# Presentation: 782540

## Important Stratigraphic and Geomorphic Concepts

- Facies

## Facies

- A sediment body or sedimentary rock distinguished by its lithology, geometry, sedimentary structures, proximity to other  sediments or sed rocks, and fossil content.
-  Formed by and characteristic of a particular depositional environment.

## Facies refers to various sediment characteristics  you might refer to a "tan, laminar-bedded, beach sandstone facies". 
Rock unit characteristics result from depositional environment (energy).
Depositional setting imprints a distinctive sediment characteristics..
 facies is a distinct kind of rock for that environment and area.

- Rock unit characteristics result from **depositional environment (energy)**.
- Depositional setting imprints a distinctive sediment characteristics..
-  facies is a distinct kind of rock for that environment and area.

## Each depositional environment grades laterally into other environments. We call this facies change when dealing with the rock record. 

A = Sandstone facies (beach environment)

B = Shale facies (offshore marine environment)

C = Limestone facies (far from sources of terrigenous input) 

- A = Sandstone facies (beach environment)
- B = Shale facies (offshore marine environment)
- C = Limestone facies (far from sources of terrigenous input)

**Notes:**
The term rock here can mean both consolidated and unconsolidated material.

## Slide 5

**Notes:**
Sediment sequences created by marine transgression (sea level rise). Note both vertical (fining upward) and lateral sediment distributions and migration of the depositional environments.

## time line

**time line**

**Notes:**
At a constant elevation, (from drill cores) one migrates laterally up-sequence (overlying facies) to left, or down-sequence (underlying facies) to right. The lateral sequence matches the vertical sequence.  Note time line – points of equal age along a lateral transect. 

## Walther's Law – (continuous deposition) 

Sedimentary environments that start out side-by-side will overlap one another over time due to transgressions or regressions. A vertical sequence of beds results. 

The vertical sequence of a facies matches the original lateral distribution of sediments and sedimentary environments. 

Transgressive sequence
Deeper water facies overlie shallow water facies.
A "deepening upward“ or “fining upward” sequence. 

- Sedimentary environments that start out side-by-side will overlap one another over time due to transgressions or regressions. A vertical sequence of beds results.
- The vertical sequence of a facies matches the original lateral distribution of sediments and sedimentary environments.
**Transgressive sequence**
- Deeper water facies overlie shallow water facies.
- A "**deepening upward**“ or “fining upward” sequence.

- Offshore
-      LS

- Beach
-  sands

- Nearshore
-       silt

- Offshore
-    Clay

## What is this facies
    Sequence?

Shallow water facies overlie deeper water facies.

A regressvive sequence
 "shallowing upward"

**    ****Sequence?**
- Shallow water facies overlie deeper water facies.
- A regressvive sequence
-  **"shallowing upward"**

**LS**

**SS**

**SH**

**Lime**
** ****SH**

**Notes:**
The facies concept is important to soil scientists because one can predict  sediment composition (texture) and distribution (spatial distribution) by an understanding of the depositional environment, which may result by marine, fluvial, glacial, eolian, or gravity processes.   

## Slide 9

**Notes:**
A “coarsening upward” sequence.  What does this imply about facies migration and geologic history?.  Where is the time line?

## Laws of Stratigraphy

**Superposition**- youngest on top
**Original lateral continuity**- erosion cuts valleys
**Original horizontality**- most sediments deposited in horizontal layers, or nearly so.
**Cross-cutting relations**-  A feature must be younger than the rock, sediment, or surface it cuts
**Inclusions**- must be older than their host

**Notes:**
Some major stratigraphic principles. 

## Basic Stratigraphic Priniciples

**Nicolaus Steno (1638-1687)**

- fossil descriptions
- first stratigrapher
- Steno's Laws

- Superposition
- Original Horizontality
- Original Lateral Continuity

## Law  of  Superposition

***youngest material on top; ***
***except if inverted***
**Fundamental principle for age relationships in sedimentary rocks (sediments) and extrusive volcanics**

## Superposition

- Younger

## Steno's Laws

**Superposition**

## limey mudstone over coal;  ND

*E.E. Gamble*

## E.E. Gamble

*E.E. Gamble*

- Two till units that sandwich an outwash;  MN

## soil geomorphic analogue 

**soil geomorphic analogue **
**2** **Holocene alluviums; fragipan (dryer altithermal), vs. humid environment.      MS**

***Wysocki***

**Notes:**
Superposition has direct application in soils.

## Pleistocene Loess Deposits Eastern WA

**Pleistocene Loess Deposits Eastern WA**

**Gamble**

**Notes:**
Note both superposition and cross cutting (hillslope beveling).

- Original Continuity

- Steno’s law of

**Notes:**
Original basin extent depositional setting control the sediment distribution. Despite present physical separation and compositional variation the strata are age equivalent    

## Lateral Continuity

## Slide 21

## Badlands, SD

*E.E. Gamble*

## Cross-cutting  Relations

*	** *relative age relationships* *

***A feature is younger than the rock, sediment, surface, or other feature that it cuts. ***

## Relative Age Tools: Cross-Cutting Relations

- A rock unit must always be *older* than any feature that cuts or disrupts it (e.g., faults, metamorphism, igneous intrusions).

**Notes:**
What is the time sequence?  What is the age of the fault?

## Cross-cutting RelationshipsArray features A, B, C, D, E by age.

**A**

**B**

**C**

**D**

**E**

## Cross Cutting Surface

**Cross Cutting Surface**

**Notes:**
Cross cutting relationship by hillslope erosion or processes.

## Converging, backwearing side slopes

**Converging, backwearing side slopes**
- ( St. Peter ss (Boone soil) over Prairie Du Chein dolomite;   River Falls, WI )

*Wysocki*

**Notes:**
What is the age of the colluvium above the bedrock?

## 		   Inset Relationship

***	******	******   ******Inset Relationship***
*   **( type of cross-cutting relationship )*

**Notes:**
Note both the stratigraphic and topopgraphic (elevation) relationship.
In this diagram Bed 2 is topographically lower, but stratigrapically above
 Bed 1.  Note also that the stratigraphic contact must be observed at a specific and limited location. 

## inset relationship;  northeast KS

*Wysocki*

**Notes:**
Inset examle

## channel fill; note topo.  / Big Nemaha R., NE

*Wysocki*

**Notes:**
Holocene channel fills Nemeha River.  Terrace or Flood Plain?

## Cross-Cutting Relations and Inclusions

**Notes:**
What is the age of the granite?  What do the (field observations) rock inclusions, contact zone, and granite pebbles indicate about age.  

## Facing of Strata:how some sedimentary structures indicate if beds are overturned..

**Notes:**
Compositional details and primary observation can indicate age and site history.

## Hutton’s “Great unconformity” 
at Siccar point, 
eastern Scotland

- Hutton’s “Great unconformity”
- at Siccar point,
- eastern Scotland

**Notes:**
Age and geologic context at Hutton’s “Great unconformity”.

## Relative Time

- Superposition (Steno)
- Lateral Continuity (Steno)
- Original Horizontality (Steno)
- Inclusions (Lyell)
- Cross-cutting Relationships (Lyell)

**Notes:**
Major principles for age assessment.

## Relative Time

## the Batholith, and the Limestone and Shale units.   

**Quiz - Array by age:  Faults A & B, Dikes A & B,  **
**the Batholith, and the Limestone and Shale units.**** ****  **

## Shale 		Youngest

**Dike A**
**Dike B**
**Batholith**
**Fault B**
**Fault A **
**Limestone  ****	****Oldest**