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Providencia Island, composed of pre-Miocene and Miocene volcanic rocks, is surrounded by an extensive coral reef complex which, from east to west, can besubdivided morphologically and ecologically into the following subparallel units:a Fore-reef terrace: a bare rocky flat, from one to several kilometers broad, sloping gently from the reef to a morphological break below 30 m which marks the beginning of the outer slope.b Barrier reef: more than 100 m broad and totalling some 30 km in length, it rises up to near low-tide level. Coherent in the north and in the south, its middle section is a chain of coral pillars. A profuse growth of MiIIepora,Palythoa and abundant coralline algae covers the reef crest, where locally a true algal ridge is developed.c Lagoon: includes a broad and shallow lagoonal terrace adjacent to barrier reef and a deeper lagoon basin, both locally connected by steep -sand cliffs-.  From the lagoon floor, covered by bare sand and coral rubble, numerouspatch reefs and coral heads to various heights.d Leeward shelf: rocky flats with scattered coral growth extend from the shore to a steep escarpment at 20 or more meters depth marking the beginning of the western outer slope. Patch reefs and sandy flats are equally abundant.Submarine terraces, escarpments and valleys, as well as an irregular outline of many reefs reflect a complex geomorphological history of the insular shelf duringPleistocene, which is in part concealed by Holocene reef growth and sedimentation., Providencia Island, composed of pre-Miocene and Miocene volcanic rocks, is surrounded by an extensive coral reef complex which, from east to west, can besubdivided morphologically and ecologically into the following subparallel units:a Fore-reef terrace: a bare rocky flat, from one to several kilometers broad, sloping gently from the reef to a morphological break below 30 m which marks the beginning of the outer slope.b Barrier reef: more than 100 m broad and totalling some 30 km in length, it rises up to near low-tide level. Coherent in the north and in the south, its middle section is a chain of coral pillars. A profuse growth of MiIIepora,Palythoa and abundant coralline algae covers the reef crest, where locally a true algal ridge is developed.c Lagoon: includes a broad and shallow lagoonal terrace adjacent to barrier reef and a deeper lagoon basin, both locally connected by steep -sand cliffs-.  From the lagoon floor, covered by bare sand and coral rubble, numerouspatch reefs and coral heads to various heights.d Leeward shelf: rocky flats with scattered coral growth extend from the shore to a steep escarpment at 20 or more meters depth marking the beginning of the western outer slope. Patch reefs and sandy flats are equally abundant.Submarine terraces, escarpments and valleys, as well as an irregular outline of many reefs reflect a complex geomorphological history of the insular shelf duringPleistocene, which is in part concealed by Holocene reef growth and sedimentation

Tipo de documento: Artículo - Article

Palabras clave: Geology, Earth Sciences, Pre-Miocene, Miocene, volcanic rocks, coral reef, Fore-reef terrace, Barrier reef, Lagoon, Leeward shelf, Submarine terraces, Pleistocene, Geología, Ciencias de la tierra, Geociencias, Pre-Miocene, Miocene, volcanic rocks, coral reef, Fore-reef terrace, Barrier reef, Lagoon, Leeward shelf, Submarine terraces, Pleistocene





Fuente: http://www.bdigital.unal.edu.co


Introducción



GEOLOGIA COLOMBIANA No.
15,1986 pp.116-134 RECENT CORAL REEFS AND GEOLOGIC HISTORY OF PROVIDENCIA ISLAND (WESTERN CARIBBEAN SEA, COLOMBIA) JORN GEISTER 1 CONTENTS Pligina ABSTRACT •.•.•.•.•••.•. , 1.
INTRODUCTION •.•. ·············· 2.
DESCRIPTION OF THE RECENT REEF COMPLEX .•.•. 2.1.
FORE-REEF TERRACE AND OUTER SLOPE 2.2.
WINDWARD BARRIER REEF 2.2.1. 2.2.2. 2.2.3. 2.3. 2.3.3. 2.4. 2.4.2. 2.4.3. 4. 5. . SHELF AREA W OF THE ISLANDS .
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• • • • • • • • • • • • • .
• • .
• • -LAWRANCE REEF- ••••••••••••••••••••••••••••••• THE OUTER SLOPE AT -BLUE HOLE- .•••••••••••••••••• NOTE ON THE RECENT CORAL FAUNA OF PROVIDENCIA . THE GEOLOGIC HISTORY OF THE ISLAND .•.••••.••.•. 3.1.
TERTIARY VOLCANISM AND REEF SEDIMENTATION . 3.2.
PLEISTOCENE TO RECENT GEOMORPHOLOGY AND REEF FOR· MATION . 3.3.
POSSIBLE ORIGIN OF THE CONTEMPORARY INSULAR SHELF MORPHOLOGY . ACKNOWLEDGEMENTS .••••••.••••.•.•• · .• ··· REFERENCES •••••••.••.•.•. : •.••••••••.••• , •••.•.•••. 2.5. 3. . LAGOONAL TERRACES AND LAGOONAL BASINS •.••••.••••. PATCH REEFS AND RIBBON REEFS • • • • • • • • • • .
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• FRINGING REEF ••••••••.••.••.•.••.•••••••.••••• LEEWARD SHELF AND OUTER SLOPE 2.4.1. . . THE COHERENT BARRIER REEF .••••.•.••.•••••.• THE INCOHERENT BARRIER REEF • • • • • • • • • • • • • • • • .
• ••• FORE-REEF TERRACE EXTENDING TO NEAR LOW-TIDE LEVEL •• LAGOON WITH PATCH REEFS AND FRINGING REEF 2.3.1. 2.3.2. . 1) GeololilChe8 Institut Unive...






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