Zululand Group
ulwandle lwaseNdiya luzelwe
Amatshe okuqala akheka olwandle olusha (Indian Ocean) ama-silts kanye nama-sandstone esikhathi se-Cretaceous ngaphezu kweminyaka eyizigidi eziyikhulu namashumi amane nanhlanu kuya kwezingamashumi ayisithupha nanhlanu edlule (145-65 Ma). Lamatshe asolwandle abekeka ngesikhathi esifanayo lapho ama-dinosaur amakhulu agcwala emhlabeni.
Fossils from the Zululand group at Lake St. Lucia
Ngaso leso sikhathi izilwane ezinkulu ezifana neminenke ezingacishe zibe imitha ezibizwa ngokuthi ama-ammonite, aphila olwandle olufudumele. Amagobongo azo ayatholakala kuwona wonke amatshe esikhathi se-Cretaceous avelile, njengasogwini oluzungeze ichibi lase-St Lucia.
Specimens: Geology Education Museum
Amaphuzu amaningi akhomba noma avumelana nokuthi esikhathini 65 Ma esedlule i-meteorite enkulu yashaya e-Chicxulub (Mexico), yaholela ekulahlekeni emhlabeni wonke kwezilwane ezihlanganisa ama-ammonite nama-dinosaur.
Cretaceous Paleogene extinction event
K-T extinction
The Cretaceous period ended 65 million years ago and is marked by the Cretaceous- Plaeogene extinction also knows as the KT or KPg- extinction event. The extinction event was not only restricted to life forms on land, but also included many groups of marine organisms.
This extinction event eliminated a vast number of species. Based on marine fossils, it is estimated that 75% or more of all species became extinct.
Based on Iridium evidence (Iridium is abundant in asteroids and comets) scientists suggested that an asteroid struck the Earth at the time of the K–Pg boundary.
Although the concurrence of the end-Cretaceous extinctions with the Chicxulub asteroid impact strongly supports the impact hypothesis, some scientists continue to support other contributing causes: volcanic eruptions, climate change, sea level change, and other impact events.
Ammonites
Coastal processes
Ammonites were marine animals belonging to the class Cephalopoda. They appeared in the lower Devonian and were extinct by the end of the Cretaceous Period. Although they resemble the living Nautilus they are more closely related to octopuses and squids.
Ammonites typically have an external chambered shell, planispirally coiled and often ornamented with ribs and knobs. The ammonite’s shell was divided into chambers separated by walls known as septa. Where the septa joined the shell wall, intricate lines of varying complexity (known as sutures) are visible. Ammonoids are important as index fossils because of their rapid evolution and wide distribution in shallow marine waters.
