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Acacus - First Earthcache in Libya EarthCache

Hidden : 01/14/2008
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Size: Size:   other (other)

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Geocache Description:

Tadrart Acacus is a desert area in western Libya and is part of the Sahara. It has a large variation of landscapes, from differently coloured sanddunes to arches, gorges, rocks and mountains.

Some geoarchaeological characteristics of the Tadrart Acacus:

Travertine: Travertine deposits have been found in numerous caves and rock shelters within the Tadrart Acacus, developed in fractures and in the joins between strata. The formation of travertine requires a higher availability of water than is at present the case. A research of an Italian-Libyan Archaeological Mission involved the uranium/thorium dating of these deposits, and the definition of the isotopic composition of stable isotopes of oxygen and carbon. Dates range from 14.000 to 10.000 years B.C., and the samples show isotopic depletion. It can be said, that they were formed by meteoric water, indicating intense monsoon rains in the central Sahara at the beginning of the Holocene.

Rock varnish: Rock varnish is a fine film rich in manganese which covers the surface of sandstone exposed to the atmosphere. Its origins are generally attributed to microbial activity under humid conditions in the past. The Italian-Libyan team obtained some consistent radiocarbon datings for this substance (spanning the Early and Middle Holocene); however, it is not entirely clear what part of the varnish has been dated. The rock varnish in the Messak Settafet, as shown by microscopy, is composed of three microlayers of different composition, belonging to three different phases of the Holocene.The innermost layer is rich in alluvial clay, indicating humid conditions (Wet Holocene); the presence of P205 indicates biological activity during deposition. The second microlayer is rich in manganese, and is of bacterial origin; the outer layer is made up of aeolian quartz dust, and was formed during the Late Holocene desertification. Lake Deposits: Lake sediments found in the interdune corridors indicate the presence of palaeolakes in the ergs, the result of higher levels of rainfall. During the Holocene intense precipitation caused the oversaturation of the dunes and consequently a rise in the water table. Radiocarbon dating indicates the presence of lakes between 8.400 and 4.600 years B.C. The sedimentary facies, composed of peat, carbonated mud, and then a gypsum crust, shows the gradual rise in water levels in the lake, and the subsequent drying up of the basin. The molluscs present in the sediment and the fragments of ostrich eggs near the deposits represent a register of the isotopic composition of the waters of the lakes, and of the rates of precipitation in surrounding areas.

How to get there: The asphalt roads end in Awaynat. (N25°47.165 E010°34.510) To enter the desert, you need a permission of the Libyan authorities and a 4x4. You must be accompanied by an official represetative of the tourism police as well.

How to log this cache: On the given coordinates, you find the rock formation that you see on the picture. In English, it is called “The thumb”.
1. What`s the Tuareg name of it? Send an email to, and replace the xxxx by the Tuareg name of the “thumb”. (4 letters). Notice: There might be two different spellings. We look for the one, that ends with a “d”. You get an autoreply, when your answer is correct. It is recommended to write at least one or two sentences in your mail, otherwise it might be concidered as spam, and the autoresponder does not work.
2. Post a photo showing you with your GPSr in front of the "thumb"-rock.
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