Detecting detrital carbonate in shale successions - Relevance for evaluation of depositional setting and sequence stratigraphic interpretation

Schieber, Jüergen; Shao, Xinhe

doi:10.1016/j.marpetgeo.2021.105130

Cited by 10 publications

(6 citation statements)

References 71 publications

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“…The near absence of carbonate minerals in the sediment indicates that none were produced during weathering in the hinterland outcrop. Had they formed there, such carbonates could have been transported the comparatively short distance to the crater floor (Zuffa, 1980; Schieber & Shao, 2021). This absence, despite the abundance of atmospheric CO 2 , indicates that the pH of weathering fluids remained too acidic to form the siderite, ankerite and magnesite computed for weathering of basalt in the source terrain, i.e.…”

Section: Integration and Interpretation Of Observations In A Sequence...mentioning

confidence: 99%

Mars is a mirror – Understanding the Pahrump Hills mudstones from a perspective of Earth analogues

Schieber

Bohacs²,

Coleman

et al. 2022

Sedimentology

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Mudstone‐dominated lacustrine strata in the Pahrump Hills area of Gale Crater, Mars, have the most extensive data set of physical and geochemical observations yet collected. Although sparse by Earth standards, a source‐to‐sink portrayal of the sedimentary system that differs substantially from previous work has been extracted by integrating sedimentology, stratigraphy, mineral and elemental analyses, geochemical modelling, laboratory experiments and Earth analogues in a sequence‐stratigraphic and palaeogeographical framework. Approximately 3.5 Ga, these 15 m thick strata contain five facies that range from fine to coarse detrital mudstone with abundant sediment‐incorporative evaporite pseudomorphs. The section is dominated by first‐cycle grains of minimally weathered primary igneous minerals but with four distinct compositions. Bedding in the mudstones comprises planar‐parallel beds, current ripples and wave‐induced structures, with common and widespread truncation. The absence of primary desiccation and synaeresis cracks is probably due to minimal clay‐mineral content, as supported by laboratory experiments. Evaporite minerals formed on and within detrital muds shortly after accumulation by evapoconcentration and cooling. The succession contains 16 parasequences in five depositional sequences with all the sequence‐stratigraphic elements known from terrestrial strata. Two of the sequence boundaries are unconformities that record significant shifts in the behaviour and palaeogeographical configuration of the fluvio‐lacustrine system. This contrasts with the previous view that all facies are genetically related. Most of the variability in rock composition can be attributed to stratigraphic changes in provenance that integrate changing drainage basin configurations, type of exposed bedrock and changes in weathering regime. These strata are interpreted as evaporative lake deposits that accumulated in an underfilled lake basin with closed surface hydrography but through‐flowing groundwater. Lake waters were saline to hypersaline, and lake levels, shorelines and salinities fluctuated greatly at various temporal scales.

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Section: Integration and Interpretation Of Observations In A Sequence...mentioning

confidence: 99%

Mars is a mirror – Understanding the Pahrump Hills mudstones from a perspective of Earth analogues

Schieber

Bohacs²,

Coleman

et al. 2022

Sedimentology

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“…(4) The core zones of terrigenous dolomite grains appear cloudy, and the grains are generally 100–200 μm in size. This type of dolomite was not observed in this study . (5) The carbonates abundance of terrigenous origin is generally only a few percent because carbonates are easily dissolved during transport.…”

Section: Discussionmentioning

confidence: 69%

“…This type of dolomite was not observed in this study. 12 (5) The carbonates abundance of terrigenous origin is generally only a few percent because carbonates are easily dissolved during transport. However, the carbonate content of the investigative formations can be as high as 10 percent (Figure 2).…”

Section: Carbonate Mineral Enrichmentmentioning

confidence: 99%

“…However, the carbonate content of the investigative formations can be as high as 10 percent (Figure 2). 12 The formulation for dolomite formation in sediments can be simplified as follows , and the presence of SO 4 2− which tend to combine with Mg 2+ to create Mg−SO 4 . 44 However, bacteria change the chemistry of pore fluids through sulfate reduction and methanogenesis, promoting dolomite precipitation (Table 3).…”

