Comments on “Chronology of Vesuvius' activity from A.D. 79 to 1631 based on archeomagnetism of lavas and historical sources” by C. Principe et al., Bull Volcanol

Lanza, Roberto; Zanella, Elena

doi:10.1007/s00445-005-0030-9

Cited by 11 publications

(9 citation statements)

References 15 publications

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“…Similarly, our evidence of sites from the same flow yielding non‐overlapping confidence cones (i.e., Lav19–Lav11/13 and Lav24–Lav25, Table 2) has also been reported elsewhere [ Hagstrum and Champion , 1994; Speranza et al , 2006a]. There are several possible sources yielding scatter of paleomagnetic directions from a given volcanic unit (see comprehensive discussions by Urrutia‐Fucugauchi et al [2004] and Lanza and Zanella [2006]).…”

Section: Sources Of Directional Scatter and Paleomagnetic Inclinationsupporting

confidence: 83%

Holocene eruptive history of the Stromboli volcano: Constraints from paleomagnetic dating

et al. 2008

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[1] We report on paleomagnetic directions gathered from 33 sites from (mostly Holocene) volcanics from Stromboli, loosely dated at present by few K/Ar and 14 C ages. In order to provide dating, the paleomagnetic directions were compared to the Holocene paleosecular variation of the geomagnetic field for the Mediterranean region, derived from direct geomagnetic observations and several archeomagnetic-paleomagnetic data sets. Petrochemical analyses from the paleomagnetic specimens revealed that each Holocene eruptive cycle of Stromboli was characterized by peculiar chemical characteristics. We suggest that before the 20th century AD paroxysms, powerful spatter-forming eruption(s) occurred during the 17th century AD, followed by three centuries of less energetic eruptions, when spattering was limited to the summit cones. A robust data set (4 sites, 52 samples) from the S. Bartolo flow, partially buried below the Stromboli village, constrains its age to 360 BC to 7 AD, in Greek-Roman times. The ca. 6200 years BP age inferred for a scoria exposed below a characteristic pyroclastic succession suggests its correlation with the Secche di Lazzaro pyroclastics, a major phreatomagmatic eruption occurring during the 6th millennium BP, synchronous with the major volcanotectonic collapse of the Sciara del Fuoco. Ages were provided for many lavas from the Neostromboli sequence (including the Labronzo, Nel Cannestrà, and Ginostra flows), indicating that huge effusive activity from lateral fissures fed by an evolving magma chamber occurred in the $6200-8000 years BP time window. The absence of volcanics with ages comprised between the 6th millennium BP and 400 BC implies a puzzling three-millennia ''eruption gap'' at Stromboli.

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Section: Sources Of Directional Scatter and Paleomagnetic Inclinationsupporting

confidence: 83%

Holocene eruptive history of the Stromboli volcano: Constraints from paleomagnetic dating

et al. 2008

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“…Most likely causes for the observed recording bias in ignimbrites are local magnetic anomalies (due to the underlying terrain and/or to already magnetized parts of the cooling volcanic unit), and/or variations in magnetic mineralogy (see Lanza and Zanella (2006), Urrutia-Fucugauchi et al (2004) and Speranza et al (2006) for an exhaustive discussion on factors affecting the fidelity of paleomagnetic recording in volcanic rocks). In any case, we stress that paleomagnetic direction variability along different stratigraphic levels of ignimbrites is very small (less than 5°) if compared to PSV variability as apparent in our data set (ca.…”

Section: Discussionmentioning

confidence: 99%

Correlation of welded ignimbrites on Pantelleria (Strait of Sicily) using paleomagnetism

