The Hollywood Window v.2.pdf

The “Hollywood Window” and the “Hollywood Bowl” The studied formation, from the Upper Ordovician (early Silurian?), comprises volcanoclastic deposits derived from alkaline basalts (SiO₂ 47–49%; Na₂O+K₂O > 5.4; Mg# 37–48), enriched in LREE, HFSE, and LILE, suggesting an enriched mantle source. The outcrops on the southeastern flank of an anticline, separated by 12.5 km, show a progressive decrease in thickness, indicating a move away from volcanic centers in a seismically active environment. Sedimentation, which occurred on a shallow marine platform with episodes of subsidence, progresses from deep-water deposits to higher-energy storm deposits and restricted platform facies. The upper interval records synsedimentary and post-depositional deformation linked to seismicity and contemporaneous volcanic activity, possibly fissure-type. The effusive activity spanned approximately 15 million years (458–443 Ma), and together with the petrochemical composition, they indicate hybrid earthquakes that combine volcano-tectonic and long-period events. The exceptionally preserved deformation structures, exposed in an area less than 9 m² that we have dubbed the "Hollywood Window," capture short-term processes in a 443 Ma record. Features include seismites, sedimentary dikes, water escape structures, volcanic ejecta, and biogenic remains (microbial mats, in situ fossils, entrained fossils, ichnofauna). Their preservation provides exceptional insights into the interaction between volcanism, seismicity, and sedimentation. The comprehensive documentation, including over 500 high-resolution images (RAW), provides insight into depositional environments, biotic responses, and sediment behavior under seismic loading prior to lithification and diagenesis.