Sed-Strat Exam II Study Guide

  1. What minerals are carbonate rocks made of?

    1. Carbonate rocks are made out of calcite, dolomite, and aragonite, all calcium carbonates


  1. What are the 3 dissolved species in the carbonate system and which predominates in the ocean?

    1. Bicarbonate - most abundant; carbonate, and dissolved carbonate acid


  1. Where are carbonate rocks made in the ocean?

    1. Can be found in reefs and platforms where there's organisms that make calcium carbonate to contribute to the rock making


  1. What is the carbonate compensation depth and why does it matter?

    1. Carbonate compensation depth is the point in the ocean where the calcium carbonate in the ocean is completely dissolved. This depth can be observed in geologic records by looking where there are no longer carbonate rocks forming in ocean sediments. The depth is also determined by how acidic the ocean is, the more CO2 in the water the higher the depth is


  1. What is the difference between eustatic (global) and local sea level?

    1. Eustatic can also mean average, so the global sea level is the average sea level across the entire ocean. Local sea level refers to levels in smaller areas like coast lines


  1. What are different ways that scientists reconstruct past sea level?

    1. Past sea level can be reconstructed by looking at sediment cores and analyzing the previous deposits. Looking for fining upwards and downwards can tell you how sea levels rose and fell, and looking for fossils like foraminiferans that live at certain depths and environments, so their presence can tell you about the ocean at that time


  1. What are the differences between a transgression vs. a regression?

    1. Transgression is a rise in sea level, and regression is a fall in sea level


  1. What are the three main factors that control sediment transport in coastal environments and therefore also the morphology of a river delta?

    1. River discharge, wave power, and tidal process. River supplies sediment, waves redistribute sediment, and tides further transport sediment


  1. What are the different types of marine organisms that produce biogenic sediment in the ocean?

    1. Biogenic sediment can be made from organisms that secrete silica or calcium carbonate. This includes microscopic phytoplankton and zooplankton


  1. What factors control the distribution of the different types of sediments observed in the deep ocean?

    1. It depends on the source of sediment and how much is available, how much activity is in the area (stronger currents won’t let fine clays settle), and things like the CCD


  1. Where are carbonate sediments primarily produced and preserved in the ocean? What factors control this distribution?

    1. Primarily produced in warm shallow waters with reefs and calcium carbonate producing organisms, and areas with planktonic organisms. Distribution depends on temperature, light availability, nutrients, and ocean acidity (CCD)


  1. What are common evaporite minerals and in what environments do they form?

    1. Halite, gypsum, anhydrite, calcite. These form from evaporation of water, so are often found in warm and arid environments


  1. What are the different types of contacts and unconformities between beds?

    1. Conformable contacts (Abrupt, gradational), Intrusive, fault. Angular, Disconformity, nonconformity, paraconformity


  1. What are the principles that underlie the discipline of stratigraphy?

    1. Principle of original horizontality, principle of lateral continuity, law of superposition, and others like inclusions and facies


  1. What are the different units of lithostratigraphy?

    1. Supergroup, Group, Formation (primary unit), Member, and Bed or Flow


  1. Are all lithostratigraphically correlated deposits deposited at the same time?

    1. No, formations can cover multiple time periods, time is not necessarily a separating factor of formations, rather changes in depositional environments


  1. Be able to describe Walther’s law in your own words.

    1. “sedimentary environments (facies) that appear in a conformable vertical sequence must have been deposited adjacent to one another laterally”


  1. What are the 3 primary factors that control transgressions and regressions?

    1. Average sea level change, tectonics (subsidence/uplift), and sediment supply


  1. Be able to identify whether a cartoon of stack parasequences represents a transgression or a regression.

    1. Ok!


  1. What is the difference between progradation, aggradation, and retrogradation?

    1. Progradation is seaward growth of sediments (sediment supply exceeds the rate of accommodation), aggradation if vertical buildup of sediments (sediment supply matches the rate of accommodation), and retrogradation is landward retreat of sediments (sediment supply is lower than the rate of accommodation)


  1. What are the different scales of cycles observed in the geologic record?

    1. Eccentricity - how circular/elliptical earth's orbit is; obliquity - angle between earth's rotational axis and orbital plane; precession - wobble of earth's axis


  1. What are the differences between the three main orbital (Milankovitch) cycles?

    1. Eccentricity - influences duration/severity of seasons; obliquity - affects seasonal variations, no tilt no variation; precession - changes where solstices and equinoxes are, combines with eccentricity

  1. How is seismic stratigraphic data generated?

    1. Vibrations sent through the earth and picked up by special equipment when the waves bounce off layer boundaries


  1. How does the locus of sedimentation change along a depositional profile in response to changes in local sea level?

    1. moves landward during relative sea-level rise (transgression) and basinward during falls (regression)