The meltwater-eroded Souris Spillway surface southwest of Estevan and south of lower Rafferty Reservoir is lined with several sets of fine lineaments, termed 'microlineaments', which are visible on airphotos. They have been identified and mapped from remotely sensed imagery, and their trends and patterns correlated with subsurface geological and geophysical datasets (see Fig. 31 insert). A regionally pervasive NE-SW set of surficial lineaments roughly parallels a dominant NE-SW bedrock joint fracture set, which in turn is closely aligned with the mid-continental plate tectonic movement trajectory and maximum horizontal compressive stress in the earth's crust, S_Hmax (see Fig. 31 insert). In this region of southeastern Saskatchewan, that trajectory orientation roughly parallels the azimuth (about 230°) of the earth's past and current crustal movement rate of about 2.5 to 4.0cm/year--which is approximately the normal growth rate of our fingernails. Significantly, such a phenomenon is a factor in determining the direction of horizontal oil wells to obtain higher production yields.

Because their enigmatic origin has been debated for more than 40 years, we pose the following questions (refer to see Fig. 31 insert): Are the intersecting sets of surficial microlineaments caused by:

Glacier flow that oriented the clasts (boulders and cobbles) in subglacial till, forming a glacially fluted lineament pattern that was exhumed and exposed during catastrophic meltwater erosion?

Leaching along systematic fractures in hard till and bedrock, and removal of soluble and non-soluble material along fractures, resulting in small settlements along the lineaments? (Concentration of higher moisture and organic contents along subtle linear depressions gives rise to their expression in airphotos, a pattern that is virtually impossible to detect on the ground.)

Propagation of fracture lineaments from depth, possibly associated with small cyclic stresses or with earth movements caused by: unloading related to deep post-Cretaceous erosion, salt dissolution in underlying evaporite beds, glacial rebound,or someother mechanism?

We need your help in predicting the origin of the different microlineament sets on the Souris Spillway floor. Toward this end, we provide each person on the bus with an airphoto along with directions for observing them. Note that the field guide book contains a selection of figures showing the following:

an airphoto showing the photolineament pattern in the Tableland area (see Fig. 31 insert);

two photographs showing faulting of Tertiary Ravenscrag beds in abandoned railway cuts( Figs. 32a and 32b);

faulting in Ravenscrag strata in a Highway 18 ditch cuts southwest of Estevan ( Figs. 33a and 33b);

iron-coated joint fractures in Floral till along the canal between Rafferty Reservoir and Boundary Reservoir (Fig. 34);

a plot of dominant trends of joints in till,in bedrock, and in faults in a coal-mine (35).

Think about these questions. We seek your answers on the return trip to Regina.

Q Figs. 31, 32a, 32b, 33a, 33b - What is the origin of faulted beds in the area around Tableland, Sk.?

Q. Figs 29, 30 - Why do the small plateau-like, erosional-remnant "islands", only a metre or so high, have teardrop shapes pointing downstream? And why do parrallel linear microdepressions originate from the downstream side of small plateaus?

Q. - What interferences might be drawn from the dense concentration of boulders ('boulder lag') on the Souris Spillway floor, if you were bidding on a contract to construct an underground water-supply pipeline from the hamlet of Hitchcock to the Souris River?

Q. Fig 31 - Looking at the array of inset diagrams in Fig. 31, can you provide a reasonable explanation for why different orientations of different surficial microlineaments sets tend to match the orientations (strikes) or deep- seated bedrock structures located deep in the earth's crust? In fact, how can you account for two or more lineament sets having different orientations on the melted-eroded Souris Spillway floor? And what is the genetic connection between the orientation of slight, subtle surficial lineaments on the upland adjoining the Souris River valley and long, linear segments of steep river valley walls west of Rafferty Dam?

Q. fig 31 - Is there any geotechnical explanation for a possible genetic connection between matching locations of the roughly concentric oval microrelief rings at ground surface (see inset) and a 60-m-high, oil-bearing carbonate reef located some 2600-m below ground surface? Is a possible explanation and analogue the very significant surface settlements occuring at some potash mines, resulting from mining a few metres of potash 1000-m below surface?

Also of note is a subtle bull's-eye ring feature in Fig. 31 (insert). It overlies and closely matches in outline and location a large oil-bearing carbonate reef located 2640 m below ground surface. Two oil wells drilled on the feature are said to have produced $10 million worth of oil during the first year of production.

So, this is a further question: Is there any genetic connection between the presence of this annular surface feature and the oil-bearing reef located 2640 m below ground surface?