Discover Anguilla and Explore the Fossils & Geodiversity of the Leeward Islands in the Caribbean
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Anguilla, a British Overseas Territory, sits on the northern edge of the Lesser Antilles, rising from the shallow Anguilla Bank as a low-lying limestone island shaped by ancient volcanism and long-term coral reef growth. Part of the Limestone Caribbees, it preserves a geological transition from Eocene volcanic foundations to Miocene and Pleistocene carbonate platforms rich in marine fossils and karst cave systems. Flat wave-cut landscapes, turquoise waters, and living reefs, and caves now define its remarkable landscape. These limestone landscapes preserve evidence of shifting sea levels, reef ecosystems, and remarkable pre-Columbian terrestrial fauna, including extinct giant rodents preserved in cave deposits. Anguilla’s wave-cut platforms, coral reefs, wetlands, and fossil sites form the backbone of its growing geotourism appeal, connecting visitors to deep Caribbean environmental change and protected marine habitats directly influenced by the forces that built the eastern Caribbean’s modern island environments over millions of years.
Rising like a ribbon from the northeastern Caribbean is Anguilla a small British Overseas Territory perched on the outer arc of the Lesser Antilles and forming the northernmost of the Leeward Islands, this limestone‑capped island combines Miocene reef geology, an Eocene volcanic activity, rich Pleistocene fossil deposits with a vibrant modern ecosystem. Today it is celebrated not only for its unspoiled beaches and coral reefs, but also for its growing reputation as a low-key luxury geotourism destination with white sandy beaches and turquoise waters.
Anguilla sits on the Anguilla Bank, a shallow carbonate platform shared with Saint Martin and Saint Barthélemy, forming part of the “Limestone Caribbees” in the outer arc of the Lesser Antilles. This chain of low‑lying islands, stretching from Anguilla to Marie‑Galante a dependency of Guadeloupe, an overseas département of France. Anguilla preserves a remarkable geological transition from early Eocene–Oligocene volcanism to millions of years of limestone and coral reef development.
Unlike the active volcanic islands farther west, the Limestone Caribbees rest on extinct volcanic foundations buried beneath thick Cenozoic carbonate deposits, creating flat, wave‑cut landscapes shaped by long‑term reef growth and tropical coastal processes. Islands such as Antigua, Barbuda, Saint Barthélemy, and La Désirade reveal this double‑arc structure with the inactive limestone arc standing in contrast to the still‑active volcanic arc near Dominica. Together, these limestone‑capped islands have been influenced by ancient volcanism, coral platform evolution, and the geological forces that shaped the eastern Caribbean’s modern coastal environments.
Beneath the postcard scenery of Little Bay, Sandy Ground and Shoal Bay arguably the most famous and celebrated beach in Anguilla, frequently ranked among the best beaches in the world lies a complex geological framework. Anguilla is fundamentally a limestone island of volcanic origin whose low‑lying, flat topography, with only a maximum elevation of around 240 feet above sea level at Crocus Hill near to Anguilla's capital called, The Valley is simply a carbonate platform draped over an older volcanic basement.
The Anguilla Formation is a Miocene reef limestone that dates from roughly 20–12 million years ago. These limestones overlie an older Eocene volcanic basement composed of tuffs and basalt, the remnants of once‑active volcanic centres that formed part of the Lesser Antilles outer arc. Over time, these volcanic rocks were uplifted, eroded, and then submerged, creating a foundation on which thick Miocene to Pleistocene carbonate deposits could accumulate.
The Anguilla Formation forms flat platforms, cliffs, and caves across much of the island. In places such as Road Village and Crocus Bay, older volcanic outcrops are exposed, offering rare glimpses of the island’s deeper geological roots. The surface landscape is distinctly karstic where chemical dissolution of the limestone by slightly acidic rainwater has produced caves, sinkholes, fissures, and solution pits. These karst features are not only visually striking but also scientifically important, as they host speleothems such as stalactites and stalagmites and preserve fossil rich cave deposits that record Pleistocene ecosystems.
Anguilla’s position on the Anguilla Bank has played a crucial role in shaping both its geology and its biogeography. During the Eocene–Oligocene, the bank’s volcanic and volcaniclastic rocks were intruded by basalt, andesite, and quartz diorite, forming a rugged volcanic terrain. As volcanism slowed and subsidence and erosion took over, this terrain was gradually drowned beneath warm, shallow seas. During the Miocene, the island area was largely submerged, allowing extensive reef growth and carbonate sedimentation. Reef limestone accumulated over the volcanic core, building the flat, wave‑cut platforms that now support both natural habitats.
