Using your computer’s search engine, conduct a search for “stromatolites.” Take
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Question
Using your computer’s search engine, conduct a search for “stromatolites.” Take a look at images of both modern and ancient stromatolites. How and where do stromatolites form today and how and where did they form in the distant past? Just how far back in the geological record do we find stromatolites? Use web resources and your textbook for answers. Also visit Kerry Cupit’s web page (Cupit, Kerry. Fossils 101. 2012. Web Page. 2 12 2012. http://www.spaceman.ca/fossil/index.php?Show=All (Links to an external site.) .) Choose any 2 fossils and provide a brief description and classification of each as well as a sketch. Find some images of sedimentary structures on the web at one of many sites that show such illustrations, for example,http://www.indiana.edu/~geol105/images/gaia_chapter_5/sedimentary_structures.htm (Links to an external site.). Make a sketch of two sedimentary structures of your choosing and briefly explain how they form and what they mean when found in sedimentary rocks.
Explanation / Answer
Modern stromatolites : Modern stromatolites are known to have a biological origin.They are formed with the help of microbes which grow in a thin layer on the sea floor.They are blue - green bacteria with sticky in nature , and small inorganic particles and sediments settle on the surface of the mesh.The layered structure of organic and inorganic material can grow to considerable domes.Modern stromatolites are first discovered in shark ,Bay Australia in 1956 and exist throughout western Australia.They are mostly found in Hyper saline lakes and marine lagoons where extreme conditions due to high saline levels present animal gazing.
Ancient Stromatolites : Ancient stromatolites formation shows the macroscopic stromatolites.These are formed due to the natural material deposition and the presence of organic globule clusters within the thin layers of the stromatolites , of arogenite , nanocrystals. Proterozoic stromatolites micro fossils include cyanobacteria and some forms of eukaryote chlorophytes .They are formed at the siyels Formation ,Glacier National Park .Proterozoic stromatolites are developed at the updip location under conditions of higher current velocities and greater sediment influx.
The two fossils : 1|)Aporrhais : Aporrhais is a genus of medium sized see snails , marine gastropped mollusks in the family Aporrhaide and the super family strmboidea.From Triassic andrecent periods (205.6 to 0.0 million years ago ) .The type of this species is Aporrhais quadrifidus Da costa.
Aporrhais pespelecan's isa type found in the Eastern Atlantic Ocean , from Norway to the Mediterranean sea.Lies below the low level in the sublittoral from 10 to 130 m depth on mud or muddy sand.
2)Orthoceras : Orthoceras is a genus of extinct nautiloid cephalopod.This is also called Orthoceratiles.This is found in limestones.Limestones that consists of monospecific assemblages of orthocene cephalopod's are called cephalopod limestones.These are found in Baltic Island of Oland off the southern coast of Sweden.
Sedimentary Rocks : Sandstone : Sandstone is also called Arenaceous.colour variable according to the type of cementing material.Rocks having silica and calcite as their cementing material are light in colour.When they contains iron oxide are red to reddish brown.Its mineral composition is Quartz is the cheif component.Small amounts of feldspar , mica , garnet etc.may also occur.cementing material may be silica , calcite, iron oxide,clay or chlorite.The common structures in sandstone are ripple marks and rain prints , current bedding, stratification.sandstone types are Orthoquarzite,Grit,graywacks,glauconite sandstone.
2)LImestone : It is a calcarious rock.Formed chemically or organically.they are white,grey or cream coloured.And contains fossils.It is soft,fossil cement and effervescence in dilute hydrochloric acid.calcium carbonate is the cheif constituent.Magensium carbonate is present in variable amounts.Limestone is a fine grained rock.Itis compact and massive.Some limestones may have oolite structure.Organic structures are common.Types are chalk,oolite limestone,Marl
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