Dolomite Petrology

Dolomite Petrology

Photomicrograph Gallery

Jay M. Gregg
Department of Geology & Geophysics
University of Missouri-Rolla

Welcome to the Dolomite Petrology Photomicrograph Gallery. This gallery is entirely dedicated to dolomites, if you want to see limestones go to the Limestone Photomicrograph Gallery. All of these photomicrographs were taken by me but the samples have a variety of sources that are discussed below.

The table below contains a thumbnail photo and description of each photomicrograph categorized under a number of headings and subheadings. The sample numbers are shown in bold face and the horizontal width of each field is shown in italics for the thin section photomicrographs. For the SEM photomicrographs the length of the scale bar is shown in italics. This is followed by a short description of the sample. If you want to just browse through the samples, arranged as in the table below, start here. Otherwise, click on the thumbnail photomicrographs below for full sized images.

As in the Limestone Gallery, most of the samples were collected by me over the years that I have been in this business. The Dolomite Gallery is more extensive than the Limestone Gallery because most of my work has been on dolomite. The photomicrographs below are arranged according to age, with the most recent first. They also are arranged to illustrate a number of themes and problems in dolomite petrology. The classification system used throughout is that of Sibley and Gregg (1987)

About the Samples:

The synthetic dolomites are from my doctoral dissertation (Gregg, 1982) at Michigan State University and were used in Gregg and Sibley (1984). The sample from Androse Island was in Duncan Sibleys collection and used in my dissertation study (but I don't remember who sent it to Duncan). The BZF samples were collected by Sal Mazzullo and Al Reid (Mazzullo et al., 1987; Gregg et al., 1992). Samples from the Pliocene of Aruba were collected by Duncan Sibley and I in early 1980 (see Sibley, 1982; Gregg and Sibley, 1984; Sibley and Gregg, 1987).

The Smackover (Jurassic) samples are all from 3 cores that Duncan Sibley and I examined in preparation for our dolomite short course. The "STR" and "SG" samples represent increasing depth with increasing sample number in each respective set. These samples display textures resulting from progressive dolomitization of oolitic grainstone. This includes dolomitization by warm basinal fluids in the case of the nonplanar textures.

The two Permian samples are from a core in the Shannon Field that I worked on when I was in the oil business in 1977. They display a beautifully preserved oolitic fabric.

Carboniferous samples are all from the Waulsortian facies and associated strata in the Irish Midlands and were collected by Aaron Johnson, Zsolt Nagy, Kevin Shelton, Ian Somerville, Peter Strogen, Wayne Wright, and myself between 1995 and the present. These rocks are of current interest because they host the world class base metal deposits of the Navan area and the Rathdowney Trend (see Wright et al., 1999; Gregg et al., 1999; Gregg et al., 2001).

The Silurian samples from the Michigan Basin were contributed by Duncan Sibley for use in our dolomite short course. These rocks display a remarkable preservation of the original limestone fabric and look like dolomites that are much younger. Compare them with the Pliocene samples from Aruba.

The Ordovician samples are from a variety of sources. Duncan Sibley contributed the samples from the Saluda Formation. I collected the samples from the Galena Group and Trenton Formation during my dissertation study (Gregg, 1982). The Gasconade Dolomite sample was used in Bob Woody's M.S. study on the effect of crystal texture on the petrophysical properties of dolomite (Woody et al. 1996).

The Cambrian samples all were collected by my colleagues, students and/or myself in our studies of the geology of southern Missouri, particularly with regard to regional fluid flow and base metal (Mississippi Valley-type) mineralization (see Gregg, 1985; Gregg, 1988, Voss et al., 1989; Gregg and Shelton, 1990; Gregg et al., 1993; He et al., 1997; Keller et al., 2000). All of the samples that have detailed porosity and permeability data in the descriptions were used in the Woody et al. (1996) study on petrophysical properties of dolomite. With regard to the samples from southern Missouri, a special thanks is due to James Palmer, of the Missouri Department of Natural Resources, Division of Geology and Land Survey, for his help over the years with core descriptions, sample and outcrop locations, and the stratigraphy of Missouri.

