal et al., 2000). Blueand beige shadings mark humid and dry conditions, respectively, which affected severalregions of tropical Africa (see main text).



– may have fundamentally influenced prehistoric cultural changes inthe EARS.

Supplementary materials related to this article can be found on-line at doi:10.1016/j.epsl.2012.03.016.

Acknowledgments

Funding has been provided by the German Research Foundation(DFG) through projects GRK1364, TR419/6-1, and STR373/16-1. Y.Garcin was also supported by an Alexander von Humboldt ResearchFellowship. J.-J. Tiercelin was supported by grants from the INSU–CNRS–ECLIPSE I & II Programs. We would like to thank the Universityof Nairobi, the Government of Kenya (Research Permits OP/13/001/23C 290 andMOEST 13/001/23C 290 to J.-J.T.), the National Oil Corpo-ration of Kenya, Wild Frontiers, and Tropic Air, for administrative andlogistical support. We also thank M.H. Trauth and A. Junginger forfield support. We are grateful to S. Nielsen for handling our samplesduring radiocarbon dating and stable isotope analysis in Kiel, to J.-F.Saliège for his part in radiocarbon age determinations, to H. Scholzand M. Glaubrecht for generously providing samples of modernsnails, to K. Grillo for useful discussions, and to three anonymous re-viewers for detailed and constructive comments. SPOT satellite im-ages (©CNES) were acquired through the ISIS-156 Project.

References

Ashley, G.M., Ndiema, E.K., Spencer, J.Q.G., Harris, J.W.K., Kiura, P.W., 2011. Paleoenvir-onmental context of archaeological sites, implications for subsistence strategiesunder Holocene climate change, northern Kenya. Geoarchaeology 26, 809–837.

Baker, B.H., Mohr, P.A., Williams, L.A.J., 1972. Geology of the eastern rift system of Afri-ca. Geol. Soc. Am. Spec. Pap. 136, 1–67.

Barthelme, J., 1977. Holocene sites north-east of Lake Turkana: a preliminary report.Azania 12, 33–41.

Barthelme, J.W., 1984. Early evidence for animal domestication in Eastern Africa. In:Clark, J.D., Brandt, S.A. (Eds.), From Hunters to Farmers: The Causes and Conse-quences of Food Production in Africa. Univ. of California Press, Berkeley, pp.200–205.

Barton, C.E., Torgersen, T., 1988. Palaeomagnetic and 210Pb estimates of sedimentationin Lake Turkana, East Africa. Palaeogeogr. Palaeoclimatol. Palaeoecol. 68, 53–59.

Beyin, A., 2011. Recent archaeological survey and excavation around the Greater Kalo-kol Area, west side of Lake Turkana: preliminary findings. Nyame Akuma 75,40–50.

Boko, M., Niang, I., Nyong, A., Vogel, C., Githeko, A., Medany, M., Osman-Elasha, B., Tabo,R., Yanda, P., 2007. Africa. In: Parry, M.L., Canziani, O.F., Palutikof, J.P., van derLinden, P.J., Hanson, C.E. (Eds.), Climate Change 2007: Impacts, Adaptation andVulnerability. : Contribution of Working Group II to the Fourth Assessment Reportof the Intergovernmental Panel on Climate Change. Cambridge Univ. Press, Cam-bridge UK, pp. 433–467.

Bronk Ramsey, C., 2001. Development of the radiocarbon calibration program OxCal.Radiocarbon 43, 355–363.

Brooks, N., 2006. Cultural responses to aridity in the Middle Holocene and increasedsocial complexity. Quat. Int. 151, 29–49.

Brown, F.H., 1975. Barbed bone points from the Lower Omo Valley, Ethiopia. Azania 10,144–148.

Brown, F.H., Carmichael, I.S.E., 1971. Quaternary volcanoes of the Lake Rudolf region: II.The lavas of North Island, South Island and the Barrier. Lithos 4, 305–323.

Brown, F.H., Fuller, C.R., 2008. Stratigraphy and tephra of the Kibish Formation, south-western Ethiopia. J. Hum. Evol. 55, 366–403.

Butzer, K.W., 1980. The Holocene lake plain of north Rudolf, East Africa. Phys. Geogr. 1,42–58.

Butzer, K.W., Thurber, D.L., 1969. Some Late Cenozoic sedimentary formations of theLower Omo Basin. Nature 222, 1138–1143.

Butzer, K.W., Brown, F.H., Thurber, D.L., 1969. Horizontal sediments of the lower Omovalley: the Kibish Formation. Quaternaria 11, 15–29.

