Limestone Petrology

Photomicrograph Gallery

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


Welcome to the Limestone Petrology Photomicrograph Gallery. All of these photomicrographs were taken by me and are from the collection used in my course in Carbonate Petrology (Geology 432) which is taught at the University of Missouri-Rolla. This gallery is entirely dedicated to limestones, if you want to see dolomites go to the Dolomite Photomicrograph Gallery.

The table below contains a thumbnail photo and description of each photomicrograph categorized under several headings. Some of the photos are used more than once, as they display a number of properties used to illustrate features under different headings. The sample numbers are shown in bold face and the horizontal width of each field is shown in italics. This is followed by a short description of the sample. If you want to just browse through the samples, arranged in numerical and alphabetical order, from start to finish, click here. Otherwise, click on the thumbnail photomicrographs below for full sized images.

Most of the samples were collected by me over the years that I have been in this business. The Inola Limestone samples are from my M.S. thesis area near Inola, Oklahoma, and were collected between 1975 and 1976. All of the Permian Basin samples were collected in 1978 while I was with Sun Oil in Midland, Texas, mostly while on a field trip with Sal Mazzullo. Thanks Sal! Many of the samples from Missouri were collected while I was with St. Joe Minerals Corporation between 1982 and 1987. Other Missouri samples I collected since coming to UMR in 1988. The samples marked c-ACS, however, are from the A. C. Spreng collection here at UMR. Samples from Cancun, Mexico were collected during the SEPM field conference on Carbonate Cements, held in Cancun in 1984 (I think). Isle of Man samples were collected in 1996 on a field trip with Jim Hendry, Jim Marshal, and others. The Waulsortian Limestone samples were mostly collected during the 1998 summer field season in southern Ireland with Ian Somerville, Wayne Wright, and Aaron Johnson.

I would like to thank several individuals who contributed carbonate samples to my teaching collection which are featured here: Duncan Sibley (Michigan State University) contributed all of the samples from the Pliocene of Bonaire and the Silurian stromatophoroids from the Michigan Basin. Jim Palmer (Missouri Division of Geology and Land Survey) contributed the ooid samples from the Great Salt Lake, Utah and Cat Cay, Bahamas. Tom Freeman gave me all of the samples with the designation c-TF and Paul Enose sent me the Cretaceous collection from the Valles Platform, Mexico. Tom and Paul donated their samples in 1988 to help me get started teaching here at UMR. I hope that they think that I made good use of them.

Back to Photographic Gallery of Carbonate Petrology Introduction Page

E-mail me at: greggjay@umr.edu

Limestone Petrology Contents

Skeletal Allochems

Peloids & Coated Allochems

Cement Fabrics

Various LS Fabrics

Waulsortian Limestone of Ireland and the Isle of Man

Rudist Build-ups, Valles Platform, Mexico

Skeletal allochems

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

Click on the thumbnail for larger image.

