British pioneers of the geology of Gibraltar, Part 3: E. B. Bailey and Royal Engineers 1943 to 1953

Edward Battersby Bailey (1881-1965), Director of the Geological Survey of Great Britain, visited the 6-km² Gibraltar peninsula twice in 1943, in transit from/to England and the Mediterranean island of Malta. He spent only five days in total on Gibraltar, but submitted two influential reports to its Fortress Headquarters, guided by rock features exposed by recent quarrying. On his recommendation, a deep borehole was drilled below the northern isthmus in an attempt to locate a supposed aquifer in Cenozoic sandstones believed to extend south from Spain, and A. L. Greig (a graduate of Imperial College, London, serving locally in the ranks of the Royal Engineers) prepared a new geological map (at 1:5,280) and a report to help guide tunnel excavation within the bedrock. Between 1945 and 1948, Lieutenant (later Captain) G. B. Alexander (a graduate of the University of Cambridge also serving in the Royal Engineers) generated a much more detailed map (at 1:2,500) of the bedrock plus superficial deposits, together with associated diagrams and geotechnical reports. These unpublished documents, and fossils collected during their preparation, influenced a re-interpretation of Gibraltar (as the remnant of an overturned limb of a klippe of Early Jurassic dolomitic limestone thrust into position during the Betic-Rif Orogeny), published by Bailey in 1953. A report to accompany Alexander's map was never completed, but documents constituting the most complete record known of his Gibraltar work are now preserved within the archives of the British Geological Survey. Reserve army officers later compiled a geological map of Gibraltar (at 1:10,000) published by the Royal Engineers in 1991. Thereafter, as garrison strength became greatly reduced, work under military auspices was increasingly superseded by civilian research.