Late Quaternary stratigraphic analysis of the Lake Malawi Rift, East Africa: An integration of drill-core and seismic-reflection data

Lyons, Richard H.; Scholz, Christopher A.; Buoniconti, Matthew R.; Martín, Matthew R.

doi:10.1016/j.palaeo.2009.04.014

Cited by 108 publications

(153 citation statements)

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“…Evidence from diatoms, ostracodes, and other paleoecological indicators, as well as seismic-reflection data show lake levels dropped by as much as ∼600 m over the past 150,000 y (8,17,18). Here we extend the lake level reconstruction to the entire ∼1.3-My drill core record, revealing that there were 24 lowstands of more than 200 m below modern; at least 15 were very severe, when water levels were reduced more than 400 m (Fig.…”

Section: Hydroclimate Proxy Analysesmentioning

confidence: 50%

“…Before ∼800 ka, the paleoclimate proxies indicate a basin occupied by a lake shallower than modern, with lake level shifts occurring every 10,000 y or less. Although that lake was shallower than the current one, the drill site was a distal and open water environment like today, dominated by hemipelagic sedimentation; this is evidenced by the broad expanse of high continuity, high amplitude, and uniformly stratified seismic facies that extend in all directions away from the drill site for many tens of kilometers (17). The high values of Ca and lower TOC in this interval, coupled with the continuous, highamplitude seismic character in this part of Lake Malawi, indicate a large lake situated in a drier environment than observed in the catchment today.…”

Section: Causative Mechanisms For Climate Variabilitymentioning

confidence: 92%

“…Drill cores from the central basin of Lake Malawi extend 380 m below lake floor at a water depth of 590 m, a site dominated by hemipelagic deposits sensitive to environmental variability (8,17). Site survey and geochronological data demonstrate that sampled sediments represent continuous sedimentation over the last ∼1.3 My (SI Appendix, Figs.…”

Section: Hydroclimate Proxy Analysesmentioning

confidence: 99%

“…Highstand sediments, deposited when the lake is at or near its current outlet level (maximum water depth ∼700 m), are characterized by high TOC, low density, low Ca, and low L* values, and are finely laminated ( Fig. 2 and SI Appendix) (8,17). Conversely, lowstand sediments are poor in organic matter, carbonate-rich, high density, and exhibit high L* values (SI Appendix, Fig.…”

Section: Hydroclimate Proxy Analysesmentioning

confidence: 99%

See 3 more Smart Citations

Continuous 1.3-million-year record of East African hydroclimate, and implications for patterns of evolution and biodiversity

Lyons

Scholz

Cohen

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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119

164

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The transport of moisture in the tropics is a critical process for the global energy budget and on geologic timescales, has markedly influenced continental landscapes, migratory pathways, and biological evolution. Here we present a continuous, first-of-its-kind 1.3-My record of continental hydroclimate and lake-level variability derived from drill core data from Lake Malawi, East Africa (9-15°S). Over the Quaternary, we observe dramatic shifts in effective moisture, resulting in large-scale changes in one of the world's largest lakes and most diverse freshwater ecosystems. Results show evidence for 24 lake level drops of more than 200 m during the Late Quaternary, including 15 lowstands when water levels were more than 400 m lower than modern. A dramatic shift is observed at the Mid-Pleistocene Transition (MPT), consistent with far-field climate forcing, which separates vastly different hydroclimate regimes before and after ∼800,000 years ago. Before 800 ka, lake levels were lower, indicating a climate drier than today, and water levels changed frequently. Following the MPT high-amplitude lake level variations dominate the record. From 800 to 100 ka, a deep, often overfilled lake occupied the basin, indicating a wetter climate, but these highstands were interrupted by prolonged intervals of extreme drought. Periods of high lake level are observed during times of high eccentricity. The extreme hydroclimate variability exerted a profound influence on the Lake Malawi endemic cichlid fish species flock; the geographically extensive habitat reconfiguration provided novel ecological opportunities, enabling new populations to differentiate rapidly to distinct species. Lake Malawi | tropical paleoclimatology | East African rift | cichlid fish | quaternary I nsolation forcing of tropical convection and shifts in the Intertropical Convergence Zone (ITCZ) are considered principal mechanisms driving tropical climate variability on geologic time scales (1-5). However, instrumental records show that the ITCZ over land is poorly characterized compared with the oceans (Fig. 1), and the transport of oceanic moisture to the hinterlands is complex, because topographic barriers redirect winds and block advection to the continental interiors (6). To document moisture transport onto the continents over geological time scales, terrestrial records of tropical paleoclimate with the length and continuity of ocean drilling records are required. Continental drilling in long-lived tropical lakes provides continuous, high-resolution paleoclimate records that extend well past the last glacial maximum (7,8), and augment shorter, well-dated records from outcrops. Lakes of great antiquity also contain numerous endemic species-notably, cichlid fishes-whose modern assemblages evolved in concert with changing climates, and which figure prominently into models of speciation and diversification (9, 10).Lake Malawi and Its Catchment Lake Malawi (Nyasa) is one of the world's largest and oldest lakes, and is situated at the southern end of the East Afri...

