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A Lifetime of Learning from Reading the Cores
I have spent a lifetime studying modern landscapes and coring the stratigraphy that
lies beneath them—the Mississippi Delta of Louisiana, the freshwater Cumberland
Marshes of Saskatchewan, the Georgia salt marshes of the east coast U.S., and the
coastal plain and barrier island systems of the Outer Banks in North Carolina. Cores
provide us a continuous record of the layers below the ground surface in areas where
we cannot see the underlying geology—a window into interpreting the past. Through
coring, I have learned how to describe and interpret geologic environments that may
become preserved in the rock record. These geologic environments include sedimentary units (facies) with specific geometries and sediment characteristics. A barrier island, for example, is a geologic environment that is characterized by
shoestring-shaped sands (sedimentary units with a defined long and narrow shape)
with laminations (sediment characteristics)—think of a beach with its black laminated sand deposits. This geometry and the laminations may be preserved in the
rock record. Studies of modern environments such as these can be used to interpret
the origin of ancient sand deposits, such as the older Quaternary shorelines and
deposits found further inland from the modern Outer Banks barrier islands, or laminated sands in much older Cretaceous rocks of the east side of the Rocky Mountains,
where a seaway in the center of North America connected the Gulf of Mexico and
the Arctic Ocean some 80 million years ago. After all, barrier islands and beaches
existed in Cretaceous times too!
By understanding landforms, the processes that formed them, and the resulting
deposits (sedimentary facies), we can develop conceptual models that help us make
predictions about the occurrences of economically valuable geologic resources,
water, and geologic hazards. For example, core studies of the modern Outer Banks
barrier islands of North Carolina help me to interpret cores that penetrate 1.8 million year old shoreline deposits further inland. An example of a conceptual model is
that heavy mineral deposits (black layers) occur along beaches associated with
modern barrier islands; hence as exploration geologists, we explore for economically valuable minerals in sand units associated with the several ancient shorelines
(step-like features that separate flat terraces) that occur further inland (Fig. 9.1).
Another conceptual model is that geologic environments such as river terraces
below a certain elevation will likely flood after the torrential rains, associated with
hurricanes. If we map the location of river terraces and know their underlying stratigraphy (some have thin sands that can soak up floodwaters, but some are underlain
by impermeable clays), we can code these with a hazard assessment—and use these
maps for land-use planning.
I am an idealist. At the end of the day, the type of research that I do--remote sensing of landforms, and defining the layers that lie beneath, should be useful in developing multi-purpose conceptual models useful to society. For example, detailed
maps of landforms along with geologic cross sections that show underlying permeable sands, impermeable muds, limestones and so on, could help predict surface
water pathways from field to stream (nitrogenous waste), and groundwater pathways through porous deposits (pollutants moving from ground surface to aquifer).
Similarly, these products are useful for creating maps of groundwater vulnerability
9 Drilling the North Carolina Coastal Plain – Discovering What Lies Beneath
A Lifetime of Learning from Reading the Cores
I have spent a lifetime studying modern landscapes and coring the stratigraphy that
lies beneath them—the Mississippi Delta of Louisiana, the freshwater Cumberland
Marshes of Saskatchewan, the Georgia salt marshes of the east coast U.S., and the
coastal plain and barrier island systems of the Outer Banks in North Carolina. Cores
provide us a continuous record of the layers below the ground surface in areas where
we cannot see the underlying geology—a window into interpreting the past. Through
coring, I have learned how to describe and interpret geologic environments that may
become preserved in the rock record. These geologic environments include sedimentary units (facies) with specific geometries and sediment characteristics. A barrier island, for example, is a geologic environment that is characterized by
shoestring-shaped sands (sedimentary units with a defined long and narrow shape)
with laminations (sediment characteristics)—think of a beach with its black laminated sand deposits. This geometry and the laminations may be preserved in the
rock record. Studies of modern environments such as these can be used to interpret
the origin of ancient sand deposits, such as the older Quaternary shorelines and
deposits found further inland from the modern Outer Banks barrier islands, or laminated sands in much older Cretaceous rocks of the east side of the Rocky Mountains,
where a seaway in the center of North America connected the Gulf of Mexico and
the Arctic Ocean some 80 million years ago. After all, barrier islands and beaches
existed in Cretaceous times too!
By understanding landforms, the processes that formed them, and the resulting
deposits (sedimentary facies), we can develop conceptual models that help us make
predictions about the occurrences of economically valuable geologic resources,
water, and geologic hazards. For example, core studies of the modern Outer Banks
barrier islands of North Carolina help me to interpret cores that penetrate 1.8 million year old shoreline deposits further inland. An example of a conceptual model is
that heavy mineral deposits (black layers) occur along beaches associated with
modern barrier islands; hence as exploration geologists, we explore for economically valuable minerals in sand units associated with the several ancient shorelines
(step-like features that separate flat terraces) that occur further inland (Fig. 9.1).
Another conceptual model is that geologic environments such as river terraces
below a certain elevation will likely flood after the torrential rains, associated with
hurricanes. If we map the location of river terraces and know their underlying stratigraphy (some have thin sands that can soak up floodwaters, but some are underlain
by impermeable clays), we can code these with a hazard assessment—and use these
maps for land-use planning.
I am an idealist. At the end of the day, the type of research that I do--remote sensing of landforms, and defining the layers that lie beneath, should be useful in developing multi-purpose conceptual models useful to society. For example, detailed
maps of landforms along with geologic cross sections that show underlying permeable sands, impermeable muds, limestones and so on, could help predict surface
water pathways from field to stream (nitrogenous waste), and groundwater pathways through porous deposits (pollutants moving from ground surface to aquifer).
Similarly, these products are useful for creating maps of groundwater vulnerability
9 Drilling the North Carolina Coastal Plain – Discovering What Lies Beneath