Description of hydration forms


The gypsum-anhydrite rock in Dingwall generates various types of stresses during gypsification, which are responsible for the formation of deformations such as: domes, wigwams, ridges, fissures, fractures and displacements (fig. 1-4). The most crucial from the point of view of the entire Diamond Grant project are domes, wigwams, as well as ridges due to the rock voids forming inside them, which in many cases are caves or rock shelters. The domes, wigwams and ridges are of similar height and dimensions, except for the length of the ridges, of course, that is two or three times greater. All three types of relief in a quarry are referred to as anhydrite hydration forms, or briefly, hydration forms.

Fig. 1. Hydration form no. 40 located in Dingwall in the eastern part of the site.
Fig. 2. Hydration form no. 66 with a distinct wigwam geometry located in the eastern part of the site.
Fig. 3. Hydration form no. 67 located in Dingwall in the eastern part of the site.
Fig. 4. Ridge in the central part of the Dingwall site documented as hydration form no.17.

During the documentation work at the abandomed Dingwall quarry, 77 hydration forms were identified throughout the site. You can read about the details of their arrangement, mutual spatial relations in the quarry on the page about the occurrence of hydration forms in Dingwall.

The results of the works used in the following text are the result of applying many research methods described here.

Dimensions of hydration forms

77 documented hydration forms are described by 4 basic values: length a, width b, relative height hr and surface area P. The data shows the diversity of the 77 forms  studied and the prevalence of certain size groups in the predominant number (Fig. 5).

Fig. 5. Basic dimension statistics describing 77 forms of hydration in Dingwall.

Taking into account the length, the longest form of hydration is form no. 17, formed as a ridge, similar to the pressure ridges documented in Pisky (Bąbel and Bogucki. 2020) characterized by a length of 23.05 m, a width of 8.02 m and a relative height of 2.08 (fig. 4). This ridge is located in the central part of the site and is by far the most distinctive object in this part of the site, right on par with the forms no. 6 and 15. The second longest form is the number “3”, which is a 13.32 m long ridge, has a width 3.63 m and a relative height of 0.86 m (Fig. 6). The third in terms of length is the form no. 6 called Ramesh’s Cave with a characteristic extensive entrance to its interior. Its external dimensions are 11.07 m long and 9.01 m wide, and the relationship of both dimensions is similar to a rather elongated round shape. Object no. 66 identified in the eastern part of the site is the shortest form and is 1.86 m long and 0.92 m wide (Fig. 2).

The relative height of the documented forms reaches the maximum value of 2.17 m (form no. 49) and the minimum height of 0.33 m (form no. 12). In both cases we are dealing with a form with a domed morphology. Form no. 12 is located in the central part of the site, while the form no. 49 called Damian’s Cave was formed in the southernmost part of the central part as well. The Damian Cave is distinguished by significant dimensions of the external morphology, equal to 9.49 and 7.12 m in plan.

Fig. 6. Ridge documented as hydration form no. 3 with a clearly twisted direction of the ridge (on the photo is F. Vladi)
Fig. 7.Hydration form no. 6 called Ramesh's cave with a domed shape located in the center of the site (in the photo from the left: D. Ługowski, F. Vladi, A. Jarzyna)
Fig. 8. Hydration form no. 49 called the Damian's Cave with a domed shape located in the southern part of the center of the site (in the photo D. Ługowski and F. Vladi)

Shape in plane

The shape in the plan defined with the use of the S elongation degree is varied and it is difficult to determine that any shape significantly dominates among the discussed forms. Generally, they can be divided into 6 irregular shapes and 71 shapes ranging in shape from round to highly elongated. Irregular forms are characterized by a complicated shape in the plan with a variable course of the ridge and branches, which makes it impossible to determine the dominant direction of elongation (fig. 9). The degree of elongation was recognized bearing in mind the important issue of the main direction of stress along which the rock rose. Unusual shapes and irregularities sometimes do not allow for its determination, but it is not always the rule, which is shown in the example of form no. 53. The vast majority of forms fall within the range of forms with an elongation degree of less than 0.5 (figs. 12, 13), however, 9% of forms are characterized by a strong elongation, as can be seen from the example of the mold no. 3 (fig. 11). Forms such as no. 14 have similar values of length and width affecting the circular outline in the plan and the difficult interpretation of the main stress axis.

Fig. 9. Hydration form no. 53 with a decidedly irregular range in the plan. The arrows define the dominant direction of the main stress axis.
Fig. 10. Hydration form no.14 of circular shape in plan with no dominant direction of narrowing.
Fig. 11. Hydration form no. 3 with a strongly elongated shape in a plan with a slightly curved course indicating slight deviations in the direction of the main stress axis.
Fig. 12. Chart of the percentage breakdown of 77 forms with shape hydration in the plan.
Histogram wydluzenie eng
Fig. 13. Histogram of the elongation degree values ​​for 71 hydration forms along with the division of these forms.

Dome shape

The dome shape K, defined by the relation of the relative height to the width of the form, was calculated for 74  hydration forms. The obtained values are quite diverse and range from 0.12 to 0.55, with the arithmetic mean value 0.27 (fig. 14). The smallest value 0.12 is characterized by hydration form no. 68 with a distinctly flat bulge in relation to the others (fig. 15). The most bulgy form documented in the Dingwall quarry is form no. 15, which owes its shape to about 43 cm thick rock plates resting against each other at the highest point (fig. 16).

Kopułowatośc eng
Fig. 14. The histogram of the dome shape K value calculated for 74 hydration forms divided into domed and tepee-shaped forms, as well as the classification of all forms in terms of the K parameter value.
Fig. 15. The dome-shaped hydration form no. 58 located in the eastern part of the site together with the values ​​of the dome shape K and the values ​​necessary for its calculation.
Fig. 16. Tepee-shaped hydration form no. 15 located in the central part of the site together with the values ​​of K and the values ​​necessary for its calculation.

Podział form ze względu na długość i wysokość względną

Histograms of the distribution of hydration forms were made at 25 cm intervals for the length and at 5 cm intervals for the relative height (Fig. 17).

The distribution of the length values made it possible to distinguish 3 categories of forms using the limit values of 4 and 8 m. The first of them are 25 small forms with a length of 0.35 m to less than 4 m, the second are medium-size forms with a length of 4 to less than 8 m, the third are large forms ranging from 8 to 23.05 m in length.

The distribution of the relative height values gave grounds for selecting 3 categories of hydration forms, this time using the limit values of 0.90 and 1.40 m. The first group consists of 42 low forms with a relative height value from 0.33 to less than 0.9 m , the second group consists of 22 forms of medium height with a height ranging from 0.9 to 1.4 m, the third, the least numerous group are the 7 tall forms ranging in height from 1.4 to 2.17 m.

Fig. 17. Histogram of length value (above) and relative height (below) with the division of forms according to these values.