Urban geology: monumental geology

My writings on urban geology are normally centred in the area around my home in Noord Holland, but sometimes I am lucky enough to travel. A personal wish that I have had since I was a teenager was to see and, if possible, board a dreadnought battleship. This whim was finally satisfied in March 2014, when I visited the last surviving dreadnought from World War I, the USN Texas, preserved at the San Jacinto Battleground State Historic Site, near Houston (Fig. 1A). What I had not realised was the battleship is interred adjacent to the site of the Battle of San Jacinto, where a rag-tag army of insurgents, following defeat at the Alamo and Goliad, decisively defeated the Mexican army in under 20 minutes in April 1836, thereby winning independence from Mexico for Texas.

Figure 1Fig. 1. Two breathtaking exhibits at the San Jacinto Battleground State Historic Site, near Houston, Texas. (A) The dreadnought battleship, USN Texas, commissioned in 1914 and a veteran of two world wars. (B) The San Jacinto Monument, built in 1936 from Cordova Cream Shellstone and the tallest memorial stone column. The San Jacinto Museum of History is in the base.

The Battle of San Jacinto is commemorated by a towering monument (Fig. 1B), which is the tallest memorial stone column, about 175m, and some 4.5m taller than the much better known Washington Monument in Washington DC. The San Jacinto Monument is visible over a wide area of this flat coastal plane and is distinctive enough at a distance, but up close it is highly distracting to the geologist (Rhodes, 2011, pp. 218-219).

Cordova Shell Stone

The San Jacinto Museum of History, located at the base of the monument, has an explanatory display that helpfully describes the facing stone of the steel-reinforced concrete structure as Cordova Cream Shellstone. This was a new name to me and my favourite reference for American building stones did not mention it (Williams, 2009). However, it appears that the name Cordova Cream Shellstone confuses the names of two limestones. Adams (2008) noted two different dimension stones (that is, natural stone or rock that has been selected and fabricated to specific sizes or shapes), namely Cordova Cream and Cordova Shell Stone, which are quarried in the Austin area of west-central Texas by the firm, Texas Quarries. Kyle (2011, fig. 5) published a colour photograph illustrating the different appearances of Cordoba Shell and Cordoba Cream stones, presumably an alternative (or erroneous?) spelling of Cordova. These building stones are extracted from the Lower Cretaceous (Comanchean = Middle Albian, about 100 to 105myrs old; Mancini & Scott, 2006, fig. 1) Walnut and/or Edwards formations (Ellison & Jones, 1984; Moore & Bebout, 1989, fig. 6; Adams, 2008), which crop out north of Austin and were deposited on an extensive, shallow-marine platform (Fisher & Rodda, 1969).

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