preliminary results, helicopter electromagnetic and magnetic survey of the seco creek area, medina...

Preliminary Results, Helicopter Electromagnetic and Magnetic Survey of the Seco Creek Area,

Medina and Uvalde Counties, Texas

Bruce D Smith, Richard Irvine, Charles D. Blome, Allan Clark, and David V Smith

Index map

Geologic studiesGeologic StudiesGeologic Studies

Four 7.5’ Four 7.5’ TopoTopo Quads Quads SecoSeco Creek AreaCreek Area

Eddie Collins (BEG) and Kyle Murray (USGS) Eddie Collins (BEG) and Kyle Murray (USGS) Digital geologic map Digital geologic map Open file report in preparationOpen file report in preparation

Chuck Chuck Blome Blome and Jason Faith (USGS) and Jason Faith (USGS) Fault and fracture mapping Fault and fracture mapping

Preliminary geologic map from Kyle and Collins HEM SURVEY

RECHARGE ZONE

RECHARGE

ZONE

CATCHMENTAREA

CATCHMENT AREA

0 5,000 10,000 15,000 20,0002,500

Meters

CONFINED

ZONE

NOT

CONFINED ZONE

Hydrology 101Hydrology 101:Hydrology 101:

Faults (fracture flow & barrier)

Lithology (aquifers and aquitards)

Karst

Seco Helicopter

2002 HEM SurveySENSOR SYSTEM 6 EM Frequencies 400 – 100,000 Hz Internal Magnetometer High Resolution GPS Laser Altimeter

Geology with flight lines

Geologic Map Showing Flight Lines

81 square miles

200 meter line spacing

Red dot – sink hole

Black USGS funding

Red EAA funding

100kHz Apparent Resistivity

25kHz Apparent Resistivity

6200Hz Apparent Resistivity

1500Hz Apparent Resistivity

400 Hz Apparent Resistivity

Depth section calculations

UBC EM1DFM

EMFLOW

Differential Depth

Line 10240

Vertical Exaggeration~x20

2000m

1 Mile

100m

TrinityGroup

Sinkhole

Del Rio ClayEdwardsGroup

nothing

SOUTH NORTH

Geophysical structurecorrelation

Mapped structurecorrelation

Sinkhole

Geology with flight lines

Geologic Map Showing Flight Lines

81 square miles

200 meter line spacing

Red dot – sink hole

Black USGS funding

Red EAA funding

Line 10500 Resistivity depth section

Vertical Exaggeration~x10

2000m

1 Mile

200m

Geophysical structure correlation

Mapped structure correlation

STRUCTURAL MAPPINGSTRUCTURAL MAPPINGSTRUCTURAL MAPPING

Many more than currently mapped Many more than currently mapped

Contact between recharge and confined zonesContact between recharge and confined zones

Contact between Contact between catchment catchment area and recharge area and recharge zone zone

KarstKarst features targeted for ground followfeatures targeted for ground follow--upup

STRATIGRAPHIC MAPPINGSTRATIGRAPHIC MAPPINGSTRATIGRAPHIC MAPPING

Upper and Lower Devils River distinguishedUpper and Lower Devils River distinguished

Del Rio marker mapped in the subsurfaceDel Rio marker mapped in the subsurface

Possible shale marker in the Glen Rose GroupPossible shale marker in the Glen Rose Group

Line 10500 location