View in EDS

Pockmarks Offshore Big Sur, California Provide Evidence for Recurrent, Regional, and Unconfined Sediment Gravity Flows.

Saved in:
Bibliographic Details
Title: Pockmarks Offshore Big Sur, California Provide Evidence for Recurrent, Regional, and Unconfined Sediment Gravity Flows.
Authors: Lundsten, E.1 (AUTHOR) eve@mbari.org, Paull, C. K.1 (AUTHOR), Gwiazda, R.1 (AUTHOR), Dobbs, S.2 (AUTHOR), Caress, D. W.1 (AUTHOR), Kuhnz, L. A.1,3 (AUTHOR), Walton, M.4,5 (AUTHOR), Nieminski, N.4,6 (AUTHOR), McGann, M.7 (AUTHOR), Lorenson, T.4 (AUTHOR), Cochrane, G.4 (AUTHOR), Addison, J.7 (AUTHOR)
Source: Journal of Geophysical Research. Earth Surface. May2024, Vol. 129 Issue 5, p1-22. 22p.
Subject Terms: *Sediments, *Biotic communities, *Atmospheric methane, Autonomous underwater vehicles, Oceanographic maps, Gravity
Geographic Terms: California
Abstract: Recent surface ship multibeam surveys of the Sur Pockmark Field, offshore Central California, reveal >5,000 pockmarks in an area that is slated to host a wind farm, between 500‐ and 1,500‐m water depth. Extensive fieldwork was conducted to characterize the seafloor environment and its recent geologic history, including visual observations with remotely operated vehicles, sediment core sampling, and high‐resolution, near‐bottom Chirp and multibeam surveys collected with autonomous underwater vehicles to capture the morphology and stratigraphy of the pockmarks. No evidence of high methane concentrations in sediments, chemosynthetic biological communities, or methane‐derived diagenetic byproducts was found. Chirp data and sediment cores showed alternating layers of slowly accumulating hemipelagic drapes interrupted by more reflective turbidite horizons that extend throughout the pockmark field and beyond. Chirp data showed multiple episodes of lateral migration over time in some of the pockmarks in association with erosion and infilling events. Laterally continuous turbidite horizons that overlay erosional surfaces indicated that pockmark migration occurred synchronously in multiple pockmarks separated by tens of kilometers. These shifts are presumed to be the result of asymmetrical erosion of the pockmark flanks caused by passing sediment gravity flows. While some pockmarks occur in chains, most are not clustered or randomly spaced but are regularly dispersed within the pockmark field. We hypothesize that intermittent, unconfined sediment gravity flows occurring over at least the last 280,000 years are the source of the regionally continuous turbidite deposits and the mechanism that maintained the regularly dispersed pockmarks. Plain Language Summary: Over 5,000 pockmarks were mapped in water depths between 500 and 1,500 m offshore Central California in an area slated to host a wind farm. Pockmarks are large circular seafloor depressions commonly believed to be formed and maintained by methane flux. Video footage from the pockmark field, detailed maps of the seafloor, sediment cores, and images of the subsurface were collected. Importantly, no significant evidence of methane gas was found in any of the collected data sets. Instead, the subsurface profiles and sediment samples indicated that the pockmarks contain layers of fine sediment deposited slowly over time alternating with sandy layers deposited by large sediment flows. These flows appear to erode the pockmark centers, and leave behind regionally continuous sandy deposits (turbidites). Some sediment flows have caused sufficient erosion to the pockmarks flanks to simultaneously shift the position of multiple pockmarks, 10s of kilometers apart. Most of the pockmarks are not randomly scattered or clustered on the seafloor but are distributed in a regular, equally spaced pattern. We hypothesize that intermittent, unconfined sediment gravity flows occurring over at least the last 280,000 years are the source of the regionally continuous turbidites and the mechanism that maintained the regularly spaced pockmarks over time. Key Points: No evidence of methane venting was found in the Sur PockmarksThe persistence and lateral migration of the Sur Pockmarks are attributed to erosion and deposition during unconfined sediment gravity flowsRecurrent, regional, and unconfined sediment gravity flows have occurred in the Sur Pockmark Field for at least ∼280,000 years [ABSTRACT FROM AUTHOR]
Copyright of Journal of Geophysical Research. Earth Surface is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
Database: GreenFILE
FullText Text:
  Availability: 0
Header DbId: 8gh
DbLabel: GreenFILE
An: 177509844
AccessLevel: 6
PubType: Academic Journal
PubTypeId: academicJournal
PreciseRelevancyScore: 0
IllustrationInfo
Items – Name: Title
  Label: Title
  Group: Ti
  Data: Pockmarks Offshore Big Sur, California Provide Evidence for Recurrent, Regional, and Unconfined Sediment Gravity Flows.