c-ACS9_10 c-ACS9_10, 3.25mm. Phylloid Algal wackestone (biomicrite). Middle Pennsylvanian, Missouri.
c-TF(C)_10 c-TF(C)_10, 3.25mm. Nicely preserved phylloid algal wackestone-grainstone. Lansing Group, Pennsylvanian, Kansas.
c-8913b_10 c-8913b_10, 3.25mm. Fossiliferous grainstone (biosparite) containing foram (left center), coralline (red) algae and green algal grains. Seroe Domi Fm., Pliocene, Bonaire, N.A.
c-8913_10 c-8913_10, 3.25mm. Fossiliferous grainstone (biosparite) containing a large Lithophyllum grain (center) as well as other coralline (red) algae grains and dasycladician (green algae) grains. The red algae are composed of high Mg calcite and the green algae of aragonite. Seroe Domi Fm., Pliocene, Bonaire, N.A.
c-8904b_10 c-8904b_10, 3.25mm. Green algal grain (Mizzia) in a fossiliferous grainstone (biosparite), note fine crystalline fringing cement and later generation of coarse blocky cement occluding interparticle porosity, also intraparticle porosity in fossil grains. Capitan Formation, Permian, southeastern New Mexico.
c-8904_10 c-8904_10, 3.25mm. Green algal grain (Mizzia) in a fossiliferous grainstone (biosparite). Very good example of fringing radial-fibrous early marine cement (aragonite neomorphosed to low Mg calcite?) with second generation of coarse blocky calcite cement. Capitan Formation, Permian, southeastern New Mexico.
c-8949_2_5 c-8949_2/5, 13mm. Fussilinid grainstone (biosparite), note early radial-fibrous cement (originally aragonite neomorphosed to low mg calcite?) and second generation of coarse blocky calcite cement. Capitan Formation, Permian, Guadeloupe Mts., southeastern New Mexico.
c-85524_25 c-85524_25, 1.4mm. Foraminifera (center) in a skeletal grainstone (lower shore face) cemented by blocky (probably fresh water) low Mg calcite cement. Pleistocene, Cancun, Mexico.
c-DS3_2_5 c-DS3_2/5, 13mm. Stromatophoroid structures. Silurian, Michigan Basin.
c-DS3_10 c-DS3_10, 3.25mm. Close-up of stromatophoroid structures shown in c-DS3_2/5. Silurian, Michigan Basin.
c-89145_2_5 c-89145_2/5, 13mm. Rugose coral in a biomicrite. Note that intraparticle porosity is filled with what appears to be 2 generations of cement. Pennsylvanian, Missouri.
c-UMR16_2/5 c-UMR16_2/5, 13mm. Tabulate coral boundstone, note high porosity. Pennsylvanian of Missouri.
c-UMR16_10 c-UMR16_10, 13mm. Close-up of tabulate coral boundstone in c-UMR16_2/5, showing septa, tabulae and 2 generations of calcite cement filling intraparticle pore space. Pennsylvanian of Missouri.
c-89173_10 c-89173_10, 3.25mm. Scleractinian coral boundstone. Pleistocene, Reef Point, Ambergris Cay, Belize.
c-UMR12_10 c-UMR12_10, 3.25mm. Skeletal grainstone including green algae, brachiopod and ostracod fragments. Middle Ordovician, Rochester, New York.
c-8539b_10 c-8539b_10, 3.25mm. Biomicrite with brachiopod fragment showing prismatic layer (upper) separated from foliated layer (lower), sections through brachiopod spines (round things) echinoderm grains and small fragments of phosphatic skeletal material (brown). Inola Limestone Mem. Pennsylvanian (Desmoinian), Rodgers Co., Oklahoma.
c-AGI1_10 c-AGI1_10, 3.25mm. Punctate brachiopods (foliated layer) and crinoid grains in a fossiliferous packstone (biomicrite). Burlington Limestone, Mississippian, Missouri.
c-IOM4C_2_5 c-IOM4C_2/5, 13mm. Articulated brachiopod in wackestone (biosparmicrite). Note geopetal filling of mud in brachiopod cavity indicating the up direction to the left. Also note the fringing radial-fibrous marine cement growing into the cavity, which postdates the geopetal filling, and second generation of coarse blocky cement. Waulsortian facies, Lower Carboniferous, southern coast of the Isle of Man, U.K.
c-IOM4_10 c-IOM4_10, 3.25mm. Close-up of c-IOM4C showing prismatic layer of brachiopod, fringing radial-fibrous marine cement and second generation of blocky cement. The fibrous cement likely was originally aragonite and later neomorphosed to low Mg calcite.
c-DS2_2_5 c-DS2_2/5, 13mm. Bryozoan associated with stromatophoroid structure. Silurian, Michigan Basin.
c-F09_10 c-F09_10, 3.25mm. Bryozoa in cryptfibrous marine cement. Waulsortian Limestone, Lower Carboniferous. Feltrim Quarry, County Dublin, Ireland.
c-8539_2_5 c-8539_2/5, 13mm. Gastropod filled with calcite cement in mud matrix. Inola Limestone Mem. Pennsylvanian (Desmoinian), Rodgers Co., Oklahoma.
c-8914_25 c-8914_25, 1.3mm. Gastropod in micrite matrix showing internal structure and orientation of aragonite(?) crystals in the shell. Seroe Domi Fm., Pliocene, Bonaire, N.A.
c-LC37_2_5 c-LC37_2/5, 13mm. Rudist packstone (packed biosparite), note large rudist grains displaying micritization and neomorphism. Middle Cretaceous, Valles Platform, Mexico.
c-LC37_10 c-LC37_10, 3.25mm. Close-up of large rudist pelecipod grain (originally aragonite) displaying low Mg calcite neomorphic fabric. Note fringing marine cement which likely was originally aragonite and now is low mg calcite. Middle Cretaceous, Valles Platform, Mexico.
c-BR03_2_5 c-BR03_2/5, 13mm. Cephlapod section displaying two generations of calcite cement, an early cryptfibrous cement (originally HMC marine cement?) and a later open space filling blocky cement. Waulsortian Limestone, Lower Carboniferous, Black Rock coastal section, County Waterford, Ireland.
c-89149_2_5 c-89149_2/5, 13mm. Crinoid grains and bryozoa in a fossiliferous packstone (biomicrite). Warsaw Limestone, Mississippian, Missouri.
c-UMR14_10 c-UMR14_10, 3.25mm. Crinoidal packstone, note syntaxial overgrowths on crinoid grains extending into micrite matrix. Burlington Limestone, Mississippian, Missouri.
c-BR03_2_5a c-BR03_2/5a, 13mm. Wackestone-packstone lithology dominated, in this instance, by crinoid (and bryozoa) skeletal debris. Waulsortian Limestone, Lower Carboniferous, Black Rock coastal section, County Waterford, Ireland.
c-OMT_2_5 c-OMT_2/5, 13mm. Trilobite grainstone-packstone containing moderate mud component (biosparmicrite). Note radial-fibrous cement. "Arkansas Rouge" decorative stone, Cambrian, Arkansas.
c-OMT_10 c-OMT_10, 3.25mm. Close-up of c-OMT field showing trilobite grainstone-packstone containing moderate mud component (biosparmicrite). Note radial-fibrous cement. "Arkansas Rouge" decorative stone, Cambrian, Arkansas.
c-TF(E)a_10 c-TF(E)a_10, 3.25mm. Bryozoa (lower left center) brachiopods, ostracod (upper right center) and echinoderm grainstone (biosparite), note syntaxial overgrowths on echinoderms. Fernvale Limestone, Ordovician, Arkansas.

