Topic
Micrite
About: Micrite is a research topic. Over the lifetime, 1128 publications have been published within this topic receiving 28533 citations.
Papers published on a yearly basis
1 / 2
Papers
TL;DR: In this article, a triangular diagram showing the relative proportions of allochems, calcite ooze matrix, and sparry calcite cement is used to define three major limestone families.
Abstract: Limestones are divisible into eleven basic types, which are relatively easy to recognize both in the laboratory and in the field. These rocks are made up of three constituents: (1) allochems, evidently transported or otherwise differentiated carbonate bodies; (2) 1-4-micron microcrystalline calcite ooze matrix, and (3) coarser and clearer sparry calcite, which in most rocks forms as a simple pore-filling cement (like the calcite cement in a quartz sandstone), and only uncommonly forms by recrystallization. Only four types of allochems are volumetrically important in limestones: (a) intraclasts (reworked fragments of penecontemporaneous carbonate sediment), (b) oolites, (c) fossils, and (d) pellets (rounded aggregates of microcrystalline calcite averaging .04-.10 mm.). All chems provide the structural framework of limestones, just as sand grains provide the structural framework of sandstones; microcrystalline calcite and sparry calcite are analogous with the clay matrix and chemical cement of sandstones. A triangular diagram showing the relative proportions of allochems, calcite ooze matrix, and sparry calcite cement is used to define three major limestone families. Family I consists of abundant allochems cemented by sparry calcite; these are the cleanly washed limestones, analogous with well sorted, clay-free sandstones and similarly formed in loci of vigorous currents. Family II consists of variable amounts of allochems embedded in a microcrystalline ooze matrix; these are the poorly washed limestones that are analogous with clayey, poorly sorted sandstones, and form in loci of ineffective currents. Family III limestones consist almost entirely of calcite ooze, hence are analogous with terrigenous claystones. Just as clayey versus non-clayey sandstones can be divided mineralogically into orthoquartzites, arkoses, and graywackes, similarly the first two limestone families are subdivided by considering the nature of the allochems. Family I includes respectively intrasparite, oosparite, biosparite, and pelsparite; family II includes intramicrite and oomicrite (both rare), biomicrite, and pelmicrite. Family III includes homogeneous ooze (micrite), and disturbed ooze with irregular openings filled with spar (dismicrite). Rocks made up largely of organisms in growth position are considered as a separate family IV (biolithite). Properties and mode of formation of each of these types are discussed briefly. Content of admixed terrigenous material or dolomite is shown by additional symbols; pure dolomites are classified on allochem content and crystal size. Recrystallization in limestone is believed to be locally abundant but of over-all minor importance. Among several types of recrystallization, that in which a former microcrystalline ooze matrix recrystallizes to 5-15-micron "microspar" is considered most common. The term "calclithite" is suggested for the terrigenous carbonate rocks, e.g., limestone conglomerates End_Page 1------------------------------ or sandstones made up of material eroded from outcrops of considerably older lithified-carbonate formations exposed in an uplifted source land.
1,261 citations
TL;DR: In this article, the authors show that the degree with which a particular carbonate component approaches either the open system or the partly closed system equilibrium is determined by its respective mineralogical stability and the water/rock ratio.
Abstract: Theoretical considerations (i.e., partition coefficients, water/rock ratio, chemistry of interstitial meteoric water) of elemental behaviour during diagenetic stabilization with meteoric waters suggests that it leads to a decrease in strontium, sodium, and possibly magnesium and an increase in manganese, iron, and zinc in progressively altered carbonates. Such elemental behaviour is exhibited by the different carbonate components of the Mississippian Burlington Limestone of Iowa and Missouri and the Silurian Read Bay Formation of Arctic Canada. In the Burlington Limestone the rock matrix (e.g., biosparite), the enclosed crinoids, and to some degree the rugose corals are chemically similar. The crinoid ossicles have average strontium content of 160 ppm, rugose corals 180 ppm, and the enclosing biosparite 120 ppm. In contrast, in the Read Bay Formation each of the above mentioned components has a specific chemistry, with 210 ppm strontium for crinoids, 780 ppm for rugose corals, and 360 ppm for their enclosing micrite matrix. These chemical trends are accompanied by textural changes of the host carbonate sediments. In the Burlington Lime tone this involves the presence of depositional sparite, whereas in the Read Bay Formation this increase in textural maturity involves the transition from micrite to microspar to minor pseudospar and sparite. The combination of these textural trends with the elemental patterns shows that the degree with which a particular carbonate component approaches either the open system or the partly closed system equilibrium is dictated by its respective mineralogical stability and the water/rock ratio. While the results show that the carbonate assemblage may act as a completely open diagenetic system (e.g., Burlington Limestone), available data for the majority of studied sequences (e.g., Read Bay Formation) suggest that diagenetic equilibration ceases while some original depositional differences in chemical composition are still preserved. This implies that diagenetic stabilization proceeds through partly closed reaction zones on solid-liquid interfaces. Transfer of the chemical and textural inform tion from the dissolving phase (original sedimentary carbonate particle) to the precipitating phase (diagenetic carbonate component) proceeds via a Messenger Film water in the reaction zone, which is in disequilibrium with the meteoric bulk aquifer water. Thus the chemical composition of carbonate components of ancient limestones may serve as a potential tool for evaluating the degree of diagenesis and for deducing the original mineralogy of the different stabilized carbonate phases. Application of this trace element model suggests that Paleozoic crinoids were composed originally of metastable high-magnesium calcite, rugose corals were composed originally of stable low-magnesium calcite or high-magnesium calcite with low Mg2+ content, and micrite was origially aragonite lime mud.
