How to Treat a Fossil in Geological Fieldwork

Complete the following article putting "some", "any", “a” or “the” in the blank spaces ( R.P. 2.3)

Fossils cannot be considered in isolation from their environment. All the features found in a fossiliferous rock must be recorded if you are to gain _______ benefit from the examination of the fossil. Note the abundance of the fossils in each fossiliferous horizon of the locality: is there _______ particular pattern? Are the fossils widespread or clustered into groups? Did _______ fossils die where they were found or were they transported there after death? Do they show _______ alignments due to currents? Different fossils may occur in different parts of the same horizon and there may be _______ lateral changes which can be traced over considerable distances. There may also be _______ vertical changes as the depth of the water the rocks were deposited in changed. Do not be over-anxious to collect _______ fossil when you find it. First, study it in place, noting its attitude and surroundings; make _______ notes with sketches if necessary. You will probably see only a small part of _______ fossils, perhaps because only a small part is exposed, or because only fragments survive. Decide how best to remove the specimen from the rock, then removes it carefully, trying to keep it intact. If you find _______ fossil deposit, don't be greedy, take only one specimen, leave _______ for others. However, you will usually only be able to collect incomplete fossils. _______ may show external features, _______ internal casts: collect both. _______ fossil left behind will be a help to those geologists that come after you. As with rocks, name the fossils in situ, but before going into the field you should revise the types you may expect to see in the rocks you will be looking at. Do not be discouraged if you cannot name _______ fossil you find; often _______ expert help is often needed in this domain. Remember you will not find _______ better clue for reconstructing the geological environment in which the fossil lived and the geological time scale.

4. ORAL COMMUNICATION-Geologic time scale.

Read the following text and pay special attention to the pronunciation of the geological periods.

The Geological Column

The geological column is the full record of the Earth’s crust rocks laid down in sequence. This column is based on rock units, each comprising rock layers created in one geological period of time. In ascending order several of the time rock units called zones make up one stage; several stages form a series; several series build a system; several systems make an erathem.

Geologic Time Scale

The geological time scale is used by geologists and other scientists to describe the timing and relationships between events that have occurred during the history of the Earth. The table of geologic periods presented here is in accordance with the dates and nomenclature proposed by the International Commission on Stratigraphy.

Current radiometric dating evidence indicates an age of the Earth of about 4570 million years old (expressed with m.y.a. or "Ma" as in "it dates from 4570 Ma"). The geological or deep time of Earth's past has been organized into various units according to events which took place in each period. Different spans of time on the time scale are usually delimited by major geological or paleontological events, such as mass extinctions. For example, the boundary between the Cretaceous period and the Paleogene period is defined by the extinction event that marked the demise of the dinosaurs and of many marine species.

History of the time scale

The principles underlying geologic (geological) time scales were laid down by Nicholas Steno in the late 17th century. Steno argued that rock layers (strata) are laid down in succession, and that each represents a "slice" of time. He also formulated the principle of superposition, which states that any given stratum is probably older than those above it and younger than those below it. Steno's principles were simple; applying them to real rocks proved complex. Over the course of the 18th century geologists came to realize that: 1) Sequences of strata were often eroded, distorted, tilted, or even inverted after deposition; 2) Strata laid down at the same time in different areas could have entirely different appearances; 3) The strata of any given area represented only part of the Earth's long history.

The first serious attempts to formulate a geological time scale that could be applied anywhere on Earth took place in the late 18th century. The most influential of those early attempts (championed by Abraham Werner, among others) divided the rocks of the Earth's crust into four types: Primary, Secondary, Tertiary, and Quaternary. Each type of rock, according to the theory, formed during a specific period in Earth history. It was thus possible to speak of a "Tertiary Period" as well as of "Tertiary Rocks." Indeed, "Tertiary" and "Quaternary" remained in use as names of geological periods well into the 20th century.

The identification of strata by the fossils they contained, pioneered by William Smith, Georges Cuvier, and Alexandre Brogniart in the early 19th century, enabled geologists to divide Earth history more finely and precisely. It also enabled them to correlate strata across national (or even continental) boundaries. If two strata (however distant in space or different in composition) contained the same fossils, chances were good that they had been laid down at the same time. Detailed studies of the strata and fossils of Europe produced, between 1820 and 1850, the sequence of geological periods still used today.

British geologists dominated the process, and the names of the periods reflect that dominance. The "Cambrian," "Ordovician," and "Silurian" periods were named after ancient British tribes (and defined using stratigraphic sequences from Wales). The "Devonian" was named for the English county of Devon, and the name "Carboniferous" was simply an adaptation of "the Coal Measures," the old British geologists' term for the same set of strata. The "Permian," though defined using strata in Russia, was delineated and named by a British geologist: Roderick Murchison.

