Abstract Outcrops of intact and seismic-scale Pennsylvanian (Serpukhovian to Moscovian) carbonate platforms in Asturias (NW Spain) were studied as analogues of the prolific subsurface reservoirs in the Pricaspian Basin (e.g., Tengiz Field). The Asturian platforms, which have been rotated 90° along the dip axis during Late Carboniferous thrusting, are visible on aerial photographs as kilometer–scale cross sections and have dimensions similar to their Pricaspian subsurface equivalents: a thickness between 1.5 and 2.0 km, a slope relief up to 850 m, slope angles up to 32°, and oblique–exponential clinoforms. A comparative study of stratal patterns, lithofacies, and petrophysical properties using aerial photography was initiated to: (1) develop a depositional model, (2) construct a seismic model for comparison with the Pricaspian subsurface, and (3) address the controls on slope declivity. Five general lithofacies–stratal pattern zones were observed: inner and outer platform, upper slope, lower slope, and toe–of–slope to basin. The platform zone has shoaling–upwards cycles with a transgressive interval of coated grainstone with oncoids, followed by normal marine algal boundstone and bioclastic grainstone to packstone and, near the top, restricted lagoonal peloidal packstone to grainstone with calcispheres. These cycles have a thickness between 2.5 and 15 m and can be traced from the platform break into the platform interior for at least 6 km. Crinoid–bivalve grainstone to rudstone intervals and lenticular mud mounds are present in the outer platform, a one– kilometer–wide zone near the platform break. Two distinctly different automicrite margins are recognized in the field: (1) low–angle slopes and ramps, deposited during the nucleation phase of the platform, of nearly pure micritic limestone, and (2) steep (26 to 32°) slopes where automicrite boundstone dominates the uppermost 300 m. Clotted peloidal micrite—automicrite—with sponges and fenestellid bryozoans, and crinoid rudstone intervals, dominate this zone. Below 300 m paleo–water depth, clast–supported lithoclastic breccia dominates the slope. Finally, below 600 to 700 m, argillaceous lime mudstone beds interfinger with grainstone to wackestone intervals of mostly platform– top–derived grains and thick intervals of upper–slope–derived breccia. Five major phases of platform development are recognized: (1) renewed flooding of the preexisting regional Serpukhovian platform, rucleation of a low-angle ramp with microbial mud deposits, aggradation and subsequent formation of a steep microbial cement boundstone margin, followed by nearly horizontal progradation (Bashkirian), (2) continued progradation with several aggradational phases (Bashkirian), (3) development of an extensive flat-topped shallow-water platform near the Bashkirian-Moscovian boundary followed by combined aggradation and progradation, (4) predominantly progradation, followed by (5) aggradation. On the steep upper slopes, over 30°, automicrite formation alternated with deposition of sand and rubble. Automicrite layers slid off and formed breccia tongues at the toe of slope whenever the shear strength of the substrate of loose sediment was exceeded. The steep slope angles were maintained by alternating automicrite growth stages and gravity-driven deposition and consequently inhibited the growth of large mud mounds. Calibration of lithofacies and stratal patterns in a large-scale platform outcrop with their potential seismic expression through synthetic seismic modeling shows great similarity with seismic data acquired in the Pricaspian subsurface. The integration and quantification of size-similar outcrop data is a first step in developing a powerful predictive tool for the exploration of the subsurface of the Pricaspian Basin.

Abstract The Carboniferous rocks of Spain crop out mainly in the Iberian Massif, which occupies almost half of the Iberian Peninsula. There are additionally a number of smaller Carboniferous inliers, separated by a Mesozoic and Tertiary cover, exposed in the Iberian Ranges, Pyrenees, Catalonian Coastal Ranges, Minorca and the Betic Cordillera (Fig. 7.1 ). Variscan and sometimes Alpine tectonism has variously overprinted these Carboniferous outcrops, commonly obscuring their original relationships. During the Carboniferous period, sedimentation was coeval with the Variscan orogeny, in contrast to earlier Palaeozoic sedimentation in a rift to passive margin setting. The strong tectonic control on Variscan sedimentation resulted in mobile, unstable basins, with sedimentary successions that show rapid temporal and spatial changes in lithofacies and thickness. This has promoted a proliferation of stratigraphic units of only local importance, making regional correlations difficult. The Carboniferous successions in Spain are generally dominated by siliciclastic rocks that vary from deep water turbidite successions to shallow marine, coal-bearing coastal and fully continental formations. Deep water turbidite successions are in many places referred to as the ‘Culm’, a term coined by Fiege (1936) , although the Culm successions of the Iberian Variscan Belt are not always Early Carboniferous in age as in the original definition. In some areas limestones are locally important or even dominant and thin, condensed units of limestones or shales are widespread during Tournaisian and Visean times. An exception to the dominantly sedimentary record is provided by volcanic and volcaniclastic rocks which are abundant in the southern