 

Peloids & Coated Allochems

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

c-ACS190_10 c-ACS190_10, 3.25mm. Pelleted grainstone (pelsparite). Joachim Limestone, Middle Ordovician, Jefferson Co., Missouri.
c-EB36_10 c-EB36_10, 3.25mm, Pelleted Mudstone, Kansas City Group, Pennsylvanian, western Missouri.
c-TF(A)_25 c-TF(A)_25, 1.3mm, Close-up of isopachous micrite cement on peloids. Note the 3 distinct generations of cement. Blake Nose Formation, Cretaceous, Florida.
c-85519_25 c-85519_25, 1.4mm, Partially coated skeletal grains from the surf zone. Holocene, Cancun, Mexico.
c-8938_100 c-8938_100, 0.35mm, Partially coated skeletal grain from surf zone. Holocene, Cancun, Mexico.
c-85520_25 c-85520_25, 1.4mm, Meniscus cement (blocky low Mg calcite- fresh water) binding coated skeletal grains (ooids) in an eolianite. Pleistocene, Cancun, Mexico.
c-85533B_25 c-85533B_25, 1.4mm, Radial and radial-concentric aragonite ooids. Great Salt Lake, Utah.
c-85533B_180 c-85533B_180, 0.52mm, SEM of radial-concentric aragonite ooids. Great Salt Lake, Utah.
c-85533B_600 c-85533B_600, 0.16mm, SEM of radial-concentric aragonite ooids showing radial orientation of fibrous aragonite crystals. Great Salt Lake, Utah.
c-85533B_750 c-85533B_750, 0.13mm, SEM of radial-concentric aragonite ooids showing radial orientation of fibrous aragonite crystals. Great Salt Lake, Utah.
c-85534_25 c-85534_25, 1.4mm, Concentric aragonite ooids, note "Maltese Cross" extinction pattern in cross polarized light. Holocene, Cat Cay, Bahamas.
c-85534_130 c-85534_130, 0.73mm, SEM of concentric aragonite ooid showing laminar habit. Holocene, Cat Cay, Bahamas.
c-85534_480 c-85534_480, 0.2mm, SEM of aragonite ooid showing concentric laminations. Holocene, Cat Cay, Bahamas.
c-85534_20K c-85534_20K, 5 µm, High magnification SEM of concentric ooid showing individual, sub-micron sized aragonite crystals. This field is located roughly in the center of the field shown in c-85534_480, so the laminations run from lower left to upper right. Note that the c-axes (long axes) of the aragonite crystals lie in a plane tangential to the surface of the ooid, although they are randomly oriented within this plane. Holocene, Cat Cay, Bahamas.
c-8936_10 c-8936_10, 3.5mm, Ooids with fringing radial-fibrous marine cement. The cement probably was originally aragonite or possibly high Mg calcite neomorphosed to low Mg calcite. Note "Maltese Cross" extinction pattern on ooids in cross polarized light. From the offshore limestone facies of the Bonneterre Dolomite, Cambrian, southeast Missouri.
c-UMR15_10 c-UMR15_10, 3.5mm, Oolitic grainstone, note dissolution of ooids along stylolite (left center). Also note partial dolomitization of the specimen. Renault Limestone, Upper Mississippian, Missouri.
c-8905A_2_5 c-8905A_2/5, 13mm, Oncolites. Capitan Fm., Permian, Guadeloupe Mts., southeastern New Mexico.

