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+Geology Resources: Common Types of Geologic Information Sources

Journal Articles

There are two types of scholarly journal articles that you are likely to come across, research articles (sometimes called primary sources) and review articles.  Both of these types of articles are peer-reviewed, and both types tend to look the same at first glance: they have an abstract and introduction, a concluding section, and a bibliography.

Both research and review articles are usually published in what are referred to as peer-reviewed journals.  You might also hear the term "scholarly journal" or "refereed journal", these all refer to the same thing.

The goal of peer review is to have other experts (reviewers) assess the quality of the research and the article before it is published.  During the peer-review process, reviewers will:

  • assess the validity of the research methods and procedures
  • evaluate the article for quality and accuracy
  • provide feedback and comments for the authors

The peer-review process is intensive and lengthy. It means that new research can take a while before it's published, but it also provides an assurance of best research practices.

Research articles

Research articles are generally the main way that new research results and interpretations are communicated in the field of geology.  Research articles will focus on one study to answer a research question.  These articles tend to be very narrowly-focused and written for geologists in that particular field.  Research articles are usually published in scholarly journals, but are sometimes collected in edited volumes (see below).

Identifying Research Articles

  Some of the main features of a research article are:

  • The abstracts often talk about performing a study or conducting an investigation.
  • There will probably be a literature review in the introductory section of the paper, but that is to provide context and is not the main focus.  .
  • Methods section that explains how the research was conducted
  • Results section that talks about all the data collected and a discussion of those results

Grasemann, B. and Stüwe, K., 2001, The development of flanking folds during simple shear and their use as kinematic indicators:
Journal of Structural Geology, v. 23, p. 715-725, doi:10.1016/S0191-8141(00)00108-5.

screenshot of the top half of the pdf of the research article, "The development of flanking folds during simple shear and their use as kinematic indicators." The abstract is: "We used a numerical finite element simulation to model the formation of flanking folds around rotating planar structures (e.g. veins, faults or dykes) in a non-linear viscous medium during ideal simple shear. If the planar structure is much more viscous than its host it does not deform and flanking folds with no displacement along the structure develop. Their vergence is consistent with the overall sense of shear. However, if the planar structure is much less viscous than its host, strain is concentrated within the structure and a secondary shear zone is developed in which slip is opposite to the overall sense of shear. Then, flanking folds develop that have a vergence, which is incompatible with the drag on structure. If the deflection of markers is not clearly preserved, then such flanking folds can be easily misinterpreted as shear bands indicating a wrong shear sense. The deflection of the foliation in flanking folds is very similar to deformed asymmetric pull-aparts and can therefore help to interpret these otherwise ambiguous shear sense criteria. Because our model (ideal simple shear boundary conditions) fails to describe back-rotation of planar structures in rocks we speculate that shear band geometries are indicative for general shear.."

Notice in the abstract, they start off explaining the modeling methods they use in the study. They describe a narrow question and how they answered it.  This is indicative of a research article where they are reporting their original results of research.

Review Articles

Review articles, sometimes called literature reviews, pull together the research and conclusion of many research articles on the same topic.  The review article synthesizes and analyzes those studies and summarizes the current state of research and suggests directions for future reearch.

Review articles are a great way to get a better understanding of the existing research on a topic, identify research questions you would like to explore and find relevant sources.

Identifying Review Articles

In review articles:

  • Many (not all) have the word "review" in the title or the abstract or the journal title.
  • The abstracts often talk about summarizing existing evidence
  • The articles often do not include a methods section, or if there is a methods section, the section discusses how the literature was found.
  • The focus is often on summarizing and analyzing a broad set of questions related to a research area.
  • The bibliographies tend to be very long and comprehensive

