Paleolimnological features of a mega-lake phase in the Makgadikgadi Basin (Kalahari, Botswana) during Marine Isotope Stage 5 inferred from diatoms

Mareike Schmidt, Markus Fuchs, Andrew C. G. Henderson, Annette Kossler, Melanie J. Leng, Anson W. Mackay, Elisha Shemang, Frank Riedel

Research output: Contribution to journalArticle

Abstract

The Makgadikgadi-Okavango-Zambezi basin (MOZB) is a structural depression in the south-western branch of the East African Rift System of the northern and middle Kalahari, central southern Africa. In the present day, the mainly dry subbasins of the MOZB are part of a long-lived lacustrine system that has likely existed since Early Pleistocene and from which an extant freshwater fish radiation emerged seeding all major river systems of southern Africa. During hydrologically favourable periods the subbasins were connected as a single mega-lake termed Lake Palaeo-Makgadikgadi. Previous geomorphological studies and OSL dates have provided evidence for repeated mega-lake periods since approximately 300 ka. The environmental and climatic implications of such large scale late Quaternary lake-level fluctuations are controversial, with the duration of mega-lake phases poorly constrained. Here, we present the first evidence for a Marine Isotope Stage (MIS) 5 mega-lake period (about 935-940 m a.s.l.) reconstructed from a diatom-rich, 30-cm-thick lacustrine sediment section, exposed close to a palaeo-shoreline of the Makgadikgadi Basin. Based upon the environmental setting and in comparison with sedimentation rates of other similar lake environments, we tentatively estimated that the highstand lasted approximately 1 ka during MIS 5d-b. The 30-cm section was sampled in 0.5-cm steps. Diatom species diversity ranges from 19 to 30 through the section. The dominant species are Pseudostaurosira brevistriata, Rhopalodia gibberula, Cyclotella meneghiniana and Epithemia sorex. The total of 60 sediment samples provide us with a record at decadal to bi-decadal resolution. Based on diatom assemblages and their oxygen isotope composition (delta O-18) we infer an alkaline and mostly oligohaline lake with shallow water conditions prevailing in MIS 5, and is potentially analogous to a Heinrich event. The climate over southern Africa during MIS 5 has been considered very arid but the hydromorphological context of our sediment section indicates that we captured a megalake period providing evidence that short-term excursions to significantly higher humidity existed. A hydrologically more favourable environment during MIS 5 than formerly presumed is in line with the early human occupation of the Kalahari.
Original languageEnglish
Pages (from-to)373-390
Number of pages18
JournalJournal of Paleolimnology
Volume58
Issue number3
Publication statusPublished - 2017

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Botswana
marine isotope stage
Bacillariophyceae
isotopes
diatom
basins
lakes
lake
basin
Southern Africa
Heinrich event
Rhopalodia
Epithemia
lacustrine environment
Cyclotella meneghiniana
highstand
lake level
seeding
lacustrine sediments
sedimentation rate

Cite this

Schmidt, M., Fuchs, M., Henderson, A. C. G., Kossler, A., Leng, M. J., Mackay, A. W., ... Riedel, F. (2017). Paleolimnological features of a mega-lake phase in the Makgadikgadi Basin (Kalahari, Botswana) during Marine Isotope Stage 5 inferred from diatoms. Journal of Paleolimnology, 58(3), 373-390.
Schmidt, Mareike ; Fuchs, Markus ; Henderson, Andrew C. G. ; Kossler, Annette ; Leng, Melanie J. ; Mackay, Anson W. ; Shemang, Elisha ; Riedel, Frank. / Paleolimnological features of a mega-lake phase in the Makgadikgadi Basin (Kalahari, Botswana) during Marine Isotope Stage 5 inferred from diatoms. In: Journal of Paleolimnology. 2017 ; Vol. 58, No. 3. pp. 373-390.
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abstract = "The Makgadikgadi-Okavango-Zambezi basin (MOZB) is a structural depression in the south-western branch of the East African Rift System of the northern and middle Kalahari, central southern Africa. In the present day, the mainly dry subbasins of the MOZB are part of a long-lived lacustrine system that has likely existed since Early Pleistocene and from which an extant freshwater fish radiation emerged seeding all major river systems of southern Africa. During hydrologically favourable periods the subbasins were connected as a single mega-lake termed Lake Palaeo-Makgadikgadi. Previous geomorphological studies and OSL dates have provided evidence for repeated mega-lake periods since approximately 300 ka. The environmental and climatic implications of such large scale late Quaternary lake-level fluctuations are controversial, with the duration of mega-lake phases poorly constrained. Here, we present the first evidence for a Marine Isotope Stage (MIS) 5 mega-lake period (about 935-940 m a.s.l.) reconstructed from a diatom-rich, 30-cm-thick lacustrine sediment section, exposed close to a palaeo-shoreline of the Makgadikgadi Basin. Based upon the environmental setting and in comparison with sedimentation rates of other similar lake environments, we tentatively estimated that the highstand lasted approximately 1 ka during MIS 5d-b. The 30-cm section was sampled in 0.5-cm steps. Diatom species diversity ranges from 19 to 30 through the section. The dominant species are Pseudostaurosira brevistriata, Rhopalodia gibberula, Cyclotella meneghiniana and Epithemia sorex. The total of 60 sediment samples provide us with a record at decadal to bi-decadal resolution. Based on diatom assemblages and their oxygen isotope composition (delta O-18) we infer an alkaline and mostly oligohaline lake with shallow water conditions prevailing in MIS 5, and is potentially analogous to a Heinrich event. The climate over southern Africa during MIS 5 has been considered very arid but the hydromorphological context of our sediment section indicates that we captured a megalake period providing evidence that short-term excursions to significantly higher humidity existed. A hydrologically more favourable environment during MIS 5 than formerly presumed is in line with the early human occupation of the Kalahari.",
author = "Mareike Schmidt and Markus Fuchs and Henderson, {Andrew C. G.} and Annette Kossler and Leng, {Melanie J.} and Mackay, {Anson W.} and Elisha Shemang and Frank Riedel",
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Schmidt, M, Fuchs, M, Henderson, ACG, Kossler, A, Leng, MJ, Mackay, AW, Shemang, E & Riedel, F 2017, 'Paleolimnological features of a mega-lake phase in the Makgadikgadi Basin (Kalahari, Botswana) during Marine Isotope Stage 5 inferred from diatoms', Journal of Paleolimnology, vol. 58, no. 3, pp. 373-390.

