Preservation of Microborings as Fluid Inclusions

-Cone-in-cone (CIC) and beef (BF) carbonate lenses ornament detachment zone faults underlying Triassic growth basins on Edgeøya. Field relationships place CIC and BF growth as during early diagenesis and a transition from hydroplastic to a later brittle-style of faulting that is marked by coarser calcite veining. Deformation is constrained to have occurred at <300 m depth. Multiple models exist for CIC formation. For the Edgeøya example, textural analysis of thin-sections suggests that small tensile fractures and carbonate shell fragments nucleated development of calcite aggregates with CIC and BF morphology within unconsolidated to poorly consolidated sediment to form asymmetric antitaxial tensile aggregates subparallel to bedding and fault surfaces. The conical forms result from differential growth on stepped, cleavage-parallel faces of fibres facing host sediment, with preferential inclusion incorporation at inner corners. The preferred directions of calcite growth are attributed to local stresses and seepage flow associated with pore pressure gradients. Substantial framboidal pyrite in the sediments represents an early phase of microbially driven sulphate reduction, which may have induced calcite mineralization. The transition to brittle-style faulting was marked by development of deformation twins in CIC/BF fibres, and a transition to coarse, blocky calcite growth in relay arrays of steeply oriented microveins. This indicates local fault-related stresses substantially changed during shallow diagenesis and lithification, an evolution attributed to changing pore pressures, seepage forces and material moduli. Calcite mineralizations at Edgeøya track the very significant changes in mechanical properties and stress states that occur during synlithification deformation at very shallow crustal levels.

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“…Buijs et al 2004;McLoughlin et al 2007). These structures have a fairly consistent width of c. 0.5-1 μm (Fig.…”

Section: E Is There Biogenic Influence?mentioning

confidence: 75%

“…The occurrence of branching tubular fluid inclusions in CIC growing in organic-rich sediment raises the possibility of a biogenic factor (e.g. Buijs et al 2004; McLoughlin et al 2007). These structures have a fairly consistent width of c. 0.5–1 μm (Fig.…”

Section: Discussionmentioning

confidence: 99%

Cone-in-cone and beef mineralization associated with Triassic growth basin faulting and shallow shale diagenesis, Edgeøya, Svalbard

2016

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“…One sample from a thrombolitic mudstone contains filamentous structures we interpret as microbial microborings (Fig. 3B, C;Buijs et al 2004).…”

Section: Carbonate Faciesmentioning

confidence: 98%

Petrography and Environmental Interpretation of Tufa Mounds and Carbonate Beds In the Jurassic Navajo Sandstone of Southeastern Utah, U.S.A.

Dorney

Parrish

Chan

et al. 2017

Journal of Sedimentary Research

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Carbonate deposits in the Jurassic Navajo Sandstone of Utah reflect deposition in interdune lakes and springs. Interdune-lake deposits consist of flat-lying carbonate units. Springs formed tufa mounds that are interpreted as subaerial, ambient-temperature, artesian-spring deposits. In the first systematic study of the petrography of the carbonate deposits in the Navajo Sandstone, eleven facies were identified in several flat-lying carbonate deposits and two tufa mounds. Fenestral mudstone and peloidal facies dominate the lacustrine deposits, whereas thrombolitic mudstone characterizes the mounds. The biota consists of ostracodes, charophytes, fish, mollusks, a possible freshwater sponge, trace fossils, and fragments of vascular plants. Features resulting from penecontemporaneous weathering provide evidence of episodic exposure of the lacustrine carbonate beds during deposition and formation of the tufa mounds under subaerial conditions. Although carbonate deposits are not rare in eolian systems, few have been studied in detail; comparisons between these and the Navajo Sandstone carbonate deposits reveal some characteristics that may be unique to the latter.

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“…Further, appreciable morphological variation, with regard to these euendolith morphotypes, can arise through diagenetic modification. In carbonate rocks, for example, linear, curved, and branched arrays of tubular fluid inclusions can form along the original microboring by calcite partitions that are precipitated during diagenesis (e.g., Buijs et al, 2004).…”

Section: Biogenic Morphology and Behaviormentioning

confidence: 99%

On Biogenicity Criteria for Endolithic Microborings on Early Earth And Beyond

McLoughlin

Brasier²,

Wacey³

et al. 2007

Astrobiology

122

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Micron-sized cavities created by the actions of rock-etching microorganisms known as euendoliths are explored as a biosignature for life on early Earth and perhaps Mars. Rock-dwelling organisms can tolerate extreme environmental stresses and are excellent candidates for the colonization of early Earth and planetary surfaces. Here, we give a brief overview of the fossil record of euendoliths in both sedimentary and volcanic rocks. We then review the current understanding of the controls upon the distribution of euendolithic microborings and use these to propose three lines of approach for testing their biogenicity: first, a geological setting that demonstrates a syngenetic origin for the euendolithic microborings; second, microboring morphologies and distributions that are suggestive of biogenic behavior and distinct from ambient inclusion trails; and third, elemental and isotopic evidence suggestive of biological processing. We use these criteria and the fossil record of terrestrial euendoliths to outline potential environments and techniques to search for endolithic microborings on Mars.

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Preservation of Microborings as Fluid Inclusions

Cited by 13 publications

References 25 publications

Cone-in-cone and beef mineralization associated with Triassic growth basin faulting and shallow shale diagenesis, Edgeøya, Svalbard

Cone-in-cone and beef mineralization associated with Triassic growth basin faulting and shallow shale diagenesis, Edgeøya, Svalbard

Petrography and Environmental Interpretation of Tufa Mounds and Carbonate Beds In the Jurassic Navajo Sandstone of Southeastern Utah, U.S.A.

On Biogenicity Criteria for Endolithic Microborings on Early Earth And Beyond

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