L5_GeologicSetting

8/12/2019 L5_GeologicSetting

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Groundwater and Geology

This week – Sediments

• Unconsolidated clasticsediments

• Semi- consolidatedsediments

• Lithified sediments

– Sandstones

– Carbonates

– Igneous & MetamorphicRocks

• Extrusives

• Intrusives• Metamorphic

– Fractures

2(Schwartz & Zhang, 2003)



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http://capp.water.usgs.gov/gwa/

http://nationalatlas.gov/natlas/Natlasstart.asp

Click here

Click here

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Unconsolidated Clastic Sediments

Permeable

lenses of sandand gravel within

glacial till showawide variation in

bed thickness,

grain size, and

sorting of grains.

North Dakota.(USGS)

(Ritzi,WSU)



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(Schwartz & Zhang, 2003)

Blanket Sand and Gravel AquifersFluvial Deposits: Riverine Alluvial Aquifers:

Meandering River: Braided River:

NASA: Madagascar NASA: Indus River, July 2003

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Braided-stream Deposits

Coarse, braided-stream deposits showing disconnected sand lenses (S) and a

variety of cobble-dominated facies ranging from poorly-sorted massive units

(Gm), to moderately-sorted horizontally-bedded units (Gh) and trough

crossbedded units (Gt). Heavy lines identify bounding surfaces between

depositional sequences. Prime Earth quarry northwest of Boise, Idaho. For

scale, quarry face is approximately 12 m high.Boise State Center for Geophysical Investigation of the Shallow Subsurfacehttp://kihei.boisestate.edu/hydrogeophysical_research_site.htm



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(~50% of total groundwater pumpage)

B A

Sand/

Silt SandSilt, Clay

B A

Point bar

deposits

Natural levees

Backswamp

River

Gravel

(sand)

Alluvial River Valleys

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Fluvial systems - Meandering rivers

Allen & Allen (1990)



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Deposition builds up the river and

eventually it breaks through the

natural levee and changes

course—channel avulsions

Usually a wide variety of sediments are found in

any borehole—complex layering of high and low K

deposits

Buried channel gravels will provide best well yields


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(Fitts, 2002)




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Often in the Midwest:

Pleistocene

Coarse Sand and Gravel

(glacial outwash)

Holocene alluvium

mixed deposits

Alluvial River Valleys in the Midwestern US

Mix of materials is good—sand, gravel give goodT,Sy, clay, silt give good S, so drawdowns are low.

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Example: Lower Mississippi River Valley

Overbank clays

Outwash sands and gravels Filled braided channels

Meandering channel depositsRiver

Loess

silts

Alluvial River Valleys in the Midwestern US



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Evolution of Mississippi River fill through the late Quaternary

Allen & Allen (1990)

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Water quality

– usually good— Si and K can be high

• SiO2 15 - 30 mg/L

• K 5 – 10 mg/L

– If buried swamp deposits, reduced conditions

cause high Fe2+, Mn, H2S

– May have high TDS in arid regions with

evaporite minerals



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• Water Development Considerations – Advantages of wells in alluvial valleys• Ease of drilling

• Shallow water tables

• Highly productive wells

• Induced infiltration from rivers and wetlands

– (esp. Midwest and Southeast)

• Shallow wells near rivers provide “free” treatment of water.

• Good water quality

– Disadvantages• Ease of pollution

• Induced infiltration (water rights issues in the West)

• Doctrine of conjunctive use

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www.windows.ucar.edu/.../sed_alluvial.html


Fluvial Deposits: Alluvial Fans



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http://ktwu.washburn.edu/journeys/

High Plains (Alluvial Fan) Aquifer

http://ktwu.washburn.edu/journeys/

Statement from US Senator Jeff Bingaman:

“Currently, the Ogallala Aquifer is being mined at a much

higher rate than it is being recharged, and is showing

alarming declines in many areas. In just the last two decades,large portions of the aquifer show drops - between 10 to 40

feet - in the water table. That kind of drop reduces the

productivity of wells and greatly increases pumping costs. It

also poses a serious threat to the long-term viability of theagricultural economy served by the aquifer.”

