The lithostratigraphic units are Stratigraphic division As an important method, the rock characteristics and rock category formation as a basis for the division of stratigraphic units. It is the general geological workers basic practical units. Lithostratigraphic unit includes a "group", "group", "long" and "layer" level four.
Lithostratigraphic units must be based on the characteristics of real rock composition as the basis, and not an earth rock physical property (electrical, Magnetic Inference or metric, radioactive and other physical properties), infer the Time interval Geological events, such as the cause, basis. Therefore, time, origin, climate, environment or events and other factors not considered in the definition of the lithostratigraphic units in the. However, lithostratigraphic unit itself is the material basis for inference of these factors.
As a kind of material composition of fossils in rocks, sometimes plays an important role in identifying a lithostratigraphic unit. But no matter under what circumstances, time, origin, climate, environment or events and other factors not considered in the definition of lithostratigraphic units. However, lithostratigraphic unit itself is the material basis for inference of these factors.
Division of metamorphic rock stratigraphic unit, still should be the basic principle of the overall consistency follows the rock characteristics. The original rocks are deposited or volcano accumulation Rock stratum The sequence, in the section with Overlapping Relationship, although the regional metamorphism, but the original rock features clear, the primary foliation is well preserved, although the sequence change, but through Structural analysis Can restore the original authentic sequence, and named according to rock stratigraphic unit division.
Lithostratigraphic units are divided into three kinds: formal lithostratigraphic units, Informal lithostratigraphic unit And Special rock strata Company.
Formal lithostratigraphic units (Formal lithostratigraphic units) is refers conforms to " Stratigraphic Guide China "On the rocks Stratigraphic division Provisions and the definition of unit, and give the lithostratigraphic unit named by naming procedures.
Classification and terminology formal lithostratigraphic units:
Group (Group) -- sequence combinations of two or two or more adjacent group or is divided into several groups.
Group (Formation) -- rock Stratigraphic division The basic unit.
Paragraph (Member) -- rock group named entity.
Layer (Bed) -- special strata within group or segment name, or the minimum in the volcano rock sequence in the unique layered rocks body -- rock flow layer (Flow).
Group is a rock Stratigraphic division The basic unit, used for Geological mapping , describe and illustrate Regional geology Features. Group field macroscopic rocks or rocks, combination of the same structure similar, similar color, showing the whole rock and Degree of metamorphism Malleable certain characteristics consistent, space, and can according to the Mapping The stratigraphic unit.
Group or by a rock ( Sedimentary rocks Volcano rock, or metamorphic), or in a rocks between other rock interlayer repeated; or by the two estimate rock alternating cross layer; also likely to very complex rock components or unique structures and compared with the other groups, regional difference.
The rocks change degree of an independent group required, no strict requirements. Mainly as a region The geological complexity , and can accurately describe the rock assemblage and clarifies the principle of geological history.
A group of unit thickness, no limit. Its thickness depends on the size of the area can be the best rock and developmental needs of stratigraphic unit size.
If a group is built on a certain scale Geological mapping In, or in the Cross section Not drawing out, this group should be regarded as unreasonable or meaningless. Although the use of a special lines exaggerated said a group practice is allowed, but such thin groups of units should be especially careful, unless it has important significance.
Segment is a group than that in the low level of formal lithostratigraphic units. A part of a group, can not be separated from the group and exist independently.
Group is not necessarily to be the whole segment. When necessary, only to a certain this interval is divided into some groups. Can enter another group from a set of lateral.
Lenses (Lens Lentil) is a group are pointed out, Geographic distribution Narrow rock body, its characteristics are different from the surrounding rocks in a special lens shaped; wedge or strap shaped body (Tongue), is a group of laterally extending beyond its body and insert that others in the group. All of them can be named, are regarded as a special shaped section; not naming and use the term period instead of time, should be regarded as Informal lithostratigraphic unit .
Within the group The reef And carbonate mound can name and is regarded as the formal segment (not named and term period instead of time, should be regarded as Informal lithostratigraphic unit ).
A group of side inserted inside other groups can be part of the other group of one while the other secondary division named sections is layer.
Layer is the smallest of the formal lithostratigraphic units. Are generally limited to those who can identify and especially useful in a layer, or a lot of monolayer composed of unit was given the name, and specify a formal lithostratigraphic units.
Like coal, oil or other economic value of some layer, generally give names, but this unit and its name is usually does not belong to the category of formal lithostratigraphic name.
