Changes

==Format for core logging==

==Format for core logging==

Recommended formats for graphic logging are given by Bebout and Loucks)<ref name=pt05r24>Bebout, D. G., Loucks, R. G., 1984, Handbook for Logging Carbonate Rocks: The University of Texas at Austin, Bureau of Economic Geology Handbook 5, 43 p.</ref> and Boyles et al.)<ref name=pt05r28>Boyles, J. M., Scott, A. J., Rine, J. M., 1986, A logging form for graphic descriptions of core and outcrop: Journal of Sedimentary Petrology, v. 56, p. 567–568., 10., 1306/212F89DB-2B24-11D7-8648000102C1865D</ref>. A completed graphic log is shown in Figure 1. Grain size, sedimentary structures, and accessories are shown in the left column. Let's look at how each type of data is handled in the graphic log.

Recommended formats for graphic logging are given by Bebout and Loucks<ref name=pt05r24>Bebout, D. G., Loucks, R. G., 1984, Handbook for Logging Carbonate Rocks: The University of Texas at Austin, Bureau of Economic Geology Handbook 5, 43 p.</ref> and Boyles et al.<ref name=pt05r28>Boyles, J. M., Scott, A. J., Rine, J. M., 1986, A logging form for graphic descriptions of core and outcrop: Journal of Sedimentary Petrology, v. 56, p. 567–568., 10., 1306/212F89DB-2B24-11D7-8648000102C1865D</ref> A completed graphic log is shown in Figure 1. Grain size, sedimentary structures, and accessories are shown in the left column. Let's look at how each type of data is handled in the graphic log.

[[file:core-description_fig1.png|thumb|{{figure number|1}}Idealized graphic log. Explanation for some symbols used for sedimentary structures, lithologies, fossils, and contacts are given. Grain size of sillclclastic rocks and Dunham's)<ref name=pt05r50>Dunham, R. J., 1962, Classification of carbonate rocks according to depositional texture, in Ham, W. E., ed., Classification of Carbonate Rocks: AAPG Memoir 1, p. 108–121.</ref> classification of limestones are indicated in the column on the left. All sedimentary structures are depicted graphically as accurately as possible. Porosity amounts in percent can be scaled as needed. (Modified from <ref name=pt05r32>Casey, J. M., 1980, Depositional systems and basin evolution of the Late Paleozoic Taos trough, northern New Mexico: Ph. D. Dissertation, The University of Texas at Austin, 236 p.</ref><ref name=pt05r28 />.)]]

[[file:core-description_fig1.png|thumb|{{figure number|1}}Idealized graphic log. Explanation for some symbols used for sedimentary structures, lithologies, fossils, and contacts are given. Grain size of sillclclastic rocks and Dunham's)<ref name=pt05r50>Dunham, R. J., 1962, Classification of carbonate rocks according to depositional texture, in Ham, W. E., ed., Classification of Carbonate Rocks: AAPG Memoir 1, p. 108–121.</ref> classification of limestones are indicated in the column on the left. All sedimentary structures are depicted graphically as accurately as possible. Porosity amounts in percent can be scaled as needed. (Modified from <ref name=pt05r32>Casey, J. M., 1980, Depositional systems and basin evolution of the Late Paleozoic Taos trough, northern New Mexico: Ph. D. Dissertation, The University of Texas at Austin, 236 p.</ref><ref name=pt05r28 />.)]]

===Sedimentary structures===

===Sedimentary structures===

Sedimentary structures are recorded to the right of and just inside the grain size curve. There is no single set of standardized symbols for sedimentary structures. Examples are given in Swanson)<ref name=pt05r150>Swanson, B. F., 1981, A simple correlation between permeabilities and mercury [[capillary pressure]]s: Journal Petroleum Technology, v. 33, p. 2498–2504., 10., 2118/8234-PA</ref> and Bebout and Loucks)<ref name=pt05r24 />. Realistic sketches of observed structures may be more useful than standard symbols. The vertical succession of sedimentary structures should be recorded as accurately as possible because this succession is often the key to successful environmental interpretation. Description, classification, and interpretation of sedimentary structures are discussed by Collinson and Thompson)<ref name=pt05r35>Collinson, J. D., Thompson, D. B., 1989, Sedimentary Structures: Boston, MA, Unwin Hyman, 207 p.</ref> and Lindholm)<ref name=pt05r103>Lindholm, R. C., 1987, A Practical Approach to Sedimentology: Boston, MA, Allen and Unwin, 276 p.</ref>.

