Lithology. The study and description of the physical character of rocks, particularly hand samples and outcropsRefers to the physical characteristics: rock type, color, mineral composition, grain size, lithological characteristics. Historical Principles. Nicolaus StenoDanish Physician1638
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2. Lithology The study and description of the physical character of rocks, particularly hand samples and outcrops
Refers to the physical characteristics: rock type, color, mineral composition, grain size, lithological characteristics
3. Historical Principles Nicolaus Steno
1638 – 1687
4. Steno’s Second Principle Principle of Original Horizontality
5. Steno’s Third Principle Principle of Original Lateral Continuity
6. Steno’s Laws (Principles) Foundation for Stratigraphy
7. Lithostratigraphic units Stratotype – a designated type unit or type section
Lithosome – mass of rock of essentially uniform character and having intertonguing relationships with adjacent masses of different lithology. (lithology)
8. Rock Units Lithostratigraphic units
9. Stratrigraphic relationships Contacts
11. Conformable contacts Abrupt contacts
Progressive gradual contacts
Intercalated contacts – increased number of thin interbeds.
13. Contacts between laterally adjacent lithosomes Pinch-outs
Progressive lateral gradation
See Figure 12.1
15. Unconformity Diastem – little hiatus, little or no erosion, minor depositional break
Hiatus – that part of a lacuna that is represented by nondeposition
Cavity, hole or gap
Unrecorded stratigraphic record at an erosion surface, consisting of (a) the record destroyed by erosion = erosional vacuity (b) the record never represented by strata = hiatus
16. Types of Unconformities Angular unconformity
18. Angular unconformity
19. Disconformity plus
20. Vertical successions of Strata Cyclic successions
Rhythmic sedimentation – Rhythmites
Autocyclic sucessions – controlled by processes within the basin
Storm beds, turbidites
Allocyclic sucessions – caused by variations external to the depositional basin
Changes in climate – eustatic sea level changes
Larger area of influence
21. Allocyclic Succession scales First-order cycles – Eustatic cycles, 200-500 million years
Too large to see in normal outcrop, large sets of data and outcrops or subsurface data
Major tectonic episodes, construction of Pangea, major continental rifting.
22. Second – order cycles
Icehouse states – cool periods
Greenhouse states – warm periods, greenhouse gases, CO2 were abundant.
Transgressive sequences – cratonic sequences.
10 to 100 of millions of years
24. Third-order cycles
Episodicities on the order of 1 to 10 million years
25. Bed-scale cycles
Less than 1 million years, 0.2 to 0.5 million years, 200,000 to 500,000 years
26. Fifth-order scales
0.01 to .2 million years
10,000 years to 200,000 years
27. Milankovitch cycles
28. Orbital Forcing Link between orbital cycles, climate, and sea level
Quaternary deposits, back to Miocene
29. Cyclostratigraphy Relationship of strata to the various cyclic sedimentation causes
30. Facies A stratigraphic body as different appearance or composition, general appearance or nature of one part of a rock body as contrasted with other parts.
Lithofacies – ss, ls, cong, silt, sh
Biofacies – fossil content – no lithology
Subfacies – subdivisions of facies
Microfacies – thin section facies
31. Law of the correlation (or succession) of facies Walther’s Law
32. Walther’s Principle A conformable vertical sequence of facies was generated by a lateral sequence of environments.
33. Lateral Succession
34. Lithofacies changes Onlap = Transgression
Fining upward sequence
Offlap = Regression
Coarsening upward sequence
35. Sea level changes Eustatic Sea-level changes – world wide sea level changes
Relative sea-level – eustatic to regional
36. Mechanisms of sea-level change Ocean steric (thermohaline) volume changes – on the order of 1 m.
Glacial accretion and wastage – 1 to 10 m.
Liquid water on land – generally less than 1 m.
Crustal deformation – 1 to 100 m.
37. Major types of stratigraphic units Lithostratigraphic units
Table 12.3 you can read and know these.
38. Correlation Demonstration of equivalency of stratigraphic units
Physical characteristics to match equivalent beds or units
Lateral continuity – trace bed or laminae from area to area
Lithologic similarity – unique kinds of rocks
Sequence of beds – multiple units used by their sequence.
Geophysical characteristics – seismic, electrical logs, sonic, radioactive, magnetic properties
39. Correlation Lithocorrelation – similar lithology, stratigraphic position
Marker beds, key beds
Biocorrelation – fossil content
Chronocorrelation - age
41. Electric logs
42. Electric log