Sed Strat Test #2

Ribbon Chert

thinly interbedded chert and shale rock which forms when underwater depositional conditions change rapidly

Oolitic Limestone

Limestone whose primary allochem are ooids, or small non-biologic limestone spheres formed in unique shallow, wave agitated, and warm marine environments

Pelloids

fecal pellets, or structureless blobs of unknown content / origin; one of Limestone’s possible allochems

Geothermal Gradient

the increase in rock temperature as depth increases (generally ~20°C / km, though depends on location).

Geostatic Pressure

the weight of overlying substances on a point (can be divided into lithostatic and hydrostatic pressure)

Lithostatic Pressure

weight of a sediment overlying a point (variable with rock density)

Hydrostatic Pressure

weight of pore fluid in rocks (variable with fluid and rock type)

Neomorphism

Diagenesis in carbonate rocks, primary type of neomorphism is the transformation of micrite into sparry calcite

Geopetal Filling

the process by which empty spaces in carbonate rock are filled with sediment post deposition; you can use the fillings to determine original orientation

Syntaxial Overgrowth

Diagenetic process where a mineral grows a crystalline structure on top of an already existing crystal of that same mineral

Authigenesis

the formation of new crystalline structures in sedimentary rock after deposition, oftentimes precipitated by water

Pyritization

a diagenetic process by which biologic remnants are replaced with pyrite

Conodonts

marine fossils which change as color as they are exposed to higher temperatures; conodont color can help indicate the level of diagenesis

Superposition

old rocks exist below younger ones

Inclusion

a feature which is present entirely within another is older

Cross-Cutting

a cut across multiple features is younger than all of those features

Faunal Succession

in similarly-aged rocks, fossils succeed each other in the same order

Lithostratigraphic Heirarchy

supergroup - group - formation - member - band

Type Locality

a location where a geologic unit is well exposed and displays the characteristics and variability of said unit

Walthers Principle of Facies

states that in an unbroken sequence, laterally adjacent facies can be superimposed vertically in a stratigraphic section as the environment shifts

Conformable Boundaries

a geologic boundary where the change is gradual and continuous

Graduational Boundary

a type of conformable boundary which is gradual and implies slow and continuous change in the nature of deposition

Intercalated Boundary

a type of conformable boundary where each rock layer is interbedded, with one bed becoming more thick and frequent until the boundary ends

Non-Conformities

a sedimentary rock unit overlying an unconformity which itself overlies igneous or metamorphic rocks (which are unstratified)

Disconformities

Two sedimentary rock units with an unconformity between them

Angular Unconformities

a flat sedimentary rock unit overlying an older / folded sedimentary rock unit