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Section: Hydroclimate Proxy Analysesmentioning

confidence: 50%

Section: Causative Mechanisms For Climate Variabilitymentioning

confidence: 92%

Section: Hydroclimate Proxy Analysesmentioning

confidence: 99%

Section: Hydroclimate Proxy Analysesmentioning

confidence: 99%

See 2 more Smart Citations

Continuous 1.3-million-year record of East African hydroclimate, and implications for patterns of evolution and biodiversity

Lyons

Scholz

Cohen

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

119

164

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“…Reconstruction of Cohen et al (2007), left, based upon wet-sieved variables only. Lake-level reconstruction based upon the principle component analysis from this study (PC1) overlain by the estimated depth curve (dashed line) of Lyons et al (2011); depth estimates are based upon shoreline markers identified from seismic surveys of the lake basin. Arrows highlight significant lowstands observed in other late Pleistocene cores from Lake Malawi.…”

Section: -136 Ka (Diatom Zones M1 and M2)mentioning

confidence: 99%

Late Pleistocene paleohydrography and diatom paleoecology of the central basin of Lake Malawi, Africa

Stone

Westover

Cohen

2011

Palaeogeography, Palaeoclimatology, Palaeoecology

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Present‐day kinematics of the East African Rift

et al. 2014

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The East African Rift (EAR) is a type locale for investigating the processes that drive continental rifting and breakup. The current kinematics of this ∼5000 km long divergent plate boundary between the Nubia and Somalia plates is starting to be unraveled thanks to a recent augmentation of space geodetic data in Africa. Here we use a new data set combining episodic GPS measurements with continuous measurements on the Nubian, Somalian, and Antarctic plates, together with earthquake slip vector directions and geologic indicators along the Southwest Indian Ridge to update the present-day kinematics of the EAR. We use geological and seismological data to determine the main rift faults and solve for rigid block rotations while accounting for elastic strain accumulation on locked active faults. We find that the data are best fit with a model that includes three microplates embedded within the EAR, between Nubia and Somalia (Victoria, Rovuma, and Lwandle), consistent with previous findings but with slower extension rates. We find that earthquake slip vectors provide information that is consistent with the GPS velocities and helps to significantly reduce uncertainties of plate angular velocity estimates. We also find that 3.16 Myr MORVEL average spreading rates along the Southwest Indian Ridge are systematically faster than prediction from GPS data alone. This likely indicates that outward displacement along the SWIR is larger than the default value used in the MORVEL plate motion model.

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Late Quaternary stratigraphic analysis of the Lake Malawi Rift, East Africa: An integration of drill-core and seismic-reflection data

Cited by 108 publications

References 70 publications

Continuous 1.3-million-year record of East African hydroclimate, and implications for patterns of evolution and biodiversity

Continuous 1.3-million-year record of East African hydroclimate, and implications for patterns of evolution and biodiversity

Late Pleistocene paleohydrography and diatom paleoecology of the central basin of Lake Malawi, Africa

Present‐day kinematics of the East African Rift

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