1,110 citations
TL;DR: In this article, a sequence analysis of the Dolomite boundary sediments reveals a minor sequence boundary in the late Permian followed by extremely rapid transgression leading to the development of the relatively deep water pyritic micrite, a maximum flooding surface at the Permo-Triassic boundary.
476 citations
TL;DR: The preservation of molluscan shells as calcite casts is commonly a result of their centripetal replacement, while on the sea floor, by a stable micrite envelope, which grows in three stages: (1) algae bore into the shell wall, (2) the algal filaments die and decay, (3) micritic aragonite fills the tubes as discussed by the authors.
Abstract: The preservation of molluscan shells as calcite casts is commonly a result of their centripetal replacement, while on the sea floor, by a stable micrite envelope. This grows in three stages: (1) algae bore into the shell wall, (2) the algal filaments die and decay, (3) micritic aragonite fills the tubes. Later, if the skeletal sand is exposed to fresh water as a result of uplift or a fall in sea level, or to a suitable brine deep under the sea floor, the residual molluscan shell is dissolved but the envelope remains intact. It forms an empty mould that is subsequently filled with drusy calcite. Complete replacement of skeletal grains by micritic aragonite yields cryptocrystalline grains like Ming's “grains of aragonite matrix” and the grains in Beales's “bahamite”. Through a study of compaction fabrics it may be possible to decide whether an envelope-bearing limestone was cemented above sea level or below the sea floor.
388 citations
TL;DR: More than a dozen hydrocarbon seep-carbonate occurrences in late Jurassic to late Cretaceous forearc and accretionary prism strata, western California, accumulated in turbidite/fault-hosted or serpentine diapir-related settings were analyzed for their petrographic, geochemical and palaeoecological attributes, and each showed a three-stage development that recorded the evolution of fluids through reducing-oxidizing-reducing conditions.
Abstract: More than a dozen hydrocarbon seep-carbonate occurrences in late Jurassic to late Cretaceous forearc and accretionary prism strata, western California, accumulated in turbidite/fault-hosted or serpentine diapir-related settings. Three sites, Paskenta, Cold Fork of Cottonwood Creek and Wilbur Springs, were analyzed for their petrographic, geochemical and palaeoecological attributes, and each showed a three-stage development that recorded the evolution of fluids through reducing‐oxidizing‐reducing conditions. The first stage constituted diffusive, reduced fluid seepage (CH4, H2S) through seafloor sediments, as indicated by Fe-rich detrital micrite, corroded surfaces encrusted with framboidal pyrite, anhedral yellow calcite and negative cement stable isotopic signatures (d 13 C as low as � 35.5% PDB; d 18 Oa s low as � 10.8% PDB). Mega-invertebrates, adapted to reduced conditions and/or bacterial chemosymbiosis, colonized the sites during this earliest period of fluid seepage. A second, early stage of centralized venting at the seafloor followed, which was coincident with hydrocarbon migration, as evidenced by nonluminescent fibrous cements with d 13 C values as low as � 43.7% PDB, elevated d 18 O (up to þ2.3% PDB), petroleum inclusions, marine borings and lack of pyrite. Throughout these early phases of hydrocarbon seepage, microbial sediments were preserved as layered and clotted, nondetrital micrites. A final late-stage of development marked a return to reducing conditions during burial diagenesis, as implied by pore-associated Mn-rich cement phases with bright cathodoluminescent patterns, and negative d 18 O signatures (as low as � 14% PDB). These recurring patterns among sites highlight similarities in the hydrogeological evolution of the Mesozoic convergent margin of California, which influenced local geochemical conditions and organism responses. A comparison of stable carbon and oxygen isotopic data for 33 globally distributed seep-carbonates, ranging in age from Devonian to Recent, delineated three groupings that reflect variable fluid input, different tectono-sedimentary regimes and time‐temperature-dependent burial diagenesis.
314 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2025 | 3 |
| 2024 | 8 |
| 2023 | 52 |
| 2022 | 48 |
| 2021 | 38 |
| 2020 | 30 |