Several travertine units of Pleistocene age occur in the area between Acquasanta Terme and Ascoli Piceno (Marche, central Italy). The Umbria-Marche region is characterized by a recent tectonic extension, which has been active since the late Pliocene-early Pleistocene. The extension is superimposed on a Miocene-Pliocene compressional tectonic phase that formed the Umbria-Marche fold-and-thrust belt. The travertine deposits are precipitated by H2S-rich subaerial hydrothermal spring (about 32°C). These units were analyzed within two quarries that show different depositional systems and are placed at two different elevations: Tancredi quarry (451m) and Cardi quarry (335m). These elevations relate to different depositional phases and ages; in fact the lower unit is the youngest due to its position along the fluvial valley incision of the Tronto River. Tancredi quarry displays two main depositional environments: slope (30-40m thick, 50m wide) and depression (max 30m thick 100m wide). The slope is smooth, 30-45° steep and is composed of carbonate fabrics of fast-flowing water such as feather crystals (3-10cm thick), pisoidal grainstone (2-40cm thick), microsparitic crusts with irregular voids (3-10cm thick) and breccia with terrigenous matrix (25cm thick). The depression system mostly consists of deposits of slow flowing water: flat layers of shrubs (dipping 2-3°) 2-25cm in height and variable lateral continuity, paper thin rafts (2-25cm high), coated bubbles (2-3mm in diameter) and microsparitic irregular voids (2-10cm thick). Cardi quarry shows a slope system (30m thick, 70m wide) composed of smooth slope (25-30m high) and waterfalls (7-10m high). Most of the deposits are high energy and are similar to those of Tancredi quarry: feather crystals (5-30cm thick), pisoidal grainstone (until 30cm thick) and microsparitic crusts with irregular voids (cm lenses); while the shrubs (2-30cm thick), rafts (maximum 10cm thick), reeds and coated bubbles occur only in the distal part of waterfalls (slow flow pools). Higher primary porosity occurs 1) in fabrics deposited in slow flowing thermal water (slightly inclined, shrub-rich pools, depressions), and 2) where there is evidence of interruption in water flow and travertine deposition (discontinuities marked by breccias and overlying reed and coated bubble rich layers). The studies on travertine Acquasanta will provide information about the type of fabric facies, porosity, diagenesis and geometry spatial evolution.
|Titolo:||Depositional System, Petrography and Facies Analysis of Pleistocene Travertine in Southern Marche, Central Italy|
DELLA PORTA, GIOVANNA (Secondo)
|Data di pubblicazione:||24-ott-2011|
|Parole Chiave:||hydrothermal travertine ; carbonate fabrics ; Marche|
|Settore Scientifico Disciplinare:||Settore GEO/02 - Geologia Stratigrafica e Sedimentologica|
|Citazione:||Depositional System, Petrography and Facies Analysis of Pleistocene Travertine in Southern Marche, Central Italy / A. De Bernardo, G. Della Porta, E. Capezzuoli, F. Barilaro. ((Intervento presentato al convegno AAPG International Conference and Exhibition tenutosi a Milan nel 2011.|
|Appare nelle tipologie:||14 - Intervento a convegno non pubblicato|