lab virtual field trip

.pdf

School

Citrus College *

*We aren’t endorsed by this school

Course

MISC

Subject

Geology

Date

Dec 6, 2023

Type

pdf

Pages

2

Uploaded by valeriezuniga49

Report
Instructions: Explore the entirety of the gorge. Interact with 5 different media icons and summarize each (#1-5 with Media Title). Once you finish your trip, answer the following questions based on what you've learned: #6 How old are the Banded Iron Formations in Karijini Gorge? What eon is that? (See the Geologic Timescale). #7 Why do Banded Iron Formations mainly disappear from the rock record after the Precambrian? Media Icons: #1: Conventional interpretation of the BIFs The conventional interpretation is that there had to be a bit of oxygen locally and that it was produced by photosynthetic microbes. Very similar to modern equivalence in western australia. #2 Lamination Lamination is the fine layers in all kinds of sedimentary rocks and its the layering for which the banded eye formation gets its name #3 Supergene weathering and alterations Rocks can be altered from the original rock it once was, it can lose its lamination. Over 70 million years water has been dissolving silica from the rocks and it enriches the iron oxide. #4 Unique structures on gorge floor The gorge floor has what are called diagenetic structures. It's important to know that they are not stromatolites like they were first believed to have been and they are not fossils either. #5 Microbes that can make rust There are other types of microbes that can make rust, they photosynthesize and they simply haven't figured out how to make oxygen. They take its iron and its electrons and this is also another hypothesis that some scientists believe might be how banded iron could have formed before microbes.
#6 How old are the Banded Iron Formations in Karijini Gorge? What eon is that? (See the Geologic Timescale). The banded iron formation in Karijini Gorge are about 2500 million years old and it was in the Proterozoic Eon. #7 Why do Banded Iron Formations mainly disappear from the rock record after the Precambrian? In summary, the disappearance of Banded Iron Formations from the rock record after the Precambrian is mainly due to shifts in ocean chemistry, evolution of oxygen levels in the atmosphere and oceans, biological activity, and changes in tectonic processes that collectively altered the conditions required for the formation and preservation of BIFs.
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