– Name: Author
  Label: Authors
  Group: Au
  Data: <searchLink fieldCode="AR" term="%22Lundsten%2C+E%2E%22">Lundsten, E.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<i> eve@mbari.org</i><br /><searchLink fieldCode="AR" term="%22Paull%2C+C%2E+K%2E%22">Paull, C. K.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Gwiazda%2C+R%2E%22">Gwiazda, R.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Dobbs%2C+S%2E%22">Dobbs, S.</searchLink><relatesTo>2</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Caress%2C+D%2E+W%2E%22">Caress, D. W.</searchLink><relatesTo>1</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Kuhnz%2C+L%2E+A%2E%22">Kuhnz, L. A.</searchLink><relatesTo>1,3</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Walton%2C+M%2E%22">Walton, M.</searchLink><relatesTo>4,5</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Nieminski%2C+N%2E%22">Nieminski, N.</searchLink><relatesTo>4,6</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22McGann%2C+M%2E%22">McGann, M.</searchLink><relatesTo>7</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Lorenson%2C+T%2E%22">Lorenson, T.</searchLink><relatesTo>4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Cochrane%2C+G%2E%22">Cochrane, G.</searchLink><relatesTo>4</relatesTo> (AUTHOR)<br /><searchLink fieldCode="AR" term="%22Addison%2C+J%2E%22">Addison, J.</searchLink><relatesTo>7</relatesTo> (AUTHOR)
– Name: TitleSource
  Label: Source
  Group: Src
  Data: <searchLink fieldCode="JN" term="%22Journal+of+Geophysical+Research%2E+Earth+Surface%22">Journal of Geophysical Research. Earth Surface</searchLink>. May2024, Vol. 129 Issue 5, p1-22. 22p.
– Name: Subject
  Label: Subject Terms
  Group: Su
  Data: *<searchLink fieldCode="DE" term="%22Sediments%22">Sediments</searchLink><br />*<searchLink fieldCode="DE" term="%22Biotic+communities%22">Biotic communities</searchLink><br />*<searchLink fieldCode="DE" term="%22Atmospheric+methane%22">Atmospheric methane</searchLink><br /><searchLink fieldCode="DE" term="%22Autonomous+underwater+vehicles%22">Autonomous underwater vehicles</searchLink><br /><searchLink fieldCode="DE" term="%22Oceanographic+maps%22">Oceanographic maps</searchLink><br /><searchLink fieldCode="DE" term="%22Gravity%22">Gravity</searchLink>
– Name: SubjectGeographic
  Label: Geographic Terms
  Group: Su
  Data: <searchLink fieldCode="DE" term="%22California%22">California</searchLink>
– Name: Abstract
  Label: Abstract
  Group: Ab
  Data: Recent surface ship multibeam surveys of the Sur Pockmark Field, offshore Central California, reveal >5,000 pockmarks in an area that is slated to host a wind farm, between 500‐ and 1,500‐m water depth. Extensive fieldwork was conducted to characterize the seafloor environment and its recent geologic history, including visual observations with remotely operated vehicles, sediment core sampling, and high‐resolution, near‐bottom Chirp and multibeam surveys collected with autonomous underwater vehicles to capture the morphology and stratigraphy of the pockmarks. No evidence of high methane concentrations in sediments, chemosynthetic biological communities, or methane‐derived diagenetic byproducts was found. Chirp data and sediment cores showed alternating layers of slowly accumulating hemipelagic drapes interrupted by more reflective turbidite horizons that extend throughout the pockmark field and beyond. Chirp data showed multiple episodes of lateral migration over time in some of the pockmarks in association with erosion and infilling events. Laterally continuous turbidite horizons that overlay erosional surfaces indicated that pockmark migration occurred synchronously in multiple pockmarks separated by tens of kilometers. These shifts are presumed to be the result of asymmetrical erosion of the pockmark flanks caused by passing sediment gravity flows. While some pockmarks occur in chains, most are not clustered or randomly spaced but are regularly dispersed within the pockmark field. We hypothesize that intermittent, unconfined sediment gravity flows occurring over at least the last 280,000 years are the source of the regionally continuous turbidite deposits and the mechanism that maintained the regularly dispersed pockmarks. Plain Language Summary: Over 5,000 pockmarks were mapped in water depths between 500 and 1,500 m offshore Central California in an area slated to host a wind farm. Pockmarks