Interesting Geoformation at Fort San Severino (Matanzas, Cuba)

In this post, I will attempt to merge two of my favorite sciences of the past - historical archaeology and geology - by discussing a geological formation underlying the colonial fort San Severino, in the picturesque bay of Matanzas, northwestern Cuba.

Underlying all architectural structures there are geological formations. They serve as the foundation for the structures that we build on them or as a quarry for the myriad of construction materials and necessary natural resources derived from them. They are true substructures to our daily existence and a constant reminder of the importance of geology in our everyday life.

Figure 1: View of Fort San Severino's position in the northern coastline of Matanzas bay. 

Background on Fort San Severino

Fort San Severino is a 322-year-old Spanish colonial fort, and the oldest surviving architectural structure in the city of Matanzas (fig.1, 3). The city of Matanzas is itself a tricentennial port city on the north coast of Cuba that acquired world fame during the sugar boom of the 19th century (Hernandez, 2006). I will dedicate a whole post on this marvelous city and its history later (hint hint).

Map of Matanzas city, in Matanzas province, Cuba:
the setting of Fort San Severino (localized slightly offs center of map) . From Atlas de Cuba (1969). North is up.

San Severino was planned as a component within the military protection belt of the region of Havana. This region had a geopolitical span that included the small population of Matanzas (Alfonso, 1854). The bay of Matanzas was spottily underpopulated then but had frequent illicit trade along with sporadic pirate attacks. This illicit commerce and pirate raids, in a way, prompted the Spanish crown for its protection (Alfonso, 1854). The most famous incident is without a doubt that of the Dutch privateer Piet Hein when his ships attacked and possessed the Spanish treasure fleet (the Silver Fleet or Silverloot) right on the bay in 1628 (fig. 2). Other previous, but of nevertheless interesting occurrences include that of the Veracruz fleet who took refuge in the bay running from Jacques de Sore in 1555, and the capture of Francesco Estroce by Pedro Menendez Marquez in 1580 (Dominguez, 1959). An instance in which the bay of Matanzas served as a military-strategic locality.

Figure 2: Woodcut engraving commemorating the possession of the Silver Fleet by Piet Hien (shown in the upper left corner) on the bay of Matanzas (shown on the insert map of Cuba on left lower corner) This illustration is idealized because the hills surrounding the bay are of a gentle slope, like an amphitheater, not as steep as shown here.

Plans for the construction of the fort began in the 1680s, but the first stone was not placed until the fall of 1693 when the city was officially founded (Alfonso, 1854; Hernandez, 2006). In fact, this post is about its building stones, its masonry, and the Jaimanitas formation, which is its underlying geological setting. The Jaimanitas formation was originally called coastal "Seboruco" by Alexander Humboldt, and other geographers of the 18th and 19th century, but not described until 1940 (Lexicon, 2014:47). Both the masonry and the Jaimanitas Fm. are biogenic fossil-rich limestones formed in shallow warm marine environments, and its coastal span is also the geological substrate to other coastal military forts around the bay.

There are many ways to classify limestone. This is usually done based on its composition and content. Limestone is a carbonate sedimentary rock most commonly formed in warm and shallow clear waters, formed from the accumulation and compaction of reef debris, bits of coral, shells, alga, sand, and even fish fecal pellets within a Calcium carbonate matrix. The definitions given below are a form of lithological classification, which pertains to the macroscopic aspect of the rock or simply those aspects visible to the naked eye. In the petrographic sense or the microscopic characteristics of the rock, such limestones are named for the particulates or clasts that make them up and the type matrix or cement that holds everything together (fig. 4-7).

Fort San Severino sits on the Jaimanitas Formation, an uplifted coralline limestone formed underwater from coral reef rubble, sand, and microscopic microorganisms during the latter part of the Pleistocene epoch, between 180,000 and 82,000 thousand years ago. This formation surrounds the coastal parameter of the bay of Matanzas, and most of the Cuban archipelago (Cabrera and Penalver, 2003).

Recent uplifting due to plate movements and the resulting adjusting and readjusting of consequent fractures of the rock has raised or uplifted some of these massive reef biomes above present sea level, providing a geological setting to the region where fort Severino lies. One can now walk on what used to be coral reefs 5-10 meters below water during the Pleistocene (fig. 3-5).

Figure 3: Fort San Severino, where the masonry merges into the underlying Jaimanitas Formation
at Santa Ana bastion; photo looking North.

Formations

Geologic formations are the basic units of lithostratigraphy (from the Greek lithos = meaning rock, and the Latin stratum = layer), which is a technical term for the science that studies rock layers, their age, and their origins. There are many practical and intellectual benefits for human society in their study. In the practical sense, knowing about rock beds and their possible age is essential for a bundle of everyday practicalities such as basic materials, the discovery of fossil fuels or minerals, and many other resources that right now many take for granted. Geology is inseparably linked to human social and economic development and advance.

