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[MIS15-05] The preservation of radiolarians across the Jurassic-Cretaceous (J/K) boundary in the Bosso Valley section, Central Italy
Keywords:preservation, radiolarians, Jurassic-Cretaceous (J/K) boundary
Thin sections of 19 samples were observed to elucidate the relationship between lithology and preservation of radiolarians. Three samples of micritic limestone below the JKB (Beds 73, 75, and 77) and two samples above the JKB were collected for analyzing. The limestone samples were immersed in 10% hydrochloric acid for 30 to 60 minutes, then washed, dried and examined under a binocular microscope and a scanning electron microscope.
Radiolarians are abundant both in the chert bands or nodules and in the limestone. Preservation of radiolarians varies in different parts because of the diagenesis. Surfaces of etched limestone are observed and divided into different parts, based on the preservation of radiolarians. Radiolarians are generally calcified in the pure lime beds. Radiolarians are generally bad preserved in the chert bands or nodules. Well-preserved radiolarians are located inside the lime part near the chert bands or nodules. Primary results of radiolarian assemblages near the JKB are proposed. Limestones near chert layers or nodules in the Bosso Valley section enable radiolarian biostratigraphic study across the JKB.