Most of the exposed rocks in the Judean Hills are Cretaceous carbonates – sedimentary rocks composed primarily of carbonate minerals. The Cretaceous period (145 to 66 million years ago) began with the rifting of the giant continent Pangea, followed by the subsequent flooding of the new continental edges. Lands now bordering the Eastern Mediterranean then flanked the Tethyan Ocean.

Carbonate rocks found in the Judean Hills originate in a huge carbonate platform that extended between the open Tethys Sea in the northwest and the Arabo-Nubian Massif in the southeast during the Cretaceous. The edge of the platform was situated close, and parallel, to the present-day coastline of Israel and Sinai. Both high and low energy carbonates, sandstones, and shales were deposited over the platform to a thickness of about 1.5 km.

Limestone is a sedimentary rock composed primarily of calcite, a calcium carbonate mineral with a chemical composition of calcium carbonate (CaCO3). Sources for the calcite in limestone include seashells – when shelled animals that use calcium carbonate in the water to build their shells die, the remains of their shells accumulate on the sea or lake floor. Under the right conditions, large amounts of shell debris eventually get buried under other sediment and compress into rock. Limestone is usually a biological sedimentary rock – forming from the accumulation of shell, coral, algal, fecal, and other organic debris but it can also form by chemical sedimentary processes, such as the precipitation of calcium carbonate from lake or ocean water.

The term “fossil” literally means “dug up,” which comes from the Latin word fossilis. A fossil refers to any remains or traces of past life that are preserved in the rock record. Fossils are formed when minerals such as calcium carbonate envelope or replace bones and other organic matter, hardening or casting them within a rock matrix that remains unchanged for millions of years. Thus, they include the organisms remains, such as plant or animal tissues, shells, teeth or bones and even bacteria, but can also include traces of life such as footprints or worm burrows. Fossils tell us about the history of life on Earth, which we refer to as the fossil record.

Fossiliferous limestone is a limestone that contains obvious and abundant fossils, usually marine invertebrates such as brachiopods, crinoids, mollusks, gastropods, and coral. These are the normal shell and skeletal fossils found in many types of limestone. Fossiliferous limestone often contains information about the environment of deposition, and where the organisms lived (or were deposited). When examining the range of fossils found in the Judean region, we see evidence of a wide array of marine organisms that used to inhabit the Tethys Sea over different eras, from the Jurassic to the Cretaceous.

The fossils found in the Judean Hills region were typically formed in a process commonly referred to as “casts and molds” – types of fossilization where the physical characteristics of organisms are impressed onto rocks. Typically, the hard parts of an organism (shells of mollusks, skeletal structures of coelenterates, bones and teeth of vertebrate, chitinous exoskeleton of arthropods, trunks of trees, and many sphenophyte) leave the best impressions. These hard structures are usually composed of calcium carbonate, calcium phosphate, silica, or chitin, and do not decay as easily. The rigidity of the hard body parts also allows the sediment to form around the organism. Soft body parts decay too fast for impressions to form and are not rigid enough for a mold to set around.

The fossilization process begins when the whole organism or hard body part is trapped in sediments. Because most of these body parts are typically composed of substances which are soluble in carbonated water, this entrapment usually occurs in coarse and porous rock such as sandstones. The porous nature of the rock enables the carbonated ground water to permeate and dissolve the original tissue, leaving a detailed mold of the organism.

Two types of molds result from this process: external and internal. An external mold is created with the dissolution of the organic which then leaves an empty cavity imprinted with the external details of the organism. An internal mold may form with hollow structures. The “shell” of the organism is filled with various inorganic materials such as sediment or crystals. When the shell dissolves, it leaves an impression of the interior surface of the shells (e.g., muscle scars) on the material. Natural casts are formed when minerals are deposited within the mold.

While fossil evidence of many different organisms is found in the region vineyards, certain groups are more prominent than others. Of these groups, the most abundant is the Mollusca. Mollusks are a group of animals without backbones (invertebrates) that have an unsegmented body, often covered by a shell (exceptions include octopuses and squid). Mollusk shells are usually coiled, either strongly (such as in snails and some cephalopods) or weakly (as in bivalves). The fossilized remains of these marine creatures, relics of the vast Tethys Sea – constantly being discovered– serve as a reminder of the ancient history and origins of the Judean Hills’ unique terroir.

 

Bibliography:

E. Sass, A. Bein. (1982). The Cretaceous carbonate platform in Israel. Cretaceous Research, Volume 3, Issues 1–2, 135-144.

Scarpa, D. (1990). THE GEOLOGY OF THE CREMISAN VALLEY, BEIT JALA. Bethlehem University Journal, 9, 7–31.

Lowenstam, H. A. (1942). Geology of the Eastern Nazareth Mountains, Palestine: I. Cretaceous Stratigraph. The Journal of Geology, 50(7), 813–845.

Salvini-Plawen, L. (2023, March 22). Mollusk. Encyclopedia Britannica. https://www.britannica.com/animal/mollusk

Bentov, S., Abehsera, S., Sagi, A. (2016). The Mineralized Exoskeletons of Crustaceans. Cohen, E., Moussian, B. (eds) Extracellular Composite Matrices in Arthropods. Springer, Cham. https://doi.org/10.1007/978-3-319-40740-1_5

Fossil. (2023). Merriam-Webster Dictionary. https://www.merriam-webster.com/dictionary/fossil.