Project Area. Funded by the Illinois Department of Transportation Springfield, Illinois

Transcription

1 Three-dimensional Geologic Mapping for Transportation Planning in Central-northern northern Illinois: Data Selection, Map Construction, and Model Development Richard C. Berg, E. Donald McKay, Donald A. Keefer, Robert A. Bauer, Patrick D. Johnstone, Barbara J. Stiff, Andre Pugin, C. Pius Weibel, Andrew J. Stumpf, Timothy H. Larson, Wen-June Su, Greg T. Homrighous Illinois State Geological Survey Project Area Funded by the Illinois Department of Transportation Springfield, Illinois

2 Introduction - Purpose of Study Illinois Department of Transportation (IDOT) contracted with the ISGS to prepare for a highway improvement project along a 24-mile (39 km) segment of Illinois Route 29 in cen- tral-northern Illinois. Project Area 15-month, 3-D 3 D geological mapping program supports: s Developing derivative maps to address construction conditions. Predicting geologic hazards (landslides and mine subsidence). Locating groundwater supplies for rest areas and other development that may follow highway construction. Supporting IDOT=s s Environmental Impact Statement by character- izing hydrological conditions, slope stability, erosion and sedimenta- tion,, and showing how geology potentially impacts ecological systems.

3 Introduction - Brief Study Area Characterization Located on west side of the Illinois River, there are 3 distinct geologic environments: Southern 8.6 miles (13.8 km) - steep/highly dissected bluff (~200 ft (61m) high) composed of shale, limestone, and coal overlain by thin (<50ft/15m) glacial deposits. Northern 5.0 miles (8.1 km) - thick (>200 ft/60m) glacial deposits overlying a buried bedrock valley. Middle and extreme southern 10.4 miles (16.7 km) - Illinois River floodplain and Wisconsin Episode outwash terrace deposits.

4 Introduction & Brief Study Area Characterization Drift Thickness Map with Major Bedrock Valleys Present-day Illinois River generally parallels the bedrock valley that carried the ancestral Missis- sippi River about 20,500 years ago. Maximum Wisconsin glacial advance diverted the ancestral Mississippi west to its present course. Multiple glacial advances interacted with the Mississippi River in an area of significant bed- rock relief - numerous episodes of erosion, dep- osition, and stability. Result is a succession of glacial, fluvial, eolian, and alluvial deposits and interglacial paleosols. > 500 feet < 100 Driftless Project Area

5 Introduction Modeling Boundaries Because of the geological complexities, two 3-D 3 D geological models were developed: A regional model,, covering about 200 mi 2 (518 km 2 ) centering on the highway, and delineating unlithified materials from land surface to the bedrock surface - mapping necessary to better understand the geology and increase our ability to predict the lithostratigraphic units near IL29. A more detailed model,, covering the area about 200 feet (61m) on either side of the highway centerline, also was compiled to differentiate lithologic units to a depth of about 50 feet (15m) and provide highway engineers with needed site-specific specific information.

6 Data Compilation and Evaluation ISGS procedure: Compile and evaluate existing borehole data (ISGS and IDOT). Select the available data. Field investigations to verify existing information/fill in data gaps. Database used to compile the maps and models consisted of: Descriptive logs water wells. Descriptive logs highway test borings (123 - <10 feet deep). 40 shallow hand-auger auger borings. 17 test borings for coal, an oil pipeline, and other engineering work. Descriptions and samples from 251 field exposures. Continuous cores and geophysical logs from 7 ISGS boreholes. About 9 line-miles of seismic reflection profiles to help define depth to the bedrock surface along the southern portion of the highway.

7 ArcView GIS I-1004 Hennepin W-234 Bureau Co. X-321 X-295 Henry Putnam Co. La Salle Co. Rt. 29 River X-308 Lacon Stark Co. Peoria Co. Illinois 0 6 miles Chillicothe Marshall Co.

