The Kem Kem Group (commonly known as the Kem Kem beds ) is a geological group in the Kem Kem region of eastern Morocco, whose strata date back to the Cenomanian stage of the Late Cretaceous . Its strata are subdivided into two geological formations, with the lower Ifezouane Formation and the upper Aoufous Formation used for the strata on the eastern side of the Atlas Mountains ( Tinghir ), with the Gara Sbaa Formation and Douira Formation used in the southern Tafilalt region. It is exposed on an escarpment along the Algeria–Morocco border .
13-630: The unit unconformably overlies Paleozoic marine units of Cambrian , Silurian and Devonian ages and is itself capped by limestone platform rock of Cenomanian- Turonian age. It primarily consists of freshwater and estuarine deltaic deposits. The lower Gara Sbaa Formation primarily consists of fine and medium grained sandstone , while the Douira Formation consists of fining-upward, coarse-to-fine grained sandstones intercalated with siltstones , variegated mudstones , and occasional thin gypsiferous evaporites . Dinosaur remains are among
26-728: A fossil material of a member of the genus Uromastyx . Lapparentophis L. ragei Two isolated trunk vertebrae An early snake. Madtsoiidae indet. Indeterminate Vertebrae An early snake. ? Nigerophiidae indet. Indeterminate Dorsal vertebrae An early snake. Norisophis N. begaa One posterior and two mid-trunk vertebrae A stem -snake. Indeterminate A mid-trunk vertebra Simoliophis cf. S. libycus Vertebrae An early snake. Dirqadim D. schaefferi A Euraxemydid Galianemys G. emringeri A Cearachelyin Hamadachelys H. escuilliei A tooth enamel identified as cf. Sarcosuchus
39-520: A freshwater habitat located near a river delta (with some estuarine influence that increased over time as the sea level rose), the Kem Kem deposits were quickly submerged by the sea during the Cenomanian-Turonian boundary event , and are thus overlaid by the marine deposits of the younger latest Cenomanian and early-mid Turonian -aged Akrabou Formation , which was formerly also considered a member of
52-421: Is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger layer, but the term is used to describe any break in the sedimentary geologic record . The significance of angular unconformity (see below)
65-485: Is deposited against older strata thus influencing its bedding structure. A blended unconformity is a type of disconformity or nonconformity with no distinct separation plane or contact, sometimes consisting of soils, paleosols , or beds of pebbles derived from the underlying rock. Araripesuchus Too Many Requests If you report this error to the Wikimedia System Administrators, please include
78-487: The Kem Kem Group, but has been differentiated from it in more recent studies due to their differing paleoenvironments. Bicuspidon B. hogreli A polyglyphanodontid lizard. J. aleadonta Partial mandible with teeth. An iguanian belonging to the group Acrodonta , possibly a relative of the uromastycine agamids . Argued by Vullo et al. (2022) to actually come from Quaternary beds, and to be based on
91-591: The fossils that have been recovered from the group. Recent fossil evidence in the form of isolated large abelisaurid bones and comparisons with other similarly aged deposits elsewhere in Africa indicates that the fauna of the Kem Kem Group (specifically in regard to the numerous predatory theropod dinosaurs ) may have been mixed together due to the harsh and changing geology of the region, when in reality they would likely have preferred separate habitats and likely would have been separated by millions of years. Although preserving
104-538: The next deposition. The local record for that time interval is missing and geologists must use other clues to discover that part of the geologic history of that area. The interval of geologic time not represented is called a hiatus . It is a kind of relative dating . A disconformity is an unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition. Disconformities are marked by features of subaerial erosion. This type of erosion can leave channels and paleosols in
117-523: The overlying horizontal layers. The whole sequence may later be deformed and tilted by further orogenic activity. A typical case history is presented by the Briançonnais realm (Swiss and French Prealps) during the Jurassic. Angular unconformities can occur in ash fall layers of pyroclastic rock deposited by volcanoes during explosive eruptions . In these cases, the hiatus in deposition represented by
130-543: The rock record. A nonconformity exists between sedimentary rocks and metamorphic or igneous rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock. Namely, if the rock below the break is igneous or has lost its bedding due to metamorphism, then the plane of juncture is a nonconformity. An angular unconformity is an unconformity where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with
143-526: The unconformity may be geologically very short – hours, days or weeks. A paraconformity is a type of unconformity in which the sedimentary layers above and below the unconformity are parallel, but there is no obvious erosional break between them. A break in sedimentation is indicated, for example, by fossil evidence. It is also called nondepositional unconformity or pseudoconformity. Short paraconformities are called diastems . A buttress unconformity also known as onlap unconformity, occurs when younger bedding
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#1732858546307156-460: Was discovered from the Ifezouane Formation. Aegisuchus A. witmeri "Partial braincase of a large individual with skull roof, temporal, and occipital regions." An aegyptosuchid that may be a synonym of Laganosuchus. Antaeusuchus A. taouzensis Paired mandibles and a partial right mandible A peirosaurid . Araripesuchus Unconformity An unconformity
169-506: Was shown by James Hutton , who found examples of Hutton's Unconformity at Jedburgh in 1787 and at Siccar Point in Berwickshire in 1788, both in Scotland. The rocks above an unconformity are younger than the rocks beneath (unless the sequence has been overturned). An unconformity represents time during which no sediments were preserved in a region or were subsequently eroded before
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