Heat flow and temperature gradient data from Spain #

Abstract #

This dataset provides geothermal gradient and heat flow estimates derived from temperature loggings in 187 oil exploration wells across Spain, including 43 located in offshore marine areas. The measurements were used to create a preliminary heat flow map of the Iberian Peninsula and surrounding shelf waters. The mean heat flow on land is 82 mW m⁻², while offshore areas exhibit higher values averaging 99 mW m⁻²—both exceeding the European continental average. A regional trend shows increasing heat flow toward the Mediterranean coast, which inversely correlates with crustal thickness. Corresponding Moho temperatures range from 720°C in central Spain to 880°C near the southeastern coast. These data are critical for understanding regional lithospheric structure and the geothermal regime in tectonically active zones of southern Europe.

Methods #

Systematic geothermal investigations in Spain began in 1978 under the coordination of the Spanish Institute of Geology and Mines. This dataset compiles all deep borehole temperature logs available from hydrocarbon exploration activities. Of 346 logged wells, 187 were selected for inclusion based on data quality: 144 located on land and 43 in coastal or shelf marine regions.

Temperature-depth profiles were evaluated for thermal equilibrium. Non-equilibrated logs were either excluded or corrected using the method of Lachenbruch and Brewer (1959), which estimates undisturbed subsurface temperatures based on individual logging curves. Gradient values were then converted to heat flow estimates using a constant thermal conductivity of 2.1 W m⁻¹ K⁻¹ (5 mcal cm⁻¹ s⁻¹ °C⁻¹). Each heat flow value is associated with geographic coordinates and includes metadata such as the number of logging runs and correction method applied.

The dataset is limited to sedimentary basins in the eastern half of the Iberian Peninsula due to the use of oil wells, and therefore does not include geothermal information from crystalline terrains in the western regions.

Other #

This study provides the first systematic geothermal heat flow dataset for Spain and its adjacent marine areas. The results show that heat flow across the Iberian Peninsula exceeds the European average (Cermak and Hurtig, 1977). The lowest values (50–60 mW m⁻²) occur in the Burgos Basin and Basque Country, while the highest (up to 110 mW m⁻²) are found along the southeastern and southwestern coastal zones, including the Alboran Sea and the Catalan margin.

These spatial patterns correspond to variations in crustal thickness, with thinner crusts near the coast associated with elevated heat flow and higher mantle heat contributions. Moho temperatures calculated from these data range from 720°C in central Spain to 880°C near Cartagena.

The high coastal and offshore heat flow correlates with a Neogene volcanic arc encircling the southern and eastern perimeter of the peninsula. Volcanic features associated with this arc include the Almeria and Valencian coasts, the Columbretes Islands, and offshore volcanic structures near Tarragona. These geodynamic features likely reflect ongoing lithospheric processes such as back-arc extension and mantle upwelling in the western Mediterranean tectonic regime.