Monday, November 16, 2009
New Madrid Earthquake and Graben
New Madrid Earthquake and Graben
The earthquake of 1811-12 was a historic event; people lived along the Mississippi River in New Madrid, MO and passed along anecdotes of the great quake. The river was reported to have reversed course- flowing into the sunken lands of Missouri and Arkansas. The sunken lands remain, forming a graben and Big Lake, on the Arkansas side. These have been dammed along Hiway 18, and the sink is a resource for the Federal Fish and Wildfowl and State Parks. I have investigated the geochemistry and geology for the part that is pertinent to the ancestral holdings of my Dad and his homesteading of a part of the area.
I believe that the larger dynamics in the area include the Crowley’s Ridge- a N30E oriented feature, similar to the orientation of Big Lake along the part with which I am familiar. There is a large elliptical cell presented on Google Earth, centered about the 36N 90W coordinates, and it encloses the ridge, graben, and Mississippi River until the junction of the Ohio River. This is shown below:
Notice that this cell is elliptical, contrasting with most circular cells found throughout USA. There are others that I have investigated: Sacramento Valley-Sierras, CA, Long Island, NY, Death Valley, and Black Sea. I will isolate the primary factor which has made these different from other common Coriolis rotating cells. Refer to my spherical or circular Model below to see why this is important.
First look at one other elliptical cell: Sierra-Valley, CA and how it rotates vertically, forming an ellipse with the elevated portion located on the east side: Now I have amassed sufficient case studies to form an idealized MODEL.
Back to the case study of the Mississipi River and New Madrid cell, we can use my published (SPWLA Journal ca. 1974) idealized model for water distribution in a large basin to show how the various segments of the elliptical cell are influenced by orientation and how the fluids move throughout the basin- according to the driving forces Heat and Pressure:
The above model shows that the faster rotation of the Core- relative to the Crust- forms sinks, depressions and grabens on the west side of a linear- which is an independently-moving mechanical or thermal action. The faster rotation is assumed to be the result of two factors:
1. The viscosity of the Mantle is smaller than that of the Crust, because of higher temperature at depth and because of the higher iron and other mineral content; and,
2. The tidal influence of the Moon is greater on the Crust (being closer and with a lesser time lag), so that it is slowed more.
Consequently, there is a vertical rotation of a portion of the Crust, which results in sinking on the west side and rising on the east side of the linear. For the case of the New Madrid earthquake and sink, the sinks occur west of the Mississippi River (which is linear for the elliptical cell shown), and the uplift occurs on the east side. This vertical rotation could be considered to be a reaction to the drag of the Mantle on the base of the Crust, and it is sensitive to the positioning of the Polar Axis. Each time the axis is moved due to a mechanical strike of a meteor or asteroid, the vector of the Coriolis Force is shifted (since it depends upon the rotation of the Earth).
I will assume that the last significant strike was at the KT boundary, since this seems to have determined the last initiation of the HI-Emperor seamount chain. The measured times for both KT and the oldest seamount near the Aleutian Chain are about the same- near 65 million years.
As a result of all this, the Crust sinks and becomes under extension for the west side of the vertically-rotating cell, and basins are formed which continues to sink so long as the portion of the Crust continues to react to the differential rotation rate of Crust segment versus the Mantle. A good example of this is the Anadarko Basin, OK, but we will focus on the New Madrid sink.
The above Google Earth photo and model shows that the basin on the west side of the Mississippi is being extended, because of the slower rotation rate there. The rotation rate is slower because of the thinner crust on that side, which has a lesser push by Coriolis force with the lesser Crust mass. This extension results in better paths for fluid movement- particularly hydrocarbons. The down-dropping inside the grabens creates temporary artesian pressure, and I have witnessed this in water wells on neighboring farms in Mississippi County, AR. There is the complication of an increase of heat with the friction of the down drop, and this temperature increase drives out methane from the stratigraphic column- which can also result in artesian pressure, whenever the gas cannot escape as fast as it is vaporized.
A segment of the Crust between the uplifted east half (east of the river) and the outer west boundary incurs sinking, and we will concentrate on the BASIN. Below is a schematic for an idealized basin, existing between uplifts or higher elevations on its lateral boundaries:
These boundaries will occur on the east and west sides, according to the model- reacting to Coriolis Force and the west to east drag of the Mantle. This is the case for basins I have studied in the USA, but there is the complication due to drag at a 45 degree or less angle for basins such as the Sacramento valley and for the case at hand- the New Madrid sink. The model above shows that there is still an eastward vector for the cell, even when it is tilted away from a N-S linear.