Hudleston, P.J. and Treagus, S.H., 2010, Information from folds: A review: Journal of Structural Geology, v. 32, p. 2042-2071, doi:10.1016/j.jsg.2010.08.011.
screenshot of the top part of the pdf of the article "Information from folds: A review." The abstract reads: "Folds are spectacular geological structures that are seen in layered rock on many different scales. To mark 30 years of the Journal of Structural Geology, we review the information that can be gained from studies of folds in theory, experiment and nature. We first review theoretical considerations and modeling, from classical approaches to current developments. The subject is dominated by single-layer fold theory, with the assumption of perfect layer-parallel shortening, but we also review multilayer fold theory and modeling, and folding of layers that are oblique to principal stresses and strains. This work demonstrates that viscosity ratio, degree of non-linearity of the flow law, anisotropy, and the thickness and spacing distribution of layers of different competence are all important in determining the nature and strength of the folding instability. Theory and modeling provide the basis for obtaining rheological information from natural folds, through analysis of wavelength/thickness ratios of single layer folds, and fold shapes. They also provide a basis for estimating the bulk strain from folded layers. Information about folding mechanisms can be obtained by analysis of cleavage and fabric patterns in folded rocks, and the history of deformation can be revealed by understanding how asymmetry can develop in folds, by how folds develop in shear zones, and how folds develop in more complex three-dimensional deformations."
In this review article, you can see a few clues that it is a review: the title has the word "review" in it, the topic is relatively broad, and the abstract talks about reviewing the topic.

Gray Literature

Gray Literature

Gray literature is kind of a "catch all" term that refers to types of research that are either unpublished or have been published in noncommercial forms.  While some gray literature is available on the web, be aware that some may be hard to get a hold of.

Gray literature can be very important in geology, so it's a good idea to understand what is out there and how to find it.

Examples of gray literature include:

  • Government reports, including national and state geological survey reports
  • Conference proceedings
  • Geological and geophysical surveys
  • Industry reports
  • Field trip guide books
Advantages of Gray Literature
  • Timeliness: Results of studies may appear in gray literature 12 to 18 months before being published via traditional channels.
  • Flexibility: Rather than waiting years for the publication of a revised edition, authors, editors, and web content creators can update the information when needed.
  • Accessibility: There is a great abundance of gray literature that is freely available, either in print or on the web.
Disadvantages of Gray Literature
  • Credibility: Since gray literature is rarely peer-reviewed, it can be harder to assess its reliability.  
  • Accessibility: While much of the gray literature is available on the web, some pieces may be difficult to find. This is especially true for field trip books
  • Findability: Much of the gray literature is not indexed in library catalogs or databases, so even if it is available on the web, it can be hard to find.


A lot of geologic information is shared on websites.  When you're looking for websites, you'll want to think critically about who is responsible for that website and whether that makes them a credible source.  This isn't always easy as some websites don't share that information, so you may need to dig a bit.

Generally, government agencies that are responsible for geologic information, professional geologic societies, and geology departments at universities are considered credible sources.


You can categorize scholarly geology books into two main categories: edited volumes and monographs.

Edited Volumes:

These books function more as collections of research articles around a single topic.  You will notice that the volume will have an editor or editors, and each chapter is written by a different group of authors.  The editors are experts in the topic who organize but do not write each chapter.  Each chapter will look like a research article that you would find in a journal, with an abstract, methodology, results, conclusions, and a bibliography.  Many of these undergo peer-review.


screen shot of the first page of a chapter in the edited volume. The title is "Optimal use of multibeam technology in the study of shelf morphdynamics" by John E Hughes Clarke.  The first page has an abstract and the beginning of the Introduction section.Here is what the first page of one of the chapters looks like, it looks almost exactly like a journal article, there is an abstract and the Introduction section. If you continue to read the article, you'll find method, conclusions and a lengthy bibliography:


Monographs are full books written on a topic, usually with one or just a few authors.  Unlike the edited volumes that pull together related works all written by different people, the chapters in the monograph are all written by the same authors and are generally meant to be read as a whole.  The authors are experts in the area, but they're not reporting new research results.  Instead, they are providing a more comprehensive overview of the topic.  Books like these can give you a good broad understanding of a topic, but they will not have the latest research because monographs can take quite a long time to publish.


screen shot of the first page of chapter 3: Phanerozoic Granites.  The page has one section heading : 3.1 Occurrence.Here is what the first page of one of the chapters in this book looks like.  It has a chapter title and section headings, but no author listed (becuase the author Sung Kwun Chough has written all the chapters of this book) and no abstract.  If you continued to read this chapter, you will find information about phanerozoic granites, but not a report of a specific research study. There are no results or conclusions or bibliography.