Marker is a widespread and lithology special thin layer, can be named as formal lithostratigraphic units.
Rock flow layer (Flow) is a lithostratigraphic unit the smallest volcano lava, level and Sedimentary rocks In the "layer". It can be used in its structure, components, stacking sequence to distinguish. General rock flow layer is Informal lithostratigraphic unit .
The layer thickness is usually 1 centimeters to several meters thick. Thickness of the layer is called" Laminae "(Laminae). Only by the limitations of layer is the layer of lithostratigraphic units.
Layer can exist in the segment, there can not segment the group. A special layer can be from a group or segment into another group or segment while retaining the original name.
Group is better than the group of high level formal lithostratigraphic units. Group can consist of two or two or more adjacent or related with common lithology (or Lithology combination ) characteristics of the groups to; sometimes it may be a not yet in-depth study, not yet a packet, a detailed study may be divided into several groups of rock series. When necessary, the group can be subdivided into several subsets, or two or more than two adjacent and have common lithology ( Lithology combination ) characteristics of the group formed a supergroup. Group Unit layer Is it contained, each unit of layer type. Group is not necessarily to be merged into the group, only in order to more effectively carry out contrast research in large range, or the need for the preparation of small scale maps and the group as the group. The formation thickness and deposition Time interval The reason is not effective construction group.
An informal lithostratigraphic units (Informal lithostratigraphic units) is proposed for some special needs a no name, nor with the named rock body formal lithostratigraphic units. Considering the practical purpose rather than considering rock body recognition of rock characteristics consistent, such as aquifer, Coal seam , Oil sand The ore bearing layer, quarrying, reef or other economic value layer, even to the geographical names, is an informal lithostratigraphic unit. When using the Chinese phonetic alphabet or translated into English, unit terms first letter not capitalized.
Based on the rock formation rock body, shape or other non rock characteristics identified, such as sliding sediments, sliding body, sliding layer, olistolith, diapir, salt plug, Cycle layer And so on, can be used as Informal lithostratigraphic unit Name.
Special rock strata (Special lithostratigraphic units) relative to the normal rock stratum proposed, two were used in the rock bodies of different types (strata). The formation of normal rock formation, with stratigraphic formation law of superposition, fossil sequence and the law The Walter phase rule , the rock (or rock) characteristics and structure, sequence and stratigraphic relationships in the field Stratigraphic section Easy identification and longitudinal, transverse and recourse; Special rock strata The original, mainly stratified or non stratified rock body (stratum) suffered different degrees and the late tectonic stages, Metamorphism And MAGMATISM The formation of strong influence and transformation of a rock body (stratum), the original formation of the order has been severely damaged, rock characteristics, structure and tectonic or all suffered significant transformation and restructuring, or large scale thrusting and displacement, which is used for normal rock strata Classification method The or and contrast.
A special lithostratigraphic unit can consist of one or more primitive stratified or non stratified rock (strata) body stand structure, Metamorphism , Magmatic activity Such transformation, reorganization; can also is a kind of primitive stratified or non stratified rock (strata) body structure, metamorphism transformation into a plurality of Special rock strata Company.
Special rock strata Often represent early The crust Rock assemblage (or complex tectonic belt Orogenic belt ) an important component, is the direct record and crust evolution, ancient ocean continent transition. Therefore, to strengthen the Special rock strata The study has significance, is the use of modern Stratigraphy Part of the solution to the evolution of the earth an important direction of this important issue. Therefore, this guide lists the following special lithostratigraphic unit: Yan Qun , rock group, complex, ophiolite melange, Sliding rock , Tectonic rocks Etc. (before three class as a formal unit, after the four general informal stratigraphic unit), to attention.
Yan Qun Is Special rock strata The unit is equivalent to a formal unit normal lithostratigraphic unit group level. They are in the senior Metamorphic rocks District, or Orogenic belt The main body, due to complicated or strong granite Magmatic activity Influence, or because of Anatexis Lead to Regional migmatization Formed a set of complete sequence cannot be established supracrustal rocks. This kind of rock association, often present top, bottom is not full, and special Structural surface The confining, or metamorphic granitic intrusions or complex genesis of granitic rocks which contained; Rock stratum Is often affected by the strong ductile shearing caused intense mylonitization, the original stratigraphic sequence suffered intense destruction, it is difficult to restore the stratigraphic sequence complete.
