The pyroclastic tonsteins of the Sabero Coalfield, north-western Spain, and their relationship to the stratigraphy and structural geology

Thermal history of the Sabero Coalfield (Southern Cantabrian Zone, NW Spain) as revealed by apatite fission track analyses from tonstein horizons: implications for timing of coalification

“…Over 2000 m of Stephanian A-B clastic sediments (conglomerates, sandstones, and shales with intercalated coal seams with tonsteins) were deposited unconformably on older Palaeozoic rocks in the Sabero Coalfield (Heward 1978;Knight 1983;Wagner and Winkler-Prins 1985;Knight et al 2000;Colmenero et al 2008). The Stephanian A strata contain about 20 coal seams and coal intercalations, whose thickness ranges from 0.3 to 2.0 m, and the Stephanian B strata contain over 50 coal seams and coal intercalations, with thicknesses between 0.1 and 3.5 m (Knight 1983;Knight et al 2000;Colmenero et al 2008).…”

“…The Stephanian A strata contain about 20 coal seams and coal intercalations, whose thickness ranges from 0.3 to 2.0 m, and the Stephanian B strata contain over 50 coal seams and coal intercalations, with thicknesses between 0.1 and 3.5 m (Knight 1983;Knight et al 2000;Colmenero et al 2008). Major folding of Stephanian sequences occurred in either Late Stephanian or Early Permian times (Reading 1975;Heward and Reading 1980;Wagner and Winkler-Prins 1985).…”

“…1) that cross-cuts the coalfield and displaces the unconformably overlying Cretaceous rocks in the west. During its latest movement, this fault acted as a thrust plane, producing a downthrown displacement of about 400 m to the north (Evers 1967;Knight 1983;Knight et al 2000). Previous studies related to thermal history of the study area…”

“…This study examines the thermal history of one of these small basins (~12-15 km long and 3-4 km wide) located along the eastern end of the Sabero-Gordon fault line (Fig. 1) that contains the Sabero Coalfield (Heward and Reading 1980;Knight 1983;Knight et al 2000). As little is known about the post-Variscan cooling history of this region (Carrière 2006;Grobe et al 2010), we conducted an apatite fission track (AFT) thermochronometry study to define the thermal history of the Late Carboniferous (Stephanian) sediments of the Sabero Coalfield.…”

“…As little is known about the post-Variscan cooling history of this region (Carrière 2006;Grobe et al 2010), we conducted an apatite fission track (AFT) thermochronometry study to define the thermal history of the Late Carboniferous (Stephanian) sediments of the Sabero Coalfield. The Sabero sedimentary sequence includes volcanic ash layers (tonsteins; Knight et al 2000;Botor 2005) that provide precise time-temperature reference points in the stratigraphy, essential for accurate thermal history reconstruction.…”