British geologists were also responsible for the grouping of periods into Eras and the subdivision of the Tertiary and Quaternary periods into epochs.

When William Smith and Sir Charles Lyell first recognized that rock strata represented successive time periods, there was no way to determine what time scale they represented. Creationists proposed dates of only a few thousand years, while others suggested large (and even infinite) ages. For over 100 years, the age of the Earth and of the rock strata was the subject of considerable debate. Advances in the latter part of the 20th century allowed radioactive dating to provide relatively firm dates to geological horizons. In the intervening century and a half, geologists and paleontologists constructed time scales based solely on the relative positions of different strata and fossils.

In 1977, the Global Commission on Stratigraphy (now the International Commission) started an effort to define global references (Global Boundary Stratotype Sections and Points) for geologic periods and faunal stages.

Terminology

The major divisions are shown in the scale of relative geologic time (Table 1), which is arranged in chronological order with the oldest division at the bottom, the youngest at the top.

Eons are the largest intervals of geologic time and are hundreds of millions of years in duration. In the time scale the Phanerozoic Eon is the most recent eon and began 570 million years ago. Eons are divided into smaller time intervals known as eras. In the time scale the Phanerozoic is divided into three eras: Cenozoic, Mesozoic and Paleozoic. Very significant events in Earth's history are used to determine the boundaries of the eras.

Eras are subdivided into periods. The events that bound the periods are wide-spread in their extent but are not as significant as those which bound the eras. In the time scale above you can see that the Paleozoic is subdivided into the Permian, Carboniferous, Devonian, Silurian, Ordovician and Cambrian periods.

Finer subdivisions of time are possible and the periods are subdivided into epochs. Geologists tend to talk in terms of Upper/Late, Lower/Early and Middle parts of periods and other units – e.g. "Upper Jurassic", "Middle Cambrian". Upper, Middle, and Lower are terms applied to the rocks themselves, as in "Upper Jurassic sandstone," while Late, Middle, and Early are applied to time, as in "Early Jurassic deposition" or "fossils of Early Jurassic age." The adjectives are capitalized when the subdivision is formally recognized, and lower case when not; thus "early Miocene" but "Early Jurassic." Because geologic units occurring at the same time but from different parts of the world can often look different and contain different fossils, there are many examples where the same period was historically given different names in different locales. It is a key aspect of the work of the International Commission on Stratigraphy to reconcile this conflicting terminology and define universal horizons that can be used around the world

Geologic Time Scale

EON	ERA	PERIOD	EPOCH	AGE (my)
PHANEROZOIC	CENOZOIC	Quaternary	Holocene	0.01
			Pleistocene	1.6
		Neogene	Pliocene	5.3
			Miocene	24
		Paleogene	Oligocene	37
			Eocene	58
			Paleocene	66
	MESOZOIC	Cretaceous	Late	144
			Middle
			Early
		Jurassic	Late	208
			Middle
			Early
		Triassic	Late	245
			Middle
			Early
	PALEOZOIC	Permian	Late	286
			Middle
			Early
		Carboniferous	Late	360
			Middle
			Early
		Devonian	Late	408
			Middle
			Early
		Silurian	Late	438
			Middle
			Early
		Ordovician	Late	505
			Middle
			Early
		Cambrian	Late	570
			Middle
			Early
PROTEROZOIC	Also known as Precambrian			2500
ARCHEAN				3960

Table 1: Geologic Time Scale

LISTENING COMPREHENSION

5.1. You will hear a radio report about fossils. Answer statements 1-10 by writing T (for True) and F (for False):

1. Fossils are restricted to sedimentary rocks, as well as igneous and metamorphic.

2. The process of fossilization takes place over long periods of time.

3. Oxygen plays an important role in the process of fossilization.

4. Fossils are usually preserved in different rocks.

5. Diagenesis is known as reduction, accompanied by some chemical reactions.

6. Coal was formed as a result of carbonization.

7. Fossils are simply interesting and beautiful structures.

8. The word fossil refers to anything in the ground.

9. Petrifaction has the same meaning as fossils.

10. Fossils can be divided into several groups.

5 .2. Listen to the report once more. Then, for statements 11-20, complete the notes that summarize what the speaker says. You will need to write a word or a short phrase in each box.

11. The Latin word fodere means .

12. The term fossil means the direct evidence of life.

13. Fossils are usually found in .

14. The process of takes place over a long time.

15. The organisms begin after death.

16. The process of takes place in the presence of oxygen.

17. The process of takes place in the absence of oxygen.

18. The hard parts of organisms resist .

19. The fossils are covered by layers of .

20. is the increase of pressure in the pore spaces o

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5.1 Geologic Time-the Earth in Context