H. Williams               HISTORICAL GEOLOGY

EXAM 4 REVIEW

CENOZOIC GEOLOGY

EARLY CENOZOIC :

Gulf Coast: Main area of marine transgressions and regressions during Cenozoic, this, combined with pronounced subsidence, resulted in about 10,000 m of Cenozoic sediments underlying the Gulf Coast.

East Coast: Relatively quite during the Cenozoic. The erosion of the Appalachians continued, producing subdued, rounded mountains (characteristic of ancient mountains). The coastal plain and continental shelf continued to be built from clastics in the northeast and carbonates in the southeast (Florida).

Rockies: Continuing uplift and erosion shaped the Rockies into rugged, sharp peaks (characteristic of youthful mountains). In some areas, large fault blocks were pushed up to form mountain ranges, such as the Tetons of Wyoming.

West Coast Tectonics: Subduction down much of the west coast stopped in the Cenozoic, as the the Farallon Plate and the east Pacific Rise were swallowed by the subduction zone. Remnants of the Farallon Plate remain today as the Cocos Plate and the Juan de Fuca Plate. The subducting Juan de Fuca plate has formed a volcanic arc inland - the Cascades Range. Much of the former subduction zone on the west coast has become a transform fault - the San Andreas Fault.

Basin And Range Province: Tensional forces developed in large areas of Nevada, Arizona, New Mexico and South California during the Cenozoic, probably resulting from the change from subduction to transform fault along the craton margin and heat flow from subduction. The result was basin and range topography, characterized by tilted fault blocks, normal faults, grabens and horsts.

Colorado Plateau: A large block of crust in the southwest remained relatively undeformed, but was uplifted during the Cenozoic (5 -10 mybp), forming the Colorado Plateau. Streams cut down into the plateau as it was lifted up, forming deep canyons, including the Grand Canyon (2600 m deep). The Colorado Plateau is surrounded by lava flows from faults around the margins of the plateau. 

Tethys Seaway: Closure of the Tethys Seaway was completed during the Cenozoic. Africa collided with Europe about 40 million years ago. India collided with Asia about 10 million years ago.

CENOZOIC LIFE/HUMAN ORIGINS: The CENOZOIC = "Age of Mammals". Mammals evolved characteristics that were adaptations to the changing environment. Perhaps the most important of these environmental changes was the appearance of GRASSES and vast PRAIRIES in the Miocene Epoch. Why did grasslands expand during the Cenozoic? The answer involves orogenic activity, winds, rain, climate and back arc basin sedimentation. Many ungulates (hoofed mammals) are grazing animals (Ruminants - adapted to grass diet). Ungulates are classified according to the number of toes; PERISSODACTYLS = odd-toed (middle toe carried weight-> single hoof; ARTIODACTYLS = even-toed (middle 2 toes carried weight -> cloven hoof). Other important orders included the carnivorous predators that preyed on the grazing mammals - ORDER CARNIVORA; and the mammals with trunks, forerunners of the modern elephant -ORDER PROBOSCIDEA.

Particularly important, of course, was the evolution of the order PRIMATES. The primates evolved into the Late Cenozoic ancestors of Homo sapiens, who appeared in the Pleistocene.

Human Origins: Many primate characteristics developed in response to a life in the trees and then a life on the open prairie, as forests were replaced by grasslands in the Miocene. Some of those characteristics are: 5 digits; opposable thumb; grasping hand; non-specialized teeth; complex vocal capability; color vision; closely-spaced eyes; smaller snout; flatter face (LAST 3 -> STEREO VISION). The order PRIMATES is divided into 2 suborders; the more primitive PROSIMIANS ("pre-monkeys") which lack some of the characteristics above (e.g. STEREO VISION), and the more advanced ANTHROPOIDS (including modern monkeys, apes and man), which have more of these characteristics. The classification scheme is based on grouping together primates with similar features into progressively narrower subdivisions i.e. Order (e.g. Anthropoidea) = collection of similar families; Family (e.g. Hominidae) = collection of similar genera; Genus (e.g. Homo) = collection of similar species; Species (e.g. sapiens) = collection of similar individuals. One of the families that developed from the anthropoids - HOMINIDAE - consisted of African apes and humans ("the family of Man"). It was from this family that Homo sapiens, the species of "Modern Man" evolved. Recap terminology:
SUPER FAMILY, HOMINOIDEA, "hominoids," all apes and humans.
FAMILY HOMINIDAE, "hominids," African apes and humans.
SUB FAMILY HOMININAE, "hominins," HUMANS: all members of the genus Homo and their extinct fully bipedal ancestors.

