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Zorluk: ZorFunction of Detail in Context

In the mid-twentieth century, Cesare Emiliani revolutionized paleoclimatology by measuring the ratio of oxygen-18 to oxygen-16 in fossilized planktonic foraminifera extracted from deep-sea sediment cores. Emiliani argued that these isotopic ratios served as a direct paleothermometer, asserting that lower ratios of oxygen-18 corresponded directly to warmer sea-surface temperatures during Pleistocene interglacial periods. However, this interpretation rested on the tenuous assumption that the isotopic baseline of seawater remained invariant across climatic epochs. Because evaporating water vapor preferentially incorporates the lighter oxygen-16 isotope, immense continental ice sheets sequester significant amounts of oxygen-16 during glacial maxima, thereby enriching the global ocean in oxygen-18 regardless of ambient thermal conditions. To decouple these confounding influences, geochemist Nicholas Shackleton analyzed benthic foraminifera retrieved from equatorial Pacific abyssal sediments. Because abyssal bottom waters maintain nearly constant temperatures near freezing irrespective of orbital cycles, Shackleton demonstrated that fluctuations in benthic isotopic ratios must reflect shifts in global continental ice volume rather than localized sea-surface temperature changes, necessitating a major reinterpretation of Emiliani's climatic timeline.

Which of the following most accurately describes the primary purpose of the author's reference to Nicholas Shackleton's analysis of benthic foraminifera?

  1. A
    reiterate the geochemical properties of benthic calcite shells retrieved from equatorial Pacific sediments
  2. B
    suggest that Pleistocene orbital cycles caused significant fluctuations in the temperature of equatorial abyssal waters
  3. introduce an empirical investigation that isolated one of two confounding variables affecting marine isotopic measurementsCevap
  4. D
    refute the claim that continental ice-sheet expansion alters the baseline ratio of oxygen isotopes in seawater
  5. E
    argue that benthic organism fossilization is fundamentally superior to pelagic fossilization for reconstructing surface atmospheric trends

Cevap

The reference to Nicholas Shackleton's analysis of benthic foraminifera serves primarily to introduce an empirical investigation that isolated one of two confounding variables affecting marine isotopic measurements.
The passage establishes that Emiliani's interpretation was compromised because oxygen isotope ratios reflect two intertwined variables: seawater temperature and continental ice volume. Shackleton's investigation of benthic foraminifera from thermally stable abyssal waters held temperature constant, successfully isolating the ice-volume variable and resolving the ambiguity in Emiliani's original timeline.

Adım Adım Çözüm

1
Locate the target detail within the passage and analyze its immediate textual context.
The reference to Shackleton's analysis follows the explanation that oxygen isotope ratios are influenced simultaneously by ambient temperature and continental ice volume.
Understanding the surrounding argumentative tension reveals the exact purpose for which the author introduces the empirical study.
2
Analyze the structural role of the detail in resolving the stated problem.
Because abyssal waters remain thermally invariant, studying benthic foraminifera held temperature constant and isolated global continental ice volume as the sole driver of isotopic variation.
Identifying how the cited study resolves the methodological confounding allows for formulating the rhetorical function.
3
Match the identified rhetorical role to the option that captures this function abstractly.
The option indicating the introduction of an empirical investigation that isolated one of two confounding variables accurately describes this function.
The correct response must state the structural purpose rather than merely repeating descriptive content.

Anahtar Kavram

Function of Detail in Context (Rhetorical Role Analysis)
Tahmini Süre:2m 15s
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Konular

Function of Detail in Context

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