SOURCES of ROCK and FOSSIL DATA

• SURFACE DATA:

Equipment:

- Measuring Tools

- Collecting Tools

- Recording Equipment

• SUBSURFACE DATA:

- Core Logging

SOURCES of GEOPHYSICAL DATA

• Remote Sensing

• Geophysical Well Logs

- S.P.

- Resistivity

- Induction

- Dipmeter

- Radioactivity

- Sonic

- Caliper

- Temperature

• Reflection Seismic Survey

• Gravity

• Magnetic

Lithostratigraphic Units

Supergroup

Group A

Formation A

Member A

Member B

Member C

Formation B

Member D

Member E

Member F

Formation CMember G

Member H

Group B

Formation D

Member I

Member J

Member K

Member L

Member M

Formation E

Member N

Member O

Member P

Member Q

Formation F

Member R

Member S

Member T

Supergroup|

Group|

Formation|

Member|

Bed

• Lithostratigraphy is a sub-discipline of stratigraphy, the geological science associated with the study of strata or rock layers. Major focuses include geochronology, comparative geology, and petrology. In general a stratum will be primarily igneous or sedimentary relating to how the rock was formed.

Sedimentary layers are laid down by deposition of sediment associated with weathering processes, decaying organic matters (biogenic) or through chemical precipitation. These layers are distinguishable as having many fossils and are important for the study of biostratigraphy.

Igneous layers are either plutonic or volcanic in character depending upon the cooling rate of the rock. These layers are generally devoid of fossils and represent intrusions and volcanic activity that occurred over the geologic history of the area.

• A lithostratigraphic unit conforms to the law of superposition, which state that in any succession of strata, not disturbed or overturned since deposition, younger rocks lies above older rocks. The law of horizontal continuity states that a set of bed extends and can be traceable over a large area.

• Lithostratigraphic units are recognized and defined on the basis of observable rock characteristics. The descriptions of strata based on physical appearance define facies. Lithostratigraphic units are only defined by lithic characteristics, and not by age.

• Stratotype : A designated type of unit consisting of accessible rocks that contain clear-cut characteristics that are characteristic for a particular lithostratigraphic unit.

Lithosome: Masses of rock of essentially uniform character and having interchanging relationships with adjacent masses of different lithology. E.g.: Shale lithosome, limestone lithosome…

Lithostratigraphic Example:

Grand Canyon

Principles (Laws) of Stratigraphy

Principle of…• Original Horizontality

• Superposition• Lateral Continuity

• Cross Cutting Relationships

• Inclusions• Faunal Succession

Walther’s Law

Nicholas Steno

1. Principle of Original Horizontality

A stratigraphic section of Ordovician rock exposed in central Tennessee, USA. The sediments composing these rocks were formed in an ocean and deposited in horizontal layers.

2. Principle of Superposition

Youngest Strata

Oldest Strata

Stratigraphic column on north shore of Isfjorden, Svalbard, Norway. Since there is no overturning, the rock at the bottom is older than the rock on the top by the Principle of Superposition.

3. Principle of Lateral Continuity

Lateral Continuity

4. Principle of Cross Cutting Relationships

5. Principle of Inclusions

Stratigraphic Relationship

• Two types of contact: Conformable and Unconformable.

• Conformable: Unbroken deposition, no break or hiatus (break or interruption in the continuity of the geological record). The surface strata resulting is called a conformity.

• Two types of contact between conformable strata: Abrupt contacts

(Directly separate beds of distinctly different lithology, minor depositional break, called Diastems) Gradational contact (Gradual change in deposition, mixing zone).

Unconformable: Period of erosion/non-deposition. The surface stratum resulting is called an unconformity.

Four types of unconformity

• Angular unconformity Younger sediment lies upon an eroded surface of tilted or folded older rocks. The older rock dips at a different angle than the younger.

• Disconformity The contact between younger and older beds is marked by visible, irregular erosional surfaces. Paleosol might develop right above the disconformity surface because of the non-deposition setting.

• Paraconformity The bedding plans below and above the unconformity are parallel. A time gap is present but there is no erosion, just a non-deposition period.

• Nonconformity Relatively young sediments are deposited right above older Igneous or metamorphic rocks.

Disconformity with the Lower Cretaceous Edwards Formation overlying a Lower Permian limestone; hiatus is about 165 million years; Texas.

