Paleoecological analysis of foraminiferal, ostracod and molluscan assemblages from Holocene marine sediments of La Starza sequences (Pozzuoli, Italy) allows us to point out the following evidences: - changes in paleobathymetry, gradually increasing from 10-20 m at the base to a maximum of about 40-50 m. Marine facies are rapidly replaced by continental sediments (beach sands) towards the top. The change in paleobathymetry is hypothetically correlated to the bradyseismic effects developed between 6000 and 4000 years B.P.; -low pH values and low calcium carbonate content, chiefly in the basal part of the sequence, as testified by impoverished assemblages, evidences of dissolution on various shell types, and absence of porcellaneous foraminifers; -low dissolved oxygen content, suggested by the the absence of agglutinated foraminifers and, conversely, by the abundance of Nonionella turgid. Elphidium excavatum and inflated morphotypes of Ammonia tepida and Protelphidium granosum; - rather low environmental energy testified by the constant presence among the ostracods of instars and numerous complete carapaces belonging to genera with feeble hinge; - evolution, toward the top of the sequences, from assemblages characteristic of sandy-muddy bottoms to those of muddy bottoms, with episodic evidences of seagrass, as suggested by the structural and functional (trophic organization) changes affecting the mollusk fauna; - predation phenomena recorded both on micro and macrofauna. Two new species, Asterigerinata mariae n.sp. (foraminiferida), and Loxoconcha eubea n. sp. (Ostracoda), are also described and illustrated.

Paleoecologia dei depositi terrazzati de La Starza (Pozzuoli).

BARRA, DIANA;SGARRELLA, FRANCA
1990

Abstract

Paleoecological analysis of foraminiferal, ostracod and molluscan assemblages from Holocene marine sediments of La Starza sequences (Pozzuoli, Italy) allows us to point out the following evidences: - changes in paleobathymetry, gradually increasing from 10-20 m at the base to a maximum of about 40-50 m. Marine facies are rapidly replaced by continental sediments (beach sands) towards the top. The change in paleobathymetry is hypothetically correlated to the bradyseismic effects developed between 6000 and 4000 years B.P.; -low pH values and low calcium carbonate content, chiefly in the basal part of the sequence, as testified by impoverished assemblages, evidences of dissolution on various shell types, and absence of porcellaneous foraminifers; -low dissolved oxygen content, suggested by the the absence of agglutinated foraminifers and, conversely, by the abundance of Nonionella turgid. Elphidium excavatum and inflated morphotypes of Ammonia tepida and Protelphidium granosum; - rather low environmental energy testified by the constant presence among the ostracods of instars and numerous complete carapaces belonging to genera with feeble hinge; - evolution, toward the top of the sequences, from assemblages characteristic of sandy-muddy bottoms to those of muddy bottoms, with episodic evidences of seagrass, as suggested by the structural and functional (trophic organization) changes affecting the mollusk fauna; - predation phenomena recorded both on micro and macrofauna. Two new species, Asterigerinata mariae n.sp. (foraminiferida), and Loxoconcha eubea n. sp. (Ostracoda), are also described and illustrated.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11588/195349
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