CaymANNature: Cayman Rocks – Caymanite and Phytokarst

Grand Cayman, Cayman Brac, and Little Cayman are located on the Cayman Ridge which forms the southern margin of the North American Plate.

North American Tectonic Plate

Caribbean Basin map

Caribbean Tectonic Plate

Cayman Islands Bedrock Formations

Ironshore Formation Limestone only, most of Grand Cayman

Cayman Formation mainly Dolostone, Hell and Ironwood Forest only in western Grand Cayman, Prospect, Spotts (not Prospect Point), Bodden Town and south coast to Frank Sound, EAST END, Old Man Bay, Mastic and Canaan Land area and Cayman Kai – Rum Point coastal area.

Pedro Formation Limestone and Dolostone, Pedro St James area only

Sangamon Terrace coastal East End to Colliers, Rogers Wreck Point

Pedro Formation (also called Pedro Castle Formation)

Pedro bluff, Pedro St. James, Grand Cayman

Pedro Formation rock is above the Cayman Formation rock.
The line of Cayman Unconformity is the white line which marks the contact between the two.
Pedro Quarry wall is about 7 meters high. April 24, 2016.

Geologic features of Grand Cayman.

Ironshore Formation, Cayman Formation (on the western peninsula it occurs only in Hell in West Bay, and the Ironwood Forest, south of George Town), Pedro Formation (Pedro St. James area only) and Sangamon Terrace (East End only).
Islands from the Sea, Geologic Stories of Cayman by Murray A. Roed, p.53.

Islands from the Sea, Geologic Stories of Cayman

by Murray A. Roed, 2006.

Coral Bones - Cayman Geology

Caymanite

Caymanite, the multi-layered semi-precious gem stone, at its type area, is an uncommon variety of dolostone originally reported from locations in the Miocene Cayman Formation in the Cayman Islands: the Bluff in Cayman Brac and the East End on Grand Cayman. The various colours result from different metals: black and grays from manganese, the red hues from iron, blue and green from copper, and so on.

CAYMANITE is a laminated, multicoloured (white, red and black) limestone, converted to dolstone,
which fills or partly fills cavities in the Bluff Group of rocks of the Cayman Islands.
The Bluff Group includes the Brac Formation, Cayman Formation and Pedro Castle Formation.
(Islands from the Sea, Geologic Stories of Cayman by Murray A. Roed, p.51 & 158).
Photo: Ann Stafford, Grand Cayman, Sept. 7, 2007.

Caymanite

Caymanite fish and Elkhorn Coral fossils by Horacio Esteban.

Photo: Ann Stafford, Feb. 11, 2016.

Esteban Gallery

Soul of a Caymanite Sculptor

Launa’s Caymanite and other Jewlery
Ann Stafford, Grand Cayman, Oct. 24, 2013

Caymanite

Dolostone

Dolostone or dolomite rock is a sedimentary carbonate rock that contains a high percentage of the mineral dolomite, CaMg(CO₃)₂.

Cayman Land and Sea - pictures

Phytokarst

Phytokarst is pinnacle rock of the Cayman Formation dolostone (limestone with magnesium).
Roots of trees and shrubs penetrate through the rocks to get water. The roots secrete acids.
Microbes bore their way into dolostone to produce the sharp, grey-black weathered surface of the jagged pinnacles which contrasts with the white colour of the unaltered host rocks.

Phytokarst - the sharp, grey-black weathered surface, contrasting with the white colour of the unaltered host rock. Colliers Wilderness Reserve, East End. Nov. 5, 2015.
Colliers Wilderness Reserve photos

Hell and the Ironwood Forest

the only areas of Cayman Formation on Grand Cayman's western peninsula.

Cayman Formation - Hell in West Bay and the Ironwood Forest, George Town, Grand Cayman.

Islands from the Sea, Geologic Stories of Cayman by Murray A. Roed

Hell - pinnacled phytokarst rock in West Bay. It is NOT volcanic.

HELL sign

The sharp gray-coloured pinnacled Cayman Formation dolostone rock is phytokarst.

Phytokarst pinnacle rock of the Cayman Formation in the Ironwood Forest, Grand Cayman.

Photo: Ann Stafford, April 1, 2008.

Old George – Hohenbergia caymanensis, Critically Endangered Grand Cayman endemic giant Bromeliad perched on pinnacled Dolostone phytokarst rock in the Ironwood Forest.

Photo: Ann Stafford, Grand Cayman, March 25, 2008