Butzer, K.W., Isaac, G.L., Richardson, J.L., Washbourn-Kamau, C., 1972. Radiocarbon dat-ing of east African lake levels. Science 175, 1069–1076.

Cerling, T.E., 1979. Paleochemistry of Plio-Pleistocene Lake Turkana, Kenya. Palaeo-geogr. Palaeoclimatol. Palaeoecol. 27, 247–285.

Cerling, T.E., 1986. A mass-balance approach to basin sedimentation: constraints on therecent history of the Turkana basin. Palaeogeogr. Palaeoclimatol. Palaeoecol. 54,63–86.

Chase, B.M., Meadows, M.E., Carr, A.S., Reimer, P.J., 2010. Evidence for progressive Ho-locene aridification in southern Africa recorded in Namibian hyrax middens: impli-cations for African monsoon dynamics and the “African Humid Period”. Quat. Res.74, 36–45.

Claussen, M., Kubatzki, C., Brovkin, V., Ganopolski, A., Hoelzmann, P., Pachur, H.J., 1999.Simulation of an abrupt change in Saharan vegetation in the mid-Holocene. Geo-phys. Res. Lett. 26, 2037–2040.

Cohen, A.S., 1986. Distribution and faunal associations of benthic invertebrates at LakeTurkana, Kenya. Hydrobiologia 141, 179–197.

Cole, J.M., Goldstein, S.L., deMenocal, P.B., Hemming, S.R., Grousset, F.E., 2009. Contrast-ing compositions of Saharan dust in the eastern Atlantic Ocean during the last de-glaciation and African Humid Period. Earth Planet. Sci. Lett. 278, 257–266.

deMenocal, P., Ortiz, J., Guilderson, T., Adkins, J., Sarnthein, M., Baker, L., Yarusinsky, M.,2000. Abrupt onset and termination of the African Humid Period: rapid climate re-sponses to gradual insolation forcing. Quat. Sci. Rev. 19, 347–361.

Dunkelman, T.J., Rosendahl, B.R., Karson, J.A., 1989. Structure and stratigraphy of theTurkana rift from seismic reflection data. J. Afr. Earth Sci. 8, 489–510.

East African Meteorological Department, 1975. Climatological statistics for East Africa.Part 1: Kenya. East African Community/East African Meteorological Department,Nairobi, Kenya. 92 pp.

Ehret, C., 1974. Ethiopians and East African: The Problem of Contacts. East African Pub.House, Nairobi, Kenya.

Farr, T.G., Rosen, P.A., Caro, E., Crippen, R., Duren, R., Hensley, S., Kobrick, M., Paller, M.,Rodriguez, E., Roth, L., Seal, D., Shaffer, S., Shimada, J., Umland, J., Werner, M., Oskin,M., Burbank, D., Alsdorf, D., 2007. The shuttle radar topography mission. Rev. Geo-phys. 45, RG2004. doi:10.1029/2005RG000183.

Ferguson, A.J.D., Harbott, B.J., 1982. Geographical, physical, and chemical aspects ofLake Turkana. In: Hopson, A.J. (Ed.), Lake Turkana: A Report of the Findings ofthe Lake Turkana Project, 1972–1975. Overseas Development Administration, Lon-don, England, pp. 1–110.

Garcin, Y., Junginger, A., Melnick, D., Olago, D.O., Strecker, M.R., Trauth, M.H., 2009. LatePleistocene–Holocene rise and collapse of Lake Suguta, northern Kenya Rift. Quat.Sci. Rev. 28, 911–925.

Gasse, F., 1977. Evolution of Lake Abhé (Ethiopia and TFAI), from 70,000 b.p. Nature265, 42–45.

Gasse, E., Street, F.A., 1978. Late Quaternary lake-level fluctuations and environmentsof the northern Rift Valley and Afar Region (Ethiopia and Djibouti). Palaeogeogr.Palaeoclimatol. Palaeoecol. 24, 279–325.

Gifford-Gonzalez, D., 1998. Early pastoralists in East Africa: ecological and social di-mensions. J. Anthropol. Archaeol. 17, 166–200.

Gillespie, R., Street-Perrott, F.A., Switsur, R., 1983. Post-glacial arid episodes in Ethiopiahave implications for climate prediction. Nature 306, 680–683.

Grove, A.T., Street, F.A., Goudie, A.S., 1975. Former lake levels and climatic change in theRift Valley of Southern Ethiopia. Geogr. J. 141, 177–194.

Halfman, J.D., Johnson, T.C., 1988. High-resolution record of cyclic climatic-change dur-ing the past 4 ka from Lake Turkana, Kenya. Geology 16, 496–500.

