In general, why are cephalopods and planktonic foraminifera likely to be less useful than bryozoa in bathymetric analyses?What general statement can be made about the paleobathymetry of a stratum containing abundant crinoids (see Fig. 12.10)?Note that the neritic-benthic environment (littoral-sublittoral zone) contains greater numbers and diversity of organisms. What factors may account for this? Figure 12.10 General depth distribution of some of the groups of marine fossil and living invertebrates ### Ocean Zones and Marine Organism Distribution#### Diagram OverviewThis diagram illustrates the relationship between ocean depth and various marine life forms across different oceanic zones. The upper part of the diagram shows depth in meters (ranging from 0 to 2000 meters) and correlates these depths with specific oceanic zones. The lower part displays the distribution and abundance of various marine organisms within these zones.#### Oceanic Zones1. **Littoral Zone**: - Located between high tide and low tide levels. - Includes the Intertidal zone.2. **Subtital Zone**: - Extends beyond the low tide mark to a depth of 200 meters.3. **Bathyal Zone**: - Ranges from 200 meters to approximately 2000 meters.4. **Abyssal Zone**: - Beyond 2000 meters.#### Marine Organism Distribution- **Calcareous Sponges**: Found from the littoral to bathyal zones, with varying abundance.- **Siliceous Sponges**: Present mainly in the bathyal and abyssal zones.- **Reef Corals**: Abundant primarily within the subtital zone.- **Crinoids**: Distributed across subtital to bathyal zones.- **Blastoids and Stelleroids**: Found from subtital to bathyal zones, with lesser frequency compared to crinoids.- **Holothuroids (Sea Cucumbers)**: Spread from subtital to abyssal zones.- **Echinoids (Sea Urchins)**: Present in the subtital zone with range extending to the bathyal zone.- **Bryozoa**: Found in both subtital and bathyal zones.- **Brachiopods**: Both articulate and inarticulate forms are present, spanning subtital to bathyal zones.- **Cephalopods, Gastropods, and Pelecypods**: These groups have a wide range, from subtital to bathyal zones.- **Trilobites**: Mainly in the bathyal zone.- **Calcareous Algae**: Limited to areas categorized above subtital zones.#### Abundance Key- **Solid Lines**: Depict abundance in a specific range.- **Dashed Lines**: Indicate organisms that are "rare to common" in certain depths.This diagram provides a visual representation

Analysing bathymetry entails examining the distribution of organisms with respect to water depth. Regarding planktonic foraminifera, bryozoa, and cephalopods, there are a few reasons why bryozoa might be more beneficial for these kinds of analyses than cephalopods and planktonic foraminifera:1. Preference for sediment:Cephalopods: A large number of cephalopods actively swim in the water column, including squids and octopuses. Because they can migrate freely, they might not have a strong relationship with particular bathymetric zones.Marine microorganisms known as planktonic foraminifera are tiny and float in the water column. They have no direct connection to any particular substrates or bathymetric zones.On the other hand, bryozoa are frequently sessile (attached to a substrate), and certain species exhibit preferences for particular substrates or depths.2. Habitat Specifity: The group of animals known as cephalopods is diverse and includes a large variety of ecological niches. Since they might live at different depths, they are less accurate bathymetric markers.Planktonic Foraminifera: These organisms are less restricted to particular depths because they float freely and can be found throughout the water column.Bryozoa: These colonies can be found in many bathymetric zones and frequently show preferences for particular substrates. Some depth ranges may have higher populations or more diversity of certain species.3. Preservation and identification: Cephalopods: Because of their delicate body components, cephalopod remnants may not retain well in sediments, which limits their usefulness for paleontological or sedimentary analyses.Planktonic Foraminifera: Due to their small size, planktonic foraminifera are difficult to detect and thoroughly investigate, despite their excellent preservation potential in marine sediments.Bryozoa: These organisms frequently have calcareous skeletons that hold up well in sediments. Bryozoan colonies may be easier to identify in sedimentary records due to their larger size.From the figure it is quite clear that the calcareous sponges and calcareous algaes are mostly found in the region from the shore to a depth of maximum 200 meters or we can say that they are found in Littoral as well as Sublittoral zones. So from this information we can say that the limestone formation is an outcrop from this region only. Whereas the other outcrop contains silicious sponges and cephalopod fossils which are dominant in the region of Sub Littoral zone to abyssal zone. Hence it can be said that the changes in depth of the outcrop is from Littoral to Sub Littoral in the first formation and Sub Littoral to abyssal zone in the second outcrop.Solution of question no. 3: Since the fossil cephalopods are distributed from sub littoral zone to bethyl zone which is much larger in area compared to area covered by echinoids(found only in littoral zone and little part of sub littoral zone) It is much easier for an observer to determine the location of echinoids than that of cephalopods. So due to this smaller distribution of echinoids in terms of area over cephalopods it is helpful in water depth determination as compared to cephalopods.

Answered: In general, why are cephalopods and…

Applications and Investigations in Earth Science (9th Edition)

9th Edition

ISBN:9780134746241

Author:Edward J. Tarbuck, Frederick K. Lutgens, Dennis G. Tasa

Publisher:Edward J. Tarbuck, Frederick K. Lutgens, Dennis G. Tasa

Chapter1: The Study Of Minerals

Section: Chapter Questions

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In general, why are cephalopods and planktonic foraminifera likely to be less useful than bryozoa in bathymetric analyses?
What general statement can be made about the paleobathymetry of a stratum containing abundant crinoids (see Fig. 12.10)?
Note that the neritic-benthic environment (littoral-sublittoral zone) contains greater numbers and diversity of organisms. What factors may account for this?

Figure 12.10 General depth distribution of some of the groups of marine fossil and living invertebrates