Ichnology and sedimentology of the Triassic carbonates of North‐west Sardinia, Italy

Abstract

The classical Middle to Upper Triassic carbonate sections at Monte Santa\ud Giusta and Punta del Lavatoio, North-west Sardinia (Italy), referred to the\ud Muschelkalk and Keuper lithofacies group, are revisited and their trace fossil\ud content is investigated for the first time. A combined ichnological and\ud sedimentological study reveals insights into the depositional environments,\ud regional context, palaeogeography and sequence stratigraphy. The results\ud indicate deposition on a homoclinal carbonate ramp with broad facies belts.\ud All recognized trace fossils are also known from time-equivalent deposits of\ud Germany and thus indicate a close affinity between the North-west Sardinian\ud Triassic and the Germanic Basin. Only a few trace fossils are particularly\ud abundant and these indicate opportunistic colonization by their producers,\ud which is probably related to restricted endobenthic conditions due to reduced\ud oxygen and/or increased salinity. The trace fossil association can be grouped\ud into a softground suite belonging to the Cruziana ichnofacies, and a firmground\ud suite of the Glossifungites ichnofacies. This discrimination enables an\ud interpretation of the northern Monte Santa Giusta section as a carbonate\ud ramp with extensive tidal flats and abundant carbonate accumulation in a\ud relatively proximal position, whereas the southern Punta del Lavatoio section\ud exhibits broad lagoonal environments with reduced sedimentation in a deeper\ud and more Tethys-influenced area. The Sardinian sections are ichnologically\ud similar to the Anisian–Ladinian succession known from the Tatra Mountains,\ud but differ from it by having a slightly higher ichnodiversity, which again can be\ud attributed to a less restricted lagoonal environment. This study demonstrates\ud the importance of integrating trace fossil analysis in sedimentological and\ud palaeontological investigations of carbonate systems

Trace fossils from the Lower Muschelkalk of Raciborowice Górne (North Sudetic Synclinorium, SW Poland) and their palaeoenvironmental interpretation

“…According to Knaust (2008Knaust ( , 2010a, sipunculans (peanut worms) and polychaetes (eunicid-like polychaetes) are more probable tracemakers, as enteropneusts (acorn worms) are not typical bioeroders (see also Jaglarz and Uchman 2010). This ichnotaxon involves burrow system at the transition between firmgrounds and hardgrounds (Knaust and Costamagna 2012) and is a common component of the Glossifungites and Trypanites ichnofacies (Knaust 2008). B. triadicus appears not only as burrows but also as borings (Knaust 2008(Knaust , 2010bDesai and Saklani 2012).…”

“…Known from the Phanerozoic (Kaźmierczak and Pszczółkowski 1969; Goldring and Kaźmierczak 1974;Palmer 1978;Dronov et al 2002;Carmona et al 2008;Hoffman and Uchman 2008;Hoffman et al 2009); especially common in the Triassic (Szulc 1990a(Szulc , b, 2000Knaust 2007aKnaust , 2008Jaglarz and Uchman 2010;Knaust and Costamagna 2012).…”

“…is regarded a dwelling trace (domichnion), produced by suspension-feeding bivalves (Kelly and Bromley 1984;Farinati 2007;Knaust 2007a;Buatois and Encinas 2011;Knaust and Costamagna 2012) and sipunculan worms (Malpas et al 2005). Mytilidae (Lithophaga lithophaga) and Gastrochaenidae (Gastrochaena dubia) are suggested as their potential producers in modern environments (Warme 1975;Wilson and Palmer 1998;Wilson and Taylor 2001;Donovan and Hensley 2006;Perry and Smithers 2006;Wilson et al 2008;Buatois and Mángano 2011;Gibert et al 2012).…”

“…However, a few reports on the Middle Triassic carbonate successions of Germany (e.g. Knaust 1998Knaust , 2007a, southern Spain and Italy (Sardinia) (Rodríguez-Tovar et al 2007;Rodríguez-Tovar and Pérez-Valera 2008;Knaust and Costamagna 2012;Pérez-López and Pérez-Valera 2012) were published recently.…”

The ups and downs ofDiplocraterionin the Glen Rose Formation (Lower Cretaceous), Dinosaur Valley State Park, Texas (USA)

“…First, a dominance of protrusive Diplocraterion, varying depths of Diplocraterion, eroded burrow tops, crowding and cross-cutting burrows, and open-tubed (i.e. suspension feeding) forms of Rhizocorallium, all imply a progressive firming and erosion of this bed (Knaust, 2013;Knaust & Costamagna, 2012). Furthermore, all observed Rhizocorallium were restricted to the uppermost 10 cm of the Diplocraterion bed, and in one instance cut across a Diplocraterion.…”