Roll-up structures: Evidence of in situ microbial mats in late Archean deep shelf environments

Title:
Roll-up structures: Evidence of in situ microbial mats in late Archean deep shelf environments
Authors:
Simonson, Bruce M.; Carney, K. E.
Abstract:
In addition to its well-known banded iron formations, the late Archean to Paleoproterozoic Hamersley Group of Western Australia contains substantial volumes of thinly laminated carbonaceous shale and carbonate lutite. Locally, some of the laminae in these carbonates are deformed into highly distinctive folds in pockets whose cross-sections range up to about 2 cm in height and 10 cm in length. Individual folds consistently have circular hinge zones and vary in shape from simple buckles to recumbent, elastica, and even spiral geometries. Based on the strength and flexibility with which they responded to soft-sediment deformation, we infer the deformed carbonaceous laminae were bound by cohesive microbial mats. We propose the name roll-up structures for these features as they differ in subtle but important ways from most previously described soft-sediment deformation structures. Roll-up structures only occur in lutites deposited below wave base and are absent from peritidal deposits, suggesting that the microbial mats involved may not have been based on photosynthesis. Large portions of the deep sea floor could presumably have been stabilized by mats built by heterotrophic or chemoautotrophic microbes prior to the Neoproterozoic, given the lack of both predators and competing algae. Roll-up structures are potentially useful as indicators of deposition below wave base, but very few candidates have been reported anywhere else save for the coeval carbonates of the Transvaal basin of South Africa. The paucity of other examples, particularly in younger strata, means that either roll-up structures have simply not been distinguished from other types of soft-sediment deformation structures, or the microbes and/or environmental conditions required to make them are a rarity in Earth history.
Citation:
Simonson, B.M., and K.E. Carney. 1999. "Roll-up structures: Evidence of in situ microbial mats in late Archean deep shelf environments." PALAIOS 14(1): 13-24.
Publisher:
Society for Sedimentary Geology
DATE ISSUED:
1999-02
Department:
Geology
Type:
article
PUBLISHED VERSION:
10.2307/3515358
PERMANENT LINK:
http://hdl.handle.net/11282/309613

Full metadata record

DC FieldValue Language
dc.contributor.authorSimonson, Bruce M.en_US
dc.contributor.authorCarney, K. E.en_US
dc.date.accessioned2013-12-23T16:13:19Zen
dc.date.available2013-12-23T16:13:19Zen
dc.date.issued1999-02en
dc.identifier.citationSimonson, B.M., and K.E. Carney. 1999. "Roll-up structures: Evidence of in situ microbial mats in late Archean deep shelf environments." PALAIOS 14(1): 13-24.en_US
dc.identifier.issn0883-1351en_US
dc.identifier.urihttp://hdl.handle.net/11282/309613en
dc.description.abstractIn addition to its well-known banded iron formations, the late Archean to Paleoproterozoic Hamersley Group of Western Australia contains substantial volumes of thinly laminated carbonaceous shale and carbonate lutite. Locally, some of the laminae in these carbonates are deformed into highly distinctive folds in pockets whose cross-sections range up to about 2 cm in height and 10 cm in length. Individual folds consistently have circular hinge zones and vary in shape from simple buckles to recumbent, elastica, and even spiral geometries. Based on the strength and flexibility with which they responded to soft-sediment deformation, we infer the deformed carbonaceous laminae were bound by cohesive microbial mats. We propose the name roll-up structures for these features as they differ in subtle but important ways from most previously described soft-sediment deformation structures. Roll-up structures only occur in lutites deposited below wave base and are absent from peritidal deposits, suggesting that the microbial mats involved may not have been based on photosynthesis. Large portions of the deep sea floor could presumably have been stabilized by mats built by heterotrophic or chemoautotrophic microbes prior to the Neoproterozoic, given the lack of both predators and competing algae. Roll-up structures are potentially useful as indicators of deposition below wave base, but very few candidates have been reported anywhere else save for the coeval carbonates of the Transvaal basin of South Africa. The paucity of other examples, particularly in younger strata, means that either roll-up structures have simply not been distinguished from other types of soft-sediment deformation structures, or the microbes and/or environmental conditions required to make them are a rarity in Earth history.en_US
dc.language.isoen_USen_US
dc.publisherSociety for Sedimentary Geologyen_US
dc.identifier.doi10.2307/3515358en
dc.subject.departmentGeologyen_US
dc.titleRoll-up structures: Evidence of in situ microbial mats in late Archean deep shelf environmentsen_US
dc.typearticleen_US
dc.identifier.journalPalaiosen_US
dc.subject.keywordProterozoic Transvaal Supergroupen_US
dc.subject.keywordPrecambrian Hamersley Basinen_US
dc.subject.keywordSanta Barbara Basinen_US
dc.subject.keywordWestern Australiaen_US
dc.subject.keywordImpact spherulesen_US
dc.subject.keywordSouthern Africaen_US
dc.subject.keywordIron formationen_US
dc.subject.keywordFaciesen_US
dc.subject.keywordSedimentologyen_US
dc.subject.keywordStratigraphyen_US
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