The Tortonian sedimentary succession of Menorca Island (Balears, Spain) includes two stratigraphic sequences: the lower Tortonian distally-steepened carbonate ramp and the coral reef complex of late Tortonian-early Messinian age. The boundary between the two sequences corresponds to Heterosteginarich sediments in the western part of Menorca, and to a phosphatic hardground in the eastern part of the island. In the field, the hardground is represented by a dark-brown layer and a rough surface on top of the Tortonian Ramp deposits. Dark phosphate precipitates infill cracks and borings in the underlying limestone to a depth of up to 50 cm. The phosphatic hardground is overlain by planktonic rich wackestone to packstone, which penetrates downward into the fissures, borings, and vugs. This deposit is characterized also by grains of reworked phosphate, glauconite grains, small benthic foraminifers and is followed by tabular beds of bioclastic packstone to wackestone with abundant thin crusts of coralline algae. Based on the Amphistegina tests shapes and red algal assemblage of sediments below and above the hardground, and the lateral correlation with Heterostegina deposits, the bathymetry for the development of the phosphatization is estimated less than 100 m. The limited localization of the phosphatic hardground at the eastern side of the ramp indicates that a dynamic upwelling of deeper and nutrientenriched waters favored development of a phosphatic hardground. This upwelling episode is representative of the paleoceanographic settings induced by the climate conditions of the Mediterranean area during the Tortonian.

Ancient upwelling record in a phosphate hardground (Tortonian of Menorca, Balearic Islands, Spain) / Brandano, Marco; Westphal, Hildegard; Mateu Vicens, Guillem; Preto, Nereo; Obrador, Antonio. - In: MARINE AND PETROLEUM GEOLOGY. - ISSN 0264-8172. - ELETTRONICO. - 78:(2016), pp. 593-605. [10.1016/j.marpetgeo.2016.07.017]

Ancient upwelling record in a phosphate hardground (Tortonian of Menorca, Balearic Islands, Spain)

BRANDANO, Marco
;
2016

Abstract

The Tortonian sedimentary succession of Menorca Island (Balears, Spain) includes two stratigraphic sequences: the lower Tortonian distally-steepened carbonate ramp and the coral reef complex of late Tortonian-early Messinian age. The boundary between the two sequences corresponds to Heterosteginarich sediments in the western part of Menorca, and to a phosphatic hardground in the eastern part of the island. In the field, the hardground is represented by a dark-brown layer and a rough surface on top of the Tortonian Ramp deposits. Dark phosphate precipitates infill cracks and borings in the underlying limestone to a depth of up to 50 cm. The phosphatic hardground is overlain by planktonic rich wackestone to packstone, which penetrates downward into the fissures, borings, and vugs. This deposit is characterized also by grains of reworked phosphate, glauconite grains, small benthic foraminifers and is followed by tabular beds of bioclastic packstone to wackestone with abundant thin crusts of coralline algae. Based on the Amphistegina tests shapes and red algal assemblage of sediments below and above the hardground, and the lateral correlation with Heterostegina deposits, the bathymetry for the development of the phosphatization is estimated less than 100 m. The limited localization of the phosphatic hardground at the eastern side of the ramp indicates that a dynamic upwelling of deeper and nutrientenriched waters favored development of a phosphatic hardground. This upwelling episode is representative of the paleoceanographic settings induced by the climate conditions of the Mediterranean area during the Tortonian.
2016
hardground; Menorca (Spain); Miocene; phosphate; Tortonian; upwelling; oceanography; geophysics; geology; economic geology; stratigraphy
01 Pubblicazione su rivista::01a Articolo in rivista
Ancient upwelling record in a phosphate hardground (Tortonian of Menorca, Balearic Islands, Spain) / Brandano, Marco; Westphal, Hildegard; Mateu Vicens, Guillem; Preto, Nereo; Obrador, Antonio. - In: MARINE AND PETROLEUM GEOLOGY. - ISSN 0264-8172. - ELETTRONICO. - 78:(2016), pp. 593-605. [10.1016/j.marpetgeo.2016.07.017]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/926181
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