The Quaternary deposits of the Gefara Plain are comprised of three major facies – alluvial fan facies of sands and gravels which blankets the base of the Jebel Nafusa escarpment; floodplain facies of fluvial sands and silts with aeolian dunes which underlies most of the Gefara Plain and, aeolian coastal dune facies, predominantly calcarenitic, which is confined to a narrow coastal zone. Well exposed sections in the eastern part of the plain allow sub-division of the floodplain deposits into a number of mappable units defined and bounded by surfaces of stratigraphic discontinuity. The lithologies of these units are described and compared from selected type sections. The relationships between the units, their geometry, and the nature of the surfaces of stratigraphic discontinuity are discussed. It is proposed that, the lithostratigraphic sequence displayed by the Quaternary floodplain deposits of the eastern Gefara region provides a firm basis for correlation, not only with floodplain deposits in other parts of the plain but also with the other major facies developed in the area. In addition, the recognition of significant stratigraphic breaks in the sedimentary sequence combined with facies analysis lays a firm foundation for an interpretation of the geological history of the region.

Vertical, tubular borings, either simple or subdivided into cells by horizontal, spirally ornamented partitions of cemented fine silt, are common in the uppermost part of Unit Q3 of the Quaternary floodplain deposits in the eastern part of the Jeffara Plain. The structures display many features similar to those found in nests constructed by tube-dwelling, solitary wasps and bees. The size of the cells, the spiral construction of the partitions and the general architecture of the cells is closely comparable to the nest structure of the large carpenter bee Xylocopa virginica krombeini Hurd., and it is suggested that the Quarternary nests were constructed by a bee of Xylocopid type.

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The Gargaresh Formation, of Quaternary age, is shown to be comprised of six members each of which is made up from cross-bedded calcarenite dunes of aeolian origin resting on localised lenses of marine gravels and shallow-dipping, cross-bedded calcarenites of littoral type. The surfaces on which the marine deposits at the base of each member rest, are surfaces of discontinuity cut by wave action. Landwards, the surfaces are shaped by fluvial and aeolian erosion, soil formation and solution and delimit an equivalent number of members in quartzose silts of fluvio-aeolian origin making up the Jeffara Formation. Shorewards the Jeffara silts grade into, interdigitate with and, commonly, lap onto the marine deposits so that that within each depositional unit there is an overall sense of progradation reflecting advance of continental facies in response to falling sea level. A progressive seawards stacking of dune deposits with decreasing age suggests that progradation appears to have occurred at formational level also. However, while this may be true, the various elevations of the fossil beach deposits suggest that decreasing age of sea level high stands is not matched by decreasing altitudes, instead, high stands both higher and lower than present day sea level were involved in the overall drop. The possibility that variation in beach elevations may, however, reflect the influence of tectonic uplift and/or downwarp is also noted.

Study of borehole data in the foothill region of the Jabal Nafusah shows that the Suq al Jum'ah palaeowadi, which cuts the jabal east of Gharyan, comprised a major drainage channel which extended in the subsurface far out from the jabal into the southern part of the Jifarah Plain. The channel is filled with sands and gravels. Basalt lava flows, channelled along the valley in outcrop for 36 km, extend for a further 48 km in the subsurface. The palaeowadi was possibly initiated in the Pliocene and appears to have been completely filled and abandoned by the end of the Pleistocene. During Holocene rejuvenation of the drainage system, the Wadi al Majanin developed as the major wadi in the region. It did not, however, excavate the palaeowadi but instead followed a different but roughly parallel northward trend.