New insights into the palaeoenvironmental–palaeoclimatic significance and sedimentary dynamics of carbonate Lagerstätten: The lower Albian of Pietraroja (Southern Italy)

This study reports the first high-resolution, integrated facies analysis of the lowermost Albian Pietraroja Lagerst€atten (Apennine Carbonate Platform) which yields the first dinosaur (Scipionyx samniticus) found in Italy and other terrestrial vertebrates and plants. Aiming to clarify the long-debated palaeoenvironmental significance of the Pietraroja succession, the following have been carried out: (i) a field survey to establish stratigraphic position and number of the fossil Lagerst€atten; (ii) the centimetre-scale facies analysis of a new section, ca 15 m thick, consisting of two new lithostratigraphic units, the ‘Cyclically organized Limestones’ and the ‘Cherty Limestones’; (iii) the scanning electron microscopy – energy dispersive X-ray spectroscopy and backscattered electron – energy dispersive X-ray spectroscopy analyses of clay mineral proxies for palaeoclimate and non-carbonate grains; and (iv) the regional and supra-regional investigation of the event stratigraphical context of the fossil Lagerst€atten, in order to elucidate the controls on their formation. The section includes two out of the three observed fossil-rich Lagerst€atten, each up to 1.5 m thick. The arrangement of lithofacies and early diagenetic overprint defines shallow-water depositional cycles suggestive of precession and short-eccentricity periodicities. The Middle Lagerst€atte yielding Scipionyx samniticus consists of three intervals. The lower, paralic interval was deposited during arid conditions and passes gradually to the plant-rich, coastal wetland carbonaceous marls of the upper interval. The ‘Cherty Limestones’, yielding the Upper Lagerst€atte with terrestrial vertebrates, contains two spiculitic intervals suggesting the development of siliceous sponge meadows in a shallow, restricted lagoon. Genetic stratigraphy suggests that the Pietraroja Lagerst€atten were formed during glacioeustatic lowstands; interestingly, the Middle Lagerst€atte mirrors the earliest Albian sea-level lowstand (KAl1 event, ca 111.2 Myr), during a semi-continuous supply of windblown volcaniclastics. Findings herein substantiate the pivotal role of paralic–continental Lagerst€atten for deriving high-frequency palaeoclimatic dynamics and glacioeustacy from carbonate platform archives. The origin of Tethyan continental bridges between Africa and Europe during the late Aptian–earliest Albian cold interval is discussed.