Homo erectus: One of the descendants of the Australopithecus line was Homo erectus, who appeared maybe as early as 1.8 million ybp. This is the first true species of the Genus Homo. Homo erectus was widespread in Africa and Asia by 750,000 ybp. Some of the differences from Australopithecus = taller, excellent walker (feet did not turn out) and, ESPECIALLY, a larger brain (775-1300 c.c. - modern Man = 1200-1500 c.c.). This larger brain was reflected in a greater use of tools and hunting in bands. The heavy brow ridge and chinless jaw remained and distinguished Homo erectus from Homo sapiens. Homo erectus is best remembered as the stage of BRAIN ENLARGEMENT.

Homo sapiens neanderthalensis: "Neanderthal Man", named after the Neander Valley in Germany. Neanderthals probably evolved in Europe from African ancestors appearing about ~300,000 years ago. Homo sapiens evolved in Africa 300,000 years ago and spread to Europe around 50,000 years ago.The Neanderthal is considered by some a "subspecies" of Modern Man - having many similarities, but also a few differences e.g. they were shorter, had the brow ridge and chinless jaw; the rest of their skeleton was the same as modern Mans and their brains were as large as ours. The Neanderthals had a complex culture, including use of fire and a belief in "an afterlife".

Homo sapiens sapiens: or "Cro-magnon Man", spread to France about 50 000 ybp, competing with the Neanderthals and possibly causing them to become extinct by about 28 000 ybp. The Cro-magnons were essentially the same as modern Man and we descended directly from them. They developed culture even farther, including cave paintings in Europe. Cro-magnons spread all over the old world, and then, during the last glaciation crossed the Bering Strait land bridge into the "New World" - North America. Originally these Humans were hunter/gathers, but by about 10-15 000 ybp they developed agriculture, built cities and invented writing. The era of "recorded history" had began.

Early Man In The Americas: Just when Man moved into North America is still not certain. There is evidence from Human artifacts that shows people were here prior to 11 000 ybp and maybe prior to 20 000 ybp. The oldest known Human remains from South America are dated at 12 600 ybp.

 EXAMPLE QUESTIONS:

MULTIPLE CHOICE:

About 10 million years ago, during the Cenozoic, the east Pacific Rise was subducted, creating:

a. The Columbia Plateau b. The San Andreas Fault c. The Colorado Plateau d. The Sierra Nevada e. The Cascades

The great expansion of grasslands and prairies took place in the:

a. Pleistocene b. Cretaceous c. Miocene d. Holocene e. Mesozoic

"Neanderthal Man" was named after:

a. A mountain in Australia b. A cave in France c. A river in Spain d. A valley in Germany

e. A notorious heavy metal band

Hominidae are:

a. Chimps and apes   b. primitive monkeys   c. primates with human-like features   d. bipedal gorillas   e. a type of tree shrew

2. How did changing environmental conditions affect the evolution of Hominins?

3. What group of mammals includes grazing animals? What bodily changes enabled them to a. Use grass as a food source and, b. Escape predators.

4. Explain how orogenic activity, winds, rain, climate and back arc sedimentation caused the expansion of grasslands during the Cenozoic.

5. What was the Farallon Plate and what happened to it in the Cenozoic? What features of the west coast are related to the Farallon Plate?

6. Describe primate characteristics that probably developed in response to a life in the trees and then, later, on the open prairie.

7. Compare and contrast the Columbia Plateau and Colorado Plateau in terms of origin, common rocks and landforms.

8. Much of the landscape as it appears today resulted from a number of "land-forming" events of the Cenozoic. Describe the origin and present day appearance of four "land-form regions" that formed in the U.S. in the Cenozoic.

Two of these longer answer questions will be on the final; you will select one to answer.