Go to: References Cited:

Back to Photographic Gallery of Carbonate Petrology Introduction Page

E-mail me at: greggjay@umr.edu

Dolomite Petrology Contents

Synthetic Textures

Cenozoic Dolomites

Jurassic Dolomites

Permian Dolomites

Carboniferous Dolomites Planar Textures Nonplanar Textures Cement Textures Mixed Textures

Silurian Dolomites

Ordovician Dolomites Planar Textures Mixed Textures
Cambrian Dolomites Planar Textures Nonplanar Textures Cement Textures Mixed Textures

Synthetic Textures

Thumbnail, Sample Number, Width of Horizontal Field. Sample Description

Click on the thumbnail for larger image.

	d-Arca1, 10µm, SEM of pelecypod shell (Arca ponderosa) altered to nonplanar dolomite in a hydrothermal bomb (24 hrs @ 300ƒC) (from Gregg and Sibley, 1984).
	d-Arca2, 0.163, Thin section of pelecypod shell (Arca ponderosa) altered to nonplanar dolomite in a hydrothermal bomb (24 hrs @ 300ƒC) (from Gregg and Sibley, 1984).
	d-saddle, 0.1mm, SEM of pelecypod shell (Arca ponderosa) altered to nonplanar dolomite in a hydrothermal bomb. Note the development of saddle shaped open space filling dolomite cement. This is the first example of synthesis of this texture (from Gregg and Sibley, 1984).

Cenozoic Dolomites
Thumbnail, Sample Number, Width of Horizontal Field. Sample Description

Click on the thumbnail for larger image.

	d-Andros, 1.0µm, SEM of supratidal dolomite (Holocene) Androse Island, Bahamas. This dolomite is poorly ordered and calcium rich (40 mole % MgCO3) (from Gregg, 1982).
	d-BZF2, 1.0µm, SEM of dolomitized HMC lime mud (Holocene) from Tomas Savannah, Ambergris Caye, Belize. This dolomite is poorly ordered and calcium rich (from Gregg et al. 1992).
	d-BZF3, 1.0µm, SEM of dolomite replacing calcite in HMC lime mud (Holocene) from Tomas Savannah, Ambergris Caye, Belize. Note rounded edges and pitting of calcite which is undergoing dissolution.
	d-BZF4, 100µm, SEM of dolomitized soritid foraminifera in HMC lime mud (Holocene) from Tomas Savannah, Ambergris Caye, Belize (from Gregg et al. 1992).
	d-BZF5, 1.0µm, SEM of detail of dolomitized soritid foraminifera, shown in d-BZF4, showing c-axis orientation of dolomite crystals in the replaced foraminifera wall (from Gregg et al. 1992).
	d-521851_10, 3.25mm, Dolomitized coralline algal grainstone with mimetic replacement of skeletal grains. Seri Domi Fm., Pliocene, Aruba.
	d-521851_100, 0.325mm, Close-up of replacement of coralline algal grain by planar-E and-S dolomite. Seri Domi Fm., Pliocene, Aruba.
	d-8920_10, 3.25mm, Planar-E dolomite. Seri Domi Fm., Pliocene, Aruba.
	d-BD9_10, 3.25mm, Coralline algal packstone partly replaced by planar-P dolomite. Seri Domi Fm., Pliocene, Aruba.
	d-BD9_25, 1.3mm, Close-up of coralline algal packstone partly replaced by planar-P dolomite. Seri Domi Fm., Pliocene, Aruba.
	d-SC2B_10, 3.25mm, Planar-S to Planar-E dolomite with vug and intercrystal porosity and blocky calcite open-space-filling cement (stained red with alizarin red-S). Seri Domi Fm., Pliocene, Aruba.
	d-SC2B_25, 1.3mm, Close-up of planar-S dolomite. Note abundant preserved crystal face junctions. Seri Domi Fm., Pliocene, Aruba.