Halfman, J.D., Jacobson, D.F., Cannella, C.M., Haberyan, K.A., Finney, B.P., 1992. Fossil di-atoms and the mid to late Holocene paleolimnology of Lake Turkana, Kenya: a re-connaissance study. J. Paleolimnol. 7, 23–35.

Halfman, J.D., Johnson, T.C., Finney, B.P., 1994. New AMS dates, stratigraphic correla-tions and decadal climatic cycles for the past 4 ka at Lake Turkana, Kenya. Palaeo-geogr. Palaeoclimatol. Palaeoecol. 111, 83–98.

Harvey, C.P.D., Grove, A.T., 1982. A prehistoric source of the Nile. Geogr. J. 148,327–336.

Hildebrand, E.A., Grillo, K.M., 2012. Early herders and monumental sites in eastern Af-rica: dating and interpretation. Antiquity 86, 338–352.

Hildebrand, E.A., Shea, J.J., Grillo, K.M., 2011. Four middle Holocene pillar sites in WestTurkana, Kenya. J. Field Archaeol. 36, 181–200.

Hoelzmann, P., Jolly, D., Harrison, S.P., Laarif, F., Bonnefille, R., Pachur, H.J., 1998. Mid-Holocene land-surface conditions in northern Africa and the Arabian peninsula: adata set for the analysis of biogeophysical feedbacks in the climate system. GlobalBiogeochem. Cycles 12, 35–51.

Johnson, T.C., 1996. Sedimentary processes and signals of past climatic change in thelarge lakes of the East African rift valley. In: Johnson, T.C., Odada, E.O. (Eds.), TheLimnology, Climatology and Paleoclimatology of the East African Lakes. Gordonand Breach Publishers, Amsterdam, pp. 367–412.

Johnson, T.C., Halfman, J.D., Rosendahl, B.R., Lister, G.S., 1987. Climatic and tectonic ef-fects on sedimentation in a rift-valley lake: evidence from high-resolution seismicprofiles, Lake Turkana, Kenya. Geol. Soc. Am. Bull. 98, 439–447.

Jolly, D., Harrison, S.P., Damnati, B., Bonnefille, R., 1998. Simulated climate and biomesof Africa during the Late Quaternary: comparison with pollen and lake status data.Quat. Sci. Rev. 17, 629–657.

Jung, S.J.A., Davies, G.R., Ganssen, G.M., Kroon, D., 2004. Stepwise Holocene aridificationin NE Africa deduced from dust-borne radiogenic isotope records. Earth Planet. Sci.Lett. 221, 27–37.

Junginger, A., 2011. East African climate variability on different time scales: the SugutaValley in the African–Asian monsoon domain. PhD Thesis, Univ. of Potsdam, Pots-dam, Germany.

Karson, J.A., Curtis, P.C., 1994. Quaternary volcanic centers of the Turkana Rift, Kenya. J.Afr. Earth Sci. 18, 15–35.

Kröpelin, S., Verschuren, D., Lézine, A.-M., Eggermont, H., Cocquyt, C., Francus, P., Cazet,J.-P., Fagot, M., Rumes, B., Russell, J.M., Darius, F., Conley, D.J., Schuster, M., vonSuchodoletz, H., Engstrom, D.R., 2008. Climate-driven ecosystem succession inthe Sahara: the past 6000 years. Science 320, 765–768.

Kuper, R., Kröpelin, S., 2006. Climate-controlled holocene occupation in the Sahara:motor of Africa's evolution. Science 313, 803–807.

Leng, M.J., Lamb, A.L., Lamb, H.F., Telford, R.J., 1999. Palaeoclimatic implications of isotopicdata frommodern and early Holocene shells of the freshwater snailMelanoides tuber-culata, from lakes in the Ethiopian Rift Valley. J. Paleolimnol. 21, 97–106.

Leng, M.J., Lamb, A.L., Heaton, T.H.E., Marshall, J.D., Wolfe, B.B., Jones, M.D., Holmes, J.A.,Arrowsmith, C., 2006. Isotopes in lake sediments. In: Leng, M.J. (Ed.), Isotopes inPalaeoenvironmental Research. : Developments in Paleoenvironmental Research.Springer, Dordrecht, The Netherlands, pp. 147–184.



Levin, I., Kromer, B., 2004. The tropospheric 14CO2 level in mid-latitudes of the North-ern Hemisphere (1959–2003). Radiocarbon 46, 1261–1272.

Levin, N.E., Zipser, E.J., Cerling, T.E., 2009. Isotopic composition of waters from Ethiopiaand Kenya: insights into moisture sources for eastern Africa. J. Geophys. Res. 114,D23306. doi:10.1029/2009JD012166.

