Around 34 to 23 million years ago, this area was covered by shallow sea; an ideal environment for nummulites of the foraminifera class. These small single celled organisms have calcite shells with internal spiral coils divided into chambers.Once foraminifera die, their shells accumulate on the sea floor to form limestone.Nummulite is from the Latin meaning “little coin”; the road cutting here has exposed these fossils which are also known as “Angel’s coins”. Descendants of these now fossilized foraminifera can still be found living in today’s oceans.
Around 34 to 23 million years ago, this part of Oman was much lower than it is today and covered by a shallow sea. The Mid Tertiary limestone originally formed in horizontal layers on the sea floor. Over time the rock layers became slightly tilted. The land was later uplifted, then in the last 2 million years, a large wadi deposited layers of gravels of various sizes and of different origins, burying the marine formation. These gravels became cemented together to form a rock called conglomerate.Here, as there is a gap in time between the deposition of the limestone and conglomerate, the meeting of the two layers of rock is called an unconformity.
The yellow-brown rock on the banks of Wadi Al Khawd opposite was originally the sea floor. Between 55 to 34 million years ago (Eocene Age) the sea was rich in marine life and the remains of marine creatures like sea slugs, clams and coral settled in sedimentary layers. Within these layers the bones of the harder shelled animals formed jumbled groups with empty spaces as seen in the fossils. Over time, the limestone has been lifted above sea level and exposed the nodular texture of these lumpy masses of hard shells.
