Comparative Records of Time • Nature of the rock record • principles of stratigraphy: • deposition, succession, continuity and correlation • Stratigraphic tools • biological succession of life: biostratigraphy • magnetic reversals: magnetostratigraphy • progression of sedimentary rocks from changes in sea level: sequence stratigraphy • temporal excursions and sequential changes in chemical characteristics: chemostratigraphy G302 Development of the Global Environment Relative Age Dating Relative Age Dating Depositional Succession • Sedimentary rocks • deposited as beds or horizons in rock units • record and preserve depositional events • beds often discontinuous • beds can be eroded or lost • result: a gap in the temporal record known as an unconformity or hiatus G302 Development of the Global Environment Principles of Stratigraphy Principles of Stratigraphy continuous deposition erosion for 50 years renewed deposition 100 years of sediment 150 year gap resultant rock record unconformity 150 years = 100 years lost + 50 years of erosion
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Comparative Records of Time• Nature of the rock record
• principles of stratigraphy:• deposition, succession, continuity and correlation
• Stratigraphic tools
• biological succession of life: biostratigraphy
• magnetic reversals: magnetostratigraphy
• progression of sedimentary rocks fromchanges in sea level: sequence stratigraphy
• temporal excursions and sequential changes inchemical characteristics: chemostratigraphy
G302 Development of the Global Environment
Relative Age DatingRelative Age Dating
Depositional Succession• Sedimentary rocks
• deposited as beds orhorizons in rock units
• record and preservedepositional events
• beds often discontinuous
• beds can be eroded or lost• result: a gap in the
temporal record known asan unconformity or hiatus
G302 Development of the Global Environment
Principles of StratigraphyPrinciples of Stratigraphy
continuous
deposition
erosion for
50 years
renewed
deposition
100 years
of sediment
150 year gap
resultant
rock record
unconformity
150 years =100 years lost+ 50 years of
erosion
G302 Development of the Global Environment
Unconformities: Grand CanyonUnconformities: Grand Canyon
Characteristic Features• Distinct change in rock type,
1. Deposition of fossiliferous sediments (A)2. Folding (deformation) of A3. Intrusion of igneous rock (B)4. Erosion to create surface (C)5. Deposition of fossiliferous sediments (D)