From carbonate platform to euxinic sea – the collapse of an Early/Middle Devonian reef, Cantabrian Mountains (Spain)
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Date
2017-12
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Instytut Geologii UAM
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Abstract
The Santa Lucía Formation represents the major phase in Devonian reef development of the Cantabrian Zone (Cantabrian
Mountains, northwest Spain). In the present study the transition from the carbonate platform deposits of the Santa
Lucía Formation to the overlying euxinic basinal deposits of the Huergas Formation is described. These transitional
strata are connected to the Basal Choteč Event and represent a condensed sedimentation of micritic dark-grey and black
limestones with an upward increase of dark shale intercalations with iron mineralisation surfaces and storm-induced
brachiopod coquinas. The transitional beds are grouped into a new unit, the Cabornera Bed, which consists of limestone,
limestone-shale and shale facies associations, representing a sediment-starved euxinic offshore area just below
the storm wave base. Four stages in reef decline can be recognised: a reef stage, an oxygen-depleted, nutrient-rich stage,
a siliciclastic-influx stage and a pelagic-siliciclastic stage. Additional geochemical and geophysical investigations are
needed to verify the results presented herein.
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Keywords
Anoxia, Basal Choteč Event, Cantabria, carbon isotopes, Eifelian, Emsian
Citation
Geologos, 2017, 23, 3, pp. 143-161
ISBN
978-83-232187-4-6