The earliest bioeroded inorganic hard substrates in the Ordovician of Estonia appear in the Dapingian. Hardgrounds are also known from the Sandbian and Katian. Most of the bioerosion of inorganic hard substrates occurs as the boring Trypanites Mägdefrau, 1932 along with some possible Gastrochaenolites borings. North American hardground borings are more diverse than those in Baltica. In contrast...

Introduction. Nickel-rich spinel is recognized as a cosmic event marker [1-3,5]. Spinel is found in K/T boundary sections all over the world [1-3,14], in lower-middle Jurassic hardground [13], in late Pliocene sediments [4] and in upper Eocene sediments [12]. Its composition is characterized by a high nickel oxide concentration (NiO>1 wt%) and a high iron oxidation state (Fe/Fetot>70 mole%) inv...

Outcrops of the Lower Triassic (Spathian) Virgin Limestone Member (Moenkopi Formation) in the southwestern United States contain the oldest known metazoan bioherms formed in the aftermath of the endPermian mass extinction. These small buildups, up to 1.0 m in diameter and 0.2 m high, were constructed by cementing bivalves. The bivalve bioherms accreted in a shallow, subtidal environment above s...

Stromatolites, among the earliest fossils in Earth’s history, are widely distributed on margins of North China Precambrian carbonate platform. The formation processes stromatolites reveal biomineralization and evolution early life Precambrian. well-preserved stromatolitic dolostones recorded Ganjingzi Formation developed around Yuanjiagou village, southern Liaoning Province. morphology manifest...

Hardgrounds represent synsedimentary cemented stratigraphic beds that form at or near the seafloor. Borings a key line of evidence for investigations hardground development and record evolution bioerosion boring organisms. The unequivocal identification borings is done through crosscutting relationship between proposed hard substrate, such as lithoclasts and/or shells, with morphological criter...

Abstract The Jenkyns Event or Toarcian Oceanic Anoxic was an episode of severe environmental perturbations reflected in carbon isotope and other geochemical anomalies. Although well studied the epicontinental basins NW Europe, its effects are less understood open marine environments. Here we present new (carbon isotope, CaCO 3 , [Mn]) nannofossil biostratigraphic data from Tölgyhát Kisgerecse s...

Widespread mortality of reef-building coral substantially reduces the capacity for reef growth and makes available extensive bare substrate areas that in absence recovery will be eroded by a variety external internal bioeroders. Here, we analyze rates erosion on six different types carbonate substrates under situ conditions over 2-yr period. We measure vertical changes surface elevation four sp...

New ammonoid data prove an early Late Pliensbachian deepening event above the ?Late Hettangian-Sinemurian shallow-subtidal gray-reddish micro-oncoidal-foraminifera grainstone facies and ?early deeper-marine micro-oncoidal-crinoidal-ammonoid wacke- to packstone facies. Based on presence of Fuciniceras lavinianum (Fucini), Lytoceras ovimontanum Geyer Arieticeratinae gen. indet. from a hardground ...