Geology of Antigua and Barbuda

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Geologic Map Antigua Barbuda

The geology of

volcanic island arc. Both islands are the above water limestone "caps" of now inactive volcanoes. The two islands are the surface features of the undersea Barbuda Bank and have karst limestone landscapes.[1]
Barbuda is primarily flat and formed from coral reefs. The Middle Miocene Highlands Formation has limestones which are the oldest rocks on the island, rising 120 feet above sea level. The Beazer Formation and the Codrington Formation are both from the Pleistocene and include reef and lagoon related rocks.[2]

The geologic record of Antigua indicates a transition from

bryozoans, crinoid columns and sponges. The limestone Devil's Bridge, is an example of this formation.[3]

On Antigua, the south of the island is mainly calc-alkaline volcanic rock such as dacite and quartz basalt or andesite, along with limestone lenses, agglomerate and tuff formed during the Oligocene.[4] Generally andesite dominated volcanism across the island gave way to limestone and chert formation.[5]

Between 200 and 500 CE, native peoples on Antigua were active in lapidary, working local diorite, shells and carnelian as well as imported nephrite, amethyst, turquoise and serpentinite.[6]

References

  1. ^ Riva Berleant (2016-01-12). "Antigua and Barbuda" (PDF). Retrieved 2018-11-09.
  2. S2CID 130933554
    .
  3. ^ Donovan, Stephen (6 July 2017). "The geology of islands". depositsmag.com. Deposits Magazine. Retrieved 13 October 2019.
  4. ISBN 9780813711324
    .
  5. S2CID 140649360
    .
  6. ^ https://www.gia.edu/doc/Pre-Columbian-Gems-and-Ornamental-Materials-from-Antigua-West-Indies.pdf [bare URL PDF]
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