ANSWERS TO “TEST YOUR KNOWLEDGE” ON PAGE 38
Answers: 1. The answer is choice “d” or “ostracods.”
Diatoms are microscopic, aquatic, single-celled algae (phytoplankton) with hard shells made of silica. Foraminifers are single-celled, aquatic, planktonic animals with calcareous or agglutinated tests. Radiolarians are minute, single-celled, aquatic animals (zooplankton) with shells made of silica.
Ostracod Example. Image source - University of Tasmania Australia, Institute for Marine and Antarctic Studies (IMAS),
https://www.imas.utas.edu.au/zooplank- ton/image-key/ostracoda, accessed May 24, 2020.
2. Since the data we have on-hand is quite limited, at this point we can only make an educated guess. Keeping these con- straints in mind, the most likely scenario is choice “d” or “A fluvial channel overlain by a marine bar.” One would also suspect a possible unconformable contact separating the distinct sand units.
Channel sands have profiles where the grain size decreases upward from a generally scoured base. On an SP curve, a bell-shaped sequence should be expected. In contrast, shallow marine bars, regressive barrier-island sands and delta-front bars have profiles with grain size coarsening upward. This would tend to produce a funnel-shaped sequence. Graded bedding would be the expectation in a turbidite deposit. This scenario does not seem to fit the sequence of SP shapes that we have encountered. The presence of finer-grained, clay-rich to silt-rich strata would be the expectation in lacustrine environments. If this were to be the case, one would expect to see the bell-shaped sand unit overlain by an SP pattern approaching the shale base line.
3. The answer is choice “a” or “5.97 x 1024 kg.” We know that: D = M/V
(1)
In (1) above, V is the Earth’s volume. Assuming a spherical Earth, then: 3
V = (4/3)(3.1416)(6.371 x 108 cm)3 V = 1.08 x 1027 cm3
From (1) we may write: M = D x V
M = (5.51 gcm-3)(1.08 x 1027 cm3) M 5.97 x 1027 g = 5.97 x 1024 kg
(2) (3) (4)
(5) (6) (7)
Choices “b”, “c” and “d” refer to Saturn, Mars and Uranus, respectively. These are illustrated in the table to the right:
4. The answer is “b” or “False.” “Arthrodira” is an Order of armored fish (placoderms) which lived from Silurian to the end of the Devonian period, flourishing within the latter. The head and thorax of these animals were covered by armored plates while the rest of the body was either scaled or naked, depending on the species. Lacking teeth, they used the sharpened
edge of a bony plate for biting purposes. Arthrodira
Dunkleosteus ren- dering. Image source - Tennesseefossils. com affiliated with the Tennessee Geological Society, http://tennes-
seefossils.com/
Timelines10.php, accessed May 24, 2020.
40 TPG •
Jul.Aug.Sep 2020
www.aipg.org
Mercury M = 3.30 x 1023 kg Venus M = 4.86 x 1024 kg Earth M = 5.97 x 1024 kg Mars
M = 6.42 x 1023 kg
Jupiter M = 1.89 x 1027 kg Saturn M = 5.69 x 1026 kg Uranus M = 8.68 x 1025 kg Neptune M = 1.02 x 1026 kg
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