Stratigraphy and petrophysical characteristics of Lower Paleocene cool-water carbonates, Faxe quarry, Denmark

Abstract

The Faxe limestone quarry in eastern Denmark exposes Danian (Lower Paleocene) cool-water carbonate deposits. They constitute remnants of an apparent build-up that covers about 12 km2 today. The Danian deposits at Faxe are conspicuous due to their pronounced thickness of coral limestone relative to the regional carbonate system. In the Faxe quarry, scleractinian corals are uniquely exposed in up to 30 m high mounds. The rapid accumulation of scleractinians combined with induration of the mounds may locally have protected the limestone from Quaternary glacial erosion and created a Danian thickness anomaly at Faxe. The position of Faxe above a local fault-bounded basement high and the extent of coral limestone has been better defined by new mapping. A mapped lithostratigraphic surface in the quarry reveals the large-scale organisation of nested bryozoan mounds on three elongated ridges striking NW–SE. The main scleractinian coral mounds are located above this horizon. Data for reservoir characterisation, mainly of the bryozoan mounds, were collected as photographs of the outcrop, petrophysical and petrographical data from cored boreholes, and as ground-penetrating radar sections. Old boreholes and measured sections were used to reconstruct the build-up, and new nannofossil data allow a discussion of stratigraphy and accumulation rate. The petrophysical data show that common mound-building bryozoan packstone has higher permeability and lower capillary entry pressure than chalk, whereas less commonly occurring grain-dominated packstone and grainstone deposits from local higher-energy sites of the mound complex were found to have reduced amounts of coccolith mud, significantly higher permeability and a higher degree of lithification. Based on biostratigraphic age constraints, correlation of flint – limestone couplets and recog-nised hierarchical patterns, we develop a cyclostratigraphy for the middle Danian and suggest that cyclicity in lithology and petrophysical characteristics of bryozoan limestone are controlled by precession and eccentricity of the orbit of the Earth.