GEOL 332 LECTURE 18 TODAYS MATERIAL: Final Review: Terrestrial Environments Lacustrine Deposits Aeolian Deposits Carbonate Rocks Carbonate Environments Next Time: Coastal and Marine Environments

GEOL 332 Course Schedule (updated) Topic Sentences: They should summarize the paragraph. When in the first paragraph of a section, they should introduce the paragraph and the section. Results: Write about the results. Include wording describing any trends in the data, but do not discuss your interpretation of these trends (the why). The interpretation goes into the Discussion section. Introduction: Do not present specific details about the methods, just generalizations. The hypotheses should be listed in the introduction. Plots are not Tables. Tables are not Figures. Graphs are Figures.

The thermal stratification of fresh lake waters results in a more oxic, upper layer, the epilimnion, and a colder, anoxic lower layer, the hypolimnion. Sedimentation in the lake is controlled by this density stratification above and below the thermocline.

A schematic graphic sedimentary log through clastic deposits in a freshwater lake.

When an ephemeral lake receives an influx of water and sediment, mud is deposited from suspension to form a thin bed that is overlain by evaporite minerals as the water evaporates. Repetitions of this process create a series of couplets of mudstone and evaporite.

Aeolian Deposits UL: Tabular-planar cross-beds in the Navajo Sandstone, north of Kanab, UT. LL: Aeolian dune cross-bedding in sands deposited in a desert: the view is approximately 5m high. UR: Large-scale wedge-planar cross-beds (middle) between tabular cross-beds in the Navajo Sandstone, Zion nat’l. Peak, UT LR: Steeply dipping cross-strata forming tabular-planar sets in barchoid ridge dune. Strata are tangential with basal bounding planes.

http://montessorimuddle.org/2011/04/21/global-atmospheric-circulation-and-biomes/

Pressure Gradient = difference in pressure/distance The net force is directed toward the lower fluid pressure at the bottom of tank B. This net force causes water to move from higher pressure toward lower pressure. Figure 6.10: The higher water level creates higher fluid pressure at the bottom of tank A and a net force directed toward the lower fluid pressure at the bottom of tank B. This net force causes water to move from higher pressure toward lower pressure.

The closer the spacing of the isobars, the greater the pressure gradient. The greater the pressure gradient, the stronger the pressure gradient force (PGF). The stronger the PGF, the greater the wind speed. The red arrows represent the relative magnitude of the force, which is always directed from higher toward lower pressure. Figure 6.12: The closer the spacing of the isobars, the greater the pressure gradient. The greater the pressure gradient, the stronger the pressure gradient force (PGF). The stronger the PGF, the greater the wind speed. The red arrows represent the relative magnitude of the force, which is always directed from higher toward lower pressure.

Above the level of friction, air initially at rest will accelerate until it flows parallel to the isobars at a steady velocity with the pressure gradient force (PGF) balanced by the Coriolis force (CF). Wind blowing under these conditions is called geostrophic. Figure 6.16: Above the level of friction, air initially at rest will accelerate until it flows parallel to the isobars at a steady speed with the pressure gradient force (PGF) balanced by the Coriolis force (CF). Wind blowing under these conditions is called geostrophic.

Figure 6.18: Winds and related forces around areas of low and high pressure above the friction level in the Northern Hemisphere. Notice that the pressure gradient force (PGF) is in red, while the Coriolis force (CF) is in blue. Winds and related forces around areas of low and high pressure above the friction level in the Northern Hemisphere. Notice that the pressure gradient force (PGF) is in red, while the Coriolis force (CF) is in blue.

Figure 6.22: Winds and air motions associated with surface highs and lows in the Northern Hemisphere. Winds and air motions associated with surface highs and lows in the Northern Hemisphere.

The idealized wind and surface-pressure distribution over a uniformly water-covered rotating earth. Figure 7.24: The idealized wind and surface-pressure distribution over a uniformly water-covered rotating earth. http://startswithabang.com/wp-content/uploads/2008/08/water-phase-diagram.jpg

http://cnx. org/contents/db89c8f8-a27c-4685-ad2a-19d11a2a7e2e@9 http://cnx.org/contents/db89c8f8-a27c-4685-ad2a-19d11a2a7e2e@9.12:10/Principles_of_Biology The idealized wind and surface-pressure distribution over a uniformly water-covered rotating earth. Figure 7.24: The idealized wind and surface-pressure distribution over a uniformly water-covered rotating earth. http://startswithabang.com/wp-content/uploads/2008/08/water-phase-diagram.jpg

The distribution of high- and low-pressure belts at different latitudes creates wind patterns that are deflected by the Coriolis force.

During glacial periods the regions of polar high pressure are larger, creating stronger pressure gradients and hence stronger winds. In the absence of large high pressure areas at the poles in interglacial periods the pressure gradients are weaker and winds are consequently less strong.