This set of metamorphic supracrustal rocks, including metamorphic basic and ultra basic volcano rocks, paragneiss, granulite, Ma Liyan, Tie Yingyan, marble, different degrees of mylonite fossils, as well as by all kinds of rock subjected to different anatexis transformation form layered region hybrid rocks. This suite of rocks in combination with sequence significance relative in a large range of macro can be compared, large scope. Yan Qun Generally includes two or more rock group, sometimes it may also include normal lithostratigraphic unit group.
Rock group Yan Qun According to the rock (or rock), further subdivided the equivalent normal lithostratigraphic unit group level formal lithostratigraphic units. The rock with the metamorphic degree of different depths, sometimes show a moderate to strong mylonitization, schistosity, pudding, or has complex superposed folds and all kinds of plastic deformation in the strong weak rock; the primary foliation is often a part or all of the epigenetic surface for replacement; the top, the bottom boundary is often secondary structure (such as regional fault, ductile shear zone and strong deformation zone) is limited; the contact relationship between the rocks and rock group, principle of superposition in general do not accord with the original normal rock strata, but structural overlap relationships. Rock group can have certain regional extension, in a certain range can be compared.
Complex is a kind of Special rock strata Company. It is a set of large thickness, often not bottomed out, from the various types of one or several kinds of rocks (sedimentary rocks, igneous rock, metamorphic rock composed of the complex), and the irregular mixed lithology or tectonic feature extremely complex, vague that rock body of the original sequence, it is difficult to classification and mapping of individual rock or rock sequence. Part of a complex can be used as the official rock base on layer unit name, such as petrology terminology in its name, such as mulberry stem complex, Donghai complex etc.. Complex not level.
Melange is a special kind of rock (formation). It is in the active continental margin and continental collision orogenic belt range, from the various types (sedimentary rock, metamorphic rock, Huo Chengyan), different geological strata (rock), by constructing the function result, the mixed irregular accumulation of rock aggregate together. Their distribution along the tectonic boundary, some rock into a melange belt, tens of hundreds of kilometers, a few thousands kilometers. In the melange belt, some rock (or stratum body) has also preserved the sequence relationship of their own, can establish a lower group of normal lithostratigraphic unit; and the rock (or strata contact relations between the body), is generally constructed special relationship. Therefore, in the melange belt is usually to the overall establishment of normal formal lithostratigraphic unit series, can establish a Special rock strata No level of informal lithostratigraphic units in the. Melange melange because of its place in the tectonic environment of different form different band, in the active continental margin subduction is often due to formation of sedimentary melange; in the intracontinental collision orogenic belt in the formation is often the tectonic melange.
The ophiolite is the product of the interaction of the earth crust mantle layer between the turns, is a kind of oceanic crust rock combination. They recorded many important information of crust mantle interaction process, contains a set of crust mantle in different layers of rock units series, this series is generally based on bottom-up (ultrabasic rocks, cumulate rocks, gabbro diabase, basalt or sheeted dike swarm, containing deep ocean sediments intercalated layered basalt, chert and deep sea mud rock) sequence generation. They are not a single rock stratigraphic unit, but not out of order all kinds of rock mixed into the complex, but a group has obvious genetic relation and strict localization of magmatite deepwater sedimentary rocks. The ophiolite often because of tectonic action and the rocks formed a complex superposition and present the top bottom insufficiency and layered disordered state, therefore, as the Special rock strata Unit in a free level of informal institutions. In the field mapping, only in ascertaining the various rock units are sequential relationship quality, in order to ophiolite known, or only to the rock unit individual rock representation. Ophiolite in a tectonic belt in extensive range, can be compared.
Refers to the normal or special strata have been generated (or rock), due to structural or gravity (or other geological) effect, produce sliding or collapse or fall into different strata body embedded are deposited in part. Formation age they are generally different degrees at the surrounding rock, the surrounding rock and completely enclosed by special plane. When the slip (or collapse) distance is short, the slip (or collapse) are often referred to as "sliding rock, sliding layer, landslide accumulation", the only slightly older than the age of the surrounding rock, lithology and rock near, only according to its disorder bedding or broken bedding characteristics to identify. The sliding rocks can be surrounded by its normal lithostratigraphic units within a secondary informal stratigraphic unit or marker beds are described.
More typical Sliding rock Refers to a certain thickness, resulting in longer distance slip tectonic action, or collapse and displacement far strata (rock). The general was older than in surrounding rock, and the rock of the lithologic characters were also significantly different, with the perimeter of the surrounding rock for special level between the confining. This Sliding rock Body itself often appears as a good Stratigraphic section , which can perform low-level normal lithostratigraphic division. But the relation with the country rocks, the rock formation with comprehensive, biostratigraphy, chronostratigraphy and other methods to distinguish, otherwise easily lead to the rock as the same horizon view, which can draw incorrect conclusions for some important theoretical problems.
