Comments on Sedimentary Rocks 



73 



Nature of sediments 



Angular particles more 

 than 2 mm. in greatest 

 dimension 



Rounded particles more 

 than 2 mm. in greatest 

 dimension 



Sedimentary rocks 



Rubble composed of sharpstones 



Gravel composed of roundstones 



Sharpstone 



Roundstone 



CONGLOMERATE 



Angular and rounded par- 

 ticles of rocks and min- 

 erals ranging in greatest 

 dimension from 2 mm. 

 to 0.06 mm. 



Volcanic fragments = Tuff 



Mixture of rock and mineral frag- 

 ments 



Quartz + Feldspar 



Quartz + other minerals in large 

 amount 



Quartz + other minerals in small 

 amount 



Tuffstone 

 Graywacke 



.^rkose 

 Normal 



Quartzose 



SANDSTONE 



Rock and mineral parti- 

 cles ranging in greatest 

 dimension from0.06 mm. 

 to 0.001 mm. and col- 

 loidal particles les-s than 

 0.001 mm. in greatest 

 dimension 



Fe^ and Fe™ compounds 

 precipitated inorgani- 

 cally and organically as 

 concretions, nodules and 

 layers 



Impurities commonly 

 present in the layers 



Volcanic ash 



Silt particles - 0.06 to 0.001 mm. 

 Clay materials less than 0.01 mm. 

 Silt -I- Clay -|- Water = Mud 



Ashstone 

 Siltstone 

 Claystone 

 Mudstone 



Iron concretions 



Iron compounds -|- mud, silica, 

 etc. 



Concretionary 

 Precipitated 



IRONSTONE 



Siliceous inorganic frag- 

 ments less than 0.06 mm. 

 in greatest dimension 



Siliceous organic hard 

 parts and their frag- 

 ments 



Silica precipitated as 

 odiites, pisolites, etc. 



Silica precipitated from 

 suspensions and solu- 

 tions 



Inorganic fragments 



Diatom frustules, radiolarian 

 skeletons and sponge spicules 



Siliceous concretions 



Chert, flint, sinter, etc. 



Fragmental 



Concretionary 

 Precipitated 



8ILICA8T0NE 



Plant structures — spores, 



fronds, leaves, wood, etc. 



Inorganic sediment 



Waxes, resins, etc., from 



decomposition of plants 



Plant debris; inorganic impurities 

 Plant fluids 



Coal 



Calcite and Aragonite fragments 



Calcareous organic hard parts — shells, exoskeletons, plates, 

 spines, and fragments 



Organically and inorganically precipitated concretions 



Inorganically precipitated CaCOi — Evaporation, etc. 



Organically precipitated CaCOj — (1) by NHi from decom- 

 position; (2) loss of CO2 to plants; etc. 



Fragmental 



Concretionary 



Precipitated 



Dolomite fragments 

 Dolomitized organic hard parta 

 Dolomitic concretions 

 Inorganically precipitated dolomite 

 Organically precipitated dolomite 



Fragmental 



Concretionary 



Precipitated 



LIMESTONE 



DOLO8T0NE 



O be 



Fragments of anhydrite, gypsum, halite, alkali, nitrate cali- 

 che, etc. 



Fragmental 



Evaporites — minerals 

 precipitated du'ing 

 evaporation of saline 

 waters 



Anhydrite 

 Gypsum 

 chlorides 

 Nitrates 

 Other rare salts 



Precipitated 



Anhydrock 

 Gyprock 



sauna- 



8TONB 



>>T3 



•r; 0) 



S-3 



o V 



Q a 



Figure 34. Classifiication of sedimentary rocks. (From Shrock, 

 Sequence of Layered Rocks.) 