 

Cement Fabrics

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

c-8936_10, 3.5mm, Ooids with fringing radial-fibrous marine cement. The cement probably was originally aragonite or possibly high Mg calcite neomorphosed to low Mg calcite. Note "Maltese Cross" extinction pattern on ooids in cross polarized light. From the offshore limestone facies of the Bonneterre Dolomite, Cambrian, southeast Missouri.
c-8950_25 c-8950_25, 1.3mm, Close-up of radial marine cement adjacent to a fossil fragment. Offshore limestone facies of the Bonneterre Dolomite, Cambrian, southeastern Missouri.
c-OMT_10 c-OMT_10, 3.25mm, Close-up of c-OMT field showing trilobite grainstone-packstone containing moderate mud component (biosparmicrite). Note radial-fibrous cement. "Arkansas Rouge" decorative stone, Cambrian, Arkansas.
c-TF(B)_10 c-TF(B)_10, 3.25mm, Poikilotopic calcite cement surrounding dolomite crystals. Calcite cement is stained with alizarin red-S. Salamon Formation, Indiana.
c-TF(F)b_10 c-TF(F)b_10, 3.25mm, Polycrystalline "dogstooth" calcite on brachiopod fragment, note 2nd generation of blocky calcite cement. St. Clare Limestone, Silurian, Arkansas.
c-BR03_2_5 c-BR03_2/5, 13mm, Cephlapod section displaying two generations of calcite cement, an early cryptfibrous cement (originally HMC marine cement?) and a later open space filling blocky cement. Waulsortian Limestone, Lower Carboniferous, Black Rock coastal section, County Waterford, Ireland.
c-F09_10 c-F09_10, 3.25mm, Bryozoa in cryptfibrous marine cement. Waulsortian Limestone, Lower Carboniferous. Feltrim Quarry, County Dublin, Ireland.
c-IOM4C_2_5 c-IOM4C_2/5, 13mm, Articulated brachiopod in wackestone (biosparmicrite). Note geopetal filling of mud in brachiopod cavity indicating the up direction to the left. Also note the fringing radial-fibrous marine cement growing into the cavity, which postdates the geopetal filling, and second generation of coarse blocky cement. Waulsortian facies, Lower Carboniferous, southern coast of the Isle of Man, U.K.
c-IOM4_10 c-IOM4_10, 3.25mm, Close-up of c-IOM4C showing prismatic layer of brachiopod, fringing radial-fibrous marine cement and second generation of blocky cement. The fibrous cement likely was originally aragonite and later neomorphosed to low Mg calcite.
c-8539_10 c-8539_10, 3.5mm, Close-up of c-8539_2/5 showing two generations of calcite cement, small crystals adjacent to gastropod and large blocky crystals filling most of the open space. Inola Limestone Mem. Pennsylvanian (Desmoinian), Rodgers Co., Oklahoma.
c-89145_2/5 c-89145_2/5, 14mm, Rugose coral in a biomicrite. Note that intraparticle porosity is filled with what appears to be 2 generations of cement. Pennsylvanian, Missouri.
c-UMR16_10 c-UMR16_2/5, 13mm. Close-up of tabulate coral boundstone in c-UMR16_2/5, showing septa, tabulae and 2 generations of calcite cement filling intraparticle pore space. Pennsylvanian of Missouri.
c-TF(C)_50 c-TF(C)_50, 0.65mm, Aragonite whisker cement (note morphology of crystals) in primary porosity filled by blocky calcite cement. Lansing Group, Pennsylvanian, Kansas.
c-I6_25pl c-I6_25pl, 1.3mm, Blocky calcite cement filling cavities in a coral fragment. Inola Limestone Mem. Pennsylvanian (Desmoinian), Rodgers Co., Oklahoma.
c-I6b_25cl c-I6_25cl, 1.3mm, Cathodoluminescence (CL) of the field shown in c-I6_25cl revealing 2 generations of cement. Early fine crystalline, brightly CL cement lines skeletal material followed by dull to non-CL blocky cement. Pennsylvanian (Desmoinian), Rodgers Co., Oklahoma.
c-8949_2_5 c-8949_2/5, 14mm, Fussilinid grainstone (biosparite), note early radial-fibrous cement (originally aragonite neomorphosed to low mg calcite?) and second generation of coarse blocky calcite cement. Capitan Formation, Permian, Guadeloupe Mts., southeastern New Mexico.
c-8904_10 c-8904_10, 3.5mm, Green algal grain (Mizzia) in a fossiliferous grainstone (biosparite). Very good example of fringing radial-fibrous early marine cement (aragonite neomorphosed to low Mg calcite?) with second generation of coarse blocky calcite cement. Capitan Formation, Permian, southeastern New Mexico.
c-TF(D)_2_5 c-TF(D)_2/5, 13mm, Dripstone (microstalactite, vadose) cement in beachrock. Remaining porosity was later filled by blocky calcite cement. Was the 1st generation microstalactite cement aragonite or calcite? Jurassic, France.
c-TF(D)_10 c-TF(D)_10, 3.25mm, Close-up of microstalactite vadose cement in beachrock. Jurassic, France.
c-TF(A)_25 c-TF(A)_25, 1.3mm, Close-up of isopachous micrite cement on pelloids. Note the 3 distinct generations of cement. Blake Nose Formation, Cretaceous, Florida.
c-85520_25 c-85520_25, 1.4mm, Meniscus cement (blocky low Mg calcite- fresh water) binding coated skeletal grains (ooids) in an eolianite. Pleistocene, Cancun, Mexico.
c-85524_25 c-85524_25, 1.4mm, Foraminifera (center) in a skeletal grainstone (lower shore face) cemented by blocky (probably fresh water) low Mg calcite cement. Pleistocene, Cancun, Mexico.

