Lecture 18 Flashcards
(27 cards)
How far down to the successions of layers in the Earths crust go and what does this demonstrate?
10 000m. Demonstrates that Earth is OLD AF
What did John Strachi do?
Made drawings of layer successions in 1745. Discovered facious terminations
What are facious terminations?
Things that define the appearance of a layer
What are the 5 types of terminations?
Lateral, Faulting and erosion, Pinchout, Intertonguing, Lateral Gradation
What are lateral terminations?
When the layer terminates at the edges of the sedimentary basin
What is faulting and erosion?
Thing that determines the termination of a layer
What is a pinch out termination?
Occurs due to sea level changes through geological time
What are the 2 components of a pinch out termination?
Transgression and Regression
What are transgressions?
When the shore line moves forward towards the continent
What are regressions?
Shoreline moves backwards to ocean. Pinch out termination shows new layers terminate during each transgression and regression cycle.
What is intertonguing?
Successive pinch out termination. Demonstrates sea level fluctuations over a period of time,
What is lateral gradation?
Gradual facious determination. Crucial for next half century and changes in science.
Who published a book claiming that the Earth may be older than previously thought (over 70 000 years) and how did he do it?
Cont Debufont in 1774. Calculated the time of cooling for certain metals. Extrapolated that time to mass of Earth and came up with Earth’s age in hours
When did creationism lose influence in science?
1774
Who discovered that successions of rocks are either normal or turned upside down?
Thomas (something). Discovered this in the Alps.
What are mudcracks?
Structures formed from evaporation of fluid from a wet sediment Always present opening towards upper part of a layer
What are burrowings?
Areas where organisms burrowed into the rock for food/protection. Opening is always at the top of the layer
What are ripple marks?
Structures formed in a sediment by water. Asymmetrical or symmetrical. Always narrow upwards.
What do burrowings, mudcracks, and ripple marks help us to determine?
Recognizing the original position of the sea bottom.
What is one of the most important questions with stratigraphy?
How do we compare rock successions from other parts of the world?
What are conformable successsions?
Strata without depositional breaks
What are non-conformable successions (unconformities)
Strata that are separated by surfaces of discontinuity, encompassing substantial amounts of geological time. At some point, sedimentation stopped and eroded.
What are the types of unconformities?
Disconformities, Angular, Non-conformity
What is a disconformity?
Existence of sedimentary layers below and above (unconformity). Layering is parallel below and above conformity. LOwer succession is formed and uplifted, then eroded. Top hardened, sank, created sedimentation of upper layers.
