Grand Cayman, Little Cayman, and Cayman Brac are, in reality, the summits of independent fault blocks that rise from the depths of the Caribbean Sea. This book traces the geological evolution of these islands over the last 30 to 35 million years. The balance between deposition of carbonate sediments and karst development of the exposed land was dictated by the interaction between ever-changing sea levels and vertical tectonic movement of the fault blocks. Today, drinking water needed for the ever-increasing populations of the islands is supplied largely by desalinization plants that are located in accord with a detailed knowledge of the bedrock.
This book is based on an extensive data base that has been assembled over the last 40 years of field work and laboratory analyses. Noteworthy aspects of this database include:
- Approximately 60 visits to the islands over last 40 years – sampling and documentation of virtually every accessible outcrop on the islands (including some that no longer exist). Most samples have been fully documented petrographically and geochemically.
- Data from 120 wells that have been drilled to depths up to 245 m (most less than 125 m). Wells have been cored and/or chip sampled. Full documentation of drilling histories, XRD analyses of samples, extensive geochemical analyses for major and minor elements, stable isotopes, 87Sr/86Sr ratios, and Rare Earth Elements from numerous samples.
- Mapping and sampling of modern sediments, including sediment cores, from most of the lagoons around Grand Cayman.
- Extensive thin section petrography, scanning electron microscope, and electron microprobe analyses of the dolostones and limestones that form the bedrock of the islands.
- Samples and data collected from numerous caves on Grand Cayman and Cayman Brac have been used to track their developmental history.
- Detailed analyses of phosphates collected from Little Cayman.
- Detailed analyses of terra rossa collected from each of the islands.
Author(s): Brian Jones
Publisher: Springer
Year: 2022
Language: English
Pages: 294
City: Cham
Preface
Contents
1 Introduction
1.1 Introduction
1.2 Physiography of the Cayman Islands
1.3 Cayman Research—University of Alberta
1.4 Methods
1.4.1 Field Work and Drilling
1.4.2 Thin Sections
1.4.3 Scanning Electron Microscopy
1.4.4 X-Ray Diffraction Analysis
1.4.5 Electron Microprobe
1.4.6 Stable Isotope Analyses
1.4.7 87Sr/86Sr Analyses
1.4.8 Elemental and Rare Earth Elements
1.4.9 U/Th Dating
References
2 Tectonic Setting of the Cayman Islands
Abstract
2.1 Introduction
2.2 Earthquakes and Tsunamis
2.3 Tectonic Elements on the Cayman Islands
2.4 Conclusions
References
3 Bluff Group—the Brac Formation
Abstract
3.1 Introduction
3.2 Distribution
3.3 Lower Boundary
3.4 Upper Boundary
3.5 Thickness
3.6 Lithology
3.6.1 Cayman Brac
Lepidocyclina Facies
Mollusc Facies
Foraminifera Facies
Fabric Retentive Dolomite Facies
Fabric Destructive Finely Crystalline Dolomite Facies
Sucrosic Dolomite Facies
3.6.2 Grand Cayman
3.7 Porosity
3.8 Diagenesis
3.9 Dolomite Stoichiometry
3.10 Stable Isotopes
3.11 87Sr/86Sr Geochronology
3.12 Age
3.13 Depositional Regimes
3.14 Conclusions
References
4 Bluff Group—The Cayman Formation
Abstract
4.1 Introduction
4.2 Distribution
4.3 Lower Boundary
4.4 Upper Boundary
4.5 Thickness
4.6 Limestone—Dolostone Distribution
4.7 Biota
4.8 Facies
4.8.1 Grand Cayman
4.8.2 Cayman Brac
4.9 Depositional Regimes
4.10 Porosity and Permeability
4.11 Stable Isotopes
4.12 87Sr/86Sr Ratios
4.13 Age
4.13.1 Fossils
4.13.2 87Sr/86Sr Geochronology
4.13.3 Sea Level
4.14 Conclusions
References
5 Bluff Group—Pedro Castle Formation
Abstract
5.1 Introduction
5.2 Distribution
5.3 Lower Boundary
5.4 Upper Boundary
5.5 Thickness
5.6 Lithology
5.6.1 Grand Cayman
5.6.2 Cayman Brac
5.7 Stable Isotopes
5.8 Porosity and Permeability
5.9 87Sr/86Sr Geochronology
5.10 Age
5.11 Depositional Regimes
5.12 Conclusions
References
6 Diagenesis–Bluff Group
Abstract
6.1 Introduction
6.2 Dolostones of the Bluff Group
6.2.1 Dolomite Crystals
Crystal Size
Internal Structures and Compositional Zoning in Dolomite of the Cayman Islands
Hollow Dolomite Crystals
6.2.2 Low and High Calcian Dolomite
6.2.3 Distribution of Low and High Calcian Dolomite
Cayman Brac
Grand Cayman
6.2.4 Stable Isotopes
Brac Formation
Cayman Formation
Pedro Castle Formation
6.2.5 Trace Elements
Na in Dolomite/Limestones
Mn in Dolostones/Limestones
Fe in Dolostones/Limestones
Sr in Dolostones/Limestones
Rare Earth Elements in Dolostones/Limestones
6.2.6 87Sr/86Sr Ratios
Brac Formation
Cayman Formation
