The facies evolution of the Cretaceous/Tertiary sequence of NW Santander is considered in relation to the Cretaceous rifting and drifting, and Tertiary partial closure of the Bay of Biscay. Overlying the Palaeozoic basement are the fluvial Lower Triassic Buntersandstone and Upper Triassic Keuper evaporitic mudstone, deposited in a failed rift, extensional basin. Overlying Lower Jurassic carbonates are the syn-rift, continental elastics of the Vealden deposited in halfgrabens cut by transfer faults. The Vealden consists of two formations:- the lower, arenaceous-rich Barcena Mayor Fm. (braided stream environment) and the upper, argillaceous-rich Vega de Pas Fm. (meandering river). Overlying it is the Aptian Umbrera Fm. (calcarenite sheet), the Patrocinio Fm. (shoaling-up ward sandstone/marl alternation), the San Esteban Fm. (requienid/foraminiferal biomicrite of the internal platform) and the marls of the Rodezas Fm. The Upper Aptian Reocin Fm. is a requienid/foraminiferal biomicrite with thinned calcarenites deposited over active, diapiric palaeohighs. After initial marine and then equant calcite (meteoric phreatic) cementation, invasion of meteoric-derived groundwater over palaeohighs generated lenses of sucrosic dolomite in the Reocin Fm. Local mixing of further groundwater and Keuper-derived, sulphate-rich waters in karstic caverns precipitated sparry, baroque dolomite and Pb/Zn sulphides (by bacterial sulphate reduction). The clastic Lower Albian is a transgressive fluvial/estuarine/inner shelf sequence with tidal estuarine channels and sandwaves. The Middle/Upper Albian (syn-drift) has basal calcarenitic tidal sandwaves and is followed by storm/wave-reworked carbonates deposited on a homoclinal ramp. The clastic Lower Cenomanian is an estuarine/inner shelf deposit with tidal sandwaves and sandbars. The Middle/Upper Cenomanian is a storm/tide-dominated calcarenite. Outer shelf marls occur in the Turonian to Middle Campanian and the Upper Campanian to Middle Eocene is a sandy, foraminiferal inner shelf limestone. The Upper Eocene/Oligocene (syn-compression) is a carbonate slope-apron-reefal flysch deposit. It includes hemipelagic marl, neritic-derived calcarenitic turbidites and rudaceous mass flow deposits with highly polymict conglomerates. These were deposited coevally with Keuper piercement and thrust reactivation and date the Pyrenean compressional deformation here.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:580790 |
| Date | January 1986 |
| Creators | Hines, Frederick Michael |
| Contributors | Reading, H. G. |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:1d1f8c32-9fd3-44a5-ba6a-d963fa9868c0 |
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