http://www.saveourwatersupply.org/ogallala/index.html


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(Fitts, 2002)

Basin-fill Aquifers (Western US)



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Closed Basin-fill Aquifers

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Closed Basin-fill Aquifers

• Alluvial fan deposits coarse at basin margins;toward the basin center, fan deposits grow finer

• Faults can act as ground water barriers

• Water quality generally good, but can have poor quality due to evaporation

• Buried stream channels form best water sourcestoward center of basin; playa deposits in basincenters have low K



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Open (riverine) Basin-fill Aquifershttp://capp.water.usgs.gov/gwa/ch_i/I-reg_aq_systems6.html

Northern Rocky Mountains Intermontane Basins aquifer system

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Rio-Grande -

both open and closed basinshttp://capp.water.usgs.gov/gwa/ch_c/C-text4.html

USGSNASA



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Glacial-Deposit Aquifers



24(Fitts, 2002)

Glacial-Deposit Aquifers



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Mahonet Sand: Buried Alluvial Aquifer


(Ritzi,WSU)

(Ritzi,WSU)

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Semiconsolidated Clastic Sediments

NASA: Mid-Atlantic Coastal Plain

http://capp.water.usgs.gov/gwa/ch_l/L-northatl.html



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http://capp.water.usgs.gov/gwa/ch_e/E-text6.html

http://capp.water.usgs.gov/gwa/ch_e/E-text7.html

Texas Coastal Aquifer System

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Large sedimentary basins Typical rocks:

-Sandstone

-Siltstone

-Shale

-Limestone

Lithologic units, individually, are typically quite uniform and are

extensive. Locating good water bearing units is not difficult, nor is

identifying confining units

.

Oil well geophysical data is quite useful.

Consolidated Sediments: Sedimentary Rockshttp://capp.water.usgs.gov/aquiferBasics/sandstone.html

http://capp.water.usgs.gov/aquiferBasics/sandcarb.html



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Black Hills

Sandstone Aquifers: the Dakota SS

J.E. Williamson, USGS

Madison Limestone

KGS

Dakota Sandstone

D. Mayer

Cretaceous Seaway

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Sedimentary RocksOne major control on permeability is the degree of

cementation and consolidation. Medium-grained sand will

have a K of 1 to 30 cm/s, while typical corresponding

sandstone will be 0.001 to 0.5 cm/s, a reduction of 3 orders

of magnitude!

Well-log descriptions such as “well-indurated” or “friable” can be very important.

(J. Wilson, NMT)

Permian Sandstone Capping the Sandia Mountains, NM



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Sedimentary Basins

Water Quality (Distance down flow line!

) : – Typical anion sequence (Chebotarev Sequence)

HCO3- ! SO4

2- ! Cl-

– Low TDS! High TDS (higher than seawater)

Contributing factors

– Relative solubilities of CO32-, SO4

2-, and Cl-

minerals

– Common ion effect

– Ion exchange

– Ion filtration-

-

s h a l e Ion filtration:

Negative ions retained

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SO42-

Cl-

HCO3-

Rapid flow

•Much flushing

•Soluble minerals are

dissolved

Soil CO2 gives low pH

dissolution of CaCO3

Slow flow

Moderately soluble

minerals present

CaSO4 ! Ca2+ + SO42-

HCO3

- + CaSO4 !

Ca2+ + SO42- + HCO3

- !

SO42+ + H+ + CaCO3

CO2 + H2O + CaCO3

! Ca2+ + 2HCO3-

CH2O + !H2O !

