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Based on rock and fossil data from the Upper Cretaceous of the El Hassana Dome (Abu Roash, Egypt), factors controlling facies architecture and the nature of biotopes are highlighted. The succession formed on a non-rimmed shelf, the architecture of which varied from an inner to an outer shelf setting upsection. Macrobenthic biotopes are reconstructed and their palaeoecological significance assessed using a novel ternary plot. Based on diversity and community structure (770 specimens assigned to 28 bivalve and gastropod taxa), four paucispecific associations are identified. These are: 1. the ’Cucullaea’ Assemblage, a low-energy, soft-substrate, oligotrophic outer shelf environment with reduced terrigenous input dominated by infaunal bivalves and hexactinellid sponges; 2. the ’Plicatula’ Assemblage, a low energy, restricted inner shelf lagoonal setting with soupy substrates and dysoxia below the sediment water interface dominated by plicatulid and ostreid bivalves, 3. the ’Durania’ Assemblage, a high-energy, high-temperature, shoal environment dominated by elevator rudists with minor numbers of echinoids, corals and bryozoans, which together form several biostromes. and 4. The ’Trochactaeon’ Assemblage, which share the same characteristics of the Durania’ Assemblage. The paucispecific nature of these biotopes is indicative of different stress factors. Consequently, the predominant taxa exhibit different degrees.of adaptive strategies. In addition to global sea level, local tectonics have significantly affected facies distribution and biotope structure. The shallower facies during the early Turonian and the dysoxia spanning the Coniacian-Santonian were linked to synsedimentary tectonics, which formed many barriers and led to circulation restrictions. (C) 2017 Elsevier Ltd. All rights reserved.