 

Various Limestone Fabrics

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

c-8970b_2_5 c-8970b_2/5, 13mm, Fossiliferous grainstone (biosparite) displaying very high interparticle porosity. Pleistocene, Cancun, Mexico.
c-8970_10 c-8970_10, 3.25mm, Fossiliferous grainstone (biosparite) containing prominent foraminifera and scleractinian coral grains and displaying very high interparticle and intraparticle porosity. Pleistocene, Cancun, Mexico.
c-O2_2_5 c-O2_2/5, 13mm, Brachiopod-crinoid grainstone (biosparite) forming cap on phylloid algal mound. Hogshooter Limestone, Pennsylvanian, Tulsa, Oklahoma.
c-O4_2_5 c-O4_2/5, 13mm, Poorly preserved phylloid algae and other fossil grains in a wackestone (biomicrite) forming the bulk of a phylloid algal mound. Hogshooter Limestone, Pennsylvanian, Tulsa, Oklahoma.

 

Waulsortian Limestone of Ireland and the Isle of Man

See "Lees, A., and Miller, J., 1995, Waulsortian banks, in Monty, C. L. V., Bosence, D. W. J., Bridges, P. H., and Pratt, B. R., eds., Carbonate Mud-mounds their origin and evolution: International Association of Sedimentologists Special Publication 23, p. 191-271."

