Some new thoughts of definitions of terms of sedimentary facies: Based on Miall's paper(1985)

Zeng-Zhao Feng

China University of Petroleum (Beijing), Beijing, 100083, China

Abstract In recent years,the Journal of Palaeogeography(Chinese Edition and English Edition)continually received manuscripts,in which some authors are from China and some are from Pakistan,Lithuania,Morocco,South Africa, etc. The authors of these manuscripts, according to the viewpoint and method of Miall's paper(1985),selected rocks from each bed in the clastic sections of their study areas and induced some rock types,such as conglomerates, sandstones and fine-grained stones, and considered them as lithofacies. It does not conform to the definition of lithofacies. I wrote some papers, i.e., Feng (2018, 2019, 2020), to point out the problems and hope that the authors worldwide, especially Chinese authors, will not continually cite, spread and follow Miall's paper (1985) viewpoint and method blindly.

Keywords Rocks, Sediments, Sedimentary environments, Facies, Sedimentary facies, Lithofacies, Lithology,Facies analysis method,A hundred flowers blossom and a hundred schools of thought contend,Geological practice

1.Introduction

In recent years, the Journal of Palaeogeography(Chinese Edition and English Edition) continually received manuscripts in which the authors, according to the viewpoint and method of Miall's paper (1985),selected rocks from each bed in clastic sections of their study areas and presented some rock types,such as conglomerates, sandstones, fine-grained stones,etc., and considered them as lithofacies.

However, these rock types do not conform to the definition of lithofacies. Therefore, I have written some papers, i.e., Feng (2018, 2019, 2020), to point out the problems and hope that the authors worldwide,especially Chinese authors,avoid these pitfalls.

Prof. Miall is the first person who considered the rocks(in fact,the sediments)as lithofacies.However,he did not give a definition of lithofacies.He proposed a facies analysis method and utilized lithofacies to analyze facies.It confused the normal facies analysis.

My current paper is a special article to discuss the problems arising from Miall's paper (1985).

In this current paper, I will not discuss the contributions and less strictness of architectural elements proposed by Miall's paper (1985).

Please refer to Table 1 of Miall's paper(1985).

Table 1 is composed of 4 columns,i.e.,Facies code,Lithofacies,Sedimentarystructuresand Interpretation.

The Facies code and Lithofacies columns include 4 gravel types,7 sand types,and 7 fine-grained sediment types, in total 18 sediment types.

The Sedimentary structures column includes various sedimentary structures summarized according to section studies.

The Interpretation column may be sedimentary environments or sedimentary facies.

In my mind, the term lithofacies in Table 1 is not facies, but sediment types.

These 18 lithofacies in Table 1 disrupted the original stratigraphic order from the lower to upper of the clastic section in the study area of Miall's paper(1985).These lithofacies were isolated. Utilizing these lithofacies to analyze facies, i.e., utilizing facies to analyze facies, is illogical. It is impossible to identify the facies of each bed,each member,each formation,each series, etc., and impossible to identify the evolutionary rule of facies of the whole stratigraphic section in the study area.

Therefore, the theoretical significance of his method of facies analysis will be greatly reduced.The application of his method of facies analysis to other facies and to petroleum exploration and development will also be reduced.

In the following, I will discuss the definitions of facies, lithofacies, lithology and their related problems, and propose my facies analysis method.

2.The definition of facies by Pyxᴎʜ(1953), Mineralogy and Petrology Section of Beijing Petroleum Institute (1961), etc.

Pyxᴎʜ (1953), a sedimentologist from USSR, in his textbook “Oсновьi Литологии (Principles of Sedimentary Petrology), proposed: “Facies is the regular synthesis of sediments which can express their lithological and palaeontological features.Therefore,facies is the material expression of formation conditions of sediments.It should say lagoon dolostone facies but not say dolostone facies. It should say lake or lacustrine siltstone facies but not say siltstone facies”.

Mineralogy and Petrology Section of Beijing Petroleum Institute (1961), Mineralogy and Petrology Section of East China Institute (1982) and Feng(1994), succeeded and developed the definition of facies by Pyxᴎʜ (1953).

3.The definition of facies by The Encyclopedia of Sedimentology and A Dictionary of Earth Sciences

The Encyclopedia of Sedimentology (1978) cited the definition of facies by Moore (1949): “any areally restricted part of a designated stratigraphic unit which exhibits characters significantly different from those of other parts of the unit”.

I disagree with this viewpoint,because this facies is designated as part of a stratigraphic unit but not the facies of sedimentary petrology.

The Encyclopedia of Sedimentology (1978) cited another definition of facies: “Facies refers to the overall characteristics of rocks formed in a certain environment”.

I agree with this definition of facies.