Jurassic Dolomites

Thumbnail, Sample Number, Width of Horizontal Field. Sample Description

	d-STR00_10, 3.25mm, Undolomitized silty oolitic grainstone. Calcite is stained with alizarin red-S, quartz silt is unstained. Smackover Fm., Jurassic, east Texas.
	d-STR01_10, 3.25mm, Silty oolitic grainstone partly replaced by nonplanar-P dolomite. Calcite is stained with alizarin red-S. Smackover Fm., Jurassic, east Texas.
	d-STR02_10, 3.25mm, Undolomitized oolitic grainstone. Smackover Fm., Jurassic, east Texas.
	d-STR02_25, 1.3mm, Undolomitized oolitic grainstone, close-up of "smiley face." Smackover Fm., Jurassic, east Texas.
	d-STR03_10, 3.25mm, Nonplanar dolomite with stylolites and minor intercrystal porosity. Smackover Fm., Jurassic, east Texas.
	d-STR04_10, 3.25mm, Silty, argillaceous and stylolitized nonplanar dolomite. Smackover Fm., Jurassic, east Texas.
	d-STR04_2/5, 13mm, Nonplanar dolomite with open-space-filling saddle dolomite cement. Jurassic, east Texas.
	d-STR05_10, 3.25mm, Argillaceous planar-S to planar-E dolomite with stylolites. Smackover Fm., Jurassic, east Texas.
	d-STR05_25, 1.3mm, Close-up of planar-E dolomite. Smackover Fm., Jurassic, east Texas.
	d-STR06_100, 0.325mm, Close-up of oolitic grainstone replaced by planar-S dolomite. Smackover Fm., Jurassic, east Texas.
	d-STR06_25, 1.3mm, Planar-S and planar-E dolomite replacing oolitic grainstone. Smackover Fm., Jurassic, east Texas.
	d-STR07_100, 0.325mm, Close-up of planar-S dolomite. Smackover Fm., Jurassic, east Texas.
	d-STR08_25, 1.3mm, Fine crystalline planar-S dolomite. Smackover Fm., Jurassic, east Texas.
	d-STR09_2/5, 13mm, Pellet mudstone replaced by fine crystalline planar dolomite with open-space-filling saddle dolomite cement filling vugs and fractures (?) forming a "net fabric." Smackover Fm., Jurassic, east Texas.
	d-STR10_2/5, 13mm, Mudstone (?) replaced by medium to coarse crystalline planar dolomite lower left field, with large vug partly filled by saddle dolomite cement, anhydrite and opaque bitumen. Smackover Fm., Jurassic, east Texas.
	d-STR10_25, 1.3mm, Coarse crystalline planar-S dolomite (possibly altering to nonplanar dolomite) with relatively high intercrystal porosity. Smackover Fm., Jurassic, east Texas.
	d-STR11_2/5, 13mm, Field view showing planar to nonplanar dolomite transition with open-space-filling saddle dolomite cement and anhydrite. Smackover Fm., Jurassic, east Texas.
	d-STR11_10, 3.25mm, Close-up of planar to nonplanar dolomite transition. Smackover Fm., Jurassic, east Texas.
	d-SG01a_10, 3.25mm, Oolitic grainstone with matrix replaced by planar dolomite. Ooids resisted dolomitization (appear to be micritized). Smackover Fm., Jurassic, east Texas.
	d-SG01b_10, 3.25mm, A second view of oolitic grainstone with matrix replaced by planar dolomite. Ooids resisted dolomitization (appear to be micritized). Smackover Fm., Jurassic, east Texas.
	d-SG02_10, 3.25mm, Similar to d-SG01b_10 only dolomitization is more complete, replacing nearly all of the oolitic fabric. Smackover Fm., Jurassic, east Texas.
	d-SG03_10, 3.25mm, Dolomitized oolitic grainstone with oomoldic porosity. This represents d-SG02_10 taken one step further. Smackover Fm., Jurassic, east Texas.
	d-SG04_10, 3.25mm, Dolomitized oolitic grainstone with oomoldic and intercrystal porosity partly occluded by poikilotopic calcite cement. Calcite is stained with alizarin red-S. Smackover Fm., Jurassic, east Texas.
	d-SG04_25, 1.3mm, Close-up of previous field showing calcite filling intercrystal porosity in planar-E dolomite. Note that the section is to thick and the dolomite crystals too small to count crystal face junctions so accurate determination of dolomite texture is impossible. Smackover Fm., Jurassic, east Texas.

