Determining Spatial Orientation of Rock Layers with the Brunton Compass

Обзор

Source: Laboratory of Alan Lester - University of Colorado Boulder

Most rock units exhibit some form of planar surfaces or linear features. Examples include bedding-, fault-, fracture-, and joint-surfaces, and various forms of foliation and mineral alignment. The spatial orientation of these features form the critical raw data used to constrain models addressing the origin and subsequent deformation of rock units.

Although now over 100 years since its invention and introduction, the Brunton compass (Figure 1) remains a central tool in the modern geologist’s arsenal of field equipment. It is still the primary tool used to generate field data regarding the geometric orientation of planar rock surfaces or linear rock features. These orientation measurements are referred to as strike and dip, and provide the fundamental data for making geologic maps. Furthermore, the Brunton Compass can also function as a traditional compass for location exercises and triangulation. Finally, it can also serve as a pocket transit for measuring angular elevations.

Figure 1
Figure 1. The Brunton compass.

Процедура

1. Preparation

  1. Check for free needle motion. Verify that the needle is unimpeded when held in the horizontal plane. Some compasses have restrictor buttons that hold the needle in place, and if present, check to see that pushing the restrictor does not move the needle.
  2. Check the “bull’s eye bubble” centering and continuity. This bubble is one of two leveling bubbles and is used to determine horizontality of the compass. The other bubble is used for inclination measurements.
  3. Log in or to access full content. Learn more about your institution’s access to JoVE content here

Результаты

A set of strike and dip data for a non-dipping rock layer has a range of values. The precision of a single measurement is, of course, linked to mechanical compass-errors and the experience of the compass-user. The accuracy of the final analysis is dependent on the uniformity of the natural surface (many nominally “flat-lying” rock layers have some degree of inherent surface undulations) and the number of total measurements taken.

Strike and dip data are initially recorded in field notebooks, and then tran

Log in or to access full content. Learn more about your institution’s access to JoVE content here

Заявка и Краткое содержание

Geologists strive to understand the earth in four-dimensions. The goal is to interpret the structure of rocks on the surface, in the subsurface, and through time. Strike and dip information generated by the Brunton Compass is the starting point with which geologists make geologic maps, and then those maps can be used to make cross sectional diagrams, showing the structures in the subsurface (Figure 6).

Understanding rock structures in the three spatial dimensions and also through time provides a window on the physical

Log in or to access full content. Learn more about your institution’s access to JoVE content here

Теги
Brunton CompassGeologySpatial OrientationRock LayersField DataStrike And DipCompass ComponentsGeologic MapsMeasurement TechniquePlanar Surface StructureBeddingDip AngleStrike Angle

Перейти к...

0:00

Overview

0:59

Principles of the Brunton Compass

1:49

Setup of the Brunton Compass

2:42

Collection of Measurements

3:52

Results

4:33

Applications

5:18

Summary

Видео из этой коллекции:

article

Now Playing

Determining Spatial Orientation of Rock Layers with the Brunton Compass

Earth Science

25.3K Просмотры

article

Using Topographic Maps to Generate Topographic Profiles

Earth Science

31.9K Просмотры

article

Making a Geologic Cross Section

Earth Science

46.8K Просмотры

article

Physical Properties Of Minerals I: Crystals and Cleavage

Earth Science

51.5K Просмотры

article

Physical Properties Of Minerals II: Polymineralic Analysis

Earth Science

37.9K Просмотры

article

Igneous Volcanic Rock

Earth Science

39.5K Просмотры

article

Igneous Intrusive Rock

Earth Science

32.3K Просмотры

article

An Overview of bGDGT Biomarker Analysis for Paleoclimatology

Earth Science

5.4K Просмотры

article

An Overview of Alkenone Biomarker Analysis for Paleothermometry

Earth Science

7.2K Просмотры

article

Sonication Extraction of Lipid Biomarkers from Sediment

Earth Science

7.7K Просмотры

article

Soxhlet Extraction of Lipid Biomarkers from Sediment

Earth Science

18.4K Просмотры

article

Extraction of Biomarkers from Sediments - Accelerated Solvent Extraction

Earth Science

7.9K Просмотры

article

Conversion of Fatty Acid Methyl Esters by Saponification for Uk'37 Paleothermometry

Earth Science

10.1K Просмотры

article

Purification of a Total Lipid Extract with Column Chromatography

Earth Science

12.3K Просмотры

article

Removal of Branched and Cyclic Compounds by Urea Adduction for Uk'37 Paleothermometry

Earth Science

6.4K Просмотры

JoVE Logo

Исследования

Образование

О JoVE

Авторские права © 2025 MyJoVE Corporation. Все права защищены