!CH4 + !HCO3 + !H+

CH4 is due to bacterial

fermentation of organic

matter

Very slow flow

•Very soluble minerals

may be presentNaCl ! Na+ + Cl-

•Leakage of ions from

shale layers assumes

more importance

Reduction of sulfate2CH2O + SO4

2- + H+ ! HS- + 2CO2 + 2H2O

FeS

Common ion effect

reduces HCO3

organic matter

Cl-

SO42-Cl-

Chebotarev Sequence

(see Freeze & Cherry, 1979)

The water quality of old

groundwater is another issue to

take into account. Generally speaking,

the longer the residence time, the higher

the concentration of dissolved ions ingroundwater.

Groundwater tends to evolve chemically toward the composition

of sea water during the course of flow. It was observed by

Chebotarev in the Great Artesian Basin of Australia.



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Sedimentary Basins

Water supply considerations: – Advantages:

• Hydrogeology (depth to aquifer, T distribution)frequently simple and predictable.

• Wells frequently flow (at least when first drilled)

• Absence of pollution

– Disadvantages:• Depth to aquifer is frequently great and the rocks are

relatively hard (large drilling cost)

• K is usually fairly small (a long well screen is needed)

• T and S are usually both fairly small (rapid drawdown and high pumping costs)

• The water quality at considerable depths isusually poor (high TDS, Na+, F+, H2S, or Fe3

+)

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Carbonate Rocks & Aquifer Systems


http://college.hmco.com



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Limey shale overlaid by limestone.

Cumberland Plateau, Tennessee Limestone in the Sandia Mtns, NM (J. Wilson)

Fractured Carbonate Rocks


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Carbonate Aquifers

Develop wells in upper 7.5m of carbonate, where solution weathering (pavement

karst) has enhanced K. K diminishes with depth; below 15-30m the aquifer dies out.



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Carbonate Aquifer Systemshttp://capp.water.usgs.gov/aquiferBasics/carbrock.html

Karst Systems including Carbonates

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Floridan Aquifer

http://capp.water.usgs.gov/aquiferBasics/floridan.html

(Schwartz & Zhang, 2003) http://sofia.usgs.gov/publications/papers/pp1403a/index.html

TDS (mg/L)



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Edwards-Trinity Aquifer System

http://www.ci.austin.tx.us/watershed/bs_aquifer.htm

http://capp.water.usgs.gov/gwa/ch_e/E-edwards_trin2.html


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Carbonate & Karst

Dye tracer experiment, Croft Spring, Tennessee

http://www.dyetracing.com/dyetracing/dy05005.html

http://geoscape.nrcan.gc.ca

Spring Mill Lake Drainage Basin, Indiana

http://igs.indiana.edu/survey/projects/springmill/



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Carbonates

Primary porosity can vary greatly – Occasionally will have large,

interconnected pores or vugs(coquina, limestone breccia) —these are excellent aquifers:

– Frequently will have high porosity,but very low K (chalk)—these arepoor aquifers unless secondaryporosity (eg, fractures) is present:

– Mud limestone is very dense andwell cemented, low n and K—these are poor aquifersbut good dimensional stone:

www.see.leeds.ac.uk

(K. Zehnder, ETHZ)

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Carbonates

Secondary porosity very

important

– Due to a combination of fracturing

and solution

– Extreme case is karstic terrain

– The largest springs in the world

all issue from karstic limestone:

Syria, 35 to 40 m3/s

– Secondary porosity can make

carbonate rocks good aquifers

without full karstic development. – Degree of fracturing and solution

tends to decrease away from

outcrop areasSimulated flow in an open fracture chalk

system with porous and permeable

matrix. Red-yellow – high flow (fractures),green-blue - low flow (matrix).www.see.leeds.ac.uk



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Carbonates

Water development considerations – Well success is highly variable

• Wells close to each other may be either dry or

excellent producers.

• Traces or faults and fracture zones are good clues

to well success, especially intersections of fracture

zones.