Paleolimnological features of a mega-lake phase in the Makgadikgadi Basin (Kalahari, Botswana) during Marine Isotope Stage 5 inferred from diatoms. / Schmidt, Mareike; Fuchs, Markus; Henderson, Andrew C. G.; Kossler, Annette; Leng, Melanie J.; Mackay, Anson W.; Shemang, Elisha; Riedel, Frank.

In: Journal of Paleolimnology, Vol. 58, No. 3, 2017, p. 373-390.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Paleolimnological features of a mega-lake phase in the Makgadikgadi Basin (Kalahari, Botswana) during Marine Isotope Stage 5 inferred from diatoms

AU - Schmidt, Mareike

AU - Fuchs, Markus

AU - Henderson, Andrew C. G.

AU - Kossler, Annette

AU - Leng, Melanie J.

AU - Mackay, Anson W.

AU - Shemang, Elisha

AU - Riedel, Frank

PY - 2017

Y1 - 2017

N2 - The Makgadikgadi-Okavango-Zambezi basin (MOZB) is a structural depression in the south-western branch of the East African Rift System of the northern and middle Kalahari, central southern Africa. In the present day, the mainly dry subbasins of the MOZB are part of a long-lived lacustrine system that has likely existed since Early Pleistocene and from which an extant freshwater fish radiation emerged seeding all major river systems of southern Africa. During hydrologically favourable periods the subbasins were connected as a single mega-lake termed Lake Palaeo-Makgadikgadi. Previous geomorphological studies and OSL dates have provided evidence for repeated mega-lake periods since approximately 300 ka. The environmental and climatic implications of such large scale late Quaternary lake-level fluctuations are controversial, with the duration of mega-lake phases poorly constrained. Here, we present the first evidence for a Marine Isotope Stage (MIS) 5 mega-lake period (about 935-940 m a.s.l.) reconstructed from a diatom-rich, 30-cm-thick lacustrine sediment section, exposed close to a palaeo-shoreline of the Makgadikgadi Basin. Based upon the environmental setting and in comparison with sedimentation rates of other similar lake environments, we tentatively estimated that the highstand lasted approximately 1 ka during MIS 5d-b. The 30-cm section was sampled in 0.5-cm steps. Diatom species diversity ranges from 19 to 30 through the section. The dominant species are Pseudostaurosira brevistriata, Rhopalodia gibberula, Cyclotella meneghiniana and Epithemia sorex. The total of 60 sediment samples provide us with a record at decadal to bi-decadal resolution. Based on diatom assemblages and their oxygen isotope composition (delta O-18) we infer an alkaline and mostly oligohaline lake with shallow water conditions prevailing in MIS 5, and is potentially analogous to a Heinrich event. The climate over southern Africa during MIS 5 has been considered very arid but the hydromorphological context of our sediment section indicates that we captured a megalake period providing evidence that short-term excursions to significantly higher humidity existed. A hydrologically more favourable environment during MIS 5 than formerly presumed is in line with the early human occupation of the Kalahari.

AB - The Makgadikgadi-Okavango-Zambezi basin (MOZB) is a structural depression in the south-western branch of the East African Rift System of the northern and middle Kalahari, central southern Africa. In the present day, the mainly dry subbasins of the MOZB are part of a long-lived lacustrine system that has likely existed since Early Pleistocene and from which an extant freshwater fish radiation emerged seeding all major river systems of southern Africa. During hydrologically favourable periods the subbasins were connected as a single mega-lake termed Lake Palaeo-Makgadikgadi. Previous geomorphological studies and OSL dates have provided evidence for repeated mega-lake periods since approximately 300 ka. The environmental and climatic implications of such large scale late Quaternary lake-level fluctuations are controversial, with the duration of mega-lake phases poorly constrained. Here, we present the first evidence for a Marine Isotope Stage (MIS) 5 mega-lake period (about 935-940 m a.s.l.) reconstructed from a diatom-rich, 30-cm-thick lacustrine sediment section, exposed close to a palaeo-shoreline of the Makgadikgadi Basin. Based upon the environmental setting and in comparison with sedimentation rates of other similar lake environments, we tentatively estimated that the highstand lasted approximately 1 ka during MIS 5d-b. The 30-cm section was sampled in 0.5-cm steps. Diatom species diversity ranges from 19 to 30 through the section. The dominant species are Pseudostaurosira brevistriata, Rhopalodia gibberula, Cyclotella meneghiniana and Epithemia sorex. The total of 60 sediment samples provide us with a record at decadal to bi-decadal resolution. Based on diatom assemblages and their oxygen isotope composition (delta O-18) we infer an alkaline and mostly oligohaline lake with shallow water conditions prevailing in MIS 5, and is potentially analogous to a Heinrich event. The climate over southern Africa during MIS 5 has been considered very arid but the hydromorphological context of our sediment section indicates that we captured a megalake period providing evidence that short-term excursions to significantly higher humidity existed. A hydrologically more favourable environment during MIS 5 than formerly presumed is in line with the early human occupation of the Kalahari.

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