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Field visit to the site of reported heavy mineral sand deposits located along the coast of Somaliland have been completed. The area of interest consists of an approximately 120 km section of the northern Somaliland coast between degrees longitude 44° E and 45° E, and stretches between the port city of Berbera westwards to the settlement of Laghaye.
A steep escarpment, underlain by high grade gneisses of the Somali Shield and capped by Pleistocene basalts, flanks a narrow coastal plain. A topographic drop of over 600 m in 50 km is apparent. A few isolated hills occur within 15 km of the coast but generally the coastal plain is flat and rather barren. Large, low angle, alluvial fans (wadis) deliver sediment and form the dominant landform. Approximately 1 km from the coast, marine sands are evident both with and without heavy minerals. It is apparent that the coastline is prograding and very recent in age. Long elongate dune forms indicate significant longshore drift. The longshore drift is directed towards the west and characterises the shallow water currents of the area. Wave height is low as noted by absence of storm surge or high tidal deposit deposition.
The beaches sampled in all cases showed the sands to be well sorted and heavy mineral enriched. In only a few areas was a significant silty overburden observed. However, silty intercalations of alluvial wadi material are expected to be present in most areas. A shallow water table is present along most of the coastline.
Samples show between 7% and 94% THM with most samples greater than 50% THM. The split within the heavy mineral fraction was fairly uniform with ilmenite comprising 20% to 40% and magnetite forming 5% to 20%. The remainder of the heay mineral fraction is non-magnetic and dominated by garnet, zircon and monazite.
It is apparent that sand hummocks are developed extensively along all the beach areas visited. Sand has accumulated on the sea side of vegetation copses indicating the dominant wind transport direction is off-shore. These hummocks are composed of fine to medium grained sand rather than silt or dust and therefore indicate that very strong wind speeds are common (in excess of 20 km/h). In many areas fluted and wind eroded boulders were observed. Large boulders indicate the dominant wind direction to be from the south and directed offshore. The seasonal wind regime indicated from these lines of evidence is therefore regarded to be an important control on the geomorphology of the coastal plain. It provides an effective manner to winnow the silt deposited from the wadis from the heavy mineral fraction. Once the silt fraction is blown offshore longshore drift will remove it from being redeposited along the coast. Similarities with the wind concentrated diamond placers along the Namibian coast are made and it is clear that the heavy mineral sand deposits of Somaliland are unique having formed through a complex interaction of wind, fluvial and marine concentrating mechanisms.
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