Sea‑level change has repeatedly reconfigured the Anguilla Bank. During the last glacial maximum, around 18,000 years ago global sea levels fell. This drop exposed large areas of the bank and temporarily connected Anguilla, Saint Martin, and Saint Barthélemy forming a single larger landmass. As ice sheets melted and sea levels rose again, the bank was re‑flooded, isolating the islands into their modern configuration. Today, tectonic subsidence continues at a slow rate of a few each year subtly altering the island’s topography over geological timescales while coastal erosion and reef growth continually reshape its margins.
The fossil record of Anguilla is compelling. The Miocene Anguilla Formation preserves abundant marine fossils that document warm, shallow reef environments. Corals are particularly diverse, including genera such as Orbicella cavernosa (Great Star Coral), Diploastrea labyrinthiformis (Grooved Brain Coral), and Stony Corals of Stylophora, Stylocaenia, Siderastrea (Massive Starlet Coral), and Goniopora (Flowerpot Coral).
These corals, many of which have close relatives in modern Caribbean reefs, reveal the structure and biodiversity of Miocene reef ecosystems and help reconstruct patterns of carbonate deposition and ecological stability millions of years ago.
Alongside the corals, echinoderms are well represented. Species such as Echinolampas semiorbis, Echinolampas lycopersicus, Agassizia clevei, Schizaster scillae, and Clypeaster all occur as well-preserved moulds and skeletal remains in carbonate platform sediments formed in warm, shallow marine environments. Molluscs add further detail to this picture, with fossil assemblages of bivalves Amusium lyonii and Pecten species, along with the large marine gastropod Orthaulax pugnax and abundant high-spired Turritella shells. These molluscs are classic components of warm, shallow tropical seas, typically associated with coral reefs, sandy carbonate shoals, and seagrass-rich lagoons.
Tourism dominates the economy, with fishing increasing to meet visitor demand, raising concerns about reef health and fisheries sustainability. Much of the shallow coastal zone is covered by seagrass, algae, sand, and reefs, but coral communities have declined prompting efforts to strengthen marine management, monitoring, and enforcement to halt or reverse reef loss.
Because Anguilla’s exposed rock record is overwhelmingly marine and largely Neogene in age, dinosaurs are absent from its stratigraphy. By the time the Anguilla Formation was being deposited, non‑avian dinosaurs had been extinct for tens of millions of years, and the island’s setting as a shallow marine platform far from continental landmasses meant that terrestrial vertebrates were unlikely to be preserved. However, the Quaternary cave deposits of Anguilla tell a story of remarkable island endemism and extinction.
In Anguilla and throughout the Lesser Antilles, the concept of pre-Columbian terrestrial fauna describes the native land animals that occupied Caribbean islands before European contact in 1492 and before sweeping ecological change transformed island ecosystems. This deep ecological history is exceptionally well preserved in Anguilla’s karstic caves and sinkholes, including Cavannagh Cave and Pitch Apple Hole, which contain rich Pleistocene fossil assemblages formed as animals fell into natural traps later sealed by sediment. These deposits provide a long-term record of climate shifts, sea-level fluctuations, and biodiversity change across hundreds of thousands of years.
Among the most remarkable discoveries is Amblyrhiza inundata, an extinct giant rodent sometimes called the "blunt-toothed giant hutia", which may have weighed up to 200 kilograms making it one of the largest rodents known from the fossil record especially having evolved in isolated island ecosystems, where limited predators and ecological niches often drive extreme body size and specialisation. Alongside this fossil deposits preserve birds and reptiles that together reconstruct Anguilla’s ancient food webs and environments.
By the time of Amerindian habitation, terrestrial ecosystems were dominated by reptiles, seabirds, invertebrates, and smaller mammals while Indigenous peoples introduced species like Guinea Pigs and rabbit-like rodents called Agoutis for food. Following European colonisation, invasive predators and habitat disruption triggered widespread extinctions, reshaping island biodiversity.
Anguilla’s modern landscape is inseparable from its deep geological and fossil history. Miocene reef limestones of the Anguilla Formation now form the cliffs and headlands framing its beaches, while coastal wetlands, salt ponds, and mangrove lagoons fill low‑lying depressions in the carbonate platform, creating rich habitats for birds, fish, and invertebrates. Limestone shrublands and dry forests rooted in karstic bedrock support endemic species adapted to drought and salt. It is this fragile framework that underwrites Anguilla’s thriving ecotourism: at Shoal Bay and Little Bay, snorkellers and scuba divers explore living coral reefs that mirror fossil reef systems, kayakers weave through mangrove channels, and birdwatchers scan wetlands backed by wave‑cut limestone platforms. Guided tours of caves, fossil sites, and coastal outcrops reveal stalactites, fossil‑rich limestones, and the imprint of sea‑level change, tectonics, and karstification making Anguilla a compact must-visit Caribbean destination.
