Shallow-water pockmark formation in temperate estuaries: A consideration of origins in the western gulf of Maine with special focus on Belfast Bay

Rogers, Jeffrey N.; Kelley, Joseph T.; Belknap, Daniel F.; Gontz, Allen; Barnhardt, Walter A.

doi:10.1016/j.margeo.2005.07.011

Cited by 67 publications

(78 citation statements)

References 44 publications

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“…Differential erosion of bedrock associated with Marine Geology 329-331 (2012) [34][35][36][37][38][39][40][41][42][43][44][45] glaciations, coupled with Holocene sea-level rise, formed an irregular coastal and inner shelf region characterized by numerous estuaries and bays (Kelley, 1987;Kelley et al, 1989), and littered by pockmarks (Rogers et al, 2006). In cross section, the coastal embayments are 10-60 m deep bedrock-framed depressions filled with sediment termed 'nearshore basins' .…”

Section: Regional Settingmentioning

confidence: 99%

“…Extensive geophysical surveys indicate that methane and pockmarks occur in Holocene sediments throughout Maine and New Brunswick's muddy estuaries (Scanlon and Knebel, 1989;Shipp, 1989;Fader, 1991;Barnhardt et al, 1996;Gontz, 2005;Rogers et al, 2006). Inconsistent evidence for venting (Kelley et al, 1994;Ussler et al, 2003), a dearth of methanotropes (Wildish et al, 2008), and nominal seafloor change (Brothers et al, 2011a) suggests these pockmark fields currently experience minimal fluid-escape activity.…”

Section: Regional Settingmentioning

confidence: 99%

“…Geochemical sampling (Ussler et al, 2003) suggest that the region's methane is microbial in origin, although the stratigraphic source of the gas remains undetermined. Barnhardt et al (1997), Gontz (2005) and Kelley et al (2010) found micro-and macro-fossil evidence for drowned coastal wetlands in core sampling, and Rogers et al (2006) proposed that such deposits provided a concentrated source of organic material that evolved into methane, and, by inference, formed regional pockmarks. They suggested such organic layers would occur at the base of the Holocene in topographic lows where it was protected from the erosive effects of the last transgression.…”

Section: Regional Settingmentioning

confidence: 99%

“…In eastern North America pockmark fields are not reported south of Long Island Sound (Fleisher et al, 2001;Poppe et al, 2006), despite the abundance of well-studied, gassy, muddy estuaries (e.g., Reeburgh, 1969;Schubel, 1974;Hagen and Vogt, 1998;Martens et al, 1998). The absence of pockmarks south of the glacial terminus suggests that local and regional heterogeneities, possibly related to glacial or sea-level history or bedrock geology, influence pockmark field distribution (e.g., Rogers et al, 2006). This paper focuses on three estuarine pockmark fields in the Gulf of Maine and Bay of Fundy (Figs.…”

Section: Introductionmentioning

confidence: 99%

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Shallow stratigraphic control on pockmark distribution in north temperate estuaries

et al. 2012

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Pockmark fields occur throughout northern North American temperate estuaries despite the absence of extensive thermogenic hydrocarbon deposits typically associated with pockmarks. In such settings, the origins of the gas and triggering mechanism(s) responsible for pockmark formation are not obvious. Nor is it known why pockmarks proliferate in this region but do not occur south of the glacial terminus in eastern North America. This paper tests two hypotheses addressing these knowledge gaps: 1) the region's unique sea-level history provided a terrestrial deposit that sourced the gas responsible for pockmark formation; and 2) the region's physiography controls pockmarks distribution. This study integrates over 2500 km of high-resolution swath bathymetry, Chirp seismic reflection profiles and vibracore data acquired in three estuarine pockmark fields in the Gulf of Maine and Bay of Fundy. Vibracores sampled a hydric paleosol lacking the organic-rich upper horizons, indicating that an organic-rich terrestrial deposit was eroded prior to pockmark formation. This observation suggests that the gas, which is presumably responsible for the formation of the pockmarks, originated in Holocene estuarine sediments (loss on ignition 3.5-10%), not terrestrial deposits that were subsequently drowned and buried by mud. The 7470 pockmarks identified in this study are non-randomly clustered. Pockmark size and distribution relate to Holocene sediment thickness (r 2 =0.60), basin morphology and glacial deposits. The irregular underlying topography that dictates Holocene sediment thickness may ultimately play a more important role in temperate estuarine pockmark distribution than drowned terrestrial deposits. These results give insight into the conditions necessary for pockmark formation in nearshore coastal environments.Published by Elsevier B.V.