A Dictionary of Earth Sciences by the Editorial Committee of A Dictionary of Earth Sciences(2006), in its Basic Disciplines Volume, proposed:“sedimentary facies is the material expression of sedimentary environment. Sedimentary facies is the sum of all primary features, including petrological,palaeontological and petrogeochemical features, of sedimentary environment.

Table 1 Lithofacies classification,from Miall(1985).

I agree with this definition of sedimentary facies,i.e., facies.

4.My definition of facies

On the basis of Pyxᴎʜ (1953), Mineralogy and Petrology Section of Beijing Petroleum Institute(1961), Mineralogy and Petrology Section of East China Petroleum Institute (1982), and Feng (1994,2018, 2019, 2020), I summarized the definition of facies as the following 5 sentences:

(1) Sedimentary rocks are not facies.

(2) Sedimentary environments are not facies.

(3)The sum of sedimentary rocks plus sedimentary environments is facies.

(4) Sedimentary rocks formed in sedimentary environments, therefore the lithological and palaeontological features of sedimentary rocks can reflect the sedimentary environments.

(5) We can utilize these features of sedimentary rocks to analyze and restore their sedimentary environments. This is facies analysis.

The above 5 sentences are my definition of facies today.

5.The definitions of lithofacies

The term lithofacies is widely used in Chinese sedimentary petrology and lithofacies palaeogeography.However, its definition is debated.

5.1. The definition of lithofacies of the Glossary of Geology by The American Geological Institute (1973)

The American Geological Institute (1973)mentioned 4 definitions of the term lithofacies, i.e.,

ⓐ, ⓑ, ⓒand ⓓ.

I disagree with ⓐand ⓒ, because these two definitions belong to stratigraphic unit but not belong to sedimentary petrology or sedimentology.

The definition of ⓑis “A term used by Moore(1949) to signify any particular kind of sedimentary rock or distinguishable rock record formed under common environments of deposits”.

But, in the conclusion of Moore (1949), he concluded the definition of lithofacies: “The rock record of any sedimentary environment, including both physical and organic characters, is designated by the term “lithology”.

It means that Moore (1949) considered the rock record of any sedimentary environment as“lithology”.

I disagree with his viewpoint which Moore (1949)considered lithofacies as “lithology”.

Regarding the definition of ⓓ, The Glossary of Geology by the American Geological Institute (1973)pointed out the terms of lithology, lithologic type,lithologic unit and formation.

Inmymind,thetermsoflithology,lithologictypeand lithologic unit are the features,types and units of sedimentary rocks. These terms are not lithofacies. About the formation,it may be the formative process of sedimentary rocks and may not be the stratigraphic unit“formation” (组). The meaning of these terms is not clear.None of these terms are lithofacies.

In a word, I disagree with the definitions of lithofacies,i,e.,ⓐ,ⓑ,ⓒand ⓓof the Glossary of Geology by The American Geological Institute(1973).

5.2. The definition of lithofacies by A Dictionary of Earth Sciences (2006)

The Editorial committee of A Dictionary of Earth Sciences, Basic Disciplines (2006)proposed:

“lithofacies refers to the facies of sedimentary rocks.It reflects the features of a certain sedimentary environment, including all the physical, chemical(mineralogical and petrological) and biological features,such as a glauconitic sandstone facies of marine strata in the Paleozoic which reflected shallow sea environment”.

I agree with this definition of lithofacies.

In the definition, the terms lithofacies, facies and sedimentary facies are synonymous terms.

Therefore, we should say “shallow sea glauconitic sandstone facies”, not say “glauconitic sandstone facies”. We should not disregard sedimentary environments.

If there were no sedimentary environments, the sedimentary rocks would not be lithofacies or facies.

6.My facies analysis methodology

6.1. Recognizing rocks and preliminarily determining facies

During the study of outcrop section, we should recognize various rocks, such as clastic rocks, sparry limestone,limemud limestone,intraclastic limestone,oolitic limestone, coarse crystalline dolostone,medium crystalline dolostone, silt-sized crystalline to mud-sized crystalline dolostone (penecontemporaneous dolostone), siliceous rock, etc.

According to the quantitative features and qualitative features of sedimentary rocks, we can determine facies preliminarily.

For a more definitive and precise facies, the polarizing microscope data and other laboratory test data are necessary.

The two-dimensional quantitative column figure can illustrate the final product of facies analysis.

Since the stratigraphic order of study section was not disturbed,we can analyze facies of all beds,members,formations,series,etc.,of the section and establish the evolutionary rule of facies of the whole section.

6.2. Single factor analysis and multifactor comprehensive mapping method

In my teaching and scientific researches, I continuously utilized the single factor analysis and multifactor comprehensive mapping method.