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

c-F01_10 c-F01_10, 3.25mm, Micritic mudstone displaying grumulous (clotted) fabric (upper field). Waulsortian limestone, massive mudstone lithology, Lower Carboniferous. Feltrim Quarry, County Dublin, Ireland.
c-F09_10 c-F09_10, 3.25mm, Bryozoa in crypto-fibrous (marine) calcite cement. Waulsortian Limestone, Lower Carboniferous. Feltrim Quarry, County Dublin, Ireland.
c-F09_2_5a c-F09_2/5a, 13mm, Stromatactis mudstone displaying geopetal mud laminations within a cavity followed by early brecciation and crypto-fibrous calcite cement. Waulsortian Limestone, Lower Carboniferous. Feltrim Quarry, County Dublin, Ireland. Waulsortian Limestone, Lower Carboniferous. Feltrim Quarry, County Dublin, Ireland.
c-F09_2_5b c-F09_2/5b, 13mm, Stromatactis mudstone containing a cavity lined with crypto-fibrous calcite cement and filled by blocky calcite cement. Waulsortian Limestone, Lower Carboniferous. Feltrim Quarry, County Dublin, Ireland. Waulsortian Limestone, Lower Carboniferous. Feltrim Quarry, County Dublin, Ireland.
c-F9_12pl c-F9_12/5pl, 2.8mm, Stromatactis mudstone containing a cavity lined with crypto-fibrous calcite cement and filled by blocky calcite cement. Waulsortian Limestone, Lower Carboniferous. Feltrim Quarry, County Dublin, Ireland. Waulsortian Limestone, Lower Carboniferous. Feltrim Quarry, County Dublin, Ireland.
c-F9_12cl c-F9_12/5cl, 2.8mm, Cathodoluminescence (CL) image of field shown in c-F9_12/5pl. Note mottled CL properties of with crypto-fibrous calcite cement and dark to dull CL banding of blocky calcite cement. Waulsortian Limestone, Lower Carboniferous. Feltrim Quarry, County Dublin, Ireland.
c-BR03_2_5 c-BR03_2/5, 13mm, Cephlapod section displaying two generations of calcite cement, an early cryptfibrous cement (originally HMC marine cement?) and a later open space filling blocky cement. Waulsortian Limestone, Lower Carboniferous, Black Rock coastal section, County Waterford, Ireland.
c-BR03_2_5a c-BR03_2/5a, 13mm, Wackestone-packstone lithology dominated, in this instance, by crinoid (and bryozoa) skeletal debris. Waulsortian Limestone, Lower Carboniferous, Black Rock coastal section, County Waterford, Ireland.
c-IOM4C_2_5 c-IOM4C_2/5, 13mm, Articulated brachiopod in wackestone (biosparmicrite). Note geopetal filling of mud in brachiopod cavity indicating the up direction to the left. Also note the fringing radial-fibrous marine cement growing into the cavity, which postdates the geopetal filling, and second generation of coarse blocky cement. Waulsortian facies, Lower Carboniferous, southern coast of the Isle of Man, U.K.
c-IOM4_10 c-IOM4_10, 3.25mm, Close-up of c-IOM4C showing prismatic layer of brachiopod, fringing radial-fibrous marine cement and second generation of blocky cement. The fibrous cement likely was originally aragonite and later neomorphosed to low Mg calcite.

 

Rudist Build-ups, Valles Platform, Mexico

See "Enose, P., 1986, Diagenesis of Mid-Cretaceous Rudist Reefs, Valles Platform, Mexico, in Schroeder, J. H., and Purser, B. H., eds., Reef diagenesis: Berlin, Springer Verlag, p. 160-185."

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

c-LC37_10 c-LC37_10, 3.25mm, Close-up of large rudist pelecipod grain (originally aragonite) displaying low Mg calcite neomorphic fabric. Note fringing marine cement which likely was originally aragonite and now is low mg calcite. Middle Cretaceous, Valles Platform, Mexico.
c-LC37_2_5 c-LC37_2/5, 13mm, Rudist packstone (packed biosparite), note large rudist grains displaying micritization and neomorphism. Middle Cretaceous, Valles Platform, Mexico.
c-TQ22-5_2_5 c-TQ22-5_2/5, 13mm, Neomorphic fabrics replacing skeletal material in a rudist reef. Middle Cretaceous, Valles Platform, Mexico.
c-TQ33_10 c-TQ33_10, 3.25mm, Rudist skeletal grainstone (biomicrite) with cement filled and unaltered (?) rudist fragments. Middle Cretaceous, Valles Platform, Mexico.
c-TQ33_25 c-TQ33_25, 1.3mm, Close-up showing micrite envelope developed around a rudist skeletal fragment filled with two generations of cement. Middle Cretaceous, Valles Platform, Mexico.
c-TQ35a_10 c-TQ35a_10, 3.25mm, Large rudist grain filled by "neospar" as opposed to open space filling cement. Note orientation of crystals is to upper left as opposed to radially inward from micrite envelope and unimodal crystal size as opposed to open space filling cement in c-TQ33. Middle Cretaceous, Valles Platform, Mexico.
c-TQ35b_10 c-TQ35b_10, 3.25mm, Open space filling cement in rudist skeletal grain preserved by micrite envelope. Note two distinct generations of cement, small crystals adjacent to micrite envelope and 2nd generation of coarse blocky crystals filling interior. Middle Cretaceous, Valles Platform, Mexico.
c-TQ35c_25 c-TQ35c_25, 1.3mm, Close-up of field in c-TQ35b showing two generations of cement relative to the micrite envelopes. Middle Cretaceous, Valles Platform, Mexico.

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