8 Data Compilation and Evaluation Well Verification Verifying the locations of water wells and evaluating the accuracy cy of their logs required considerable time. Locations were verified by: b Comparing the owner of record listed on the permit with plat books (and in some cases orthophotos). Telephoning well owners/drillers to ask them of drilling locations. Finding addresses in computer white- and yellow-pages directories. Field checking. Accuracy of logs was evaluated by comparing their content with infor- mation of known accuracy from nearby test borings and described outcrops. Records with over generalized logs, or logs obviously inconsistent with the known geology were labeled as suspect.

9 Development of a Conceptual Regional Geologic Framework (1) Routine evaluation of published and unpublished work (including ISGS field notes, theses, ISGS reports, maps, aquifer studies, and a regional geologic studies. Initial stratigraphic model included 26 lithostratigraphic units - the present model includes 13 units. (2) Description, measurement, and sampling of outcrops. Confirmed aspects of the conceptual model. Provided a good hands-on feel for what appeared to be the major till and glacial-fluvial units of the upland area. Became the basis for assigning the various materials described in i water wells and highway borings to units in the lithostratigraphic ic model.

10 ArcView 3.2 Our technological goal: To use relatively low-cost computing technology to supplement and improve traditional geologic field mapping by organizing and managing geologic data, enabling rigorous 2-D 2 D and 3-D 3 D geologic modeling, and producing credible, high-quality products (databases, maps, and models) efficiently. We began the project in Oct., 2001, walking stream valleys, such as Rattlesnake Hollow, to identify, examine, and sample outcrops. IL 29

11 Tiskilwa Fm. - diamicton Delavan Mbr. - diamicton Ashmore Tongue - outwash Roxana Fm. - loess Sangamon Geosol X295 - Rattlesnake Hollow Chillicothe 7.5-minute minute Quad. In the field, we identified mappable lithostratigraphic units that comprise an Pearl Fm. - outwash Upland succession 1.25 m Loess Tills & outwash Wisconsin Wisconsin Glasford Fm. - diamicton Loess Wisconsin Paleosols Tills & outwash Outwash Bedrock Wisc.. & Sangamon Illinois Pre-Illinois Pennsylvanian

12 Henry Fm. - outwash X308 - Sandy Creek Henry 7.5-minute Quadrangle Valley-fill succession, infilling the ancestral Mississippi River Valley Undifferentiated outwash of the Ashmore Tongue, Pearl Fm. & Sankoty Mbr. Lithology Alluvium Outwash Till(s) Bedrock Episode Holocene Wisconsin, Illinois, & Pre-Illinois Illinois, Pre-Illinois? Pennsylvanian

13 ISGS Borehole I-1004I Putnam 7.5-minute minute Quadrangle Elevation (feet) Clay (%) Natural Gamma (cps) We drilled stratigraphic test holes to characterize the major Quaternary units and to help determine their distribution and thickness.

14 and refined our conceptual stratigraphic framework. West Rattlesnake Hollow Sandy Creek East Pennsylvanian Bedrock Illinois River Ancestral Mississippi River Valley

15 Borehole W234 Oracle & ArcView 3.2 Driller's Log: Driller s description Depth of Base Thickness sandy black dirt 6 6 yellow clay gray clay red clay sand & gravel red clay w/sd & gvl streaks gray green clay W gravel sand Locations were 178 stored 14 as red clay Arc coverages 190 or 12 sand & gravel shapefiles layered red clay w/sd & gvl streaks gray-green green clay sand gravel green shale at Using Oracle and Arc, we automated all water well, engineering, and other test- hole Tables records, were which managed supplied in the Arc, bulk Oracle of available and Excel subsurface information.

16 W234 X,Y elev RockWorks99 We migrated well records from the database into RockWorks and converted well-by by-well each driller s non-standard descriptions to standard lithologic terminology via lithology pick lists. W234 Lithology table Lithology pick list Lithology keyword table

17 We created a lithologic strip log for each borehole and outcrop and used a project- specific pick list of stratigraphic units to assign lithostratigraphic interpretations. RockWorks99 Strat unit pick list Reddish brown loam-textured diamicton, mainly basal till with thin interbeds of sand and gravel that occurs above the Roxana Silt & Sangamon paleosol: Tiskilwa Formation, Wedron Group deposited in the Peoria Sublobe of the Lake Michigan Lobe during the latter part of the Wisconsin Episode, 21,000 to 18,000 RCYBP

