Cambrian and Ordovician

Chapter 10 of historical Geology

with the paleozoic eon brought

abundant life, dramatic change in rock types, atmosphere change from icehouse to greenhouse (oxygen started to build up)

how short and how many days existed in the early paleozoic

21hrs, 430 days per year

how can we tell that North America’s margins are passive

they have thick prisms of sediments on newly shifted margins and thin sediments over craton

epeiric seas

relatively shallow, geographically wide-spread bodies of water covered large parts of the continent

what was a change with the beaches in the cambrain

they were mature, primarily quartz sandstone beaches, as opposed to the dirty greywhackies they used to be

arches

topographically high areas that influenced surrounding sedimentation; areas of extremely shallow water or even islands

basins

topographically lows that act as receptacles for sediments; oval in plan; thickest beds in center; like michigan basin

transgressions

deposit sediments on cratons

regressions

erosion and unconformities

sequences

large packages bound by craton-wide unconformities

6 sequences on craton Paleozoic to recent

Sauk, Tippecanoe, Kaskaskia, Absaroka, Zuni, and Tejas

Sauk sequence started

635 myo

what occured during the Sauk sequence

transgression Sauk Sea flooded at least ¾ of the north american craton and left only canadian shield and transcontinental arch above sea level

sediment multicycle

repeated erosion, transportation, and deposition

the lowest rock unit during the paleozoic is usually

ripple marks, which indicate a shallow water deposit on the beach

why would weathering be different during the paleozoic

there were no land plants, so wind was the most common weathering fatcor

2 types of sandstone during the paleozoic

ripple marks and small scale cross-beds that have fossils

frosting and large scale cross-beds that lack fossils

frosting implies

wind transport

ripple marks imply

water deposition

Sauk sequence concludes in

Early Ordovician

the sauk sequence contains

limestone and is truncated by a big unconformity

tippecanoe transgression started in

middle ordovician

St. Peter sandstone is called supermature b/c

over 99% is quartz that is well-sorted and well-rounded

what form of tippecanoe covers Wisconsin, Illinois, Iowa, and Oklahoma

St. Peter sandstone

St. Peter sandstone is part of which sequence

tippecanoe

clastic wedge

accumulation of clastic sediment deposited next to an uplifted area

cambrian life includes

trilobites, archaeocyathans, primitive brachiopods, archaic mollusks, archaic echinoderms

what happened to all experimental groups of cambrian life

they went extinct except for lingula

what was the dominant fossil of the cambrian

trilobites