Permian Dolomites

Thumbnail, Sample Number, Width of Horizontal Field. Sample Description

	d-B539a_10,3.25mm,Oolitic grainstone replaced by fine crystalline planar-S dolomite with interoolitic space filled by anhydrite. Note that nuclei of some of the ooids are quartz grains. Sun Oil Co. Shannon B unit, San Andres Fm., Permian, Crockett Co., Texas.
	d-B539_10,3.25mm,Oolitic grainstone replaced by fine crystalline planar-S dolomite with interoolitic space filled by anhydrite. Sun Oil Co. Shannon B unit (1973 ft), San Andres Fm., Permian, Crockett Co., Texas.

Carboniferous Dolomites

Thumbnail, Sample Number, Width of Horizontal Field. Sample Description

Planar Textures

	d-BL07_10, 3.25mm, Planar dolomite partially replacing skeletal mudstone. Note that the mudstone component is preferentially dolomitized. Calcite is stained with alizarin red-S. Waulsortian facies, Lower Carboniferous, Ballybeg Quarry, County Cork, Ireland.
	d-BL08_25, 1.3mm, Planar dolomite replacing lime mudstone. Note relatively high intercrystal porosity. Waulsortian facies, Lower Carboniferous, Ballybeg Quarry, County Cork, Ireland.
	d-BR6_25pl, 1.3mm, Planar dolomite partially replacing lime mudstone. Large vug in left field contains crypto-fibrous calcite cement. Waulsortian facies, Lower Carboniferous, Black Rock Coast, County Waterford, Ireland.
	d-BR6_25cl, 1.3mm, Cathodoluminescence (CL) of field shown in d-BR6_25pl showing bright red planar dolomite crystals replacing dull orange limestone. Waulsortian facies, Lower Carboniferous, Black Rock Coast, County Waterford, Ireland.
	d-BR8A_25, 1.3mm, Fine crystalline planar dolomite replacing skeletal mudstone. Waulsortian facies, Lower Carboniferous, Black Rock Coast, County Waterford, Ireland.
	d-F6_50pl, 0.65mm, Planar dolomite rhombs replacing lime mudstone. Supra-Waulsortian (about 6 feet above the top of the Waulsortian). Feltrim Quarry, County Dublin, Ireland.
	d-F6_50cl, 0.65mm, Cathodoluminescence (CL) of field shown in d-F6_50pl showing compositional zoning in dolomite rhombs replacing lime mudstone. Supra-Waulsortian (about 6 feet above the top of the Waulsortian). Feltrim Quarry, County Dublin, Ireland.

Nonplanar Textures

	d-M5-2_10, 3.25mm, Nonplanar dolomite replacing skeletal grainstone with original texture preserved as "ghosts." Dolomitization here appears to be related to faults and selectively dolomitized grainstones. Malahide Limestone, Malahide Coast, County Dublin, Ireland.
	d-M5-3_2/5 , 13mm, Nonplanar dolomite replacing crinoidal grainstone with preservation of original texture as "ghosts" structures. Note cross cutting veins filled with dolomite cement. Malahide Limestone, Malahide Coast, County Dublin, Ireland.
	d-M5-3_10, 3.25mm, Close-up of nonplanar dolomite replacing crinoidal grainstone. Note excellent preservation of original texture (as ghosts) in the nonplanar mosaic. Crinoid and bryozoa can be made out as well as open space filling marine cement. Malahide Limestone, Malahide Coast, County Dublin, Ireland.
	d-LK318-07_10, 3.25mm, Coarse crystalline nonplanar dolomite replacing a skeletal mudstone(?). Waulsortian facies, Lower Carboniferous, Rathdowney Trend, County Tipperary, Ireland.

