Comment on “The insular shelves of the Faial‐Pico Ridge (Azores archipelago): A morphological record of its evolution” by Quartau et al.

Marques, F.O.; Hildenbrand, A.; Zanon, Vittorio; Boulesteix, Thomas

doi:10.1002/2015gc006052

Cited by 3 publications

(20 citation statements)

References 38 publications

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“…Marques et al . [] suggested that islands in the Azores develop through shoreline progradation of successive generations of coastal lava deltas over the slopes of the islands. The seaward progradation of lavas over steep offshore slopes generates lava‐fed delta structures similar to Gilbert‐type river deltas [ Jones and Nelson , ; Ramalho et al ., ].…”

Section: Influence Of Subsidence In the Development Of Insular Shelvementioning

confidence: 99%

“…In this reply to Marques et al . [], we will show how the morphologies of the Azorean insular shelves are incompatible with their suggestion of having formed by volcanic progradation and rapid subsidence. Essentially, unless modified by recent volcanism, the shelf bedrocks beneath thin sand deposits present smooth surfaces that have lower gradients than the adjacent subaerial volcanoes and do not continue the subaerial volcano slopes as speculated by Marques et al .…”

Section: Introductionmentioning

confidence: 99%

“…Essentially, unless modified by recent volcanism, the shelf bedrocks beneath thin sand deposits present smooth surfaces that have lower gradients than the adjacent subaerial volcanoes and do not continue the subaerial volcano slopes as speculated by Marques et al . [] but instead lie well below them. Thus, insular shelves in the Azores show a typical wave erosional morphology, although often modified by volcanic progradation [ Quartau et al ., ; Quartau and Mitchell , ; Quartau et al ., ].…”

Section: Introductionmentioning

confidence: 99%

“…The present‐day depths of their shelf edges show that older portions of the islands have subsided, although their long‐term (10 5 −10 6 years) subsidence rates are normally one order of magnitude lower than the rates considered by Marques et al . []. Although the Azores lie in a tectonically active region, deformation is concentrated along active faults that present normal slip‐rate components, usually of the order of tenths of mm/a [ Madeira and Brum da Silveira , ; Madeira et al ., ], and do not produce widespread subsidence as Marques et al .…”

Section: Introductionmentioning

confidence: 99%

“…Although the Azores lie in a tectonically active region, deformation is concentrated along active faults that present normal slip‐rate components, usually of the order of tenths of mm/a [ Madeira and Brum da Silveira , ; Madeira et al ., ], and do not produce widespread subsidence as Marques et al . [] suggested.…”

Section: Introductionmentioning

confidence: 99%

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Reply to comment by Marques et al. on “The insular shelves of the Faial‐Pico Ridge (Azores archipelago): A morphological record of its evolution”

Quartau

Madeira

Mitchell

et al. 2016

Geochem Geophys Geosyst

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Section: Influence Of Subsidence In the Development Of Insular Shelvementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Reply to comment by Marques et al. on “The insular shelves of the Faial‐Pico Ridge (Azores archipelago): A morphological record of its evolution”

Quartau

Madeira

Mitchell

et al. 2016

Geochem Geophys Geosyst

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The evolution of Santa Maria Island in the context of the Azores Triple Junction

Marques

Hildenbrand

Costa³

et al. 2020

Bull Volcanol

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is the oldest island in the Azores, formerly belonging to the Eurasia plate and currently the only one sitting on the Nubia Plate, thus sharing a geodynamic evolution with the Azores Triple Junction. It is therefore important to evaluate the effects of active tectonics on the evolution of Santa Maria, for example on its vertical movements. We present new stratigraphic, geomorphologic, structural and geochronological data from Santa Maria which shed further light on how a volcanic ocean island evolves in a tectonically active setting. Santa Maria island started with a first shield volcano (Old Volcanic Complex) that emerged ca. 6.0 Ma ago and was active until ca. 5.3 Ma. The short time span between the first and second shield volcanoes (ca. 0.3 Ma) and the preservation of only the western flank of this first shield volcano indicate an initial flank collapse at ca. 5 Ma. The collapse scar was covered by an eastwards dipping sedimentary complex (Intermediate Sedimentary Complex), with a likely tsunami deposit at the base. A second shield volcano (Young Volcanic Complex) rapidly grew on these sediments from 4.8 to 3.8 Ma, and the island subsided by more than 100 m. At 3.7 Ma, a second flank collapse occurred, as inferred from the missing summit and eastern flank. Volcanism then resumed (3.6 to 2.8 Ma), giving rise to Strombolian cones lying unconformably on the collapse scar, and conformable parasitic cones on the unaffected flank. Submarine lavas occurring at up to 200 m altitude with a youngest age of 3.0 Ma indicate major uplift of the island since, at most, that time. Here we interpret uplift as the result of rift flank uplift on the southern shoulder of the nearby Terceira Rift in the last ca. 1.5 Ma.

