An ancient fossilized tree found in Montana was initially classified by paleontologists as dating to the Cretaceous period (approximately 100...
GMAT Information and Ideas : (Ideas) Questions
An ancient fossilized tree found in Montana was initially classified by paleontologists as dating to the Cretaceous period (approximately 100 million years ago) based on the surrounding rock formation. However, when geologist Dr. Maria Santos and her research team performed detailed analysis using advanced spectrometry, they found traces of volcanic ash containing zircon crystals with uranium-lead ratios consistent with an age of only 15 million years. Therefore, the team concluded that _____
Which choice most logically completes the text?
Cretaceous period fossils cannot contain volcanic ash deposits.
uranium-lead dating methods are unreliable for fossil analysis.
the volcanic ash must have been contaminated by modern materials.
the fossil could not have originated during the Cretaceous period.
Step 1: Decode and Map the Passage
Part A: Create Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| 'An ancient fossilized tree found in Montana was initially classified by paleontologists as dating to the Cretaceous period (approximately 100 million years ago) based on the surrounding rock formation.' |
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| 'However, when geologist Dr. Maria Santos and her research team performed detailed analysis using advanced spectrometry, they found traces of volcanic ash containing zircon crystals with uranium-lead ratios consistent with an age of only 15 million years.' |
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| 'Therefore, the team concluded that _____' |
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Part B: Provide Passage Architecture & Core Elements
Main Point: New scientific evidence contradicts the initial age classification of an ancient fossilized tree.
Argument Flow: The passage presents a classic scientific revision scenario. Initially, paleontologists classified the fossil as 100 million years old based on surrounding rock. However, Dr. Santos' team used more precise dating methods and found evidence suggesting the fossil is only 15 million years old.
Step 2: Interpret the Question Precisely
This is a fill-in-the-blank question asking us to choose the best logical connector. The answer must create the right relationship between what comes before and after the blank.
Step 3: Prethink the Answer
- The evidence shows a conflict: initial dating said 100 million years (Cretaceous), but new, more precise testing shows 15 million years
- When newer, more advanced methods contradict older methods, the logical conclusion is that the newer evidence is more reliable
- Since the advanced spectrometry shows 15 million years, and the Cretaceous period was approximately 100 million years ago, the fossil cannot actually be from the Cretaceous period
Cretaceous period fossils cannot contain volcanic ash deposits.
- Makes a general claim about what Cretaceous fossils can contain, but the passage is about this specific fossil's age, not establishing rules about all Cretaceous fossils
uranium-lead dating methods are unreliable for fossil analysis.
- Questions the reliability of uranium-lead dating methods, but the passage presents no evidence that the dating method is unreliable
the volcanic ash must have been contaminated by modern materials.
- Suggests contamination, but there's no evidence in the passage suggesting this
the fossil could not have originated during the Cretaceous period.
- Directly concludes that the fossil couldn't be from the Cretaceous period
- This matches our prethinking: if the fossil is 15 million years old, it cannot be from a period that occurred 100 million years ago