This document provides guidance on techniques for acquiring sedimentological data from clastic rocks, including sedimentary logging. The key points covered include: 1. The essential equipment needed for sedimentary logging includes a notebook, measuring tools, and grain size comparator. 2. An important initial step is selecting a representative logging route that is physically accessible and shows continuity. 3. Descriptions of lithological units like mudstones and sandstones involve semi-quantitative scales for aspects like bioturbation. 4. Logs are plotted using scales for lithology, thickness, and grain size. Sedimentary structures are coded onto the log. 5. Example logs and exercises are provided to demonstrate plotting techniques and

1. Techniques to acquire
sedimentological data on clastics
Basics of sedimentary logging, examples of logs,
‘chequer’ plots (exercises)

2. What is needed to make
a sedimentological log?
1 – A trained person
2 – Notebook and pencil
3 – Measuring stick/tape
4 – Geological compass
5 – Grain-size comparator
6 – Drafting paper

3. The first important decision to make:
The selection of a logging route
A
B
C
D
Selection criteria:
• Representative for the studied succession/area
• Physically accessible (without an excessive risk)
• Maximum continuity (minimum gaps, preferably no faults)

4. Logging from well cores
What is a drilling core?

5. Logging from well cores
What is a drilling core?

6. Logging from well cores
What is a drilling core?

7. Logging from well cores
What is a drilling core?

8. Logging from well cores
What is a drilling core?

9. Description of a mud/mudrock unit
Semi-quantitative
scale is used

10. Types of heterolithic bedding
Useful graphic scheme
for log plotting

11. Semi-quantitative scale of bioturbation

12. Description of a sand/sandstone unit
Ripple cross-lamination
LARGE-SCALE PLANAR/TROUGH
CROSS-STRATIFICATION
SMALL-SCALE PLANAR/TROUGH
CROSS-STRATIFICATION

13. Description of a gravel/gravelstone unit

14. The plotting of log

15. The selection of the log scale
The log scale to be used is the second important decision to make. The choice
of vertical scale depends on the thickness of the thinnest bed that we wish to
show graphically to scale in the log:
The smallest recognizable line-spacing acceptable for the log graphics (say, 1 mm)
Thickness of the thinnest bed/unit to be shown ‘to scale’ in the log graphics (in mm)
For example: If the thinnest bed to be shown to scale is 10 cm (= 100 mm) and
we want it to be no thinner than 2 mm in our log drawing, then the
appropriate scale is 2/100 or 1:50.
Log scale =
Important decision to make

16. Lithology column
Thickness scale
(stratigraphic height
or depth)
Grain-size scale
Mud
Sedimentological
information
(column)
The plotting of log

17. 17
DESCRIPTIVE WORKSHEET
(the scheme must respect a pre-fixed scale or
rappresentation: es.: 1:50, 1:100 …)

18. How to use the grain-size scale to plot the log
clay silt
mud
(clay/silt)
v.fine sand
silt/v.fine sand (silty or ‘lower’ v.fine sand)
fine sand
v.fine/fine sand or ‘lower’ fine sand
medium sand
fine/medium sand or ‘lower’ medium sand
medium/coarse or ‘lower’ coarse sand
coarse sand
v. coarse sand
coarse/v.coarse or ‘lower’ v.coarse sand
v.coarse sand/granules or fine granule gravel
granule gravel
pebble gravel
granule/pebble gravel or fine pebble gravel
cobble gravel
pebble/cobble gravel or fine cobble gravel
boulder gravel
cobble/boulder gravel or fine boulder gravel
This is just to not have the clay plot too narrow.
The scale practically begins here.
Lithology
column
Sedimentological information

19. 19
How to code the sedimentological information

20. How to code the other information

21. A graphically coded, easy-to-read
complete descriptive information
The sedimentological log

22. Log examples

23. Caliper
Gamma Neutron
Density
Log examples

24. Log examples

25. Logs with facies ’chequer’ plots

26. Logs with facies ’chequer’ plots
The main advantages of chequer plot:
• Serves as a guide to the facies location in the log.
• Gives an overview of the vertical facies distribution in the succession.
• Helps to describe facies.
• Helps greatly to distinguish facies associations.

