Date: A Analyae photographs X and Y in Fig. A6.9.1 of a Kansas rock and the mode
ID: 286734 • Letter: D
Question
Date: A Analyae photographs X and Y in Fig. A6.9.1 of a Kansas rock and the modern-day seafloor near Cape Cod, respectively X. Pennsylvanian-age rock from Kansas (290 Myr old) Sand-sized fragments of fossil shells comprise the rock 10x close-up of thin section Y. Modern seafloor environment, 40 m d 16 km north of Cape Cod Photo includes clastic sediment from the continent, bioclastics, and living organisms. +1% gravel * 90% sand 9% mud Figure A6.9.1 I. How are the modern environment (Photograph Y) and Kansas rock (Photograph X) the same? 2. How are the modern environment (Photograph Y) and Kansas rock (Photograph X) different? 3. Today, this part of Kansas is rolling hills and farm fields. Describe the environment in which the sediment in this rock sample (Photograph X) was deposited there about 290 million years ago. REFLECT & DISCUSS What would have to happen to the sediment in Photograph X to turn it into sedimentary rock? 184Explanation / Answer
A. 1. Both X and Y are marine deposits, X is consolidated sedimentary rock formed 200 mya But Y is recent. Organisms seen in X and Y are almost same. Notice the living starfish and fossilised star fish.
A.2 From the grainsize identification, Y formed in near shore environment, becuse it contain more sand grains. and Upon consilidation Y will form into sandstone.
X on the other hand, may have been formed in deep marine conditions, because of consideraby larger fossil grains present in them. And X is a limestone.
A3. Around 290 mya, this deposits was under sea, may be a geosynclinal basin, where sediments are deposited, and got consolifdated ito limestones and sandstone. Later at some point , due to regression of sea and intense uplift. rolling hills were formed.
6.8
1. Both sediments are formed from mud, clay or other fine grain particles, and while it is still wet organisms have travelled through them and imprinted their tracks on it.
2. Difference between both the images are.One is a present day condition with a mamalian track imprinted on it and the second one is a sedimetary rock with dinosaur track on it.
3. Environment in which coelphysis lived was warm, tropical climate with monsoon and summers. Thus the track was preserved in soft mud of that area and the mud got dried up. and subjucted to burial after that.
6.7
1. Arrow position: Draw an arrow pointing towards south west, following the cross bedding on the zoomed image.
2.This cross bedding indicate a steady state flow, because. they are almost parallel in the image.
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