Sedimentary structures are recorded to the right of and just inside the grain size curve. There is no single set of standardized symbols for sedimentary structures. Examples are given in Swanson)<ref name=pt05r150>Swanson, B. F., 1981, A simple correlation between permeabilities and mercury [[capillary pressure]]s: Journal Petroleum Technology, v. 33, p. 2498–2504., 10., 2118/8234-PA</ref> and Bebout and Loucks)<ref name=pt05r24 />. Realistic sketches of observed structures may be more useful than standard symbols. The vertical succession of sedimentary structures should be recorded as accurately as possible because this succession is often the key to successful environmental interpretation. Description, classification, and interpretation of sedimentary structures are discussed by Collinson and Thompson<ref name=pt05r35>Collinson, J. D., Thompson, D. B., 1989, Sedimentary Structures: Boston, MA, Unwin Hyman, 207 p.</ref> and Lindholm)<ref name=pt05r103>Lindholm, R. C., 1987, A Practical Approach to Sedimentology: Boston, MA, Allen and Unwin, 276 p.</ref>.

===Accessories===

===Accessories===

Fossils, trace fossils, diagenetic and structural features, and other accessories are shown on the far right side of the left column of a graphic log. Standard symbols for these features are found in Swanson)<ref name=pt05r150 /> and Bebout and Loucks)<ref name=pt05r24 />.

Fossils, trace fossils, diagenetic and structural features, and other accessories are shown on the far right side of the left column of a graphic log. Standard symbols for these features are found in Swanson<ref name=pt05r150 /> and Bebout and Loucks.<ref name=pt05r24 />

===Thickness===

===Thickness===

===Lithology===

===Lithology===

Dominant lithologies and the nature of the contact between lithologic units are recorded in the “Rock Type and Contacts” column near the middle of a graphic log (Figure 1). Standardized symbols for illustrating lithologies are available and are presented by Tucker)<ref name=pt05r157>Tucker, M. E., 1982, The Field Description of Sedimentary Rocks: United Kingdom, The Open University Press, 112 p.</ref> and Lindholm)<ref name=pt05r103 />. If more than one lithology or interbedded lithologies exist within an interval, lithologies should be logged by estimating the percent volume of each lithology and noting the terrigenous clastic lithologies to the left of the chemical rocks. Contacts between lithologies are recognized in core as gradational, interbedded, or sharp. Some sharp contacts are probably erosional and may represent unconformity surfaces. Additional information such as the presence of root structures and early diagenetic cements may aid in determining the true nature of sharp contacts.

Dominant lithologies and the nature of the contact between lithologic units are recorded in the “Rock Type and Contacts” column near the middle of a graphic log (Figure 1). Standardized symbols for illustrating lithologies are available and are presented by Tucker.<ref name=pt05r157>Tucker, M. E., 1982, The Field Description of Sedimentary Rocks: United Kingdom, The Open University Press, 112 p.</ref> and Lindholm)<ref name=pt05r103 /> If more than one lithology or interbedded lithologies exist within an interval, lithologies should be logged by estimating the percent volume of each lithology and noting the terrigenous clastic lithologies to the left of the chemical rocks. Contacts between lithologies are recognized in core as gradational, interbedded, or sharp. Some sharp contacts are probably erosional and may represent unconformity surfaces. Additional information such as the presence of root structures and early diagenetic cements may aid in determining the true nature of sharp contacts.

===Maturity===

===Maturity===

Textural maturity of sandstone units is recorded in the next column to the right (“Textural Maturity” in Figure 1) and is described following the method outlined by Folk)<ref name=pt05r57>Folk, R. L., 1974, Petrology of Sedimentary Rocks: Austin, TX, Hemphill Publishers, 159 p.</ref>. Detrital clay (matrix) content and the sorting and roundness of grains are all considered in the determination of textural maturity. Because it is difficult to estimate the relative abundance of detrital versus authigenic clay without thin section or scanning electron microscope data, care must be taken in making estimates of detrital clay content. Image charts can be used for estimating sorting and roundness (Figure 2).

