The evidence for macroscopic life during the Palaeoproterozoic era (2.5-1.6 Gyr ago) is controversial. Except for the nearly 2-Gyr-old coil-shaped fossil Grypania spiralis, which may have been eukaryotic, evidence for morphological and taxonomic biodiversification of macroorganisms only occurs towards the beginning of the Mesoproterozoic era (1.6-1.0 Gyr). Here we report the discovery of centimetre-sized structures from the 2.1-Gyr-old black shales of the Palaeoproterozoic Francevillian B Formation in Gabon, which we interpret as highly organized and spatially discrete populations of colonial organisms. The structures are up to 12 cm in size and have characteristic shapes, with a simple but distinct ground pattern of flexible sheets and, usually, a permeating radial fabric. Geochemical analyses suggest that the sediments were deposited under an oxygenated water column. Carbon and sulphur isotopic data indicate that the structures were distinct biogenic objects, fossilized by pyritization early in the formation of the rock. The growth patterns deduced from the fossil morphologies suggest that the organisms showed cell-to-cell signalling and coordinated responses, as is commonly associated with multicellular organization. The Gabon fossils, occurring after the 2.45-2.32-Gyr increase in atmospheric oxygen concentration, may be seen as ancient representatives of multicellular life, which expanded so rapidly 1.5 Gyr later, in the Cambrian explosion.
The Touissit-Bou Beker district of strata-bound Zn-Pb deposits is hosted in Aaleno-Bajocian dolomites and localized at the Morocco-Algeria frontier in the Pays (Zone) des Horsts (Fig. 1), a part of the Mesozoic Oran Meseta, extending from Taourirt (Morocco) to Tlemcen (Algeria). Localization maps and geologic descriptions have been given elsewhere (Rajlich, 1983;Dupuy, 1984 Dupuy, , 1985.From east to the west, the most important mines are El Abed (Algeria), Touissit and Bou Beker (Moroccco, presently abandoned), and Mekta and Beddiane (Morocco). Information on the metal contents (Dupuy, 1984) is given in Table 1. There are two classic interpretations of the origin of this district: an epigenetic origin (Bouladon, 1948), i.e., migrations of solutions related to faults cutting porous dolomitic levels where deposition of the ore occurred (Claveau et al., 1952; Voirin, 1965), or a syngenetic sedimentary origin (Samson, 1965, 1973). Recent descriptions and interpretations of the Mekta deposit, mined since 1976, have been published (Rajlich, 1983;Dupuy, 1984 Dupuy, , 1986. From lithological and structural data, Rajlich concluded an epigenetic origin with deposition of the ore during late Tertiary times. A model age from lead isotopes corresponding to the Mesozoic was determined and the isotopic compositions are similar to lead from the Bleiberg and Upper Silesia deposits. The mineralization was ascribed to the Mississippi Valley type, the deposited metals and sulfur being assumed to have been transported by brines originating from the evaporite-bearing basin of the Haret plateaus to the south of Mekta.
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