Pedro Castle Formation
Modern Seawater
Potential Problems with 87Sr/86Sr Ratios
Brac Formation
Cayman Formation and Pedro Castle Formation
Comparison with Other Island Dolostones
6.3 Discussion
6.4 Conclusions
References
7 Ironshore Formation
Abstract
7.1 Introduction
7.2 Distribution
7.3 Lower Boundary
7.4 Upper Boundary
7.5 Thickness
7.6 Internal Stratigraphy
7.6.1 Lithological and Biological Characteristics of Units A to F
7.7 The 6 m Sea Level Notch
7.8 Key Exposures of the Ironshore Formation
7.8.1 Grand Cayman
Salt Creek
Canary Lane Quarry
Boat Launch, Northwest Coast
7.8.2 Cayman Brac
7.8.3 Little Cayman
Little Cayman Quarry
Salt Rocks
Unnamed Hill
7.9 Biota of the Ironshore Formation
7.9.1 Corals
7.9.2 Rhodolites
7.9.3 Stromatolites
7.9.4 Bivalves and Gastropods
7.10 Trace Elements
7.11 Diagenesis in the Ironshore Formation
7.11.1 Alteration of Skeletal Material
Strombus Gigas Shells
Corals
7.11.2 Calcretes
7.11.3 Rhizoliths
7.11.4 Roots and Caliche
7.11.5 Roots and Peloids
7.12 Conclusions
References
8 Modern Carbonate Environments
Abstract
8.1 Introduction
8.2 The Coastal Shelves of the Cayman Islands
8.3 Corals and Coral Reefs
8.3.1 Modern Corals of the Cayman Islands
8.3.2 Shelf-Edge Reef of Grand Cayman
8.4 Lagoons of Grand Cayman
8.4.1 North Sound
The Fresh-Brackish Water Association
The Marine Facies Association
Rare Earth Elements
Age
Facies Architecture
8.4.2 South Sound
Facies
Age of Sediments
Facies Changes Through Time
Sedimentary Processes
8.4.3 Frank Sound and Pease Bay
Facies
Facies Changes Through Time
Foraminifera in Frank Sound
8.4.4 East Sound
8.5 Bioerosion
8.6 Temporal Changes in Surface Seawater Temperatures
8.7 The Critical Role of Thalassia in the Lagoons of the Cayman Islands
8.8 Impact of Storms on the Coastal Areas of the Cayman Islands
8.8.1 Storm Boulders
8.8.2 Boulder Ramparts
8.8.3 Storm Impact on Lagoonal Sediments
8.9 Vermetid Buildups
8.10 Beachrock
8.11 Conclusions
References
9 Karst on the Cayman Islands
Abstract
9.1 Introduction
9.2 Modern Karst of the Cayman Islands
9.2.1 Phytokarst
9.2.2 Caves and Speleothems on Cayman Brac
Caves in the Brac Formation
Caves in the Cayman Formation
Cave Speleothems
Notch Speleothems
9.2.3 Caves and Speleothems on Grand Cayman
The Twilight Zone
Stalactites and Stalagmites
Cave Pearls
Calcite Versus Aragonite Precipitation
Comparison of Notch Speleothems and Cave Speleothems
9.3 Vertebrate Fossils
9.4 Paleokarst on the Cayman Islands
9.4.1 Paleokarst Surfaces
The Brac Unconformity
The Cayman Unconformity
The Pedro Castle Unconformity
9.5 Subsurface Paleokarst Features
9.5.1 Caymanite
9.5.2 Paleo-Caves
9.5.3 Sinkholes, Joints, and Other Cavities
9.6 Conclusions
References
10 Terra Rossa, Phosphate, and Mangrove Swamps
Abstract
10.1 Introduction
10.2 Terra Rossa
10.2.1 Stratigraphic Distribution of Lithified Terra Rossa on the Cayman Islands
10.2.2 Composition
Clays, X-ray Amorphous Material, Anatase, Hematite, Goethite, and Manganese Precipitates
Biofragments
Glaebules
Clay-Coated Grains and Terra Rossa Ooids
Fractures
10.2.3 Stable Isotopes
10.2.4 Rare Earth Elements
10.2.5 Origin of Terra Rossa on the Cayman Islands
10.3 Phosphate Deposits
10.3.1 Composition of Phosphatic Limestone
10.3.2 Petrography of Phosphatic Limestones
Lithoclasts and Detrital Phosphate Grains
Glaebules
Phosphate Rafts
Matrix
Microbes
Calcite Cement
10.3.3 Stable Isotopes
10.3.4 Rare Earth Elements
10.3.5 Origin of Phosphate Deposits
10.4 Mangrove Deposits
10.4.1 Barkers Peninsula and West Bay Peninsula
10.4.2 Barkers Peninsula and West Bay Peninsula
Laminated and Non-laminated Crusts
Plastic Mud
Peat
10.4.3 South Sound
10.4.4 Age and Development of Mangrove Swamps
10.5 Conclusions
References
11 Hydrogeology
Abstract
11.1 Introduction
11.1.1 Stage I
11.1.2 Stage II
11.1.3 Stage III
11.2 Bedrock Geology
11.3 Porosity and Permeability
11.4 Rainfall
11.5 Freshwater Lenses
11.5.1 Joints, Factures, and Water Lenses
11.5.2 Groundwater on the Cayman Islands
Seawater
Rainwater
Pond Water
Water in Sinkholes
Cave Water
Groundwater—Perched Water Zone
Groundwater—Highly Brackish to Saline Water
11.5.3 Hydrochemical Facies
Chloride Ions
Bicarbonate Ions
Calcium and Magnesium Ions
11.6 Groundwater Calcite and Dolomite Saturation States
11.6.1 Rainwater
11.6.2 Perched Water
11.6.3 Groundwater—Fresh Water Zone
11.6.4 Groundwater—Lightly Brackish Water Zone
11.6.5 Groundwater—Types I and II
11.7 Groundwater and Bedrock in and Around the East End Freshwater Lens
11.8 Development of Reverse Osmosis Plants
11.9 Conclusions
References
Appendix_1