Textural maturity of sandstone units is recorded in the next column to the right (“Textural Maturity” in Figure 1) and is described following the method outlined by Folk.<ref name=pt05r57>Folk, R. L., 1974, Petrology of Sedimentary Rocks: Austin, TX, Hemphill Publishers, 159 p.</ref> Detrital clay (matrix) content and the sorting and roundness of grains are all considered in the determination of textural maturity. Because it is difficult to estimate the relative abundance of detrital versus authigenic clay without thin section or scanning electron microscope data, care must be taken in making estimates of detrital clay content. Image charts can be used for estimating sorting and roundness (Figure 2).

[[file:core-description_fig2.png|thumb|{{figure number|2}}(a) Comparison chart for sorting and sorting classes. (Modified from <ref name=pt05r125>Pettijohn, F. J., Porter, P. E., Siever, R., 1987, Sand and Sandstone, 2nd. ed.: New York, Springer-Verlag, 553 p.</ref>.) (b) Comparison chart for roundness and sphericity. (Modified from <ref name=pt05r130>Powers, M. C., 1953, A new roundness scale for sedimentary particles: Journal Sedimentary Petrology, v. 23, p. 117–119.</ref>.)]]

[[file:core-description_fig2.png|thumb|{{figure number|2}}(a) Comparison chart for sorting and sorting classes. (Modified from <ref name=pt05r125>Pettijohn, F. J., Porter, P. E., Siever, R., 1987, Sand and Sandstone, 2nd. ed.: New York, Springer-Verlag, 553 p.</ref>.) (b) Comparison chart for roundness and sphericity. (Modified from <ref name=pt05r130>Powers, M. C., 1953, A new roundness scale for sedimentary particles: Journal Sedimentary Petrology, v. 23, p. 117–119.</ref>.)]]

===Porosity===

===Porosity===

Identification of porosity type and a qualitative estimate of porosity abundance should be made in the column labeled “Porosity.” For carbonate rocks, the porosity classification scheme discussed by Choquette and Pray)<ref name=pt05r34>Choquette, P. W., Pray, L. C., 1970, Geological nomenclature and classification of porosity in sedimentary carbonates: AAPG Bulletin, v. 54, p. 207–250.</ref> is recommended. For siliciclastic rocks, four types of porosity are common:

Identification of porosity type and a qualitative estimate of porosity abundance should be made in the column labeled “Porosity.” For carbonate rocks, the porosity classification scheme discussed by Choquette and Pray<ref name=pt05r34>Choquette, P. W., Pray, L. C., 1970, Geological nomenclature and classification of porosity in sedimentary carbonates: AAPG Bulletin, v. 54, p. 207–250.</ref> is recommended. For siliciclastic rocks, four types of porosity are common:

* Intergranular

* Intergranular

* Intragranular or moldic

* Intragranular or moldic

* Microporosity

* Microporosity

* Fracture (<xref ref-type="bibr" rid="pt05r127">Pittman, 1979</xref>)

* Fracture (Pittman, 1979)

Of these, microporosity is the most difficult to recognize with a binocular microscope. The existence of microporosity is suggested by the presence of detrital or authigenic clays in sandstones. Accurate laboratory or thin section determinations of porosity types and percentages should always augment the estimates made during core logging. (For more on porosity classification schemes, see chapter on “Porosity” in Part 5.)

Of these, microporosity is the most difficult to recognize with a binocular microscope. The existence of microporosity is suggested by the presence of detrital or authigenic clays in sandstones. Accurate laboratory or thin section determinations of porosity types and percentages should always augment the estimates made during core logging. (For more on porosity classification schemes, see chapter on “Porosity” in Part 5.)

===Comments===

===Comments===

Information not recorded elsewhere on the form can be included in the “Comments” column on the far right (Figure 1). Such items as color, presence of hydrocarbon residue, and inferred depositional environment can be placed here. Color should be determined using the standard color chart distributed by the Geological Society of America<ref name=pt05r67>Goddard, E. N., 1979, Rock-Color Chart: Boulder, CO, Geological Society of America.</ref>.

Information not recorded elsewhere on the form can be included in the “Comments” column on the far right (Figure 1). Such items as color, presence of hydrocarbon residue, and inferred depositional environment can be placed here. Color should be determined using the standard color chart distributed by the Geological Society of America.<ref name=pt05r67>Goddard, E. N., 1979, Rock-Color Chart: Boulder, CO, Geological Society of America.</ref>.

==Rock-log calibration==

==Rock-log calibration==