Implications of a combined biostratigraphic and palaeomagnetic study of the Umbrian Maiolica Formation

S Cirilli, P Márton, L Vigli - Earth and Planetary Science Letters, 1984 - Elsevier
S Cirilli, P Márton, L Vigli
Earth and Planetary Science Letters, 1984Elsevier
The study of a 275.5 m thick section of white, pelagic limestones occupying the valley of the
Fonte del Giordano river on the southern slope of Mt. Montagnola has yielded a
biostratigraphically controlled clear magnetic reversal pattern after thermal cleaning. The
magnetic stratigraphy of the lower 131 m of the section (Calpionellid zones) is correlatable
with the M-sequence of oceanic magnetic anomalies between M-19 and M-14. The reversal
stratigraphy of the upper 81.5 m of the section (Radiolaria zone) has also been tied to the …
Abstract
The study of a 275.5 m thick section of white, pelagic limestones occupying the valley of the Fonte del Giordano river on the southern slope of Mt. Montagnola has yielded a biostratigraphically controlled clear magnetic reversal pattern after thermal cleaning. The magnetic stratigraphy of the lower 131 m of the section (Calpionellid zones) is correlatable with the M-sequence of oceanic magnetic anomalies between M-19 and M-14. The reversal stratigraphy of the upper 81.5 m of the section (Radiolaria zone) has also been tied to the oceanic polarity time scale by making linear interpolation for a missing 63 m thickness underneath it.
Besides the Fonte del Giordano section two Berriasian outcrops each with a different bedding attitude were studied at Gubbio and near Cagli for tectonic tilt test giving positive results. The mean palaeomagnetic pole position for the Late Jurassic/Early Cretaceous after bedding correction is: Φ = 19.1°, Λ = 288.2°, k = 148.7, α95 = 10.2° (N = 3), confirming the presence of a large swing in the polar path, a common behaviour of apparent polar wandering for the peri-Adriatic region during this time.
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