1. Cyclothem record sea-level cycles. What is the lithologic and stratigraphic e

Question

1. Cyclothem record sea-level cycles. What is the lithologic and stratigraphic evidence that you can use to identify the regressive part of the cycle?

NAME: Meco Silnen SECTION: DATE: LITHOSTRATIGRAPHY EXERCISES PRAIRIE BLUF PROVIDENCE SAN Relative to this east-west transect, in which direction was the paleo-shoreline? East or west? Describe your evi- dence for this decision. RIPLEY FORNIAT BL DEMOPOLIS CHALK CUSSETA SAND ARCOLA LIMEST IMESTONE ME MOOREVILLE CHALK FORMATION 3 In isolated areas of east-central Alabama, the Prairie Bluff Chalk directly overlies the Cusseta Sand. How can this be explained? 2. Take another look at Figure 4.4. What sea-level change do these sequences record? (REGRESSION) 3. Examine the regressive sequence in box 5 of Figure 4.8c. What might happen to this sequence if regression continued such that the shoreline moved to the approxi mate position of box 5? What lithology would you expect to find deposited over the sand? (CONGLOMERATE) (SAND) (SILT/MUD) (CARBONATE) B What might happen to the sequence near box 5if the shoreline migrates even further seaward (ie, to the right of box 6)? LITHOSTRATIGRAPHY 4-7

Explanation / Answer

From the cyclothem cycle of the succession the sequence is mostly between chalk and sand formations . So where in the paleorecord the line is intruded into the chalk formations that is a regressive phase and where there is intrusion of chalk formation in sand formation that is the transgressive phase . In the diagram DEMOPOLIS CHALK is intruded by the CUSSETA SAND which had a regressive phase hence sand bed intruded into the chalk .

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