Reconocimiento del fenómeno prostitucional en la trama del Estado

The recording of rock type consists of two fundamental parts: the basic rock name (e.g., dolomite, limestone, sandstone), and the proper compositional or textural classification term (e.g., lithic, oolitic grainstone).

II. Color

Color of rocks may be a mass effect of the colors of the component grains, or result from the color of the cement or matrix, or staining of these. Colors may occur in combinations and patterns, e.g., mottled, banded, spotted, variegated. It is recommended that colors be described on wet samples under ten-power magnification. If is important to use the same source of light all the time and to use constant magnification for all routine logging. General terms, such as dark grey and medium brown, generally suffice.

Ferruginous, carbonaceous, siliceous, and calcareous matter are the most important staining or coloring agents. From limonite or hematite come yellow, red, or brown shades. Gray to black color can result from the presence of carbonaceous or phosphatic material, iron sulfide, or manganese. Glauconite, ferrous iron, serpentine, chlorite, and apatite impart green coloring. Red or orange mottling is derived from surface weathering or subsurface oxidation by the action of circulating waters.

The colors of cuttings may be alerted, after the samples are caught, by oxidation caused by storage in a damp place, insufficient drying after washing, or by overheating. Bit or pipe fragments in samples can rust and stain the samples. Drilling mud additives may also cause staining.

Place a wet sample next to color swatches, to determine which color most closely matches the dominant color of the sample.

III. Texture

Texture is a function of the size, shape, and arrangement of the constituent elements of a rock.

 Grain or crystal sizes

Size, grades and sorting of sediments are important characteristics. They have a bearing on the porosity and the permeability of the rocks and may be a reflection of the environment in which sediment was deposited. Size classifications are to be based on a Wentworth scale. The surface data logger should not try to record size grades without reference to a standard comparator of mounted sieved sand grains. Other comparators are photomicrographs of thin sections showing both grain size and sorting. Both simple and useful is a photographic grid of half-millimeter squares, which may be placed near the microscope.

Rock sample examples:

Quartz pebbles: Generally,

white, clear or milky, but iron staining can give an orange hue. Often seen in Putnam and Clay counties, but may be seen elsewhere.

Sand: Can be most any color.

Grains generally composed of quartz or calcite. If grains are cemented together, it may be sandstone. Often found with clay, limestone, or phosphate.

Sand with clay: Sand sized

grains held together with clay. Sample easily crumbles or can be shaped if sufficient clay sized material. Grains are limestone, phosphate, shell pieces, and quartz in this sample.

Clay: Can be most any color

green, olive, gray, bluish green, and grayish green are most common in. Clay can be squeezed into a ribbon or rolled into shapes. Often mixed with sand, shell, or phosphate.

Coquina: Coquina is composed

primarily of shell hash that has been tightly cemented together. Shell beds look similar in drill cuttings, but may have more clay and sand.

Salt: White, dirty white, and off

white. Generally, sand with quartz and phosphate (black or brown grains in photo) or heavy minerals (titanium-based), may exist with salt.

Chert: Can be most any color.

Rock is very hard and breaks with sharp edges or conchoidal fracture. Occurs as nodules, lenses, beds, or within fractures or voids. Often called flint.

Limestone: Component grains

form a framework held together by calcite cement, which appears as clear to milky white between the grains. This sample is mostly limestone grains, but brown dolostone can also be seen.

Limestone with fossils: Similar

to the above in that grains comprise the majority of the rock and the inter-granular space is filled with hardened lime mud. Enlargement shows that a portion is fossil coral with mud infilling.

Dolostone: It is recrystallized

dolostone. In this sample, rhombohedral shaped dolomite crystals can be seen in the enlargement. Acid reaction may be barely perceptible when applied. A hammer was needed to break the sample.

Dolostone: Similar to above,

except grains are supporting the rock. This sample has limestone, dolostone, and chert grains with some fossil pieces. The limestone grains will fizz more vigorously than the dolostone or chert.

Gypsum: Generally white but

may have bluish tint or brown staining. Soft can scratch with fingernails. Occurs as nodules, beds, or infilling in voids or fractures. Flat faces of crystals

 Shape

Shape of grains has long been used to decode the history of a deposit of which the grains are a part. Shape involves both sphericity and roundness.

Sphericity refers to a comparison of the surface area of a sphere of the same volume as

the grain, with the surface area of the grain itself. For practical purposes, distinction is usually made in large particles based on axial ratios and in grains by visual comparison with charts.

Roundness that refers to the sharpness of the edges and corners of a fragment is an

important characteristic that deserves careful attention in detailed logging. Five degrees of rounding are described as follows:

Angular edges and corners sharp, little or no evidence of wear. Subangular faces untouched but edges and corners rounded.

Subrounded edges and corners rounded to smooth curves; areas of original faces reduced. Rounded Original faces destroyed, but some comparatively flat faces may be present; all

original edges and corners smoothed off to rather broad curves.

Well rounded no original faces, edges, or corners remain; entire surface consists of broad

curves, flat areas are absent.

Sorting

Sorting is a measure of the size frequency distribution of grains in a sediment or rock. It involves shape, roundness, specific gravity, and mineral composition as well as size. A classification given by Payne (1942) that can be applied to these factors is:

Good: 90% in one or two size classes Fair: 90% in three or our size classes Poor: 90% in five or more size classes

Values that are more precise may be determined by direct comparison with sorting comparators.