Sliding rock The origin, is a kind of special lithostratigraphic units; the material composition, when it formed by layered or stratified rock body, it can be a formal lithostratigraphic units, and can be formally rocks with low level Stratigraphic division ; when it by non stratified rock body, there is no level Informal lithostratigraphic unit .
The formation of the special secondary structure rock combination in the tectonic belt or structural surface, such as tectonic breccia, Mylonite Etc.. When the thickness is small, can be used as a special level or special signs layers view; when the thickness reaches a certain size and there is considerable in the lateral extension, can be an independent Special rock strata Unit, its boundaries Structural surface The confining, its internal structure has been completely because of tectonic action arising as a result of strong Shear deformation Or a non layered disordered state. Tectonic rock is a kind of no level of informal stratigraphic unit special stratigraphic units.
No matter which consists of one level or what rock each formal lithostratigraphic units, should have a highly summarized, refining the text clear definition; at the same time, specify a the unit's definition of layer type (typical section) or typical location is important.
For the laminated rock stratigraphic unit, is based on the definition of a Rock stratum Sequence of Unit layer . The lithostratigraphic unit non lamellar or of unknown causes of metamorphic rock, the definition should be based on a unit according to the special place of the following definitions, namely the typical location.
The typical location of stratified rock stratigraphic unit layer type and non layered rock stratigraphic unit can be selected at outcrops, tunnel, mine or bore. Name of unit in the name of the best from layer is located and the typical sites.
Layer type Or a typical place once specified, generally do not change, only when it is specified or described clearly wrong to be variable column. If the original layer or typical locations exposed range, complex structure, difficult to close or not representative of the unit, should be added to specify a (or several) reference section (first layer) or reference location. But the reference section or reference location should be assisted in The original layer Or the original typical place, not to replace the original layer or a typical place.
Lithostratigraphic unit group and the group of the following Layer type Usually Unit layer . The group is usually Composite layer .
In a region, dip solution corrosion, exposed is not good and do not specify any complete and continuous profile as Unit layer When specified, only the typical area or a typical place without specifying a stratotype section. In this case, the profile can meet the underlying and overlying units change on boundary layer type identification, is very important, at this time Unit layer Is a typical place or typical area in between, between the boundary layer type Rock stratum The composition.
Elsewhere in recognition of the unit, not considering the stratigraphic thickness, thin section or time span, but must be in accordance with the Layer type Surface is defined the same rock composition and in layer type section of equivalent positions.
The line of lithostratigraphic units designated in the lithologic spatially variable, but also can be placed in the transition zone. Both in the longitudinal and transverse, determining the boundaries of should be clearly reflected changes in the rocks.
Boundary boundary boundary lithostratigraphic unit often oblique time surface or fossil zones or other stratigraphic units.
The lithology is very similar to the rock (strata) body often contain discontinuous, false integration of local or small or Unconformity In general, should not only because of the existence of this type of deposition discontinuous and is divided into two or more than two lithostratigraphic units, unless there is also an easy to determine rock characteristics change line. Changes in general, but also by the regional Unconformity Or intermittently spaced adjacent strata lithology, even if there is no clear differences that can be divided, also should avoid to contact them into a lithostratigraphic unit. Under normal circumstances, the group (especially within the group and section) should not be Unconformity ; embedded discontinuous should not be seen in the group, group also very rare. A parallel discontinuities can be within the group, the group also may have a small parallel discontinuities.
A lithostratigraphic units and their boundaries should be from the stratotype or typical place to extend outward. This extends as far as just that the establishment of the units in the layer or typical location based on the typical rock exists, or through indirect evidence that existed.
In exposed rock characteristics is not good, it is difficult to prove the consistency of local, units and their boundaries can borrow ever use of landform, rock composition evidence, electric logging curves characteristics, The earthquake The reflection spectrum And vegetation characteristics obviously as the basis to indirectly indicate the composition of rock and the identification and comparison. There are special fossils are very useful for comparison of lithostratigraphic units. Admittedly, those relying only on the use of lithostratigraphic unit, method of recourse recognition inference rock components while useful, but not directly to the rock stratigraphic marker based. Surface rock stratigraphic unit formation is an important auxiliary means of mapping, if in no other interference factors in place, the boundary between lithostratigraphic unit to determine the variation characteristics and rock in the topography of the consistent bead is desirable.