Cement Textures

	d-BB4_12/5pl, 2.8mm, Vug filling, pink saddle dolomite cement. Aghmacart Formation, Lower Carboniferous, Bennetsbridge Quarry, County Kilkenny, Ireland.
	d-BB4_12/5cl, 2.8mm, Cathodoluminescence image of pink saddle dolomite cement. Note the distinct compositional zonation. Aghmacart Formation, Lower Carboniferous, Bennetsbridge Quarry, County Kilkenny, Ireland.
	d-BB4_500, 0.165mm, Field of 2 phase fluid inclusions (liquid and vapor) in a late diagenetic vein filling dolomite cement. Aghmacart Formation, Lower Carboniferous, Bennetsbridge Quarry, County Kilkenny, Ireland.
	d-163215_12pl, 2.8mm, Cross polarized light image of dolomite breccia showing rhombic dolomite cement followed by late diagenetic blocky calcite cement and pyrobitumen (opaque). Waulsortian dolomite, lower Carboniferous, Rikardstown, County Kildare, Ireland.
	d-163215_12cl, 2.8mm, Cathodoluminescence (CL) of field shown in d-163215_12pl. Note distinctive compositional zonation in dolomite cement followed by bright yellow CL of calcite cement, pyrobitumen appears as black. Waulsortian facies, lower Carboniferous, Rikardstown, County Kildare, Ireland.
	d-LK318-34_12pl, 2.8mm, Fracture filling dolomite cement in a silty dolomite. Base of carbonate section just overlying the Old Red Sandstone. Lower Carboniferous, Rathdowney Trend, County Tipperary, Ireland.
	d-LK318-34_12cl, 2.8mm, Cathodoluminescence micrograph of field shown in d-LK318-34_12pl. Base of carbonate section just overlying the Old Red Sandstone. Lower Carboniferous, Rathdowney Trend, County Tipperary, Ireland.
	d-N1013-45_50pl, 0.65mm, Open space filling epigenetic dolomite cement. "Pale Beds" (Sub-Waulsortian), Lower Carboniferous, Navan, County Meath, Ireland.
	d-N1013-45_50cl, 0.65mm, Cathodoluminescence micrograph of field shown in d-N1013-45_50pl. Note the compositional zoning and compare it to d-LK318-34_12cl andd-163215_12cl. "Pale Beds" (Sub-Waulsortian), Lower Carboniferous, Navan, County Meath, Ireland.

Mixed Textures

	d-1653/24-6_2/5, 13mm, Dolomitized skeletal mudstone(?) displaying "White matrix breccia" texture. Clasts are replaced by fine crystalline planar dolomite and matrix by coarse nonplanar dolomite and epigenetic dolomite cement. Waulsortian facies, Lower Carboniferous, Rathdowney Trend, County Tipperary, Ireland.
	d-3785/6-09_2/5, 13mm, Dolomitized crinoid fragment (lower left field) with "feather texture" nonplanar dolomite replacing crypto-fibrous calcite cement. Mudstone components of this sample are replaced by planar-s dolomite. Waulsortian facies, Lower Carboniferous, Rathdowney Trend, County Tipperary, Ireland.
	d-3785/6-11_10, 3.25mm, Nonplanar dolomite partially replacing crypto-fibrous calcite cement. Calcite is stained with alizarin red-S. Waulsortian facies, Lower Carboniferous, Rathdowney Trend, County Tipperary, Ireland.
	d-BR07_10, 3.25mm, Dolomitized skeletal mudstone near fault. Fine crystalline planar dolomite (left field) is altering to coarse crystalline nonplanar dolomite (right field). Waulsortian facies, Lower Carboniferous, Black Rock Coast, County Waterford, Ireland.

Silurian Dolomites

Thumbnail, Sample Number, Width of Horizontal Field. Sample Description

	d-MAU2a_10, 3.25mm, Mimetic dolomite replacement of coral by planar dolomite. Silurian "reef," Michigan.
	d-MAU2b_10, 3.25mm, Planar-S dolomite with vug porosity. Silurian "reef," Michigan.
	d-MAU2_25, 1.3mm, Close-up of mimetic dolomite replacement of coral by planar dolomite. Silurian "reef," Michigan.
	d-MAU4_10, 3.25mm, Mimetic dolomite replacement of isopachous (low mg calcite) vadose cement. Note the ghosts of the original calcite cement. Silurian "reef," Michigan.
	d-MAU4_25, 1.3mm, Close-up of mimetic replacement of isopachous (low mg calcite) vadose cement. Are dolomite intercrystal boundaries planar or nonplanar? Silurian "reef," Michigan.
	d-MAU5_10, 3.25mm, Mimetic dolomite replacement of bryozoa (low Mg calcite). Silurian "reef," Michigan.