Geochemical re-arrangement of water and shale contents I have found from results I have published long ago (SPWLA, 60’s), that the column of earth and its water fraction constituents, above oil and gas deposits, is anomalous. There are the following dissolved components which are measured in produced water (either shallow water wells, or deep oil tests), which are exotic for ground water near hydrocarbons:
a. Major cations, or Na, K, Ca, and Mg in exaggerated amounts;
b. Major anions, or Cl, HCO3, SO4, and sulfide- deviated from normal;
c. Minor cations and anions increase in total amount, for B, F, As, and Li; and,
d. Fe, S, Mn, and metals incur valence change.
Further, there is a separation by a gas deposit of the bicarbonate ion in water from the Sulfate ion. Of course, the double-valence for SO4 is sieved by fine-grained sedimentary rocks (shale and siltstone), and it lags in its movement from the fracture which emitted it, compared to easily-moved Bicarbonate, Na and K. All of the last three are single-valent and have smaller ionic radius and move through small fractures- particularly K and Na.
Consequently, as gas (methane, H2S, or CO2) moves upward through fractures created by Coriolis rotation-shear, it separates in a temporary trap according to density. CO2, being heavier, is found on the down dip side of a methane deposit. The heavier sulfate lags, due to its double valence and to its larger ionic size, and is expected to reside near the fracture which delivered it. Location then of a bicarbonated water deposit should then be an indicator of proximity to a CH4 reservoir.
What creates this gas reservoir and its exotic neighbors?
The Coriolis rotation and shear creates increasing permeability as the movement continues. The movement is motivated by an independent activity, such as shear laterally along the Mississippi River from a larger cell’s lateral movement or from vertical rotation above the Mantle which is moving at a slightly faster rate than the Crust. This faster rate of the Mantle rotation is caused by the lesser tidal friction from the Moon’s daily, monthly, and yearly change of the Moon’s position relative to the Earth and to the Ecliptic (which is the annual path around the sun- where the Moon has a tilt of about 5 degrees to the annual path).
The important feature is that there are better paths for fluid movement where shear occurs, and this path is created by rotation- either horizontally or vertically. Simultaneously, this shear occurs both in the subsurface and at the ground surface, so that water drainage finds the easiest path for downhill movement and creates river valleys in circular patterns. It is expected that all rivers have a circular portion somewhere in their presentation.
The End result of all this is that a basin has extension and allows easy access for rainwater to flow downward into the shallow Meteoric Zone. Below that, the porosity and permeability are reduced due to compaction and graben rock stress, and fluids are more stagnant (increasing TDS and major cations and anions- the Mineralized Zone).
Deeper yet, the composition of water becomes more chemically-reduced with stinking compounds and rare constituents- the Chemically-reduced Zone. Finally, the deepest zone I have investigated (in geothermal tests) is that of Acid waters. As with vulcanism, there is increased acidity and chemical reduction, with As, Li, and minor constituents common in the water. An easily found indicator of this zone is pyrite in cuttings, stink from sulfur, and a calcite cap at the top (which may seal in abnormally-high pressure, similarly to the chemically-reduced zone).
Practical use of the 3D rotating Coriolis cellThe model for rotation of the Crustal cells in three dimensions has many practical aspects:
1. Location of the Linear feature which initiates the rotation of a circular stream geometry allows an estimate of the horizontal diameter of the resulting rotation (deviation of the linear from a straight line indicates the termination of the circumscribed cell) ,and this should influence exploration programs;
2. The fastest fracture formation and associated fissures are found on the outer extremities of the cell (these are the paths of greatest permeability for fluid movement);
3. The circumference will also be recorded by the appearance of laterally-striated slickensides;
4. Shear will result in HEAT OF FRICTION, producing warm springs, or for large cells hot water, Geothermal areas, or vulcanism;
5. The increase of temperature and pressure, associated with increased shear and friction, should determine the location of mineral deposits- due to dumping at points of reduced T and P;
6. This DYNAMIC MODEL OF ROTATION OF PORTIONS OF THE CRUST- BOTH HORIZONTALLY AN VERTICALLY- should help define the perimeters of an exploration program (whether for hydrocarbons, minerals or geothermal areas; and,