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Section: Regional Settingmentioning

confidence: 99%

Section: Regional Settingmentioning

confidence: 99%

Section: Regional Settingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Shallow stratigraphic control on pockmark distribution in north temperate estuaries

et al. 2012

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“…Recently, researchers have drawn considerable attention to the shallow biogenic gas in the near-surface marine and coastal sediments such as bay or estuarine deposits and late Quaternary incised-valley fills (García-García et al 2007;Xu et al 2009;Lin et al 2010;Zhang et al 2013;Jones et al 2014;Okay and Aydemir 2016), in terms of the shallow-burial depth ranging from several tens of meters to hundreds of meters and easy exploitation with low investment and high benefit. Commercial reservoirs of shallow biogenic gas have been widely found in the world, including the North Sea (Heggland 1997; Vielstädte et al 2015), Ria de Vigo incised valley, Spain (Garcia-Gil et al 2002), western Gulf of Maine, USA (Rogers et al 2006), and Lawrence Estuary, Canada (Pinet et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Characteristics and accumulation model of the late Quaternary shallow biogenic gas in the modern Changjiang delta area, eastern China

Zhang

Lin

2017

Pet. Sci.

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The Changjiang (Yangtze) is one of the largest rivers in the world. It formed a huge incised valley at its mouth during the Last Glacial Maximum; the incised-valley fill, approximately 80-110 m thick, supplies an important foundation for the generation of shallow biogenic-gas reservoirs. Two cores and 13 cone penetration tests were used to elaborate the characteristics, formation mechanism, and distribution of the shallow biogenic-gas reservoirs in the study area. The natural gas is mainly composed of CH 4 (generally[95%) with a d 13 C CH4 and d 13 C CO2 of -75.8 to -67.7% and -34.5 to -6.6%, respectively, and a dD CH4 of -215 to -185%, indicating a biogenic origin by the carbon dioxide reduction pathway. Commercial biogenic gas occurs primarily in the sand bodies of fluvial-channel, floodplain, and paleo-estuary facies with a burial depth of 50-80 m. Gas sources as well as cap beds are gray to yellowish-gray mud of floodplain, paleoestuary, and offshore shallow marine facies. The organic matter in gas sources is dominated by immature type III kerogen (gas prone). The difference in permeability (about 4-6 orders of magnitude) between cap beds and reservoirs makes the cap beds effectively prevent the upward escape of gas in the reservoirs. This formation mechanism is consistent with that for the shallow biogenic gas in the late Quaternary Qiantang River incised valley to the south. Therefore, this study should provide further insight into understanding the formation and distribution of shallow biogenic gas in other similar postglacial incised-valley systems.

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Stratigraphic framework of gas accumulations in the Ría de Pontevedra (NW Spain)

et al. 2007

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Shallow-water pockmark formation in temperate estuaries: A consideration of origins in the western gulf of Maine with special focus on Belfast Bay

Cited by 67 publications

References 44 publications

Shallow stratigraphic control on pockmark distribution in north temperate estuaries

Shallow stratigraphic control on pockmark distribution in north temperate estuaries

Characteristics and accumulation model of the late Quaternary shallow biogenic gas in the modern Changjiang delta area, eastern China

Stratigraphic framework of gas accumulations in the Ría de Pontevedra (NW Spain)

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