Chronology Geology of New England

1 chronology

1.1 overview
1.2 archean , proterozoic eons
1.3 paleozoic era

1.3.1 cambrian period
1.3.2 ordovician period
1.3.3 silurian period
1.3.4 devonian period
1.3.5 carboniferous , permian periods


1.4 mesozoic era

1.4.1 triassic period
1.4.2 jurassic period
1.4.3 cretaceous period


1.5 cenozoic era

1.5.1 paleogene period
1.5.2 neogene period
1.5.3 quaternary period
1.5.4 surficial deposits

1.5.4.1 erosional processes
1.5.4.2 pleistocene epoch
1.5.4.3 holocene epoch

chronology
overview

the bedrock geology of new england heavily influenced various tectonic events have occurred since paleozoic era including accretion of land masses formed various continental terranes mesozoic rifting of hartford basin.

archean , proterozoic eons

in archean eon western massachusetts , vermont eastern edge of laurentia (now canadian shield). laurentia believed have originated @ end of hadean, making 1 of oldest regions continental crust, evidenced discovery of acasta gneiss in canada. @ end of hadean massive eruptions of felsic lava became cool enough form permanent crust. felsic nature of laurentia allowed float on denser ocean basins surrounded it, not submerged under then-forming oceans. during archean eon surface of new england coastal desert covered silica-rich sediments outcroppings of granite bedrock.

paleozoic era

starting in paleozoic era supercontinent pannotia began break up, forming smaller continents including laurentia (north america , greenland), gondwana, baltica, , siberia. @ same time sea levels rising, resulted in flooding of of continents shallow epicontinental seas. followed 3 periods of extensive orogeny. of geology in new england based on formation of appalachian mountains through series of paleozoic accretion episodes terminal collision between laurentia (proto–north america) , gondwana (proto–africa–south america) @ ca. 300 ma.

cambrian period

ordovician period

during middle ordovician, during taconic orogeny, volcanic island arcs collided east coast of north america causing extensive metamorphism, faulting, , uplift, result of taconic mountains on border of new york , new england.

silurian period

devonian period

the acadian orogeny took place during middle late devonian. following subduction of iapetus ocean floor, microcontinent avalonia slammed eastern north america, caused period of metamorphism, faulting, , mountain building. evidence these events can found within littleton formation on summits of presidential range in northern new hampshire , southern maine. littleton formation deposited in devonian, approximately 409 million years ago gander and/or avalon terrane source. . lower part of formation found proximal bronson hill island arc , consists of basaltic , rhyolitic volcanic rocks along low grade metamorphic shale while upper part of formation consists of youngest rocks of presidential range. after taconic orogeny, occurred during middle ordovician (474-455 ma), humber seaway on way closure , dashwoods microcontinent accreted laurentia. led accretion of oceanic terranes including bay of islands in newfoundland , thetford mines ophiolites in quebec. additionally, late-ordovician-early silurian mélange present, consisted of blueschists , deepwater deposits, , indicates subduction continued during time. finally, closure of tetagouche-exploits back-arc in silurian (430 ma) accreted bulk of ganderia laurentia. event known salinic orogeny , responsible of bedrock found in new brunswick, newfoundland, , maine .

other littleton formation, presidential range includes rangeley sequence consists of silurian , devonian turbidite sequences, silurian rangeley formation, middle late silurian perry mountain, smalls falls, , madrid formations. area has experienced extensive deformation expressed pre-metamorphic faults, various folds, thrust faults, , doming. evidence igneous activity include early-devonian (408 ma) diorites, mid-devonian (390-400 ma) granites, , carboniferous (360-350 ma) granites .

carboniferous , permian periods

the alleghenian orogeny occurred during late paleozoic , result of collision of africa north america during formation of pangea. collision events produced tremendous occurrences of thrust faults, folding, , metamorphism. result of collision event huge mountain belt formed ran east coast of north america canada , baltica, had collided greenland , northern north america. rocks newly deformed , folded coast far allegheny plateau , adirondack mountains of new york.although modern-day appalachian mountains have been heavily weathered on time, thought once rival himalayas in size.

mesozoic era
triassic period

jurassic period

depiction of process of caldera collapse, in case mount mazama representative of general progression.