27. Exercises

28. Exercise 1

29. Exercise 1
The formula for log scale
In our case:
The thinnest units in the log data sheet are mudstone beds 10 cm in thickness.
To show such a bed graphically in the log, we don’t need more 2 mm thickness.
2 mm
Log scale = = 1/50
100 mm
Scale 1:50 means 2 cm in log = 1 m in outcrop

30. Exercise 1
22 cm will be needed

31. Exercise 2

32. Mudstone
Sandstone with planar
parallel stratification
Sandstone with trough
cross-stratification
Sandstone with tangential
planar cross-stratification
Sandstone with angular
planar cross-stratification
Sandstone with trough
cross-lamination
Sandstone with planar
cross-lamination
A
B1
B2
C1
C2
D
E
A B1 B2 C1 C2 D E
Flow power
Exercise 2
11
13
7
2
1
3
4
5
6
8
9
10
12
14

33. APPENDIX

34. Bedforms and sedimentary structures produced by unidirectional current
(hydraulic bedform stability diagram)

35. Bedforms and sedimentary structures
produced by waves (oscillatory current)
Bedforms and sedimentary structures produced by
combined flow (waves + unidirectional current)
Hummocky cross-stratification
Swaley cross-stratification
Combined-flow ripple cross-lamination
Planar parallel stratification

36. Bedforms produced by waves and combined flow
WAVES ONLY
Planar parallel stratification
Wave ripple cross-lamination
Plane-bed transport
3D wave ripples
2D wave ripples
Wave ripple cross-lamination
Rolling-grain ripples
”Wispy” subparallel lamination
COMBINED FLOW
(WAVES + UNIDIRECTIONAL CURRENT)
Ripple-scalebedforms
(≤~7cminrelief)
(No dune-scale bedforms)
Combined-flow 2D ripples
Combined-flow ripple cross-lamination
Combined-flow 3D ripples
Combined-flow ripple cross-lamination
Isotropic HCS
Moderately anisotropic HCS
Strongly anisotropic HCS
UUC > UO
Swaley cross-stratification
Sedimentaccretiondominates
3D wave scour-and-fill
Planar parallel stratification
Plane-bed transport (domination of
strong waves or strong current)
INCREASINGROLEOFCURRENT
Ripple-scalebedforms
(≤~7cminrelief)
Dune-scalebedforms
(>~7cminheight)
UUC > UO
UUC < UO
UUC ≈ UO
UUC < UO
2D
3D
3D
3D
transition

37. Subaqueous sediment-gravity
flows and their deposits
(modified from Mutti, 1992)
*HDTC = TC that showed evidence of excess sediment concentration manifested by
rapid, non-tractional deposition in the form of Bouma a-division or traction
carpet (Lowe 1982).
non-graded
Bouma notation: Tace Tabcd Tbcde Tcde Tde
*
graded at least in upper
part
....

38. Stratigraphic correlations
How to compile a 2-D log correlation panel
(exercises)

39. A STRATIGRAPHIC CORRELATION is a 2-D reconstruction of thicknesses and surfaces among
two or more sedimentological logs acquired in the same lithostratigraphic units.
Before to correlate logs, we need a DATUM which must be recognized in every logs.
Correlation on facies level

40. Log correlation panel
Correlation on facies-association level

41. Logs as a facies documentation for schematic cross-section

42. Exercise 3

44. Depositional architectures in
clastic systems
Main architectural elements (strata, stratasets,
stratal terminations, bounding surfaces)

45. What DEPOSITIONAL ARCHITECTURES are?
They are physical elements observable at different scales within the sedimentary bodies,
including stratal geometries, bounding surfaces, discontinuities, etc. that are useful to
describe the geometries of the various composing units.
Why DEPOSITIONAL ARCHITECTURES are so important?
Depositional architectures are important for several reasons:
(i) they allow us to reconstruct the sedimentary dynamics of ancient systems (i.e.,
sediment accumulation rate, energy of the depositional environment, directions of
the paleo-flows, rates of progradation vs. aggradation, position and role played by
the relative sea-level, etc.);
(ii) they help us in recognising the nature of the investigated systems (i.e.,
continental, transitional, shallow-marine vs. deep-marine, etc.);
(iii) they indicate important elements in the analysis of the sedimentary basin
including them;
(iv) they have important implications in the assessment of reservoir potentials;
(v) they are useful in the comprehension of their modern analogues.