are large circular seafloor depressions commonly believed to be formed and maintained by methane flux. Video footage from the pockmark field, detailed maps of the seafloor, sediment cores, and images of the subsurface were collected. Importantly, no significant evidence of methane gas was found in any of the collected data sets. Instead, the subsurface profiles and sediment samples indicated that the pockmarks contain layers of fine sediment deposited slowly over time alternating with sandy layers deposited by large sediment flows. These flows appear to erode the pockmark centers, and leave behind regionally continuous sandy deposits (turbidites). Some sediment flows have caused sufficient erosion to the pockmarks flanks to simultaneously shift the position of multiple pockmarks, 10s of kilometers apart. Most of the pockmarks are not randomly scattered or clustered on the seafloor but are distributed in a regular, equally spaced pattern. We hypothesize that intermittent, unconfined sediment gravity flows occurring over at least the last 280,000 years are the source of the regionally continuous turbidites and the mechanism that maintained the regularly spaced pockmarks over time. Key Points: No evidence of methane venting was found in the Sur PockmarksThe persistence and lateral migration of the Sur Pockmarks are attributed to erosion and deposition during unconfined sediment gravity flowsRecurrent, regional, and unconfined sediment gravity flows have occurred in the Sur Pockmark Field for at least ∼280,000 years [ABSTRACT FROM AUTHOR]
– Name: AbstractSuppliedCopyright
  Label:
  Group: Ab
  Data: <i>Copyright of Journal of Geophysical Research. Earth Surface is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites without the copyright holder's express written permission. Additionally, content may not be used with any artificial intelligence tools or machine learning technologies. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract.</i> (Copyright applies to all Abstracts.)
PLink https://search.ebscohost.com/login.aspx?direct=true&site=eds-live&db=8gh&AN=177509844
RecordInfo BibRecord:
  BibEntity:
    Identifiers:
      – Type: doi
        Value: 10.1029/2023JF007374
    Languages:
      – Code: eng
        Text: English
    PhysicalDescription:
      Pagination:
        PageCount: 22
        StartPage: 1
    Subjects:
      – SubjectFull: Sediments
        Type: general
      – SubjectFull: Biotic communities
        Type: general
      – SubjectFull: Atmospheric methane
        Type: general
      – SubjectFull: Autonomous underwater vehicles
        Type: general
      – SubjectFull: Oceanographic maps
        Type: general
      – SubjectFull: Gravity
        Type: general
      – SubjectFull: California
        Type: general
    Titles:
      – TitleFull: Pockmarks Offshore Big Sur, California Provide Evidence for Recurrent, Regional, and Unconfined Sediment Gravity Flows.
        Type: main
  BibRelationships:
    HasContributorRelationships:
      – PersonEntity:
          Name:
            NameFull: Lundsten, E.
      – PersonEntity:
          Name:
            NameFull: Paull, C. K.
      – PersonEntity:
          Name:
            NameFull: Gwiazda, R.
      – PersonEntity:
          Name:
            NameFull: Dobbs, S.
      – PersonEntity:
          Name:
            NameFull: Caress, D. W.
      – PersonEntity:
          Name:
            NameFull: Kuhnz, L. A.
      – PersonEntity:
          Name:
            NameFull: Walton, M.
      – PersonEntity:
          Name:
            NameFull: Nieminski, N.
      – PersonEntity:
          Name:
            NameFull: McGann, M.
      – PersonEntity:
          Name:
            NameFull: Lorenson, T.
      – PersonEntity:
          Name:
            NameFull: Cochrane, G.
      – PersonEntity:
          Name:
            NameFull: Addison, J.
    IsPartOfRelationships:
      – BibEntity:
          Dates:
            – D: 01
              M: 05
              Text: May2024
              Type: published
              Y: 2024
          Identifiers:
            – Type: issn-print
              Value: 21699003
          Numbering:
            – Type: volume
              Value: 129
            – Type: issue
              Value: 5
          Titles:
            – TitleFull: Journal of Geophysical Research. Earth Surface
              Type: main
ResultId 1