Aeolian ripples, dunes and draas are three distinct types of aeolian bedform.

Four of the main aeolian dune types, their forms determined by the direction of the prevailing wind(s) and the availability of sand. The small ‘rose diagrams’ indicate the likely distribution of palaeowind indicators if the dunes resulted in cross-bedded sandstone.

Sand supply and the variability of prevailing wind directions control the types of dunes formed.

Carbonate Rock Classes & Environments Folk Dunham

The Folk classification of carbonate sedimentary rocks. This scheme is the most commonly used for thin sections.

The Dunham classification of carbonate sedimentary rocks. This scheme is the most commonly used for description of limestones in the field and in hand specimen. Fig. 3.6 The Dunham classification of carbonate sedimentary rocks (Dunham 1962) with modifications by Embry & Klovan (1971). This scheme is the most commonly used for description of limestones in the field and in hand specimen.

The relations between water depth and biogenic carbonate productivity, which is greatest in the photic zone. Fig. 15.1 The relations between water depth and biogenic carbonate productivity, which is greatest in the photic zone.

The types of carbonate platform in shallow marine environments. Fig. 15.2 The types of carbonate platform in shallow marine environments.

Fig. 15.3 Different groups of organisms have been important producers of carbonate sedimentary material through the Phanerozoic; limestones of different ages therefore tend to have different biogenic components.

Morphological features of a carbonate coastal environment with a barrier protecting a lagoon. Fig. 15.4 Morphological features of a carbonate coastal environment with a barrier protecting a lagoon.

A carbonate-dominated coast with a barrier island in an arid climatic setting: evaporation in the protected lagoon results in increased salinity and the precipitation of evaporite minerals in the lagoon. Fig. 15.5 A carbonate-dominated coast with a barrier island in an arid climatic setting: evaporation in the protected lagoon results in increased salinity and the precipitation of evaporite minerals in the lagoon.

Three general types of saline lake can be distinguished on the basis of their chemistry. http://myweb.astate.edu/mdraganj/cationanion.html

In arid coastal settings a sabkha environment may develop. Fig. 15.6 In arid coastal settings a sabkha environment may develop. Evaporation in the supratidal zone results in saline water being drawn up through the coastal sediments and the precipitation of evaporite minerals within and on the sediment surface.

Tide-influenced coastal carbonate environments. Fig. 15.7 Tide-influenced coastal carbonate environments.

Modern corals in a fringing reef Modern corals in a fringing reef. The hard parts of the coral and other organisms form a boundstone deposit. Fig. 15.8 Modern coral atolls. Fig. 15.9 Modern corals in a fringing reef. The hard parts of the coral and other organisms form a boundstone deposit. Modern coral atolls.

The type and abundance of carbonate reefs has varied through the Phanerozoic. Fig. 15.10 The type and abundance of carbonate reefs has varied through the Phanerozoic (data from Tucker, 1992).

The core of a Devonian reef flanked by steeply dipping forereef deposits on the right-hand side of the exposure. Fig. 15.11 The core of a Devonian reef flanked by steeply dipping forereef deposits on the right-hand side of the exposure.

Facies distribution in a reef complex. Fig. 15.12 Facies distribution in a reef complex.

Reefs can be recognized as occurring in three settings: (a) barrier reefs form offshore on the shelf and protect a lagoon behind them, (b) fringing reefs build at the coastline and (c) patch reefs or atolls are found isolated offshore, for instance on a seamount. Fig. 15.13 Reefs can be recognized as occurring in three settings: (a) barrier reefs form offshore on the shelf and protect a lagoon behind them, (b) fringing reefs build at the coastline and (c) patch reefs or atolls are found isolated offshore, for instance on a seamount.

Generalized facies distributions on carbonate platforms: (a) ramps, (b) non-rimmed shelves and (c) rimmed shelves. Fig. 15.15 Generalized facies distributions on carbonate platforms: (a) ramps, (b) non-rimmed shelves and (c) rimmed shelves.

Schematic graphic log of a carbonate ramp succession. Fig. 15.16 Schematic graphic log of a carbonate ramp succession.

Schematic graphic log of a non-rimmed carbonate shelf succession. Fig. 15.17 Schematic graphic log of a non-rimmed carbonate shelf succession.

Schematic graphic log of a rimmed carbonate shelf succession. Fig. 15.18 Schematic graphic log of a rimmed carbonate shelf succession.

Settings where barred basins can result in thick successions of evaporites. Fig. 15.19 Settings where barred basins can result in thick successions of evaporites.

(a) A barred basin, ‘bulls-eye’ pattern model of evaporite deposition; (b) a barred basin ‘teardrop’ pattern model of evaporite deposition. Fig. 15.20 (a) A barred basin, ‘bulls-eye’ pattern model of evaporite deposition; (b) a barred basin ‘teardrop’ pattern model of evaporite deposition.