Marine Sedimentation (Chapter 4)

Figure 04.COP: Marine Sedimentation
- Depicts various aspects of marine sedimentation processes.
Table 04.T01: Wentworth Grain-Size Scale
- Adapted from Wentworth, C. K.
- Source: Journal of Geology 30 (1922): 377–392.

Figure 04.01: Hjulström’s Diagram
- Illustrates average current velocities needed for erosion, transportation, and deposition of sediment particles based on size.
- Key Points:
- Strong currents are required to erode fine materials such as clay and silt as indicated by the broad upper curve.
- Weak currents can erode fine to medium sand.
- Particle transport is directly related to size.
- Deposition occurs when current speed is below a critical value shown on the lower curve.
- Letters A, B, and C reference specific discussions in the text.

Figure 04.B01_01AB: Gear for Sampling Sediment
- (a) Durable bottom dredge used for hard rock sampling.
- (b) Grab samplers for collecting surface sediments.
Figure 04.B01_03: A geologist onboard the Japanese drilling ship Chikyu examines sediment particles to interpret ancient environments.
Figure 04.B01_02AB: Corers
- (a) Heavyweight drives a core barrel into sediment.
- (b) Piston corers yield longer samples than gravity corers because of a piston mechanism in the core barrel.

Figure 04.02A: Shelf Sedimentation
- Assumes bottom energy is inversely related to depth; sediments transition from coarse sands and gravels onshore to mud at the shelf break.
Figure 04.02B
- Indicates a sea-level drop of 130-140 meters about 15,000 years ago, followed by a Holocene rise to current levels, affecting sedimentation.
Figure 04.03A
- Shows shorelines displacing seaward by over 100 kilometers during the last glacial period; modern sea-level rise threatens major cities.
Figure 04.04A
- Depicts sediment variance with latitude:
- Biogenic sediment predominant in low latitudes.
- Terrigenous sediment in middle latitudes.
- Glacial-marine sediment in polar regions.
Figure 04.04B
- Indicates approximately 60% of shelf sediment is relict; meaning deposited under past conditions no longer present.

Figure 04.B02A
- Satellite image of dust plumes from Africa into the Atlantic Ocean.
Figure 04.B02B
- Displays general flow paths of dust from northern Africa due to desertification.
Figure 04.B02C
- Increments in dust fallout in Greenland, linked to land use and climate changes in central Asia since 1800.
Figure 04.B02D
- Red tide in Florida linked to wind-borne iron-rich dust from North Africa.

Figure 04.19ABCD: Paleogeography of North America
- Discusses geological events in the Cretaceous period:
- Rifting and sinking in the eastern North America as the Atlantic Ocean formed.
- Central and western regions covered by shallow seas with active volcanoes.
- Erosion of Appalachian Mountain sediments deposited on the continental margin.

Figure 04.06ABC
- Details the evolution of a passive Atlantic-type margin over millions of years, with rifting followed by sedimentation and coral growth during subsidence.

Figure 04.07AB
- Identifies three zones of a subduction boundary:
- Volcanic arc.
- Arc-trench gap with sediment basin and accretionary prism.
- Deep-sea trench.
Sediment is accumulated through erosion from the volcanic arc and scraping of deep-sea deposits onto the accretionary prism, resulting in systematic widening over time.

Figure 04.B03
- Observes a slow drop in average global temperature since 1000 CE, followed by a sharp rise in the early 20th century due to greenhouse gases, particularly CO2.

Figure 04.08
- Carbonate shelves are located in tropical and subtropical shallow, warm waters, promoting carbonate-secreting organism growth, with minimal river sediment interference.

Figure 04.09A!!B
- Discusses terrigenous, pelagic, and hydrogenous sedimentation in the deep sea, with terrigenous sediment being the result of rock breakdown on land and biological production leading to pelagic sediment accumulation.
Highlights significant sources of terrigenous debris, including the Asian and Amazon rivers.

Figure 04.B04
- Describes the event of Glacial Lake Iroquois drainage, which led to increased sedimentation in marine environments through catastrophic flooding.

Figure 04.10A!!B
- Explains the movement of sediment via turbidity currents down slopes, responsible for significant sediment transport past continental shelves and into deep-sea regions.

Figure 04.12A!!B
- Discusses ice rafting, whereby glaciers discharge their sediment load into oceans as they melt, forming a band of glacial-marine sediment around Antarctica, shaped by historic climatic conditions.

Figure 04.13
- Explains how ratios of kaolinite and chlorite help trace clay mineral sources in deep-sea sediments based on geographical distribution and sediment transport processes.

Figure 04.14A!!F
- Displays common microfossils including foraminifera, pteropods, coccolithophores, radiolaria, and diatoms, highlighting biological activity in marine sediment production.

Figures 04.15A!!B and 04.16A!!B**
- Showcases the stratification and sedimentation rates of deep-sea deposits, identifying terrigenous materials, red clays, and oozes based on proximity to land and water depths.

Figure 04.17
- Details the layered sediment stratigraphy over seafloor basalt crust observed in the Atlantic, illustrating patterns related to seafloor spreading.
Figure 04.18A!!C
- Contrasts stratigraphic complexity in the Pacific basin versus the Atlantic basin, highlighting differences in sedimentation processes and geological activity.

Figures 04.B05_01!!03AB
- Explores tectonic activity in the Mediterranean region, historical drying of the Mediterranean Sea, and subsequent refilling events linked to Atlantic seawater influx.

A comprehensive overview of sedimentation processes, sediment types, and their implications on geology, ecology, and future predictions regarding sea-level changes and climate impacts.