although there not active volcanoes in new hampshire or new england, white mountains region of state contains strong evidence of volcanic approximately 145 million years ago. volcanic formation in white mountains has been estimated have occurred between late jurassic , cretaceous periods, , have coincided separation of pangaea. pangaea broke apart , land masses shifting, large features white mountains formed; @ same time, multitude of cracks occurring, magma rose , filled many of these voids. in manner calderas formed throughout white mountains magma receded; these calderas subsequently erupted on scale dwarfing 1980 eruption of mount st. helens. results of these massive eruptions can found in such places ossipee mountains, located proximal white mountains. ossipee mountains contain substantial amounts of volcanic rock, , many ring dikes across region indicate there once active volcano on site. volcanic rocks can found throughout white mountains beyond ossipee region, further confirming eruptions occurred across area millions of years ago.

cretaceous period

cenozoic era
paleogene period

neogene period

quaternary period

much of geomorphology , surficial deposits of new england result of glaciation in quaternary period. scoured new england landscape reveals evidence of wisconsin glacial period. 

surficial deposits

the continental ice sheet on new england more mile thick in places. grinding , plucking on landscape created wore down topography , created poorly sorted sorted surficial deposits. large terminal moraines composed of poorly sorted till present along coasts , can identified thin, patchy, , stony texture . maine bordered moraines identify terminus margins of past ice bodies. waldoboro terminal moraine sits on southeastern coast, while highland front moraine parallels northwestern border. large continental ice sheets (see laurentide ice sheet) created large moraines, takes time long, lumpy ridges form @ massive scale .

new england best known high density of erratics, displaced rocks differ immediate bedrock composition of region , range size of pebbles boulders. surfaces rounded , polished due rasping. while bedrock of area largely igneous granite, erratics sandstone , slate blocks . sedimentary erratics visible across highest peak in maine, mount katahdin.

glacial outwash sorted , stratified due systematic nature of stoke’s law visible in gravel pits in maine s grafton notch state park outwash plains composed of alternating layers of sand , gravel have been deposited in deltas of glacial lakes , alluvial fans.

erosional processes

the slow , grinding movement of continental ice sheets , alpine glaciers across landscape creates erosional landforms. abrasion, plucking, , freeze-thaw action creates u-shaped valley unique glacial erosion.

the intense pressure ice causes abrasion. process carves striations, or grooves, bedrock glacier moves down slope. glacial striations determine direction of glacier; visible outcrops in white mountains, instance, indicate ice flow toward south-southeast . abrasion produces rock flour visible in glacial outwash plains across new england.

maine has of longest eskers in world . climate began warm, glaciers began melt , drainage meltwater under glacier formed huge torrents of sediment that, when compacted, left long , sinuous ridge or kame. moose cave in grafton notch speculated have been formed in part subglacial river . abol esker in baxter state park notable serpentine kame.

kame , kettle topography commonplace across maine. hummocky morphology includes kettle ponds , kettle lakes “steep-sided, bowl-shaped depressions in glacial drift deposits” large blocks of ice melted glacier recessed.

other notable glacial features include cirques. mt. katahdin , bigelow range have circular divets indicative of glacial erosion.

pleistocene epoch

holocene epoch

following glacial melting of laurentide ice sheet, new vegetation , warmer climate caused new new england become inhabitable human settlers. new climate, combined ample supply of hard volcanic rock , other natural features, created ideal area human settlement. these settlers fashioned tools, such arrowheads, surficial rhyolite deposits found near have been river valley settlements.

the white pine rose in new england shortly after first deglaciation.

the melting of laurentide ice sheet (beginning 18,000 cal yr bp), covered new england landscape until late pleistocene era, caused significant ecological , climatic change in region. except number of abrupt climate reversals, extreme being cold reversal of younger dryas, climate of region experienced rise in temperature (of 2˚ celsius) during holocene. fossil pollen findings indicate increased temperature in region paralleled new vegetation patterns, such rise of hemlock , white pine in new hampshire , white mountains. these vegetation shifts created ecological environments in region habitation migratory caribou, hunted human settlers, possible. these settlers have moved formed dune fields, produced wind erosion of glacial outwash deposits, such found in ohio valley, in hudson , connecticut river valleys, , in israel river valley. human settlers have populated these river valleys in order observe caribou migrating northeast along newly formed rivers.