Boundaries:Conformable Bed Contacts

Gradational Sharp

Boundaries:Unconformities

Gaps in Rock = Gaps in Time

Types of Unconformities: Nonconformity

Nonconformity - Grand Canyon

Using Inclusions to Recognize a Nonconformity

• Fragments of a rock unit (xenolith meaning foreign rock) which are included in another (host) rock unit must be older than the host rock. This may occur in sedimentary environments, where pieces of pre-existing rock can be ripped up and included in younger sediments. Alternatively, when igneous rocks are intruded, fragments of the country rock may be incorporated into the intrustion.*

Types of Unconformities: Angular Unconformity

Formation of an Angular Unconformity

Angular Unconformity in the Grand Canyon

The Angular Unconformity

at Siccar Point, Scotland

Source: Edward A. Hay, De Anza College, Cupertino, CA

Types of Unconformities: Disconformity

Formation of a Disconformity

Walther’s Law

Johannes Walther(1860-1937)

Concept ofSedimentary Facies

Sedimentary Facies refers to all of the characteristics of a particular

rock unit.The characteristics of the rock unit

come from the depositional environment.

Facies

Depositional Environments

Sedimentary Depositional Environment describes the combination of physical, chemical and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be formed after lithification, if the sediment is preserved in the rock record

Types of depositional environment

Continental

• Alluvial

• Aeolian

• Fluvial

• Lacustrine

Continental

• ALLUVIAL- Alluvium (from the Latin, alluvius, from alluere, "to wash against") is loose, unconsolidated (not cemented together into a solid rock), soil or sediments, eroded, deposited, and reshaped by water in some form in a non-marine setting.

Continental

Alluvium is typically made up of a variety of materials, including fine particles of silt and clay and larger particles of sand and gravel. When this loose alluvial material is deposited or cemented into a lithological unit, or lithified, it would be called an alluvial deposit.

• The term "alluvium" is not typically used in situations where the formation of the sediment can clearly be attributed to another geologic process that is well described. This includes (but is not limited to): lake sediments (lacustrine), river sediments (fluvial), or glacially-derived sediments (glacial till).

• Most, if not all, alluvium is very young (Quaternary in age), and is often referred to as "cover" because of the fact that these sediments obscure the underlying bedrock. Most sedimentary material that fills a basin ("basin fill") that is not lithified is typically lumped together in the term alluvial.

• Alluvium can contain valuable ores such as gold and platinum and a wide variety of gemstones. Such concentrations of valuable ores is termed a placer deposit.

Section of alluvium at the Blue Ribbon Mine in Alaska

Outcrop of Enon Conglomerate formed by Alluvial deposits in the Gamtoos Valley, Eastern Cape, South Africa

An alluvial fan is a fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads typically at the exit of a canyon onto a flatter plain. A convergence of neighboring alluvial fans into a single apron of deposits against a slope is called a bajada, or compound alluvial fan.

A vast alluvial fan blossoms across the desolate landscape between the Kunlun and Altun mountain ranges that form the southern border of the Taklamakan Desert in Xinjiang.

Alluvial fan in the French Pyrenees

Continental

• EOLIAN - processes pertain to the activity of the winds and more specifically, to the winds' ability to shape the surface of the Earth and other planets. Winds may erode, transport, and deposit materials, and are effective agents in regions with sparse vegetation and a large supply of unconsolidated sediments.

• Although water is much more powerful than wind, aeolian processes are important in arid environments such as deserts.

• The term is derived from the name of the Greek god, Æolus, the keeper of the winds.

Particles are transported by winds through:

• suspension

• saltation

• creep.

Crossbedding of sandstone near Mt. Carmel road, Zion Canyon, indicating wind action and sand dune formation prior to formation of rock.

• FLUVIAL is used to refer to the processes associated with rivers and streams and the deposits and landforms created by them.

Channel pattern

• Straight river, which are found in the most tectonically incised/active areas. This is more of a hypothetical end-member, and are not often found in nature. Straight-type channels can be found at alluvial fans.

• Meandering rivers which form a sinuous path in a usually low-gradient plain toward the end of a fluvial system.

• Braided rivers, which form in (tectonically active) areas that have a larger sedimentary load than the discharge of the river and a high gradient.

• Anastomosed River is a rare case of a relatively straight, complicated vertical sequence of river deposits with banks held together by dense vegetation.

• Lacustrine -lake (from Latin laus) is a terrain feature, a body of liquid on the surface of a world that is localized to the bottom of basin (another type of landform or terrain feature; that is, it is not global) and moves slowly if it moves at all. Another definition is, a body of fresh or salt water of considerable size that is surrounded by land

On Earth, a body of water is considered a lake when it is inland, not part of the ocean, is larger and deeper than a pond, and is fed by a river.

• Natural lakes on Earth are generally found in mountainous areas, rift zones, and areas with ongoing or recent glaciation. Other lakes are found along the courses of mature rivers. In some parts of the world, there are many lakes because of chaotic drainage patterns left over from the last Ice Age.

• All lakes are temporary over geologic time scales, as they will slowly fill in with sediments or spill out of the basin containing them.

