Marine Sedimentation (Chapter 4)

Flashcards covering key vocabulary, sampling methods, and sediment types from Chapter 4 of “Invitation to Oceanography” regarding marine sedimentation.

Wentworth Grain-Size Scale

A scale used to grade and class terms for classic sediments based on particle size.

Hjulstöm’s diagram

A plot showing the average current velocities necessary for the erosion, transportation, and deposition of sediment particles of different sizes.

Grab samplers

Devices used to collect surface sediments by taking a “bite” out of the sea bottom.

Piston corer

A sampling device that uses a piston in the core barrel to take much longer sediment cores than a gravity corer.

Holocene sea-level rise

The event occurring over the last $15,000$ years where sea level rose from approximately $130$ to $140\,m$ below its present level.

Relict sediments

Sediment that blankets about $60\%$ of the world’s continental shelves, deposited in the past under conditions no longer evident and not in equilibrium with present-day environments.

Terrigenous sediment

Sediment derived from the breakdown of rocks on land and supplied to the deep sea by bulk emplacement, typically dominating middle latitudes.

Biogenic sediment

Sediment derived from biological production, such as carbonate-secreting organisms, which dominates low latitudes.

Glacial-marine sediment

Sediment dominated by ice-rafted debris, primarily found in polar regions.

Accretionary prism

A part of the arc-trench gap in a subduction boundary where deep-sea deposits and trench sediments are scraped off the descending plate and plastered onto the margin.

Hydrogenous sediments

Sediments formed by chemical precipitates directly from seawater.

Bulk emplacement

The transport of large masses of sediment to the deep sea, including processes like slumping and turbidity currents.

Turbidity current

A high-density mixture of sediment and water that flows down submarine canyons and inclines, often depositing graded bedding on the deep-ocean floor.

Ice rafting

A transport process where glaciers extending into the ocean disintegrate into icebergs, which then release their sediment load as they melt.

Kaolinite

A clay mineral that abounds in pelagic deposits of tropical latitudes.

Chlorite

A clay mineral that abounds in pelagic deposits of polar latitudes.

Foraminifera

Common microfossils found in calcium carbonate-rich biogenic oozes.

Coccolithophores

Microscopic organisms whose remains contribute to biogenic oozes.

Ferromanganese nodules

Authigenic deposits characterized by concentric layering, particularly abundant in the Pacific and South Atlantic Oceans.

Carbonate Compensation Depth (CCD)

The specific depth in the ocean below which carbonate materials dissolve; it influences the formation of basal ooze layers.

Anhydrite and stromatolites

Indicators of shallow, high-salinity conditions uncovered by deep-sea drilling in the Mediterranean Sea, dating to the Miocene age.