Liu, Z., Wang, Y., Gallimore, R., Gasse, F., Johnson, T., deMenocal, P., Adkins, J., Notaro,M., Prenticer, I.C., Kutzbach, J., Jacob, R., Behling, P., Wang, L., Ong, E., 2007. Simu-lating the transient evolution and abrupt change of Northern Africa atmosphere–ocean-terrestrial ecosystem in the Holocene. Quat. Sci. Rev. 26, 1818–1837.

Lynch, B.M., Robbins, L.H., 1978. Namoratunga: the first archeoastronomical evidencein sub-Saharan Africa. Science 200, 766–768.

Lynch, B.M., Robbins, L.H., 1979. Cushitic and Nilotic prehistory: new archaeological ev-idence from north–west Kenya. J. Afr. Hist. 20, 319–328.

Marshall, F., Stewart, K., Barthelme, J., 1984. Early domestic stock at Dongodien inNorthern Kenya. Azania 19, 120–127.

Marshall, M.H., Lamb, H.F., Huws, D., Davies, S.J., Bates, R., Bloemendal, J., Boyle, J., Leng,M.J., Umer, M., Bryant, C., 2011. Late Pleistocene and Holocene drought events atLake Tana, the source of the Blue Nile. Global Planet. Change 78, 147–161.

McGlue, M.M., Soreghan, M.J., Michel, E., Todd, J.A., Cohen, A.S., Mischler, J., O'Connell,C.S., Castañeda, O.S., Hartwell, R.J., Lezzar, K.E., Nkotagu, H.H., 2010. Environmentalcontrols on shell-rich facies in tropical lacustrine rifts: a view from Lake Tanganyi-ka's littoral. Palaios 25, 426–438.

Melnick, D., Garcin, Y., Quinteros, J., Strecker, M.R., Olago, D.O., Tiercelin, J.-J., this vol-ume. Steady rifting in northern Kenya inferred from deformed Holocene lakeshorelines of the Suguta and Turkana basins. Earth Planet. Sci. Lett.

Morley, C.K., Wescott, W.A., Stone, D.M., Harper, R.M., Wigger, S.T., Karanja, F.M., 1992.Tectonic evolution of the northern Kenyan Rift. J. Geol. Soc. London 149, 333–348.

Ndiema, K.E., Dillian, C.D., Braun, D.R., Harris, J.W.K., Kiura, P.W., 2011. Transport andsubsistence patterns at the transition to pastoralism, Koobi Fora, Kenya. Archaeo-metry 53, 1085–1098.

Nelson, C.M., 1991. Harpoon Evolution on the Spit (GaJi12) at Koobi Fora, Lake Turkana,Kenya. Nyame Akuma 36, 10–19.

Nelson, C.M., 1995. The work of the Koobi Fora field school at the Jarigole Pillar site.Kenya Past and Present 27, 49–63.

Owen, R.B., Renaut, R.W., 1986. Sedimentology, stratigraphy and palaeoenvironmentsof the Holocene Galana Boi Formation, NE Lake Turkana, Kenya. In: Frostick, L.E.(Ed.), Sedimentation in the African Rifts. Geol. Soc. London Spec. Publ, London,pp. 311–322.

Owen, R.B., Barthelme, J.W., Renaut, R.W., Vincens, A., 1982. Palaeolimnology and ar-chaeology of Holocene deposits north-east of Lake Turkana, Kenya. Nature 298,523–529.

Phillipson, D.W., 1977. Lowasera. Azania 12, 1–32.Reimer, P.J., Baillie, M.G.L., Bard, E., Bayliss, A., Beck, J.W., Blackwell, P.G., Bronk Ramsey,

C., Buck, C.E., Burr, G.S., Edwards, R.L., Friedrich, M., Grootes, P.M., Guilderson, T.P.,Hajdas, I., Heaton, T.J., Hogg, A.G., Hughen, K.A., Kaiser, K.F., Kromer, B., McCormac,F.G., Manning, S.W., Reimer, R.W., Richards, D.A., Southon, J.R., Talamo, S., Turney,C.S.M., van der Plicht, J., Weyhenmeyer, C.E., 2009. IntCal09 and Marine09 radio-carbon age calibration curves, 0–50,000 years cal BP. Radiocarbon 51, 1111–1150.

Renaut, R.W., Owen, R.B., 1980. Late Quaternary fluvio-lacustrine sedimentation andlake levels in the Baringo basin, northern Kenya, Rift Valley. Rech. Géol. Afr. 5,130–133.