2011

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Although the oldest volcanic rocks exposed at\ud Pantelleria (Strait of Sicily) are older than 300 ka, most of\ud the island is covered by the 45–50 ka Green Tuff\ud ignimbrite, thought to be related to the Cinque Denti\ud caldera, and younger lavas and scoria cones. Pre-50 ka\ud rocks (predominantly rheomorphic ignimbrites) are exposed\ud at isolated sea cliffs, and their stratigraphy and chronology\ud are not completely resolved. Based on volcanic stratigraphy\ud and K/Ar dating, it has been proposed that the older La\ud Vecchia caldera is related to ignimbrite Q (114 ka), and that\ud ignimbrites F, D, and Z (106, 94, and 79 ka, respectively)\ud were erupted after caldera formation. We report here the\ud paleomagnetic directions obtained from 23 sites in ignimbrite\ud P (133 ka) and four younger ignimbrites, and from an\ud uncorrelated (and loosely dated) welded lithic breccia thought\ud to record a caldera-forming eruption. The paleosecular\ud variation of the geomagnetic field recorded by ignimbrites is\ud used as correlative tool, with an estimated time resolution in\ud the order of 100 years. We find that ignimbrites D and Z\ud correspond, in good agreement with recent Ar/Ar ages\ud constraining the D/Z eruption to 87 ka. The welded lithic\ud breccia correlates with a thinner breccia lying just below\ud ignimbrite P at another locality, implying that collapse of the\ud La Vecchia caldera took place at ~130–160 ka. This caldera\ud was subsequently buried by ignimbrites P, Q, F, and D/Z.\ud Paleomagnetic data also show that the northern caldera\ud margin underwent a ~10° west–northwest (outwards) tilting\ud after emplacement of ignimbrite P, possibly recording magma\ud resurgence in the crust

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“…Relying on the very small α 95 values they gathered, Tanguy et al [2003], Arrighi et al [2004], and Principe et al [2004] suggest that (after comparison with a PSV reference curve) paleomagnetic dating may be achieved with an age accuracy of even ±20–30 years. This conclusion has been recently questioned by Lanza and Zanella [2006], who suggested that Principe et al [2004] did not consider several factors causing the misalignment between the paleomagnetic direction frozen in lavas and the regional geomagnetic field at the time of cooling. Such mismatch in turn would significantly increase the age uncertainty associated with paleomagnetic dating.…”

Section: Discussionmentioning

confidence: 99%

“…Unfortunately, at present there is not an overall consensus above the accuracy of the age determinations that paleomagnetic dating may yield. While some authors suggest that an age accuracy of ±20–30 years can be safely achieved [ Tanguy et al , 2003; Arrighi et al , 2004; Principe et al , 2004], others observed a quite large scatter among paleomagnetic directions from the same flow, which may translate into significantly greater uncertainties on the age determinations [ Hagstrum and Champion , 1994; Rolph , 1997; Quidelleur et al , 2005; Lanza and Zanella , 2006]. Recently, the disagreement between the paleomagnetic directions retrieved from lava flows emplaced between 1943 and 1946 A.D. at Paricutin volcano (Mexico) and the coeval direction of the geomagnetic field, has even questioned the reliability of this dating method [ Urrutia‐Fucugauchi et al , 2004].…”

Section: Introductionmentioning

confidence: 99%

How accurate is “paleomagnetic dating”? New evidence from historical lavas from Mount Etna

et al. 2006

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[1] In the last years, paleomagnetism has been increasingly used to provide emplacement ages of loosely dated volcanics. Dating is achieved by comparison of paleomagnetic directions with a given reference curve of the paleosecular variation (PSV) of the geomagnetic field. Recently, a debate has developed on the achievable precision (the a 95 value) of the paleomagnetic directions and hence on the accuracy that ''paleomagnetic dating'' can yield. At 39 different sites from Etna we paleomagnetically investigated 13 flows (four ''test flows'' with known age, and nine loosely dated flows), emplaced between 122 B.C. and 1865 A.D. We systematically drilled 12 cores per flow spaced in three (far from each other) sites and demagnetized one specimen per core by alternating field cleaning. Results from the four test flows yield age windows effectively encompassing the respective true flow ages, when dating based on Bayesian statistics at a 95% confidence level is adopted. We find a 95 values for the flow mean directions ranging between 3.3°and 5.7°(4.5°on average), which translate into accuracies of age determinations of 136-661 years (307 years on average). Such dating uncertainty is likely underestimated, as we disregarded several kinds of errors that might affect both the fidelity of paleomagnetic recording and the PSV reference curve. The strong magnetization of both the underlying terrain and the cooling flow itself and mineral magnetic variations across the flows are the most likely sources for the scatter characterizing the recording process of the magnetic field in volcanic rocks.

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Comments on “Chronology of Vesuvius' activity from A.D. 79 to 1631 based on archeomagnetism of lavas and historical sources” by C. Principe et al., Bull Volcanol

Cited by 11 publications

References 15 publications

Holocene eruptive history of the Stromboli volcano: Constraints from paleomagnetic dating

Holocene eruptive history of the Stromboli volcano: Constraints from paleomagnetic dating

Correlation of welded ignimbrites on Pantelleria (Strait of Sicily) using paleomagnetism

How accurate is “paleomagnetic dating”? New evidence from historical lavas from Mount Etna

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