Formations are often composed of several types of rocks, but with distinctive, identifiable characteristics as a whole. The limestone of the Jaimanitas Fm. is generally a fossiliferous limestone, meaning that its composition is comprised of fossilized organisms, mostly extant, which also gives it the name of organogenic limestone (Cuban Lexicon, 2014:47). When these layers of sediment form and consolidate into rock they record within themselves clues to the conditions of the environment that allowed for their formation.

Figure 4: Part of the East wall section. The stone masonry lies over the uplifted Pleistocene reef that is the Jaimanitas Fm. Bullet holes are visible in this section, a reminder of its military past. Note how the limestone was shaved to accommodate the masonry.

Figure 5: Contact between the Jaimanitas fm. underlying the eastern wall masonry.
Note that the surface of the natural rock was manicured and leveled to adopt the building blocks. 

The association of some Quaternary fossils characterizes the Jaimanitas formation, although index fossils are not yet assigned to it specifically (Cabrera and Penalver, 2003). These fossils include colonies of scleractinian corals such as Acropora and Diploria species (fig. 6) and the mollusk shells of the large queen conch Strombus gigas visible on figure 7. These fossils dot the sea walls and masonry that encases the fort.

Figure 6: Fossilized colony of the brain coral Diploria sp. in situ
within the reef rubble on the fort's old natural sea wall.

Figure 7: Fossilized queen conch Strombus gigas on one of Severino's walls.

Interesting Problem

The stones that make up the masonry of the fort are also composed of what seems to be the same limestone which generally makes up the Jaimanitas fm. But here is a contradicting problem. Local legends and some accounts recount that the stones used for the construction of the fort, quarried by slaves and prisoners, came from the hills north of the fort, and thus not from the surrounding coastal rock which is the Jaimanitas fm (Hernandez, 2006: 40). The Jaimanitas formation does not extend far away from the coast, and could not have been quarried anywhere else, except in its proximal coastal settings. Moreover, the first formation that pinches out into the hills rising behind the fort, which is the Canimar formation, is made up of marl, a softer and older limestone. Could these legends be wrong, and instead the rocks were mostly quarried right on where the fort was built?

Documentation shows this is likely so. Few letters sent from the captain general, Severino de Manzaneda to the king of Spain Charles II (in Spanish Carlos 2) dated between 1693 and 1694, hint at the extraction, in situ, of the Jaimanitas limestone using explosives (AGI/Santo Domingo, 457; Hernandez, 2006: 42). Some of these documents suggest the recycling of the rock excavated from the leveling of the moat was used as a building material as well. In one of the letters Severino mentions its usefulness because of the rock's hardness, he calls them "piedras durisimas" or really hard stones (Hernandez, 2006: 42). This could explain why most of the masonry observed at the fort resembles the Jaimanitas Fm.Yet, these are just observations that have not been properly tested. To confirm them, one would have to sample all these geological formations, and compare them lithologically and petrologically to several samples from the fort's base rock and masonry. But that will be a project for the future.

Addendum: November 24, 2016
 

It was recently brought to my attention (thanks to Odlanyer Hernández, archaeologist colleague) that the conclusion reached here from my observations were in fact tested and published in the 1980's and 90's by Samuel Gerardo, a local researcher. Gerardo found that the rocks could have indeed only come from the coastal limestones of the Jaimanitas Fm. and not the softer rocks from other formations surrounding the bay.

I want to end with words from S. Hernandez's book on Fort San Severino (my translation from Spanish) because I think with them she captures the essence, a bit of the romanticism and nostalgia associated with the investigation of such antique structure where so many things happened to human lives for so many years:

"...This investigation is just a start point, this theme is not extinct and the research must continue. Unearthing and unraveling the anecdotes and occurrences impregnated on the walls of the old fort is just a matter of time. The waters of the bay no longer wash its shore, but the sea is visible from its interior..."

San Severino: old guardian of the bay of Matanzas,
overlooking the bay in the same way it has done for the last 300 years.

References

Alfonso, Pedro. 1854. Historias de un Matancero: apuntes para la historia de Cuba, con relacion a la ciudade de San Carlos y San Severino de Matanzas. Marsal y Ca., Matanzas.

Archivo General de Indias (AGI)/Santo_Domingo, 457: Severino al Rey: feb. 1693 and 3 de nov. 1694.

Cabrera, Miguel and Leandro L. Penalver. 2003. Contribucion a la estratigrafia de la formacion Jaimanitas y su relacion estratigrafica con las demas formaciones del Pleistoceno superior. Memorias GEOMIN, 2003, La Habana, March 24-28, ISBN 959-7117-11-8.

Dominguez, F. J. Ponte, 1959. Matanzas: Biografia de Una Provincia.  

Hernandez Godoy, Silvia. 2006. El Castillo de San Severino: Insomne Caballero del Puerto de Matanzas. Ediciones Matanzas, Matanzas, Cuba.

Stratigraphic Lexicon of Cuba. 2014. Instituto de Geologia y Paleontologia, Editorial Centro Nacional de Informacion Geologica.