Ordovician Dolomites

Thumbnail, Sample Number, Width of Horizontal Field. Sample Description

Planar Textures

	d-420905_2/5, 13mm, Partly dolomitized skeletal grainstone interbedded with dolomitized argillaceous mudstone. Calcite is stained with alizarin red-S, dolomite is unstained. Saluda Fm., Middle Ordovician, Indiana.
	d-420905_25, 1.3mm, Close up of mudstonegrainstone transition showing planar dolomite crystals (unstained). Saluda Fm., Middle Ordovician, Indiana.
	d-Galena1, 0.1mm, Planar dolomite replacing limestone micrite. Note the well formed crystal face junction where the two dolomite crystals meet. Galena Group (Middle Ordovician) Iowa (from Gregg and Sibley, 1984).
	d-Galena1, 0.1mm, SEM of planar dolomite crystals (dark) replacing calcite micrite (light). Note the groove in the large dolomite crystal center that was created by the crystal face junction of an adjoining dolomite crystal that was removed during sample preparation. Galena Group (Middle Ordovician) Iowa (from Gregg and Sibley, 1984).

Mixed Textures

	d-Br3655_2/5, 13mm, Dolomitization of a skeletal wackestone, part 1. Fine crystalline planar dolomite is preferentially replacing mud component. Calcite is stained with alizarin red-S. "Cap dolomite" of the Trenton Fm., Middle Ordovician, Michigan.
	d-Br3656_50, 0.65mm, Dolomitization of a skeletal wackestone, part 2. Close-up of planar dolomite preferentially replacing mud component of skeletal wackestone. "Cap dolomite" of the Trenton Fm., Middle Ordovician, Michigan.
	d-Br3656_25, 1.3mm, Dolomitization of a skeletal wackestone, part 3. Brachiopod fragment that resisted replacement by planar dolomite which replaced surrounding lime mudstone is partially replaced by nonplanar dolomite. Note that internal structure of the brachiopod is preserved by inclusions in the nonplanar dolomite crystals. Calcite is stained with alizarin red-S. "Cap dolomite" of the Trenton Fm., Middle Ordovician, Michigan.
	d-Br3656_2/5, 13mm, Dolomitization of a skeletal wackestone, part 4. wackestone is completely dolomitized; mudstone component by earlier fine crystalline planar dolomite and skeletal components by later coarser crystalline nonplanar dolomite.
	d-4845-5_2/5, 13mm, Dolomite conglomerate with open-space-filling dolomite cement. Trenton Fm., Middle Ordovician, Michigan.
	d-4845-5_10, 3.25mm, Close-up of above showing crystal size variation between clasts and matrix. Trenton Fm., Middle Ordovician, Michigan.
	d-92197_10, 3.5mm, Nonplanar dolomite with minor scattered patches of planar-s dolomite. This sample has vug-intercrystal porosity = 7 by point count. He (effective) porosity = 3.9%, permeability = <0.5md. Gasconade Dolomite, Lower Ordovician, southeastern Missouri.

