III. Deep Sea Sediments (50 Points).

(20 points) A. Terrigenous Sediments.

1. Compare and contrast turbidites and contourites in terms of their origin, sediment structures, and their geographic distribution. (10 pts.)

2. Briefly describe the possible origins for submarine canyons and cite evidence supporting each possibility. (10 pts.)

(10 points) C. Briefly describe the characteristics of cosmogenous sediments in the deep sea, including their morphology, their distribution, their age, their implications and their usefulness.

(20 points) B. The sedimentary sequence on the left was drilled at a depth of 5700 meters in the western Pacific off the Japan Trench by the Glomar Challenger. Briefly explain the origin of this sedimentary sequence in terms of the factors controlling biogenous sedimentation in the deep sea, subsidence of ocean crust, and sedimentation rate.

A. The sedimentary sequence on the left was drilled at a depth of 3800 meters west of Bermuda in the Atlantic by the Glomar Challenger. Bermuda is an atoll sitting on top of a seamount constructed in middle Eocene time (~45 m.y. ago) on crust of late Jurassic (~150 Ma) age. In turn, this seamount sits in the middle of a large swell called the Bermuda Rise, which apparently was uplifted at the time the seamount formed. Assuming that the CCD in the North Atlantic has been at a depth of 4500 meters since the late Jurassic (which is not true), and assuming that ocean crust that is 30 Ma old lies at a depth of 4500 meters (which is true), briefly explain the origin of this sedimentary sequence in terms of the factors controlling biogenous sedimentation in the deep sea, evolution of continental margins, and subsidence of ocean crust. Use diagrams if you wish. (25 pts)

B. Also answer the following questions concerning the sequence above. (20 pts)

1. What is the color and probable composition of the clay in the interval from 1150-1250 meters? Briefly explain the reasons for your answers.

2. Sketch the sequence of sedimentary structures that would be found at 1000 meters. Label your sketch with letters usually used for the various sections of the sequence. What is this sequence called?

A. The sedimentary sequence on the left was drilled at a depth of 5000 meters in the western south Atlantic off Brasil by the Glomar Challenger. Briefly explain the origin of this sedimentary sequence in terms of the factors controlling carbonate sedimentation in the deep sea, subsidence of ocean crust, and the evolution of continental margins. (10 pts.)

A. The sedimentary sequence on the left was drilled at a depth of 6500 meters east of Japan in the Pacific by the Glomar Challenger on crust of late Jurassic (~150 Ma) age. Assuming that the CCD everwhere in the Pacific except along the Equator has been at a depth of 4500 meters since the late Jurassic (which is not true), and assuming that ocean crust that is 30 Ma old lies at a depth of 4500 meters (which is true), briefly explain the origin of this sedimentary sequence in terms of sedimentation rates, the factors controlling biogenous sedimentation in the deep sea, subsidence of ocean crust, and plate motions. Use diagrams if you wish.

B. Also answer the following questions concerning the sequence above. (20 pts)

1. What is the color and probable origin of the clay in the intervals from 575-625 meters and from 375-425 meters? Briefly explain the reasons for your answers.

2. How would this section appear in a seismic reflection profile?