The Absolute Age of the Quaternary Lacustrine Limestone of the Al Mahrúqah Formation—Murzuq Basin, Libya

Thiedig, F.; Oezen, Deniz; El-Chair, M.; Geyh, Mebus A.

doi:10.1016/b978-044450611-5/50007-6

Cited by 14 publications

(14 citation statements)

References 7 publications

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“…This finding contrasts with those of Thiedig and Geyh (2004) and Thiedig et al (2000) who applied U/Th dating to the al-Mahruqah Formation and found it to be much younger (c. 200-400 ka). Because we have so far studied different exposures, it is possible that this discrepancy lies in the fact that we are dating different sediments and thus different lake episodes.…”

Section: Brakcontrasting

confidence: 55%

“…Because we have so far studied different exposures, it is possible that this discrepancy lies in the fact that we are dating different sediments and thus different lake episodes. It was decided to investigate this by applying magnetostratigraphy to the type sections dated by Thiedig et al (2000) and Thiedig and Geyh (2004). Thus the type section of al-Mahruqah Formation near Brak (Fig.…”

Section: Brakmentioning

confidence: 99%

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DMP VIII: Palaeohydrology and palaeoenvironment

et al. 2009

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The January 2009 fieldwork season conducted geomorphological and palaeoenviromental surveys in as yet unexplored parts of the Lake Megafazzan Basin, as well as continuing research in the Wadi al-Hayat and Ubari Sand Sea. Lake Megafazzan sediments were investigated at two sites on the eastern margin of the basin. At the first site, east of Tamessah, 24 m of stratigraphy was investigated and found to consist of a lacustrine carbonate unit at the base progressing into a fluvial unit and then an upper carbonate unit. The sediments were sampled for magnetostratigraphy and cosmogenic nucleide dating in order to determine their age. Similar studies were undertaken in the vicinity of the Arial Agricultural Project, where 31 m of section were logged and sampled. Here the sediments were quite different, being composed of a deltaic sequence consisting of stacked channels and palaeosols, thought to represent the outflow delta of the palaeolake. Many new Holocene lake sediment deposits were discovered and sampled in the Wadi al-Hayat and the Ubari Sand Sea, including a 5 m section through Jarma Playa that appears to record the last arid-humid cycle. Lake Gabr 'Awn and the moat round Old Jarma were cored in order to gather a detailed picture of recent palaeoenvironmental change. Finally, we implemented a pilot geophysical survey to test the ability of state-of-the-art Ground Penetrating Radar (UltraGPR) technology for detecting and mapping buried palaeolake sediments under the dunes of the Ubari Sand Sea. The UltraGPR was found to be very effective, detecting palaeolake sediments as much as 60 m beneath the surface. Preliminary results suggest such sediments underlie much of the region. IntroductionThe palaeohydrology and palaeoenvironment sub-project of the Desert Migrations Project (DMP) focuses on palaeoclimate and hydrological change during the Quaternary in order to further our understanding of the chronology of arid/humid cycles, the nature of the contemporary palaeoenvironment and the processes that caused them. By integrating these results with those of the Pleistocene, Holocene and Garamantian archaeology (DMP sub-projects V and VI) we hope to understand the relationships between palaeoclimate-change archaeology and past human migrations in the Fazzan.Research consisted of three thematic sub-projects. First, logging and dating the stratigraphy of sediments from Lake Megafazzan (the al-Mahruqah Formation). This fieldwork concentrated on evaluation of sediments exposed on the western margin of the basin between the Arial Agricultural Project and al-Haruj al-Aswad (Fig. 1). This work has enabled us to determine the palaeogeography of the eastern margin of Lake Megafazzan from the horizontal changes in sedimentary facies; follow-up laboratory analysis will provide new insights into the palaeoenvironments associated with this giant lake and further constrain the timing of humid climate episodes.The second sub-project involved studying the younger palaeolake sediments in the Jarma region deposited by smaller Holoce...

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Section: Brakcontrasting

confidence: 55%

Section: Brakmentioning

confidence: 99%

DMP VIII: Palaeohydrology and palaeoenvironment

et al. 2009

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“…Recent palaeoenvironmental investigations have shown that Middle and Late Pleistocene interglacials may have been wetter than today (Thiedig et al, 2000;Drake et al, 2008;Geyh and Thiedig, 2008;Gallala et al, 2010), and higher water availability also is recorded for the Early and Middle Holocene (Cremaschi, 1998(Cremaschi, , 2002Zerboni, 2006Zerboni, , 2007Zerboni, , 2008Cremaschi and Zerboni, 2009;Cremaschi et al, 2010). Geyh and Thiedig (2008) identified several lacustrine terraces accumulated in the SW Fezzan during humid episodes at N420, 380-290, 260-205, and 140-125 k YBP, roughly coincident with the MIS (Marine Isotope Stage) 9, MIS 7, and MIS 5.5 interglacial periods; moreover, after Termination 1, a last phase of surface aquifers reactivation occurred during the Holocene African Humid Period, dating in the region of 9.8-5 uncal.…”

Section: Climate and Palaeoclimatementioning

confidence: 95%

“…This age determination points to a humid phase corresponding to the MIS 7, substantially in accordance with the deposition of several lacustrine carbonatic terraces in the region, recently dated by Geyh and Thiedig (2008) between 260 and 205 k YBP. Besides this chronological correspondence, Pleistocene pedogenetic phases on the Messak Settafet plateau should occur synchronously with the formation of lake deposit in the adjoining areas, such as in the Murzuq region (Thiedig et al, 2000;Geyh and Thiedig, 2008) and along the wadi Shati (Petit-Maire, 1982). Moreover, these considerations are largely in contradiction with the hypothesis proposed by Skowronek (1988), who, on the basis of several palaeopedological and sedimentological indicators, concluded that no humid-tropical soil was formed in the region since the early Tertiary.…”

Section: Soils Formation Chronology and Palaeoclimatic Implicationsmentioning

confidence: 98%

Micromorphological approach to polycyclic pedogenesis on the Messak Settafet plateau (central Sahara): Formative processes and palaeoenvironmental significance

2011

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“…TIMS uraniumseries dates suggest an age of 128 ka (Thiedig et al, 2000) to ~135 ka from 21 uraniumseries ages obtained by using shells from the coquina.…”

Section: Nahiyah Membermentioning

confidence: 99%