18 RockWorks99 We selected lines of cross section that we expected would cross boundaries and show significant trends River Illinois Illinois 0 5 miles o

19 We constructed multiple cross sections showing lithologic strip logs and stratigraphic correlations to: (1) evaluate and refine well-to to-well correlations and (2) test and refine the conceptual framework. South RockWorks99 North Adjust picks on-screen

20 We gridded and contoured tops, bottoms, and thicknesses, helping us evaluate regional trends and identify errors and anomalies. RockWorks99 Land surface Ashmore top Bedrock surface Sankoty top

21 Ashmore top RockWorks Perspective views were also helpful for error identification and trend evaluation. peaks Sankoty top pits

22 RockWorks99 Tops for 26 Quaternary units plus bedrock 7 months after the project began, we finished refining the interpretations and delivered to the modeling team the spreadsheet containing: 687 records (boreholes & outcrops)

23 Regional 3-D 3 D Model Development - Setup Individual stratigraphic surfaces were modeled and then combined into a single 3-D 3 D model. A suite of software applications were used: RockWorks 2002 and Excel - data management. ArcWorkstation and Surfer - modeling and visualizing surfaces and isopachous maps. RockWorks grid manipulations (additions, subtractions), translating grids between various software, and final 3-D 3 D model construction and visualization.

24 Regional 3-D 3 D Model Development - Setup Many units had limited extent or were difficult to distinguish, so they were combined. Final stratigraphic framework included 12 units. The first surfaces modeled were the land surface and bedrock surface. Modeled surfaces included various bottoms and tops of stratigraphic units. Surface model residuals were calculated and checked against the borehole picks. Residuals were also calculated for each surface using the overlying and underlying surface picks from the borehole data.

25 Regional 3-D 3 D Model Development - Construction Land surface model was constructed using elevation data from DLGs. Elevation data was interpolated using ArcInfo and checked against the topographic quadrangle maps. Floodplain required use of synthetic control points. Resulting grid was generalized to coincide with the dimensions of the regional model. Study area boundary Land surface

26 Regional 3-D 3 D Model Development - Construction Bedrock surface model: Data included: borehole data contours from statewide bedrock surface map land surface elevations from areas of observed and expected bedrock outcrops. Erosional surface: interpolated with drainage enforcement. Truncated from above by surficial Henry. Bedrock surface

27 Regional 3-D 3 D Model Development - Construction Sankoty Sand model (regional aquifer): Delineation of top surface was a priority during stratigraphic interpretation; this made it easier to construct a well-behaved surface model. Erosional surface: drainage enforcement Truncated by surfical Henry. Sankoty Mbr. Top

28 Regional 3-D 3 D Model Development - Construction Between the Sankoty and the Tiskilwa: 4 different sand units 2 interbedded gray tills Identification of sands and tills was problematic in well logs and field exposures.

29 Regional 3-D 3 D Model Development - Construction Modeling independent discontinuous units can be tricky. Revised stratigraphic framework, for the model, using a simplified conceptual model. Sand units limited to only under the tills. Units draping down, truncated from below. All units truncated by final outwash bottom surface and alluvium bottom surface.

30 Regional 3-D 3 D Model Development - Construction Wisconsin Episode tills and an interbedded sand were modeled from borehole data and land surface elevations. Till units are widespread and distinct. Tiskilwa Fm. isopach

31 Regional 3-D 3 D Model Development - Construction Surficial outwash was critical unit: 5 terrace features truncated distribution along bluff limited distribution in major tributaries About 120 observations and 350 synthetic control points. Interpolated using kriging,, no drainage enforcement Cahokia Alluvium thickness was generalized. Soils maps used to guide occurrence.

32 Regional 3-D 3 D Model Development Building the Final Model RockWorks2002 was used to build all surfaces into a single volume model.

33

34

35

36

37

38

39

40

41

42 X531 Lacon 7.5-minute Quadrangle Dick Berg for scale Outcrop of the Lonsdale Ls.