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What do we use the fossil record for? 3. Interpreting past environments

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Presentation on theme: "What do we use the fossil record for? 3. Interpreting past environments"— Presentation transcript:

1 What do we use the fossil record for? 3. Interpreting past environments At any one time different sediments types are being deposited in different places. No one environment stretches indefinitely far in any direction.

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5 Facies = all of the characteristics of a particular rock unit. The characteristics of the rock unit come from the depositional environment. Every depositional environment puts its own distinctive imprint on the sediment, making a particular facies. Thus, a facies is a distinct kind of rock for that area or environment.

6 A = Sandstone facies (beach environment) B = Shale facies (offshore marine environment) C = Limestone facies (far from sources of terrigenous input) Each depositional environment grades laterally into other environments.

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8 Onlap (Transgressive) Sequences Shifting Facies through Time Beach moves farther away Water gets deeper Sediment becomes finer Time Rock Unit Transgression Time Transgressive Unit Beach sandstone Near Shelf shale Far Shelf limestone FUS – Fining Upward Sequence = Transgressive Sequence

9 Offlap (Regressive) Sequences Shifting Facies through Time Beach sandstone Near Shelf shale Far Shelf limestone Beach moves closer Water gets shallower Sediment gets coarser Prograding Regression Time Transgressive Rock Unit Time Rock Unit CUS – Coarsening Upward Sequence = Regressive Sequence

10 Transgressive Sequence Regressive Sequence Beach sandstone Near Shelf shale Far Shelf limestone Beach moves closer Water gets shallower Sediment gets coarser Prograding Regression Time Transgressive Rock Unit Beach moves farther away Water gets deeper Sediment becomes finer Transgression Beach sandstone Near Shelf shale Far Shelf limestone

11 Walther's Law = sedimentary environments that started out side-by-side will end up overlapping one another over time due to transgressions and regressions. The result is a vertical sequence of beds. The vertical sequence of facies Represents former adjacent depositional environments. Which sequence of rock layers represents a transgression?


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