The single factors are the features of sedimentary rocks and some sedimentary rocks themselves with definite sedimentary environments.The single factors that I usually utilized are as follows.

(1) Thickness (m)

In the isoline map of thickness (m) of marine stratum, the isoline of zero thickness should be gradually decreased to zero, but not be suddenly decreased to zero which was induced by tectonic movement.

In the normal isoline zero area,the marginal facies of old land should be developed.

The above two points are markers of old land.

If the old land is defined,the rest of the area is old sea.

In a palaeogeographic map,the distributional map of old lands and old seas is most important.

(2) Shallow marine clastic rocks

In the isoline map of content(%)of shallow marine clastic rocks, the area of content >50% can be identified as shallow marine clastic platform.

(3) Shallow marine carbonate rocks

In the isoline map of content(%)of shallow marine carbonate rocks, the area of content >50% can be identified as shallow marine carbonate platform.

(4) Penecontemporaneous dolostone

In the isoline map of content (%) of penecontemporaneous dolostone,the area of content>50%can be identified as penecontemporaneous dolostone flat.

(5) Intraclasts

In the isoline map of content(%)of intraclasts,the content (%) of intraclast can define different intraclastic banks, such as intraclastic bank, peneintraclastic band and embryonic intraclastic bank.

(6) Ooids

In the isoline map of content (%) of ooids, the content(%)of ooids can define different oolitic banks,such as oolitic bank, oolitic penebank and oolitic embryonic bank.

(7) Fossil fragments

In the isoline map of content (%) of fossil fragments, the content (%) of fossil fragments can define different biocrowds, such as biocrowd and penebiocrowd.

(8) Gypsum

In the isoline map of content (%) of gypsum, the content (%) of gypsum can define gypsum lake and gypsum lagoon.

(9) The thin-bedded siliceous rock is the basis to define deep water basin or deep water trough.

(10) The various qualitative features, such as sedimentary structures,marine fossils and continental fossils, are important markers of facies.

(11) Other single factors (omitted)

According to the single factor analysis and multifactor comprehensive mapping method, we can accurately define facies and compose quantitatively palaeogeographic map.

To define facies is a measure for the aim.The aim is to compose a quantitative palaeogeographic map and to be predictive for exploration of petroleum and other mineral deposits. All of my monographs and papers of palaeogeography are intended to be predictive for exploration of petroleum and other mineral deposits.

For detailed discussion of my facies analysis methodology, please refer to Feng (2004, 2016a,b 2019, 2020) and Feng et al. (2013, 2014).

7.Viewpoints of some sedimentologists

7.1. The viewpoints of two sedimentologists

A sedimentologist said: Now, Prof. Miall is more than 70 years of age and is retired.It may be too late to discuss problems with him.

Another sedimentologist said: My current paper may be unsuitable, because Miall's paper (1985) was published 36 years ago.

In my mind, the viewpoints of the above two sedimentologists are very similar.They hold very tolerant attitude toward older people.

7.2. The viewpoint of a sedimentologist

A sedimentologist said: If a published paper is problematic, it can be discussed.

I agree with this viewpoint.

In my mind,a published paper does not only belong to the authors, but also belong to the academic domain.If this paper is problematic,we can adhere to the policy of “A hundred flowers blossom and a hundred schools of thought contend” to discuss it.

7.3. The viewpoints of some people

Some people said that my definition of facies may be too strict. They think that the definition of facies should be more broad and general.

In my mind,the definition of facies should be strict.I support the viewpoints of Pyxᴎʜ(1953)and A Dictionary of Earth Sciences (2006), i.e., the definition of sedimentary facies should include sedimentary rocks and sedimentary environments.We should say“lagoon dolostone facies”but not say“dolostone facies”.We should say “lacustrine siltstone facies” but not say “siltstone facies”. We should say “shallow sea glauconitic sandstone facies”but not say“glauconitic sandstone facies”.

In a word, the sedimentary rocks and sedimentary environments are two indispensable components of facies. If any one of these two components is lacking,the sedimentary rocks or sedimentary environments will not be facies any more.So,the definition of facies must be strict.

I disagree with this more general and broad viewpoint about definition of facies. It is ambiguous.

8.A hundred flowers blossom and a hundred schools of thought contend

Mao(1937)said:“The history of human knowledge tells us that the truth of many theories is incomplete and that this incompleteness is remedied through the test of practice.Many theories are erroneous and it is through the test of practice that their errors are corrected.It is why practice is the criterion of truth”.

Mao (1957) also said: “A hundred flowers blossom and a hundred schools of thought contend is the policy for promoting progress in the arts and sciences. … …Questions of right and wrong in the arts and sciences should be settled through free discussion.

