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The paradox of the Tibesti crater palaeolakes (Sahara, Northwest Chad)

Recent field work in the Tibesti Mountains opens a new chapter in the reconstruction of the last climatic cycles in the central Sahara and their lacustrine environments.

For the first time, complete lacustrine sections were sampled in the 900 m deep crater of Trou au Natron at Pic Toussidé (3,315 m a.s.l.), and in 800 m deep Era Kohor, the major sub-caldera of Emi Koussi, the Sahara’s 3,445 m high peak. The probed diatomites are located 360 and 125 m above the present-day bottom of the calderas. Studies in the 1960s suggested that lake levels in the Trou au Natron were 300–500 m high at 12,400–14,970 uncal. yrs BP. Such lake depths and resulting water volumes, however, are hardly conceivable in view of the limited intake area and precipitation-evaporation ratios which would have required local rainfall by far surpassing estimates for latitudes 19–21°N from the full-Holocene record of Lake Yoa situated 460 or 220 km southeast, and 1,550 or 2,450 m (sic) lower. New AMS dates show that previous 14C dates were wrong and that differences in altitude cannot explain the unparalleled lake depths and postglacial humid conditions 4,000–7,000 years earlier than in the surrounding Saharan regions.

 

 

 

A2 Kroepelin Fig 1 lhk 250px 2015 12
Sampling of lacustrine deposits in Era Kohor, Emi Koussi’s deepest caldera, at 125 m above present bottom.
Photo: Adam Polczyk
  A2 Kroepeling Fig 2 lhk 250px 2015 12Extracted Holocene lake remains in the Trou au Natron at Pic Toussidé at 360 m above present bottom.
Photo: Stefan Kröpelin

 

Project

 

 

 

Raising the Sahara’s most complete climate record

Raising the Sahara’s most complete climate record

Coring the complete set of deposits at the bottom of a desert lake in northeast Chad in one of the driest and most isolated parts...

Exploring the subsurface – Geophysics in the Azraq...

Exploring the subsurface – Geophysics in the Azraq Basin, Northern Jordan

Non-invasive surface geophysical techniques are a useful tool to investigate the earth’s subsurface structure. In order to identif...

Advances in laboratory analyses of the Lake Yoa lo...

Advances in laboratory analyses of the Lake Yoa long core

While planned field work in Wadi Shati in Libya was impossible for obvious reasons, progress has been made on laboratory analyses...

Resolving sedimentary deposits in the Azraq Basin/...

Resolving sedimentary deposits in the Azraq Basin/Jordan using non-invasive geophysical techniques

A second geophysical field survey was undertaken in the Azraq Basin in October 2012.  

The lakes of Ounianga – Chad's first UNESCO World...

The lakes of Ounianga – Chad's first UNESCO World Heritage site

The 19 lakes of Ounianga in the hyperarid desert of northeastern Chad are the Sahara's most important relic from her early- to mid...

Into the Sahara Desert’s Deep Past. Expedition to...

Into the Sahara Desert’s Deep Past. Expedition to the Remote Tibesti Mountains

It is hard to believe: We have sent a probe 500 million km to a comet to analyze rock samples, but no geologist has yet dug his sp...

Applied Geophysics at Lake Chew Bahir, Southern Et...

Applied Geophysics at Lake Chew Bahir, Southern Ethiopia

In November/December 2014, four scientists from the Institute of Geophysics and Meteorology of the University of Cologne conducted...

Exploring sedimentary basins in the East-African R...

Exploring sedimentary basins in the East-African Rift Valley System

Three month after the first journey to Southern Ethiopia, a group of scientists from the Institute of Geophysics and Meteorology o...

Ennedi mission

Ennedi mission

In October 2015, A2 members followed an invitation for a field trip in the Ennedi massif of NE Chad. Main purpose was the evaluati...

The paradox of the Tibesti crater palaeolakes (Sah...

The paradox of the Tibesti crater palaeolakes (Sahara, Northwest Chad)

Recent field work in the Tibesti Mountains opens a new chapter in the reconstruction of the last climatic cycles in the central Sa...

Exhibition “Tibesti - Expedition in the Sahara” at...

Exhibition “Tibesti - Expedition in the Sahara” at the Kanzlergalerie

After the well-attended exhibitions on project A2’s geoarchaeological research and related World Heritage endeavours in Northern C...

Back from another mission in the Tibesti (Central...

Back from another mission in the Tibesti (Central Sahara)

A2 members just returned from another equally demanding as rewarding four-week expedition in the Tibesti mountains. The team compr...

The Ennedi Massif: Natural and cultural landscape...

The Ennedi Massif: Natural and cultural landscape – Chad’s second World Heritage site

18 years after an initiative taken by Stefan Kröpelin in 1999, UNESCO’s World Heritage Committee has unanimously inscribed the Enn...

 

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