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Non-Hawaiian lithostratigraphy of Louisville seamounts and the formation of high-latitude oceanic islands and guyots

Buchs

Williams

Sano

et al. 2018

Journal of Volcanology and Geothermal Research

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Guyots are large seamounts with a flat summit that is generally believed to form due to constructional biogenic and/or erosional processes during the formation of volcanic islands. However, despite their large abundance in the oceans, there are still very few direct constraints on the nature and formation of guyots, in particular those formed at high latitude that lack a thick cap of shallow-marine carbonate rocks. It is largely accepted based on geophysical constraints and surficial observations/sampling that the summit platform of these guyots is shaped by wave abrasion during post-volcanic subsidence of volcanic islands. Here we provide novel constraints on this hypothesis and the summit geology of guyots with a lithostratigraphic analysis of cores from three Louisville seamounts (South Pacific) collected during Expedition 330 of the Integrated Ocean Drilling Program (IODP). Thirteen lithofacies of sedimentary and volcanic deposits are described, which include facies not previously recognized on the top of guyots, and offer a new insight into the formation of high-latitude oceanic islands on a fastmoving plate. Our results reveal that the lithostratigraphy of Louisville seamounts preserves a very consistent record of the formation and drowning of volcanic islands, with from bottom to top: (i) volcaniclastic sequences with abundant lava-fed delta deposits, (ii) submarine to subaerial shield lava flows, (iii) post-volcanic shallow to deeper marine sedimentary rocks lacking thick reef deposits, (iv) post-erosional rejuvenated volcanic rocks, and (v) pelagic sediments. Recognition of erosional boundaries between subaerial lava flows and shallow-marine sedimentary rocks provides novel support for post volcanic wave planation of guyots. However, the summit geology of Louisville seamounts is dissimilar to that of high-latitude Hawaiian-Emperor guyots that have emplaced in a similar tectonic and environmental setting and that include thicker lava stacks with apparently little lava-fed delta deposits. To explain observed lithostratigraphic discrepancy we propose that Louisville seamounts represent a distinct type of intraplate ocean volcano characterized by formation of a smaller island, with a central shield volcano surrounded by extended shallow-marine shelves formed by lava-fed deltas. In this interpretation the summit platform of Louisville-type guyots results from early (syn-volcanic) subaerial to shallow-marine constructional volcanic processes and marine erosion, enhanced by later (post-volcanic) wave planation. This contrasts with larger Hawaiian edifices that are capped by thicker shield volcanoes, and that develop an extended wave planation surface during postvolcanic subsidence (in the absence of efficient coral growth). The difference between Hawaiian-and Louisville-type volcanic islands and guyots can be explained by contrasted dynamic disequilibrium between magmatic growth, erosion, and subsidence during the island-building stage. Unlike Hawaiian-type volcanoes, Louisville seamounts are characterized by a...

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Comment on “The insular shelves of the Faial‐Pico Ridge (Azores archipelago): A morphological record of its evolution” by Quartau et al.

Cited by 3 publications

References 38 publications

Reply to comment by Marques et al. on “The insular shelves of the Faial‐Pico Ridge (Azores archipelago): A morphological record of its evolution”

Reply to comment by Marques et al. on “The insular shelves of the Faial‐Pico Ridge (Azores archipelago): A morphological record of its evolution”

The evolution of Santa Maria Island in the context of the Azores Triple Junction

Non-Hawaiian lithostratigraphy of Louisville seamounts and the formation of high-latitude oceanic islands and guyots

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