Compression

Compressi

onFractures

Fractures

Structural

effects

http://www.truenorthenv.com

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Carbonates

More water development considerations

– Water quality is usually good

• Low TDS

– Although water is very hard (mCa/mMg > 1 in LS, " 1 in dolomitic rock)

– And it can have severe pathogenic pollution

problems due to flow in fractures and

conduits, and a lack of filtering

(sinkhole landfill problems)

Hard water is water that contains

cations with a charge of +2,especially Ca2+ and Mg2+.



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Volcanic Rocks

Smithsonian

Composite Volcano

Typically the best

aquifers are

provided byinterflow breccias.0.200.001 – 0.01n

10-8 - 10-510-11 – 10-8K (m/s)

InterbedsDense Basalt

Red Point Breccia, Grand Manan

Island, New Brunswick

J. McHone, Auburn U.

With time, weathering reduces

K of interbeds.

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Volcanic Rocks, NM

(H. Guan, NMT)

(J. Wilson, NMT)

Andesite, Magdelina Mtns., NM

Tuff, Jemez Mtns., NM Fractured Tuff, LANL., NM

(J. Wilson, NMT)

Columnar

and other

vertical

jointing can

also provide

directional

conductivitywww.tropix.co.uk /

M.Helena Afonso

Porto Santo Is.,

Madeira



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Dike Impounded GW

http://www.hawaii.gov/dbedt/czm/wec/html/mountain/water/index.htm

http://capp.water.usgs.gov/gwa/ch_n/N-HItext3.html

Most of the water resourceson the Hawaiian Island of

O‘ahu are a result of the

interaction between O‘ahu's

high mountains and the high

rainfall of the tropics

This is thebulkhead in

the dike.

Behind here

is ground water. The

door is rarely

opened.

(McCoy, UoH)


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Volcanics

Water Quality

– Generally very good

• Usually has high SiO2 due to solution of

amorphous silica (~50 mg/L)

• Frequently high F and K

• Occasionally high As in hydrothermal areas



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Fractured Crystaline Rocks

(C. Cleveland, INSTAAR, CU) (J. Wilson, NMT)

Fractured Granite, Colorado Fractured Metamorphic Rock, NM

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Crystalline Rocks

• Primary Porosity – Primary porosity is very small (< 1%)

– Primary K is very small (<10-10 m/s)

• Secondary Porosity – Most porosity is due to expansion joints

and weathering near the surface.

– Most fractures and joints close within100 ft of the surface (if a well is a failure,drilling deeper generally will not help)

– Faults can provide deep fracturing.

• Storage is usually small even if K is high

• Yields are usually small (10 – 25 gpm), even for goodwells



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Crystalline Rocks

Water Quality – Generally excellent

• Usually Ca, Na, HCO3- water

• HCO3- is from soil CO2

• Ca and Na is from incongruent dissolution of

aluminosilicates

• SiO2 is moderate

– May have pollution problems due to shallow

water table, fracture flow

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Crystalline Rocks

slope

2

flat upland

3

ridge crest

4

valley

1

Likelihood of well success: 1 > 3 > 2 > 4



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Fractured Consolidated Sedimentary,

Igneous, and Metamorphic Rocks


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Fracture Flow


“Cubic Law in a single fracture”Fracture Network & Connectivity

REV??

(Pollard and Aydin, 1988).

National Research Council, Rock Fractures and Fluid Flow: Contemporary Understanding and Applications (1996)

http://fermat.nap.edu/books/0309049962/html/R1.html

Q’ = b*(b2 / 12 )*! gJ/ µ " b3

(Shapiro and Hsieh, 1994)

Mirror Lake, NH

Mirror Lake, NH



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Fractured Rock


Dual Continua:

Double PorosityDouble Permeability Models

(Storage in matrix and in fractures)

(Flow in the fracture only)(Flow in the fracture and the matrix)

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Trends of (Fractured) Rock Properties with Depth


Fracture Apertures Close with Depth

Conductivity depends on

fracture frequency (&connectivity) and

aperture.

Effect of weathering and

exfoliation (stress relief)decrease with depth

Note clustering

0

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Trends of Well Yield with Depth


Documents

L5_GeologicSetting