Neogene marine sediments and biota encapsulated between lava flows on Santa Maria Island (Azores, north‐east Atlantic): An interplay between sedimentary, erosional and volcanic processes

Abstract

Sedimentary rocks are rarely preserved on reefless volcanic oceanic islands because their sediments are mostly exported from coastal areas towards the deep sea and such islands typically undergo subsidence. In contrast, the exceptional geological record of the uplifted Santa Maria Island (Azores) provides a unique opportunity to gain insight on such coastal systems. This study focuses on a locality at Ponta do Cedro (eastern Santa Maria Island), which features a series of marine fossiliferous sediments wedged between steep lava deltas. As demonstrated by local structure, these sediments correspond to clinoforms deposited on the steep submarine slope of an active volcanic island, implying transport from shallow waters to greater depths and subsequent colonization by benthic communities. Rapid volcanic progradation eventually sealed the deposits, allowing for their preservation and providing a 3595

The upper Miocene Deurne Member of the Diest Formation revisited: unexpected results from the study of a large temporary outcrop near Antwerp International Airport, Belgium

“…The Unit 2 records slow migration of the bedforms responsible for the foresets. Colonization of the bedforms occurred when their migration was very limited or temporarily paused (Pollard et al, 1993;Uchman et al, 2020). In such conditions, packages of bioturbated and non-bioturbated foresets alternate.…”

Wave‐influenced deposition of carbonate‐rich sediment on the insular shelf of Santa Maria Island, Azores

“…Sandy clinoforms are commonly observed on shelves around other islands in the Azores (Quartau et al ., 2012, 2014, 2015) and ancient examples can also be observed in the cliffs of Santa Maria (e.g. Uchman et al ., 2020).…”

“…Wave‐influenced sandy clinoforms, which commonly occur on shelves around oceanic islands and on some continental shelves (Patruno & Helland‐Hansen, 2018), are used here to test formulae for the threshold of motion and wave‐imposed stresses. These sedimentary features have been referred to also as sand bodies (Field & Roy, 1984), sandy clinoforms (Mitchell et al ., 2012; Mitchell, 2012; Quartau et al ., 2012), depositional clinoforms (Quartau et al ., 2014, 2015), submarine depositional terraces (Chiocci & Romagnoli, 2004; Chiocci et al ., 2004; Casalbore et al ., 2017, 2018), infralittoral prograding wedges (Hernández‐Molina et al ., 2000) and sigmoidal or sedimentary wedges (Meireles et al ., 2013; Uchman et al ., 2020). They are thought to form during storms, when downwelling offshore‐directed bottom currents develop to balance wind‐driven shoreward currents, transporting inner shelf sediments seaward (Chiocci et al ., 2004; Pratson et al ., 2009; Meireles et al ., 2013; Casalbore et al ., 2017).…”

Pliocene and late Pleistocene (MIS 5e) decapod crustaceans from Santa Maria Island (Azores Archipelago: Central Atlantic): systematics, palaeoecology and palaeobiogeography

“…The Pliocene outcrops are located at elevations ranging from the sea level (e.g. Pedra‐que‐pica) up to 100–105 m (Cré and Macela), whereas the Last Interglacial (MIS 5e) outcrops are all located, as expected, at lower elevations, from the intertidal to a maximum of ~7 m at Lagoinhas (Ávila et al ., 2009a), on the north shore of Santa Maria, and ~10 m at Ponta do Cedro, on the east shore of the island (Uchman et al ., 2020). A total of 1428 lots of the DBUA‐F collection containing fossil specimens collected on Santa Maria Island were screened for decapod crustacean remains, yielding a total of 17 lots (cf.…”

“…Much effort has been put into the production of systematic inventories of several groups of invertebrates (molluscs, brachiopods, balanids, ostracods, echinoderms and bryozoans; Janssen et al ., 2008; Kroh et al ., 2008; Winkelmann et al ., 2010; Madeira et al ., 2011; Meireles et al ., 2012; Ávila et al ., 2016b, 2018b), vertebrate fossil remains (sharks, cetaceans, and bony fishes; Ávila et al ., 2012, 2015c, 2020a), ichnofossils (Santos et al ., 2015; Uchman et al ., 2016, 2017, 2018) and algae (Rebelo et al ., 2014, 2016a,b). The work on Santa Maria Island also resulted in publications regarding the study of both the geological evolutionary history of the island (Ramalho et al ., 2017) and of the physical and biological processes impacting the insular shelf (Ramalho et al ., 2013; Rovere et al ., 2016; Johnson et al ., 2017; Quartau et al ., 2018; Ricchi et al ., 2018; Uchman et al ., 2020). A recent and detailed geomorphological analysis of its insular shelf, based on a very high‐resolution bathymetrical survey, provided key information about shelf sediment transport processes (Ricchi et al ., 2020) and on the age of the latest eruptions taking place at Santa Maria Island edifice (Ramalho et al ., 2020).…”