Renssen, H., Brovkin, V., Fichefet, T., Goosse, H., 2003. Holocene climate instability dur-ing the termination of the African Humid Period. Geophys. Res. Lett. 30, 1184.doi:10.1029/2002GL016636.

Ricketts, R.D., Anderson, R.F., 1998. A direct comparison between the historical recordof lake level and the δ18O signal in carbonate sediments from Lake Turkana, Kenya.Limnol. Oceanogr. 43, 811–822.

Ricketts, R.D., Johnson, T.C., 1996. Climate change in the Turkana basin as deduced froma 4000 year long δ18O record. Earth Planet. Sci. Lett. 142, 7–17.

Ritchie, J.C., Eyles, C.H., Haynes, C.V., 1985. Sediment and pollen evidence for an Early tomid-Holocene humid period in the eastern Sahara. Nature 314, 352–355.

Robbins, L.H., 1972. Archeology in the Turkana District, Kenya. Science 176, 359–366.Robbins, L.H., 1984. Late Prehistoric aquatic and pastoral adaptations west of Lake Tur-

kana, Kenya. In: Desmond Clark, J., Brandt, S.A. (Eds.), From Hunters to Farmers:The Causes and Consequences of Food Production in Africa. Univ. of CaliforniaPress, Berkeley, pp. 206–211.

Robbins, L.H., 2006. Lake Turkana archaeology: the Holocene. Ethnohistory 53, 71–93.Shanahan, T.M., Overpeck, J.T., Wheeler, C.W., Beck, J.W., Pigati, J.S., Talbot, M.R., Scholz,

C.A., Peck, J., King, J.W., 2006. Paleoclimatic variations in West Africa from a recordof late Pleistocene and Holocene lake level stands of Lake Bosumtwi, Ghana.Palaeogeogr. Palaeoclimatol. Palaeoecol. 242, 287–302.

Shanahan, T.M., Overpeck, J.T., Anchukaitis, K.J., Beck, J.W., Cole, J.E., Dettman, D.L.,Peck, J.A., Scholz, C.A., King, J.W., 2009. Atlantic forcing of persistent drought inWest Africa. Science 324, 377–380.

Soper, R., Lynch, M., 1977. The stone-circle graves at Ng'amoritung'a, Southern TurkanaDistrict, Kenya. Azania 12, 193–208.

Stein, R.S., Briole, P., Ruegg, J.-C., Tapponnier, P., Gasse, F., 1991. Contemporary, Holo-cene, and quaternary deformation of the Asal Rift, Djibouti: implications for themechanics of slow spreading ridges. J. Geophys. Res. 96, 21789–21806.

Sutton, J.E.G., 1977. The African aqualithic. Antiquity 51, 25–34.Tiercelin, J.-J., Vincens, A., 1987. Le Demi-Graben de Baringo-Bogoria, Rift Gregory,

Kenya, 30,000 Ans d'Histoire Hydrologique et Sédimentaire. Bull. Centres deRech. Expl. Prod. Elf-Aquitaine, Pau, pp. 249–540.

Tierney, J.E., Russell, J.M., Huang, Y., Sinninghe Damsté, J.S., Hopmans, E.C., Cohen, A.S.,2008. Northern hemisphere controls on tropical southeast African climate duringthe past 60,000 years. Science 322, 252–255.

Truckle, P.H., 1976. Geology and late Cainozoic lake sediments of the Suguta Trough,Kenya. Nature 263, 380–383.

Vétel, W., Le Gall, B., Johnson, T.C., 2004. Recent tectonics in the Turkana Rift (NorthKenya): an integrated approach from drainage network, satellite imagery and re-flection seismic analyses. Basin Res. 16, 165–181.

Vincens, A., Buchet, G., Servant, M., 2010. ECOFIT Mbalang collaborators. Vegetation re-sponse to the “African Humid Period” termination in Central Cameroon (7°N)—new pollen insight from Lake Mbalang: Clim. Past, 6, pp. 281–294.

Wright, D.K., 2011. Frontier animal husbandry in the Northeast and East African Neo-lithic: a multiproxy paleoenvironmental and paleodemographic study. J. Anthro-pol. Res. 67, 213–244.

Yuretich, R.F., Cerling, T.E., 1983. Hydrogeochemistry of Lake Turkana, Kenya: mass bal-ance and mineral reactions in an alkaline lake. Geochim. Cosmochim. Acta 47,1099–1109.


east african mid-holocene wet–dry transition recorded in laketurkana, northern kenya rift

Documents

climatic history of

major climatic transition

early holocene

marked climatic transition

climatic extremes

water stress

context climatic variability

drier climate