Late-stageLate-stage volcano geomorphic evolution of the Plevolcano geomorphic evolution of the Pleistocene San Francisco Mountain, Arizona (USA), based on high-resolution DEM analysis and 40Ar/39Ar chronology

Year:

2010

Type of Publication:

Artikel

Autoren:

Karátson, Dávid; Telbisz, Tamás; Singer, Brad

Journal:

Bulletin of Volcanology

Volume:

72

Seiten:

833-846

ISSN:

0258-8900

BibTex:

@article{Dávid Karátson2010, author = "D{\'a}vid Kar{\'a}tson and Tam{\'a}s Telbisz and Brad Singer", abstract = "The cone-building volcanic activity and subsequent erosion of San Francisco Mountain, AZ, USA, were studied by using high-resolution digital elevation model (DEM) analysis and new 40 Ar/ 39 Ar dating. By defining remnants or plan{\`e}zes of the volcano flanks in DEM-derived images, the original edifice can be reconstructed. We propose a two-cone model with adjacent summit vents which were active in different times. The reconstructed cones were 4,460 and 4,350 m high a.s.l., corresponding to ∼2,160 and 2,050 m relative height, respectively. New 40 Ar/ 39 Ar data allow us to decipher the chronological details of the cone-building activity. We dated the Older and Younger Andesites of the volcano that, according to previous mapping, built the stage 2 and stage 3 stratocones, respectively. The new 40 Ar/ 39 Ar plateau ages yielded 589–556 ka for the Older and 514–505 ka for the Younger Andesites, supporting their distinct nature with a possible dormant period between. The obtained ages imply an intense final (≤100 ka long) cone-building activity, terminating ∼100 ka earlier than indicated by previous K-Ar ages. Moreover, 40 Ar/ 39 Ar dating constrains the formation of the Inner Basin, an elliptical depression in the center of the volcano initially created by flank collapse. A 530 ka age (with a ±58.4 ka 2σ error) for a post-depression dacite suggests that the collapse event is geochronologically indistinguishable from the termination of the andesitic cone-building activity. According to our DEM analysis, the original cone of San Francisco Mountain had a volume of about 80 km 3 . Of this volume, ∼7.5 km 3 was removed by the flank collapse and subsequent glacial erosion, creating the present-day enlarged Inner Basin, and ∼2 km 3 was removed from the outer valleys by erosion. Based on volumetric analysis and previous and new radiometric ages, the average long-term eruption rate of San Francisco Mountain was ∼0.2 km 3 /ka, which is a medium rate for long-lived stratovolcanoes. However, according to the new 40 Ar/ 39 Ar dates for the last ≤100 ka period, the final stratovolcanic activity was characterized by a greater ∼0.3 km 3 /ka rate.", issn = "0258-8900", journal = "Bulletin of Volcanology", note = "10.1007/s00445-010-0365-8", pages = "833-846", publisher = "Springer Berlin / Heidelberg", title = "{L}ate-stage{L}ate-stage volcano geomorphic evolution of the {P}levolcano geomorphic evolution of the {P}leistocene {S}an {F}rancisco {M}ountain, {A}rizona ({USA}), based on high-resolution {DEM} analysis and 40{A}r/39{A}r chronology", url = "http://dx.doi.org/10.1007/s00445-010-0365-8", volume = "72", year = "2010", }

Notiz:

10.1007/s00445-010-0365-8

Kurzzusammenfassung:

The cone-building volcanic activity and subsequent erosion of San Francisco Mountain, AZ, USA, were studied by using high-resolution digital elevation model (DEM) analysis and new 40 Ar/ 39 Ar dating. By defining remnants or planèzes of the volcano flanks in DEM-derived images, the original edifice can be reconstructed. We propose a two-cone model with adjacent summit vents which were active in different times. The reconstructed cones were 4,460 and 4,350 m high a.s.l., corresponding to ∼2,160 and 2,050 m relative height, respectively. New 40 Ar/ 39 Ar data allow us to decipher the chronological details of the cone-building activity. We dated the Older and Younger Andesites of the volcano that, according to previous mapping, built the stage 2 and stage 3 stratocones, respectively. The new 40 Ar/ 39 Ar plateau ages yielded 589–556 ka for the Older and 514–505 ka for the Younger Andesites, supporting their distinct nature with a possible dormant period between. The obtained ages imply an intense final (≤100 ka long) cone-building activity, terminating ∼100 ka earlier than indicated by previous K-Ar ages. Moreover, 40 Ar/ 39 Ar dating constrains the formation of the Inner Basin, an elliptical depression in the center of the volcano initially created by flank collapse. A 530 ka age (with a ±58.4 ka 2σ error) for a post-depression dacite suggests that the collapse event is geochronologically indistinguishable from the termination of the andesitic cone-building activity. According to our DEM analysis, the original cone of San Francisco Mountain had a volume of about 80 km 3 . Of this volume, ∼7.5 km 3 was removed by the flank collapse and subsequent glacial erosion, creating the present-day enlarged Inner Basin, and ∼2 km 3 was removed from the outer valleys by erosion. Based on volumetric analysis and previous and new radiometric ages, the average long-term eruption rate of San Francisco Mountain was ∼0.2 km 3 /ka, which is a medium rate for long-lived stratovolcanoes. However, according to the new 40 Ar/ 39 Ar dates for the last ≤100 ka period, the final stratovolcanic activity was characterized by a greater ∼0.3 km 3 /ka rate.