7/30/2019 Fieldwork Checklist

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FIELD NOTES INCLUSION LIST

1. Stratigraphic name of the unit, or its relations to named units.

2. Area to which description applies.

3. Nature of the terrain underlain by the unit-its topography, soils, vegetation, and outcrops.

4. Overall shape or structure of the rock unit in this area.

5. Thickness of the unit.

6. Principal kinds of rocks and their distribution in the unit.

7. Unusual rocks and their stratigraphic (or other) position and genetic implications.

8. Primary structures in the unit.a. How bedding or other layer-structures (as flow structures) are expressed, as by

color, texture, indurations, and so on.

b. Range of thicknesses and typical thicknesses of beds or other primary layer-

structures.

c. Shapes of beds or other layer-structures.

d. Primary structures within beds or other structures, as grading, laminations, cross-

stratification, channeling, and inclusions.

9. Fossils. a. Distribution of fossils, stratigraphically and laterally. b. Special characteristics of 

the more fossiliferous rocks. c. Positions and condition of fossils, as growth position,

fragmental, rounded, and any signs of reworking (Section 3-7).

10. Description of rocks, most abundant kind first.

a. Color-fresh, weathered, moist, dry (Appendix 6).

b. Firmness of fresh and of weathered rock (Appendix 4).

c. Grain sizes- range and average (or typical) sizes.d. Degree of sorting or equigranularity.

e. Typical shapes of the principal kinds of grains.

f. Fabrics (orientations) of tabular or linear grains, especially in relation to rock

structures.

g. Kinds and proportions of mineral cements, matrix, or groundmass.

h. Nature and proportion of pores (porosity) and indications of permeability. Kinds of 

grains and the approximate percent by volume of each.

11. Contacts (Fig. 3-1).

a. Sharp or gradational (describe gradations).

b. Indications of scour, unconformity, intrusive relations, or faulting.

c. Criterion or criteria for locating the contact in the field.

12. Characteristic secondary features, such as cleavage, concretions, veins or other fillings,

presence of hydrocarbons, and deformational structures, including joints.

13. Characteristics that are particularly useful in distinguishing this unit from all others in the area.14. Interpretation of the unit.

a. Geologic environment or conditions under which the unit was originally deposited or 

crystallized

b. Specific processes contributing to its origin.

c. Genetic relations to associated rocks.

d. Later modifications within the rock at grain-scale, as cementation, compaction,

autometamorphism, and recrystallization.

e. Tectonic and other structural modifications, as folding (Section 12-3), fracturing

(Sections 12-4, 5, and 6), and homogeneous strains (Section 12-2).

f. Geologic age of the unit or age relations to other rock units.

FIELD WORKFLOW

1. Look over the outcrop and nearby outcrops broadly in order to spot the principal bodies of 

rock or other materials. Do they end against faults, intrusive contacts, or unconformities?

2. Continue to study the outcrop from a moderate distance. Are the rock bodies tabular,

irregular, lenticular, or with some other distinctive shape? What are their orientations and

dimensions? If they are internally layered, are the layers parallel to any of their bounding

surfaces? In overall view, do any rock bodies appear variable? Do any contain fragments?

3. Now study the boundaries (contact surfaces) between the bodies, both at a moderate

distance and up close. Are they sharp or gradational? Do they cut across grains or structures

in either adjacent body? Do any rocks or deposits vary in color or texture near thesecontacts?

4. Break off, or scoop up, samples of the main materials, and examine weathered as well as

fresh surfaces and identify the rock or material Even if it seems obscure, give it a provisional

name.

5. Now examine the rocks closely for primary fabrics and structures. Look especially for 

structures that establish tops and bottoms of deposited layers that were once sediments or 

igneous deposits (Section 9 10). Do relations at contacts support these indications of 

sequence?

6. Look for all features indicative of depositional current direction or direction of magmatic flow.

Measure a number of them in order to judge their consistency

7. To detect deformation, see if rock layers, veins, or planar structures have been folded

(Section 12 3). If no folds are obvious, perhaps foliations, cleavages, or lineation indicate

folding

8. Whether the rocks are folded or not, examine them for grains or other small bodies that havebeen deformed into planar or linear shapes that give a measure of deformation. How are

these grains oriented relative to other structures?

9. Examine all faults, even those that displace rocks as little as a centimeter. Are there gouges

or breccia along them? Any indications of actual directions of displacement (Section 12-5)?

 Are the faults younger than other tectonic features?

10. To determine the physical state of the rocks, especially if they are sedimentary, test the

degree of compaction and cementation by hefting dry samples (porous rocks are lighter than

nonporous ones), by their reaction to breaking in the hands and to hammer blows (Appendix

4), and by the rate they soak up water. Porous fine-grained rocks tend to stick to the tongue.

Depth and strength of weathering generally increase with porosity and permeability.

11. What are the typical spacing and orientations of joints in the different rocks? Are there

secondary color changes, and are they related to fractures? Fracturing and weathering

characteristics may help in identifying the same rock unit in other outcrops (see the

subsection that follows).12. Bring together all observations made thus far in order to identify rocks and structures that

were originally obscure, or to refine identifications.

13. Systematically measure and record: (a) the thickness of each layered unit of rock; (b)

structural attitudes of all primary structures, as bedding; and (c) attitudes of all secondary

features, as folds and faults (Sections 3-5 and 3-6).

14. Make a thorough search for fossils

15. Collect rocks that seem particularly useful, either as typical samples or to resolve

identifications

16. Before interpreting the various rocks and structures, be sure that you have observed all

possible indications of relative ages of the rocks in the outcrop.