7. This can be initiated, looking at the 2D maps on Google Earth or from other Geo-produced layouts.
Below are my notes, which must now be modified in view of recent findings:
Below is a Google Photo, showing interpretations of the trends of geography since the Tertiary Eocene
The New Madrid Earthquake Zone and Big Lake, AR
Surrounding part of the Mississippi river is an active zone, which has historically exhibited an 8 Richter shake (1811-12), causing sinking of the area near New Madrid, MO sufficiently to cause the river to temporarily reverse course and to create a large sunken area known as Big Lake. Part of my family has lived in this area since WWI, so that I have a personal tale to tell about it- not only historically, but socially, geographically, and geologically.
Mississippi County is a flood plain, where in my lifetime there has occurred the 1937 inundation which brought water from Southern Missouri and the Ohio River as high as 5 feet above the flat farmlands (and 3 feet vertically into the house- now removed), about the old bungalow which was placed on 30 inch blocks. My dad remarked to me that the whole County had no more than 30 feet difference in elevation, and that he hade found “Gumbo” soil as deep as he had dug a well.Further, being a civil engineer, he watched for entities such as sand boils and raised areas where the drainage was better.
Although the Mississippi is some 20 miles to the east and could carry off storm water, the area does not drain in that direction. It tilts southward and drains to the Mississippi near the town of Helena, AR, mainly via Little River- which is east of the sunken area. This area is known for its catfishing and duck hunting, because of the sunken lands in the Big lake Fish and Wildfowl Preserve. My dad tried throughout his lifetime to move the water though drainage ditches southward, so that the cotton crops would not be drowned. Nevertheless, one year out of 7 would have a failed crop because of excess water.
Notice that the Mississippi (on the accompanying Google Map) and the next smallest rivers drain SW-ward- which is the orientation of the ancient delta of Eocene time (the youngest rock outcrop being the Wilcox formation). This is somewhat similar to the orientation of the Appalachian Chain, resulting from the Paleozoic collision of the land masses in the Eastern USA.
The area, being somewhat flat, drains poorly, and the FWS has erected a dam at Hiway 18- on the southern edge of the sunken area- so that water will retain a height sufficient to sustain fish and ducks throughout the year. To the east you can see Meanders on the Mississippi, attesting to the slight gradient of the land, and there is another sunken area where the river has straightened- the Reelfoot (Oxbow) Lake. There are yellow indicators to show major geographical and geological trends.
Below shows a Google Photo of the NE corner of Arkansas, known as Big Lake- near hiway 18
Creeks and waterways yield clues as to the underlying Crust of the Earth- in this case, loose soil for several hundred feet (flood alluvial). When Earth Tectonics produces fractures (cracks in the rocks and compacted earth), the drainage at the surface finds these easy avenues for water coming from the north. Hence waterways’ orientations tell a story as to what lies below- in this case the fractures produced by the movement of blocks of Crust which resulted in great earthquakes in the past.
This area is still active, since the great quake of 1811 is indicative of what will occur in the future. The feature I find of greater interest is that of the delta, earthquakes, and faulting being an indicator that this is a zone of spreading- the area to the west of the Mississippi River moving westward relatively to the area to the east. This would be the case for the Coriolis effect of Shear along the Misssissipi River linear portion to create highlands to the east and lowlands to the west. The first error is shown by the CCW arrows: the direction is correct for the west side of the New Madrid cell, but it is rotating CW, while the arrow to the north pertains to another cell (not the one of interest). I have since found that there are many local cells, and one must be careful to distinguish them. They must be in agreement as to direction of rotation, otherwise they will indicate geothermal regions (hot springs, for minor conflicts, and major steam or extremely hot cells for larger cell conflicts- CW vs. CW for adjoining cells).
The area SE of the sunken lands is anomalous several ways: First, with an elevation difference of only 30 feet for the whole county, there is artesian pressure delivering water to the farmers. Next, the water wells show a geochemical anomaly (in HCO3 and SO4) under the upthrown side of the obvious graben fault. Finally, sand blowouts (evidence of quake liquifaction of deeper sands) occur in slightly high areas in the farmlands.