Evidence that three seamounts off southern California were ancient islands

Paduan, J. B.; Clague, David A.; Davis, Alicé S.

doi:10.1016/j.margeo.2009.07.003

Cited by 19 publications

(17 citation statements)

References 45 publications

(66 reference statements)

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“…The glass analyses indicate losses of 60% to 95% of initial S. There is a strong correlation of decreasing S with decreasing depth (Figures 9b and 9c) and the glasses from the shallowest depths have S concentrations that overlap with the S concentrations commonly found in subaerial basalts from Hawaii [ Moore and Clague , 1987]. However, we see little other evidence to support the idea that Davidson was once an island [ Paduan et al , 2009] and conclude that these fractionated alkalic lavas had high volatile contents that caused extensive vesiculation (Figure 10) and volatile loss, under shallow to deep submarine conditions. Other alkalic lavas erupted submarine at the North Arch [ Dixon et al , 1997] and Loihi Seamount [ Dixon and Clague , 2001] have lost up to ∼50% of their initial S during magma degassing, at depths as shallow as 1050 m on Loihi or 3900–4380 m deep in the North Arch.…”

Section: Discussionmentioning

confidence: 82%

Five million years of compositionally diverse, episodic volcanism: Construction of Davidson Seamount atop an abandoned spreading center

Clague

Paduan

Duncan

et al. 2009

Geochem Geophys Geosyst

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[1] Davidson Seamount, a volcano located about 80 km off the central California coast, has a volume of 320 km 3 and consists of a series of parallel ridges serrated with steep cones. Davidson was sampled and its morphology observed during 27 ROV Tiburon dives. During those dives, 286 samples of lava, volcaniclastite, and erratics from the continental margin were collected, with additional samples from one ROV-collected push core and four gravity cores. We report glass compositions for 99 samples and 40 Ar-39 Ar incremental heating age data for 20 of the samples. The glass analyses are of hawaiite (62%), mugearite (13%), alkalic basalt (9%), and tephrite (8%), with minor transitional basalt (2%), benmoreite (2%), and trachyandesite (2%). The lithologies are irregularly distributed in space and time. The volcano erupted onto crust inferred to be 20 Ma from seafloor magnetic anomalies. Ages of the lavas range from 9.8 to 14.8 Ma. The oldest rocks are from the central ridge, and the youngest are from the flanks and southern end of the edifice. The compositions of the 18 reliably dated volcanic cones vary with age such that the oldest lavas are the most fractionated. The melts lost 65% to nearly 95% of their initial S because of bubble loss during vesiculation, and the shallowest samples have S contents similar to lava erupted subaerially in Hawaii. Despite this similarity in S contents, there is scant other evidence to suggest that Davidson was ever an island. The numerous small cones of disparate chemistry and the long eruptive period suggest episodic growth of the volcano over at least 5 Myr and perhaps as long as 10 Myr if it began to grow when the spreading ridge was abandoned.

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Section: Discussionmentioning

confidence: 82%

Five million years of compositionally diverse, episodic volcanism: Construction of Davidson Seamount atop an abandoned spreading center

Clague

Paduan

Duncan

et al. 2009

Geochem Geophys Geosyst

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“…In the absence of summit carbonate platform (i.e., drowned atoll), the flat top of Pacific guyots is generally interpreted as the result of erosion at sea level with the development of extended wave planation surfaces (Hess, 1946). To date, observations that support this erosional interpretation consist essentially of the occurrence of well-rounded clasts collected by dredging or observed during submarine dives on summit platforms (e.g., Carsola and Dietz, 1952;Hamilton, 1956;Budinger, 1967;Paduan et al, 2009). In this context, the recognition of erosional surfaces in the uppermost stratigraphy of Louisville guyots is significant to characterize erosional processes at the end of the main volcanic phase of volcanic islands.…”

Section: Erosional Summit Platformmentioning

confidence: 99%

“…Yet, it is significant to note that robust evidence for the more widely acknowledged existence of a wave planation surface on top of guyots remains equally elusive. The main direct support for this hypothesis is based on the occurrence of well-rounded clasts on top of these seamounts (e.g., Carsola and Dietz, 1952; Hamilton, 1956;Budinger, 1967;Paduan et al, 2009), but these deposits are not incompatible with the possibility of the morphology of the guyots being controlled at least in part by earlier volcanic constructional processes.…”

Section: Introductionmentioning

confidence: 99%

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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“…There are places in the ocean where this model clearly applies (e.g., Hawaiian and Cook‐Austral chains [ Crough , 1978; Detrick and Crough , 1978]), but not in the Gulf of Alaska. A total of 29 submersible dives on Gulf of Alaska seamounts (except for Cobb Seamount) found no evidence for wave erosion such as wave‐cut terraces or cobble/sand beaches such as those seen on seamounts of the coast of California [e.g., Paduan et al , 2004]. While it may be reasonable to assume that the pinnacles that extend to within 50–150 m of the sea surface on Patton and Bowie, and the terraces on the summit plateau of Cobb Seamount are all shallow enough to be within the range of past sea level drops, the flat summit plateaus found at 235 m (Bowie) to 2225 m deep (Ely) apparently were not.…”

Section: Discussionmentioning

confidence: 99%

Seamount morphology in the Bowie and Cobb hot spot trails, Gulf of Alaska

Chaytor

Keller

Duncan

et al. 2007

Geochem Geophys Geosyst

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[1] Full-coverage multibeam bathymetric mapping of twelve seamounts in the Gulf of Alaska reveals that they are characterized by flat-topped summits (rarely with summit craters) and by terraced, or step-bench, flanks. These summit plateaus contain relict volcanic features (e.g., flow levees, late-stage cones, and collapse craters) and as such must have been constructed by volcanic processes such as lava ponding above a central vent, rather than by erosion above sea level. The terraced flanks are composed of a sequence of stacked lava deltas and cones, probably tube-fed from a central lava pond, a morphology which is suggestive of long-lived, stable central lava sources and low to moderate eruption rates, indicative of significant time spent above a hot spot outlet. Most of these seamounts have summit plateaus surrounded, and cut into, by amphitheater headwall scarps, and flanks that are scarred by debris chutes, but lack visible debris accumulations at their base. We interpret the lack of blocky debris fields as evidence that the slope failures are mainly small-scale debris flows, rather than large-scale flank collapses. However, we cannot rule out the possibility that large flank-collapse blocks from early in the histories of these seamounts are now hidden beneath the thick glacio-fluvial fan deposits that cover the Gulf of Alaska seafloor. These slope failure features become smoother and longer and increase in size and abundance with increasing age of a seamount, suggesting that slope failure processes continue long after volcanic activity ceases.

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Evidence that three seamounts off southern California were ancient islands

Cited by 19 publications

References 45 publications

Five million years of compositionally diverse, episodic volcanism: Construction of Davidson Seamount atop an abandoned spreading center

Five million years of compositionally diverse, episodic volcanism: Construction of Davidson Seamount atop an abandoned spreading center

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

Seamount morphology in the Bowie and Cobb hot spot trails, Gulf of Alaska

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