46. In Stratigraphy and Sedimentology, the assessment of depositional geometries is a common
and widely used approach. Bounding surfaces, bed-set geometries, bed aspects, sedimentary
structures, etc. are usually detectable in cross-sectional stratigraphic windows, starting from
a bi-dimensional evaluation. A conventional way to obtain an exhaustive framework on bi-
dimensional depositional architectures is the so-called ‘line-drawing’, which is a
straightforward method that can be carried out by using common graphic softwares on high-
resolution photographs or photomosaics of the investigated outcrops.
50 m
1 m 1 m

47. However, this approach has several limitations, due to the incomplete exposure of the
outcrops, ‘parallax’ errors and resolution potential of the used camera and the two-
dimensionality of three-dimensional objects. In order to improve the potential effectiveness
of this approach, in the last years a number of new technologies have increasingly been
employed, including Laser Imaging Detection and Ranging (LIDAR), high-resolution
photograph acquisitions and flying drones. These methods allow a more comprehensive and
three-dimensional visualization of exposed geological bodies and integrate all the limitations
deriving from the older photo-based outcrop analyses.

48. Product: Prediction of Rock Types
– Sand within reservoir intervals
– Shale in overlying seal intervals & source intervals
Seismic Stratigraphic Analysis
– Define key stratigraphic intervals
– Determine the rock types within each interval
Seismic Facies Analysis
Input: Seismic Data (2D or 3D)
ExxonMobil course short notes
• Seismic Sequence Analysis
• Seismic Facies Analysis

49. Definitions
Seismic Facies Unit
a mappable, three dimensional seismic unit composed of
groups of reflections whose parameters differ from those
of adjacent facies units.
Seismic Facies Analysis
the description and geologic interpretation
(environmental setting, lithofacies, etc.) of seismic
reflection parameters.
ExxonMobil course short notes
Mitchum et al., 1977

50. Reflection Features Used in Mapping
ExxonMobil course short notes
Feature Significance
Reflection
Geometry
• Depositional Processes
• Bed Thickness
• Fluid Content
Wavelet
Frequency
• Lateral Stratal Continuity
• Depositional Processes
Reflection
Continuity
• Impedance Contrasts
(significant stratal surfaces)
• Bed Spacing / Tuning
• Fluid Content
Seismic
Amplitude

51. seismic analysis
distinction of
seismic facies
Interpretation
(assigning an
environmental
connotation)
Identification of
the dominant grain
size/lithology
- Line-drawing of the
main reflectors;
- Distinction between
stratigraphic and
structural contacts;
- Identification of the
main reflector
terminations (strata
terminations).
Shallow-
marine
(deltaic)
Continental
(fluvial braidplain)
Deep-marine
(transgressive-
shoaling-up)
TRANSGRESSIVE
SURFACE
EROSIONAL
SURFACE
MUDSTONE
CONGLOMERATE
SANDSTONE
SANDSTONE
- General analysis of the
seismic section;
- Comparison with eventual
crossing lines;
- Comparison with previously-
interpreted seismic
data/geological profiles.
CONGLOM.
Four main phases of procedure in the seismic interpretation
- Sequence-stratigraphic
interpretation;
- Recognition of the
meaning for the main
bounding surfaces;
- Systems tract and
possible depositional
environments/systems.
- Partition in lithological
units;
- Many possible
hypothesis.

53. Seismic geometries and reflector (stratal) termination
down-lapon-laptop-lap
off-lap
Top-lap: upper reflector
termination due to erosion
On-lap: lateral reflector
termination onto an inclined basal
surface
Downp-lap: downward/lateral
reflector termination onto a
sligthy inclined or sub-horizzontal
basal surface
Off-lap: upper reflector
termination (no erosion).

54. Exercise 4

56. Basin-scale architectures
Outcrops and seismic line-drawing
on clastic rocks (exercises)