Three-dimensional geological mapping: Workshop extended abstracts

In 1815, William Smith produced the geological map of England and Wales, which is considered to be the first formal geological map. This map could also be considered a three-dimensional (3D) map to the extent that it was accompanied by multiple cross-sections that depicted the subsurface. Since then, geological mapping has become a fundamental and core activity of the geoscience discipline, central to scientific understanding of landscape evolution, depositions of environment, and geologic history, and particularly its direct application to assessing water, energy, and mineral resources, engineering properties, hazard and risk assessments, and overall economic development potential.

A series of workshops designed to address the above application and facilitate sharing of best practices for 3D geologic mapping and modeling was initiated by Berg and Thorleifson in 2001, later joined by Russell and MacCormack. This RFG workshop is designed for those who are: (1) actively engaged in constructing sophisticated 3D geological maps and numerical models within their jurisdictions, (2) beginning the process of 3D geological mapping and modeling, and seeking guidance regarding best practices, and (3) interested in initiating a 3D mapping and modeling program within their institution and seeking guidance regarding not only the current state of best practices, but also seeking assistance in promoting the need for the program within their agency. The 2018 workshop will include presentations and discussions focusing on: (1) overall programmatic rationale, (2) developing methods and protocols necessary for model construction and validation, (3) managing large diverse data of variable quality that are required for 3D geological maps, (4) ensuring the interoperability of geologic maps and data, (5) developing visualization tools, (6) facilitating appropriate interaction between geological mappers, hydrogeologists, engineering geologists, engineers, and other scientists, and (7) delivering 3D mapping and modeling products to stakeholders, all of which will be “intertwined” with case study examples from across the globe.

Three-dimensional geologic mapping and modeling have long been a norm for oil and gas, as well as mineral resource exploration. However, its application to regional geology, groundwater, and engineering investigations is relatively new mainly because of the detail of mapping required to delineate subsurface materials, and the cost of obtaining the information (e.g., test-hole drilling and geophysical surveys). Advances in data collection and digital processing now permit the application of methodologies previously limited to the petroleum and mining industries, to mapping and modeling in 3D that can span from jurisdictional to more local geology. Particularly beginning in the late 1990s, geological survey organizations (GSOs) began to more comprehensively map the thickness, extent, and properties of multiple strata, as well as selected deformed structures, in a 3D GIS environment. Developments were driven by considerable progress in digital methods, large databases of water-well and engineering boring logs, and new drilling and geophysical tools to acquire subsurface information.

Advances in computer technology was coupled concurrently with escalating societal needs driven by land-use pressures requiring planners and health officials to make increasingly difficult decisions commonly revolving around groundwater resource evaluations and protection strategies. The situation can be particularly important in urban settings or expanding suburban areas, where there are thousands of data locations (e.g., water-well logs and engineering borings) that must be managed, evaluated, and compiled to construct accurate 3D geological maps and models at large scales. 3D geological models are quickly becoming the standard for assessing water and mineral resource potential, geological risk for both industry and government agencies, and economic development because they are effective tools to more easily explain and portray the often complex subsurface. They are also used frequently and successfully to assist with stakeholder engagement and communication.

With the advent of powerful computers (past 25 years) to manage large data sets and manipulate the data to portray complex relationships, it has been feasible to map, model, and display geology in 3D. It is imperative that geoscientists understand what these tools can do to provide insight on sedimentary environments, stratigraphy, and geologic history, and more importantly, to better explain the complexity of geological information to non-geologists. Users also typically request the input data that was used to make the maps and models. Therefore, robust yet user-friendly data bases with full metadata are also required, often along with a suite of interpretive or derivative products, as well as “user guides.”

The main focus of the workshop is to bring together geoscientists and technical staff who manage large data sets, and who need to integrate data of variable quality (such as logs from water wells) with crucial high-quality data (such as from test holes and geophysics) to construct 3D geological models of appropriate detail that can/may be used for a multitude of applications. This will be an opportunity to share new ideas and findings with people from other states, provinces, and countries who are dealing with similar challenges, and to provide updates from our previous nine workshops. Particularly important will be discussions of (1) program rationale, (2) institutional work flows, (3) how various geological surveys have dealt with various jurisdictional scientific and mapping issues, (4) the emphasis and need for jurisdiction-wide 3D geological mapping and modeling, and (5) delivering mapping and modeling products to stakeholders. For the latter, GSOs have become increasingly aware that their often “high-end” computing, visualization, and output/information delivery capabilities far exceed the capabilities of the majority of their intended users, which are often local governments. Therefore, ensuring that GSOs are able to allocate their resources appropriately to delivering this information in a format that their stakeholders want and can use is of paramount importance.

Participants are from: (1) the academic community – particularly hydrogeologists – who can benefit most from knowing that the 3D models discussed in the workshop are truly integrated and internally consistent solids models that represent the geometry, stratigraphy, hydrostratigraphy, and sedimentology of aquifer and aquiclude units, and their interrelationships, and therefore provides a sophisticated conceptual model for eventual groundwater flow modeling and estimating groundwater resource availability and yields, (2) state and national geological surveys that have been conducting geological mapping and groundwater investigations as part of their mandates, and (3) private industry that has been developing geological mapping and modeling software.