As the Editor-in-Chief of the Journal of Palaeogeography (Chinese Edition and English Edition), I have adhered to the policy of “A hundred flowers blossom and a hundred schools of thought contend”and wrote this paper both in English and in Chinese. I hope that this paper can attract the attention of authors and readers worldwide and they can participate in the discussion and contending.

In order to carry out the policy of“A hundred flowers blossom and a hundred schools of thought contend”effectively,I refined the rules which were published in Feng(2019,2020)as follows:①The speaking should be on good grounds (应言之有据) and should convince others through reasoning(应以理服人), and should not force them.②The speaking should be polite(应言之有礼)to all participants,especially to the opponents,and should not injure their personal dignity. ③We should uphold the truth and have the courage to correct our mistakes (应敢于修正错误), if the viewpoint is erroneous through the test of discussion and contending or through the test of practice.④We should be patient(应有耐心),because some problems and mistakes may not be solved by one or two papers or one or two academic discussions and contendings, and may be finally solved by geological practice. Practice is a sole criterion to solve academic controversy.

However, one or two good papers which observed to the above rules can play an important role in resolving problems and correcting mistakes.

I will be willing to observe the above rules together with the readers and authors who are willing to participate in the discussion of “A hundred flowers blossom and a hundred schools of thought contend.”

9.Conclusions

1)In recent years,the Journal of Palaeogeography(Chinese Edition and English Edition) continually received manuscripts in which the authors, according to the viewpoint and method of Miall's paper (1985),selected rocks from each bed in the clastic section of their study areas, presented some rock types and considered them as lithofacies. It did not conform to the definition of lithofacies.

2)Miall is the first person who selected rocks from each bed in the clastic section of his study area,induced some sediment types and considered them as lithofacies.These lithofacies are isolated and without consecutive order of his section from the lower to upper. Utilizing these lithofacies to analyze facies is illogical. It is impossible to identify the facies and impossible to identify the evolutionary regularity of facies of the whole stratigraphic section in his study area. His facies analysis method confused the normal facies analysis.

3) What is the definition of facies?

In section 4 of my current paper, I proposed 5 sentences as my definition of facies today.

My definition of facies is the succession and development of Pyx(1953), Mineralogy and Petrology Section of Beijing Petroleum Institute(1961),etc.

4) What is the definition of lithofacies?

Editorial Committee of A Dictionary of Earth Sciences (2006) proposed the definition of lithofacies:“Lithofacies refers to the facies of sedimentary rocks.It reflects the features of a certain sedimentary environment, including the physical, chemical (mineralogical and petrological)and biological features,such as a glauconitic sandstone facies of marine strata in the Paleozoic which reflected shallow sea environment”.

I agree with this definition of “lithofacies”.

The “facies”, “sedimentary facies” and “lithofacies”are synonymous terms.

5) What is the definition of lithology

In my mind the term lithology is defined as features, characters, properties of sedimentary rocks. It is not lithofacies.

I disagree with the viewpoint which Moore (1949)considered lithofacies as lithology.

6)My facies analysis methodology is“Single factor analysis and multifactor comprehensive mapping method”. It is a measure to the aim which is to compose quantitatively palaeogeographic map and to be predictive for exploration of petroleum and other mineral deposits.It is different from“the new method of facies analysis applied to fluvial deposits”of Miall's paper (1985).

7) A published paper does not only belong to the authors, but also belong to scientific domain. If this paper is problematic,we can adhere to the policy of“A hundred flowers blossom and a hundred schools of thought contend”to discuss and query it.

8) I hope that Prof. Miall can acknowledge the problems of his definition of facies and facies analysis method. Acknowledgement will be the beginning of new progress. Let us work together to make new contributions to sedimentary petrology, especially to fluvial deposits.

Funding

No fundings.

Availability of data and materials

The datasets used during the current study are available from the corresponding author on reasonable request.

Authors' contributions

ZZF drafted and revised the manuscript according to reviewers’ comments.

Competing interests

The author declares that he has no competing interests.

Acknowledgements

I heartily thank Yuan Wang,the Associate Editor-in-Chief of the Editorial Office of Journal of Palaeogeography (English Edition), and Dr. Xiu-Juan Zheng,the Standing Associate Editor-in-Chief of the Editorial Office of the Journal of Palaeogeography (Chinese Edition).They examined and corrected my English and Chinese manuscripts carefully and offered many suggestions.I also heartily thank Ms Ya-Jing Liu who is the typist of my English and Chinese manuscripts and typed my manuscripts more than 10 times. Without their support,it would be very difficult for me to complete these manuscripts.

I especially thank reviewers,Prof. Peter Druschke and Prof. G. Shanmugam for their comments which improved the quality of my English manuscript and the polishing of its English,especially“the speaking should be polite”. Best wishes to these reviewers.