Cambrian Dolomites

Thumbnail, Sample Number, Width of Horizontal Field. Sample Description

Planar Textures

	d-89110_10, 3.25mm, Planar-E to planar-S dolomite. Bonneterre dolomite, "reef" facies, Upper Cambrian, southeastern Missouri.
	d-89110_25, 1.3mm, Close-up of planar-E to planar-S dolomite showing interconnected porosity. This sample has intercrystal porosity = 7.8%, vug porosity = 0.6% and fracture porosity = 0.3% by point count. He (effective) porosity = 7.5%. Bonneterre dolomite, "reef" facies, Upper Cambrian, southeastern Missouri.
	d-8946_10, 3.25mm, Dolomitized oolitic grainstone (planar-S dolomite). Interoolitic space partly filled by sphalerite (opaque) which defines the original round shape of the ooids. Bonneterre Dolomite, Upper Cambrian, Casteel Mine, southeastern Missouri.
	d-89114_25, 1.3mm, Fine crystalline planar-E dolomite. This sample has intercrystal porosity = 10.5%, vug porosity = 0.4% by point count. He (effective) porosity = 3.4% and permeability = 126md. Bonneterre dolomite, "reef" facies, Upper Cambrian, southeastern Missouri.
	d-92169_25, 1.3mm, Planar-S dolomite with small vug and intercrystal porosity. This sample has intercrystal porosity = 1.2%, vug porosity = 8.1% by point count. He (effective) porosity = 6.9%, permeability = <0.5md. Bonneterre dolomite, Upper Cambrian, southeastern Missouri.
	d-92189_10, 3.25mm, Medium crystalline planar-S dolomite with channel porosity. This sample has intercrystal porosity = 0.3%, vug-channel porosity = 2.3% by point count. He (effective) porosity = 1.4%, permeability = <0.5md. Derby-Doerun Dolomite, Upper Cambrian, southeastern Missouri.
	d-92192_10, 3.25mm, Coarse crystalline planar-E dolomite. This sample has intercrystal porosity = 14.4% by point count. He (effective) porosity = 16.2%, permeability = 249.1md. Derby-Doerun Dolomite, Upper Cambrian, southeastern Missouri.
	d-92195_10, 3.25mm, Planar-E dolomite with patches of planar-S dolomite. This sample has intercrystal porosity = 16.2%, vug porosity = 14.8% by point count. He (effective) porosity = 10.4%, permeability = 12,168md. Davis Formation, Upper Cambrian, southeastern Missouri.
	d-92214_10, 3.25mm, Fine crystalline planar-S dolomite with vug porosity. This sample has intercrystal porosity = 0.8%, vug porosity = 7.5% by point count. He (effective) porosity = 10.1%, permeability = <0.5md. Bonneterre dolomite, Upper Cambrian, southeastern Missouri.

Nonplanar Textures

	d-83286_2/5, 13mm, Coarse crystalline nonplanar dolomite replacing algal laminate. Note blue epoxy denoting porosity. This sample has vug porosity = 0.9% (±1%) by point count. He (effective) porosity = 3.4% and permeability 1.9md. Bonneterre Dolomite "back reef" facies, Upper Cambrian, southeastern Missouri.
	d-83499_25pl, 1.3mm, Nonplanar dolomite partially replacing micritic mudstone as a "net fabric." Bonneterre Dolomite, "back reef" lagoonal mudstone facies, Cambrian, St. Francois Mts., southeastern Missouri.
	d-83499_25cl, 1.3mm, Cathodoluminescence photomicrograph of field shown in d-83499_25pl, displaying rare compositional zoning with nonplanar growth pattern. Bonneterre Dolomite, "back reef" lagoonal mudstone facies, Cambrian, St. Francois Mts., southeastern Missouri.
	d-89177_10, 3.25mm, Nonplanar dolomite replacing oolitic grainstone, note large vug in left field. This sample has intercrystal porosity = 0.4%, vug porosity = 8.5% by point count. He (effective) porosity = 1%, permeability = <0.5md. Bonneterre dolomite, Upper Cambrian, southeastern Missouri.
	d-89186_2/5, 13mm, Coarse crystalline nonplanar dolomite. Note vug & intercrystal porosity mainly left field. This sample has intercrystal porosity = 2.5%, vug porosity = 11.1% by point count. He (effective) porosity = 7.7%, permeability = 12.7md. Derby-Doerun Dolomite, Upper Cambrian, southeastern Missouri.
	d-83355_25p, 1.3mm, Nonplanar dolomite replacing oolitic/fossiliferous grainstone. The ghost of an ooid is just visible to the left of center field. Upper oolitic facies of the Bonneterre dolomite, Upper Cambrian, southeastern Missouri.
	d-83355_25f, 1.3mm, Epifluorescence photomicrograph of nonplanar dolomite replacing oolitic/skeletal grainstone. Epifluorescence reveals several ooids and possible skeletal fragments. Upper oolitic facies of the Bonneterre dolomite, Upper Cambrian, southeastern Missouri.