Section: Carbonate Mineral Enrichmentmentioning

confidence: 99%

“…Various grain assemblages are deposited under different paleo-environmental conditions, leading to variations in shale brittleness . For example, the quartz content are affected by terrigenous input, paleoproductivity, and volcanic activity, − the formation of authigenic pyrite is controlled by the redox conditions of bottom waters, terrestrial clastic materials would be enriched within a sedimentary basin when the hydrodynamic forces are strong, and carbonate minerals can originate from organisms skeletal and terrigenous input . Therefore, determining the effect of the sedimentary environment on shale mineral assemblages is significant for selecting favorable fracturing intervals.…”

Section: Introductionmentioning

confidence: 99%

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Factors Controlling Brittleness of the Wufeng–Longmaxi Shale in the Yangtze Platform, South China: Insights from Geochemistry and Shale Composition

Tang

et al. 2022

Energy Fuels

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Brittleness index is an important parameter used to select favorable fracturing intervals during shale gas exploitation. Mineral compositions exert a significant influence on rock brittleness, and various grain assemblages can be deposited under different paleo-environmental conditions. The Wufeng–Longmaxi marine shale is a hot spot of shale gas exploitation in China. However, for the Wufeng–Longmaxi shale, the relationship between sedimentary environments, grain assemblages, and shale brittleness are rarely discussed. To address these problems, a series of experiments including petrographic observations, mineral compositions, rock mechanics, and major (trace) element analyses were carried out on shale samples from the Wufeng–Longmaxi formations. The Wufeng–Longmaxi formations are divided into upper Longmaxi formation (ULMX), lower Longmaxi formation (LLMX), and Wufeng formation (WF). The results show that WF shale samples deposited under a sedimentary environment with low terrigenous detrital influx, suboxic depositional water, and high paleoproductivity are characterized by the highest energy-based BI, compared to ULMX and LLMX shale samples. Dolomite in the samples grew in situ during early diagenesis. Redox conditions, terrigenous detrital flux control authigenic carbonate contents, and the oxic depositional water of the ULMX formation restrain carbonate mineral formation. In contrast, the suboxic sedimentary environment of the LLMX and WF allowed the generation of carbonate minerals. Compared with the WF, the larger terrigenous detrital flux of LLMX formation do favor more authigenic carbonate formation. The paleoproductivity affects biogenic quartz generation, and abundant biogenic quartz, primarily occurring in the form of micron-size microcrystalline quartz in the shale matrix, and can connect the silt-size brittle minerals to form a mechanical framework, which makes a strong positive contribution to shale brittleness. Terrigenous detrital influx decreases brittleness because the weakening effect of terrigenous clay minerals on shale brittleness is greater than the strengthening effect of terrigenous brittle minerals on shale brittleness.

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Mineralogical and petrographic characteristics of the Ordovician-Silurian Wufeng-Longmaxi Shale in the Sichuan Basin and implications for depositional conditions and diagenesis of black shales

Qiu

Liu

Lü

et al. 2022

Marine and Petroleum Geology

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Detecting detrital carbonate in shale successions - Relevance for evaluation of depositional setting and sequence stratigraphic interpretation

Cited by 10 publications

References 71 publications

Mars is a mirror – Understanding the Pahrump Hills mudstones from a perspective of Earth analogues

Mars is a mirror – Understanding the Pahrump Hills mudstones from a perspective of Earth analogues

Factors Controlling Brittleness of the Wufeng–Longmaxi Shale in the Yangtze Platform, South China: Insights from Geochemistry and Shale Composition

Mineralogical and petrographic characteristics of the Ordovician-Silurian Wufeng-Longmaxi Shale in the Sichuan Basin and implications for depositional conditions and diagenesis of black shales

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