Transitional

• Deltaic

• Tidal

• Lagoonal

• Beach

• A delta is a landform that is created at the mouth of a river where that river flows into an ocean, sea, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river. Over long periods of time, this deposition builds the characteristic geographic pattern of a river delta.

• Herodotus the great historian coined the term delta for the Nile River delta because the sediment deposited at its mouth had the shape of the upper-case Greek letter Delta: Δ.

Types of Delta:– River-dominated deltas– Wave-dominated deltas– Tide-dominated delta

• River-dominated delta, such as the Mississippi River Delta, usually take on a multi-lobed shape that results from repeated sequences of channel occupation, offshore deposition, and channel avulsion.

• When a single channel is occupied for a long period of time, its deposits extend the channel far offshore, and causes the delta to resemble a bird's foot; the term “digitate delta" is sometimes used as well. These deltas are often characterized by a main channel that divides itself into several distributary channels.

• Wave dominated deltas, wave erosion controls the shape of the delta, although deposition still outweighs the amount of erosion and the delta is able to advance into the sea. Deltas of this form, such as the Nile Delta, tend to have a characteristic Greek-capital-delta shape .

The Ganges-Brahmaputra River delta in India and Bangladesh is a massive tide-dominated delta. It is one of the most fertile regions in the world.

Tidal deltas behave differently from river- and wave-dominated deltas, which tend to have a few main distributaries. Once a wave- or river- distributary silts up, it is abandoned, and a new channel forms elsewhere.

In a tidal delta, new distributaries are formed during times when there's a lot of water around - such as floods or storm surges. These distributaries slowly silt up at a pretty constant rate until they fizzle out.

Tides are the rise and fall of sea levels caused by the combined effects of the rotation of the Earth and the gravitational forces exerted by the Moon and the Sun. The tides occur with a period of approximately 12 and a half hours and are influenced by the shape of the near-shore bottom

• Erosion is also an important control in tide dominated deltas, such as the Ganges Delta, which may be mainly submarine, with prominent sand bars and ridges. This tends to produce a "dendritic" structure. Tidal deltas behave differently from river- and wave-dominated deltas, which tend to have a few main distributaries.

Lagoon is a body of comparatively shallow salt or brackish water separated from the deeper sea by a shallow or exposed barrier beach, sandbank of marine origin, coral reef, or similar feature. Thus, the enclosed body of water behind a barrier reef or barrier islands or enclosed by an atoll reef is called a lagoon.

This application of lagoon in English dates from 1769. It adapted and extended the sense of the Venetian laguna

Beach is a geological landform along the shoreline of a body of water. It usually consists of loose particles which are often composed of rock, such as sand, gravel, pebbles, or cobbles. The particles of which the beach is composed can sometimes instead have biological origins, such as shell fragments or coralline algae fragments.

Marine

• Shallow water marine

• Deepwater marine

• Reef

Others

• Evaporite

• Glacial

Marine Transgression = Sea Level Rise

Marine Regression = Sea Level Fall

Walther’s LawSedimentary environments that started out side-by-side

will end up overlapping one another over time due to transgressions and regressions.

Limestone Shale Siltstone Sandstone

Reef Lagoon Near Shore Beach

Environment

Facies

Marine Trangression

Walther’s Law

Marine Regression

“The sea goes in, the sea goes out.”

Correlation

A B C

Regression

Transgression

Example of Correlation

Colorado Plateau Correlation

Colorado Plateau Correlation

6. Principle of Faunal Succession

Sketch by Baron Cuvier (1769-1832)

William “Strata” Smith

6. Principle of Faunal Succession" . . . each stratum contained organized fossils peculiar to itself, and might, in cases otherwise doubtful, be recognized and discriminated from others like it, but in a different part of the series, by examination of them."

Biostratigraphy

Defined by first and last appearance of index fossils and/or fossil assemblages

Superzone - Biozones - Subzones

Chronostratigraphy and the

Development of the Geologic Time Scale

GeologicTimeScale

Era Age (Myrs) Epoch

0.01Holocene

1.8Pleistocene

5.3Pliocene

23.8Miocene

33.6Oligocene

54.8Eocene

65Paleocene

144

206

248

290

323

354

417

443

490

543

2500

3800

Precambrian

Phanerozoic

Eon

Proterozoic

Archean

Hadean

Period

Quaternary

Tertiary

Neogene

Paleocene

Mississippian

Cenozoic

Mesozoic

Paleozoic

Cretaceous

Jurassic

Age of the Earth 4600 Myrs (4.6 Byrs)Source: Geological Society of America (1999)

Geologic Time Scale

Devonian

Silurian

Ordivician

Cambrian

Triassic

Permian

Pennsylvanian

Relative Dating of Rocks Using Stratigraphic Principles

Example 2 of Relative Time

Orbit w/o eccentricity Orbit w/ eccentricity