Cement Textures

	d-82137_50pl, 0.65mm, Late, vug filling "white sparry" dolomite cement followed by blocky quartz cement. Bonneterre Dolomite (intrashelf basin facies, basal dolomite), Cambrian, southeastern Missouri.
	d-82137_50cl, 0.65mm, Cathodoluminescence (CL) photomicrograph of field shown in d-82137_50pl displaying characteristic 4 zone CL microstratigraphy of late diagenetic dolomite cement in this region (labeled on the slide). Bonneterre Dolomite (intrashelf basin facies, basal dolomite described in Gregg, 1985), Cambrian, southeastern Missouri.
	d-83381_60pl, 0.54mm, Late, vug filling "white sparry" dolomite cement associated with Mississippi Valley-type ores. Bonneterre Dolomite, "reef" facies, Number 29 Mine, Cambrian, Viburnum Trend, southeastern Missouri.
	d-83381_60cl, 0.54mm, Cathodoluminescence (CL) photomicrograph of d-83381_60pl displaying the CL microstratigraphy typical of that region. Note that zone 2 (shown on d-85477_25cl) is missing in this part of the Viburnum Trend. Bonneterre Dolomite, "reef" facies, Number 29 Mine, Cambrian, Viburnum Trend, southeastern Missouri.
	d-83381_120, 0.20mm, SEM backscattered electron micrograph of dolomite crystal on the left in field shown in d-83381_60cl. Note that bright zones correspond to dark zones in cathodoluminescence and reflect zones with high iron composition. Bright round spots are beam damage caused by electron microprobe. Bonneterre Dolomite, "reef" facies, Number 29 Mine, Cambrian, Viburnum Trend, southeastern Missouri.
	d-85477_25pl, 1.3mm, Late, vug filling "white sparry" dolomite cement associated with Mississippi Valley-type ores. Bonneterre Dolomite, upper oolitic facies, Fletcher Mine, Cambrian, Viburnum Trend, southeastern Missouri.
	d-85477_25cl, 1.3mm, Cathodoluminescence micrograph of field shown in d-85477_25pl. Note distinctive 4 zone microstratigraphy.
	d-8605_50pl, 0.65mm, Late, vug filling "white sparry" dolomite cement containing sulfides (opaque). Bonneterre Dolomite, Cambrian, Viburnum Trend, southeastern Missouri. Bonneterre Dolomite, upper oolitic facies, Fletcher Mine, Cambrian, Viburnum Trend, southeastern Missouri.
	d-8605_50rl, 0.65mm, Reflected light photomicrograph of field shown in d-8605_50pl revealing that sulfides are pyrite (white) and chalcopyrite (gold). Bonneterre Dolomite, Cambrian, Viburnum Trend, southeastern Missouri.
	d-8605_50cl, 0.65mm, Cathodoluminescence (CL) micrograph of field shown in d-8605_50rl and pl displaying distinctive CL microstratigraphy. Note that sulfide mineralization occurs on a dissolution surface revealed by CL. Bonneterre Dolomite, Cambrian, Viburnum Trend, southeastern Missouri.

Mixed Textures

d-9210_2/5, 13mm, Nonplanar replacement dolomite and open-space-filling saddle dolomite cement with patches of fine crystalline planar dolomite (breccia clasts). Note sphalerite (opaque area) upper right field. This sample is from the Amoco Spence Trusts core in the Reelfoot Rift (see Keller et al., 2000). He porosity = 1.1% permeability <0.5md. Bonneterre Dolomite, Upper Cambrian, Dunklin Co., Missouri.

d-92185_2/5, 13mm, Nonplanar dolomite with zones of high vug and intercrystal porosity (displaying planar-E texture in areas of high intercrystal porosity). This sample has intercrystal porosity = 6.5%, vug porosity = 20.6% by point count. He (effective) porosity = 10.2%, permeability = 603.4md. Derby-Doerun Dolomite, Upper Cambrian, southeastern Missouri.

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Jay M. Gregg Department of Geology & Geophysics University of Missouri-Rolla

About the Samples:

Jay M. Gregg
Department of Geology & Geophysics
University of Missouri-Rolla