Stephen K Donovan (The Netherlands), David AT Harper (UK) and Roger W Portell (USA)
In his 2014, Ted Nield (2014) reflects on building stones and what they tell the geologist about where they are. Once upon a time, building stones in Britain were derived locally and told the informed observer something of the local geology (apart from, of course, the exotic stones imported for banks and office blocks). That is, they were built of local stone from the local quarry. Today, stone is imported from as far afield as China, where once they would have been derived locally by horse and cart or canal boat.
One place where local stone is still used is Antigua in the Lesser Antilles. For example, Jackson and Donovan (2013) described an attractive, green chloritized tuff, which is used throughout the island as a bright and distinctive building stone. Many old structures in rural areas are still constructed of stone, such as walls, buildings (including ruins) and, the subject of this article, disused windmills.
For a general introduction to the geology of Antigua, see Weiss (1994) or Donovan et al (2014). All major stratigraphic units are Upper Oligocene; the regional dip is to the northeast.
The Betty’s Hope site, in the parish of Saint Peter in eastern Antigua (Fig. 1), is an open air monument administered by the Museum of Antigua and Barbuda.
It was the first major sugar plantation on the island, dating from the 1650s, and the largest. The term ‘hope’ refers to an enclosed piece of land and Betty was daughter of Sir Christopher Codrington, Governor of the Leeward Islands (1674) and then owner of the plantation. The plantation was active until the 1940s and the buildings have been partially restored since the late 1980s. The great house (Fig. 2E) and most other buildings are in ruins, but a cotton storage house is now a visitor centre and two windmills still stand, one of which has been fully restored to working order (Fig. 2A-D) (Dyde, 1999; Anon, 2014; Murphy, 2014).
The two windmills are clustered close together on the hillside and are imposing (Fig. 2A). The unrestored windmill (Fig. 2B) shows its years and would benefit from having its stonework repointed. The stonework itself is rather blackened, particularly on the northeast side, facing into the prevailing wind direction. Openings, such as doors and windows, have been sealed. In contrast, the restored windmill (Fig. 2D) is rather splendid. It has been repointed, much of the stonework has been cleaned or is apparently new (Fig. 2C), and the visitor is free to look inside. Stone blocks are commonly between 28 and 38cm wide by 23 to 28cm tall, but the stone is only roughly cut. The entrance is on the west side, out of the prevailing wind.
Building stones, burrows and echinoids
Both windmills are made in local stone. Some blocks are obviously limestone (Fig. 3D-F) from the Antigua Formation, whereas others are sandstones and most probably from the Central Plains Group (Fig. 3A, C). Blocks that are siliciclastics (sandstones) or volcaniclastics may also be from the Basal Volcanic Suite, although both lithologies might be found in the Central Plains Group. Therefore, this one structure may include a ‘sample’ of all three of the islands major rock units. The restored mortar (Fig. 3B) is also, apparently, a local product, composed of a ground limestone with various volcanic and shelly inclusions.
Many stones around the door have either been cleaned or replaced (Fig. 2D). They also include more obvious limestones than on the windward side. A medium- to coarse-grained sandstone block in the doorway (third block up on the right of the door in Fig. 2D), presumed Central Plains Group, includes particularly obvious, large burrows (20 to 25mm in diameter), with a circular section on the two sides that are visible (Fig. 3A, C).
The orientation of the block is unknown, so the attitude of the burrows to bedding cannot be determined, which is a necessary observation to permit accurate identification. However, whatever they may be, these are the first trace fossils to be recorded from the Central Plains Group. Similar and morphologically contrasting burrows occur in some of the limestone blocks seen inside the structure (Fig. 3D, F).
The most surprising find was a brace of heart urchins sticking out of limestone blocks of the Antigua Formation within the windmill (Fig. 3E). These are distinctive and recognisable as Lovenia n. sp (sensu Poddubiuk and Rose, 1985), which is particularly common in fallen blocks around Hughes Point, in the parish of Saint Philip (Donovan et al., 2014, locality 5). However, the Hughes Point site is only accessible by wading, so this is an indication that the same horizon must have been quarried inland.
We gratefully acknowledge the support for our fieldwork in Antigua provided by National Geographic Society grant #GEFNE55-12.
Anon. 2014. Betty’s Hope. http://en.wikipedia.org/wiki/Betty’s_Hope. Accessed 17 September 2014.
Donovan, S.K., Jackson, T.A., Harper, D.A.T., Portell, R.W. & Renema, W. 2014. Classic localities explained 16: The Upper Oligocene of Antigua: the volcanic to limestone transition in a limestone Caribbee. Geology Today, 30: 151-158.
Dyde, B. 1999. Antigua and Barbuda: Heart of the Caribbean. Third edition. MacMillan Education, London, viii+151 pp.
Jackson, T.A. and Donovan, S.K. 2013. Going green: chloritized tuffs from the Oligocene of Antigua. Deposits, 36: 42-44.
Murphy, R. 2014. Betty’s Hope. http://www.archaeologyantigua.org/index.php/betty-s-hope. Accessed 17 September 2014.
Nield, Ted. 2014. Underlands: A Journey through Britain’s Lost Landscape. Granta Books, London, 288 pp.
Poddubiuk, R.H. & Rose, E.P.F. 1985. Relationships between mid-Tertiary echinoid faunas from the central Mediterranean and eastern Caribbean and their palaeobiogeographic significance. Annales Géologiques des Pays Hélleniques, 32 (for 1984): 115-127.
Weiss, M.P. 1994. Oligocene limestones of Antigua, West Indies: Neptune succeeds Vulcan. Caribbean Journal of Science, 30: 1-29.