Paleogene-Aquitanian Tectonic Breakup in the Eastern External Betic Zone (Alicante, SE Spain)

Six Paleogene-Aquitanian successions have been reconstructed in the Alicante area (eastern External Betic Zone). The lithofacies association evidences “catastrophic” syn-sedimentary tectonic processes consisting of slumps, mega-olisthostromes, “pillow-beds” and turbiditic deposits. This kind of sedimentation is related to unconformity surfaces delimiting sequence and para-sequence cycles in the stratigraphic record. The data compiled have enabled the reconstruction of the Paleogene-Aquitanian paleogeographic and geodynamic evolution of this sector of the External Betics. During the Eocene the sedimentary basin is interpreted as a narrow trough affected by (growth) folding related to blind thrust faulting with a source area from the north-western margin, while the southeastern margin remained inactive. During the Oligocene-Aquitanian, the sourcing margin becames the southeastern margin of the basin affected by a catastrophic tectonic. The activity of the margins is identified from specific sediment source areas for the platform-slope-trough system and from tectofacies analysis. The southeastern South Iberian Margin is thought to be closer to the Internal Betic Zone, which was tectonically pushing towards the South Iberian Margin. This pushing could generate a lateral progressive elimination of subbetic paleogeographic domains in the eastern Betics. This geodynamic frame could explain the development of such “catastrophic” tectono-sedimentary processes during the Late Oligocene-Early Miocene.

Geodynamic events reconstructed in the Betic, Maghrebian, and Apennine chains (central-western Tethys)

A synthetic study has been made to identify main tectono-sedimentary and geodynamic events in central-western Tethys. For this, an interdisciplinary analysis has been performed on successions belonging to tectonic units derived from Betic-Maghrebian-southern Apennine “Flysch basin” domain. The stratigraphic records of the internal, external, and mixed successions deposited in lateral basins of different chains show very similar characters, especially regarding: (a) lithostratigraphy and ages; (b) kind and provenance of supplies (immature and supermature petrofacies from internal and external margins, respectively); (c) presence of “mixed successions” (composed of alternating internal and external petrofacies) attesting to clear palaeogeographic relationships between opposite depositional systems; and (d) timing of the deformation. In addition, specific lithofacies reveal correspondence with similar sedimentary events, such as: (1) very thick silicoclastic supply concentrated in restricted time ranges indicating the main deformational phases in the margin/basin systems; (2) levels rich in black-shales, glauconian, siliceous-producers, and volcaniclastic intercalations, widespread in the studied successions and linked to particular events at the Tethyan scale (anoxic periods, starvation-upwelling, acid-intermediate penecontemporaneous volcanic activity, respectively). Tectonic influence has also been recorded by means of unconformities and tectofacies (such as turbidites, slumps, or olisthostromes, etc.), being correlated with the main deformational phases. Similar stratigraphic and tectonic events have also been found in the Calvana unit of Val Marecchia nappe (Ligurides, northern Apennine). Correlations of stratigraphic and tectonic events support the proposal of an evolutionary geodynamic model involving the presence of a “Mesomediterranean microplate” in intermediate position during Africa-Europe convergence. The closure of central-western Tethys occasioned the Betic-Maghrebian-southern Apennine oceanic branch deformation and the birth of perimediterranean chains during middle-late Miocene.

Los mármoles comerciales “Marrón Imperial” y “Marrón Emperador” (S.E. España). Caracterización petrológica y criterios de exploración

Los mármoles comerciales "Marrón Imperial" y "Marrón Emperador" son dolomías brechoides que de acuerdo con la clasificación del MIA pertenece al Grupo C de mármoles comerciales. Se determinan sus parámetros petrofísicos según la norma UNE. Sus rasgos petrológicos se estudian mediante microscopio petrográfico de luz transmitida y microscopio electrónico de barrido (MEB) (en modo de electrones secundarios y electrones retrodispersados). Estas rocas son básicamente dolomías mesocristalinas con abundantes vénulas calcíticas politexturales relacionadas con procesos de brechificación y de dolomitización. Rasgos kársticos aumentan la complejidad petrológica de estas rocas ornamentales cuyo litosoma son las dolomías masivas del Cretácico Superior (¿Turoniense?) del dominio Prebético Externo. El material explotado pertenece a una alineación morfoestructural que va desde Jumilla hasta el NE de Caudete y está relacionado con la falla Jumilla-Yecla-Caudete-Font de la Figuera. La relación entre esta falla y las dolomías turonienses son el principal criterio de exploración de estas rocas ornamentales.