Understanding Rock Types and Their Geological Structures

Property Types of Rocks: Structures in Superficies Stratification.

Forms of Sedimentation

• Desiccation Cracks: Indicate that the sediment formed was alternately wet and dry.
• Current-Trademarks: Furrows produced by erosion of a stream or by objects carried by it.
• Scars of Erosion: Produced by erosion during sedimentation.

Deformation Structures

• Load Structures: Caused by positive materials on the less dense.
• Slumps: Produced by slippage of strata.

Organizational Structures

Reef

Large formations consisting of the calcareous skeleton of organisms such as corals.

Tracks and Traces

Originated by the action of organisms that modify or destroy the original structure of sediment.

Dating Techniques

Discontinuities Stratigraphic

• Unconformities: These discontinuities are marked by erosional surfaces that preserve the parallelism between strata.
• Discrepancies: Are discontinuities that occur during the lake's stratigraphic deformation of the strata and their simultaneous erosion, as reflected by a certain angle of disposition between these strata.
• Inconformities: Discontinuities between layered materials, not normally of fire. For the development of a grievance, there should be a period of elevation followed by erosion of the rocks below.

Criteria for Polarity of the Strata

• Forms of the Layers: The layers may have a characteristic morphology that helps us to identify which was the roof.
• Internal Sedimentary Structures: Sometimes the angle of cross-stratified layers of sandy coastal dunes or sand bars also helps to establish polarity.
• Sedimentary Surface Structures of Stratification: They are essential to establish the roof stratum.

Fossils

The best fossils to establish dating are called:

• Wide Geographical Spread: They appear in widely separated fields, permitting stratigraphic correlations.
• Very Fast Evolutionary Process: They have lived in a geologically very short period of time.
• Great Ecological Tolerance: They have characteristics that have allowed them to exist in different environments and populations, constituting a large number of individuals.
• Easy to Recognize and Interpret: They cannot be confused with other species.

Dendrochronology

Study of the annual growth rings of trees, which are composed of a light and a dark side of seasonal rhythm. Every year, there are homogeneous climate rings with a characteristic thickness. Other organisms, such as some types of corals, also exhibit growth rings.

Molecular Clocks

The fact that after the evolutionary divergence of two species, mutations accumulate in their genetic material has allowed the establishment of DNA clocks. According to this fact, the greater the degree of similarity between the DNA molecules of two different species, the closer they were in the evolutionary scale.