When the sign of change in the rock layer vertical place, the symbol boundary layer top or bottom can be treated as a formal lithostratigraphic units. When the two markers between layers of rock and transverse become Layer type The rocks have substaintial distinction, should construct a new unit, even if the two sign can be traced back to the far away from the layer outside the region, also cannot have two kinds of different rock strata as the same lithostratigraphic unit processing.
General name of lithostratigraphic units should follow the general provisions of this guide for stratigraphic unit named (see 8.4). In addition, there are some additional provisions: lithostratigraphic unit name should be an appropriate local geographical names (names) and a presentation unit terms its level (group, group, layer, section), or a representative of the unit of the main rock types of rock formed by the combination of simple name (such as: Taiyuan group, the Mount Holyoke sandstone, rich Gou gneiss, Xikang slate), or the combination of the three forms (Rudong kiln lime Rock section ). The first letter of all words constitute the formal lithostratigraphic unit name in Chinese Pinyin should be capitalized. For the convenience of foreign exchange, unit terms not Pinyin and English, such as limestone, Changxin by Changxing Limestone, not Changxing Shihuiyan; five groups with Wutong Group, not Wutong Qnu.
"Soft", "hard" and "breccia" descriptive adjectives, rock term does not apply a lithostratigraphic unit name.
Spray (extrusive), metamorphic (metamorphic) and other adjectives in principle does not apply to lithostratigraphic unit name. But when they help to clarify the nature of a unit, or to provide a use value of information, such as the metamorphic rock, volcano rocks etc..
The adjective "", "", "" does not apply to formal lithostratigraphic units funded locust grade division. If you use, should be regarded as an informal lithostratigraphic unit.
A geographical name naming stratigraphic units use included in the 8.4.1 clause, the lithostratigraphic units in some special cases, there are some supplementary provisions:
When a lithostratigraphic unit in lithology, or because of Sedimentation The reason, or into the rock causes lateral changes due to deterioration or, if need to change the geographic name, depends on the degree of change, persistent changes after (or stability), as well as the contrast and continuous reliability. For the regional variability, can consider to change the name, but this change should be carefully, lest only according to some small change of lithology is proposed to build a new lithostratigraphic unit name caused confusion, especially in lithology boundaries is not obvious, with the name of a broad sense, than the use of the name two or more than two better.
Simple lithostratigraphic unit of geographic names and rock name name only use group level units, such as the Mount Holyoke sandstone, the level equivalent to the group. The section name or the name of rock layer can also use the term, but, in the rock terminology must add a unit level terms -- or layer. Generally do not rock name representation of group.
As a cause of pending non layered metamorphic rock stratigraphic unit name, a suitable geographical names should be with a representative group unit terms, or a representative of the main rock types of the simple name field rock joint.
There are formal geographical name to well lithostratigraphic units in many parts of the far shore ocean drilling. In some cases, Well drilling Lithostratigraphic units in large area and not in surface rock stratigraphic units were compared, and difficult to give the new group to find a suitable place, then from the coast, or the sea, or other characteristics of a name. Even so, this name is also very rare, so often need to use pure human naming method marked off shore marine Well drilling Lithostratigraphic units within the. The rules also apply to water Mapping Lithostratigraphic units are identified.
In the name of a lithostratigraphic unit, when using the rock terms, this term should be the most simple and easy to be accepted, the main characteristics and can represent the unit's rock name, such as limestone, sandstone, Shale , rhyolite, quartzite, gneiss, complex, complex conglomerate. Such as "clay shale" or "Sandy limestone" composite terms and "shale and sandstone" synthesis of such terms, not as rock term rock unit name in use. Also should not put an adjective in place names and terms between the rocks, such as certain black shale.
Like the tillite (Tillite), storm rocks (Tempestite), Flysch (Flysch) and sliding rock blocks (Olistolite) causes terms and tectonic lithofacies such term, be avoided in formal lithostratigraphic unit name. Because the terms and this method against research of multiple false no principle, and the causes of restrictive practices affect the unit concept itself reliability, easy to cause unnecessary disputes.
Revised or re definition of an established formal lithostratigraphic unit and not change its name, should have proposed the creation of a new unit as many reasons and the same procedure (see 8.7). About to change the unit of geographical names, rock terms or level terms.
The relevant entry -- Geologic time unit , Chronostratigraphic units , Biostratigraphic units