The ‘‘Sirente crater field,’’ Italy, revisited

A scientific debate has developed in the last few years as to whether a 130 m diameter
sag pond surrounded by a saddle-shaped rim and neighboring smaller sags from the
Sirente Plain (Abruzzi, Italy) represent the only known Italian meteoritic crater field,
a mud volcano, or an anthropogenic feature. To decipher the nature of the Sirente
landforms, we carried out geophysical and geochemical investigations. Geoelectric
profiles document two karstified shelf carbonate ridges lying at 10–40 m depth below
calcareous lacustrine silts (and deeper more conductive sediments, likely soils/tephra)
filling the plain. The smaller sags lie just above the ridges, implying a karstic origin,
whereas the main sag (also resting above a carbonate ridge) shows no roots in excess of
10–20 m depth, in contrast to the "crater" interpretation. High-resolution magnetic
surveys reveal negative/positive anomaly stripes in correspondence with the buried ridges/
valleys, respectively. The smaller sags, as well as the main crater are located in the domain
of negative residuals. The positive long-wavelength magnetic signature is likely due
to the strongly susceptive soils/tephra filling the buried valleys. Magnetic modeling shows
that the field observed over the crater is incompatible with the field generated by a
buried meteorite with realistic characteristics. The smaller sags are characterized by
small magnetic anomaly couplets, perfectly reproducible considering the susceptibility
contrast between the fill-in soil and the surrounding silts. Our data show that the Sirente
crater and the minor depressions are simply the results of human activity and karstic
processes, respectively.

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