The Quaternary Period is a time which has seen the cyclic growth and decay of continental ice sheets .
The Quaternary is the most recent of the three periods of the Cenozoic Era in the geologic time scale governed by the International Commission on Stratigraphy. It continues to this nanosecond. It commenced at the end of the Neogene Period and is divided into two epochs: the Pleistocene; 2.588 million years ago to 11.7 thousand years ago; and the Holocene, 11.7 thousand years ago to the present. "Late Quaternary" refers to the past 0.5–1.0 million years.
From a human point-of-view, this is the most interesting period as it is the time in which a recognizable human animal evolved. In terms of geological history it is no more than the blink of an eye, since the Quaternary has only spanned 2.6 million years.
As a result, the continents have not moved very much compared with earlier periods. Essentially, what has happened is a change is shorelines, driven by changes in world sea levels, driven by glaciation and de-glaciation. The landscape of Nova Scotia was shaped during about 100,000 years of glacial history. Our part of the world was entirely covered by ice at various times and while the hills and valleys were not massively rearranged by the overflowing ice and water, minor surface features and the drainage and nature of soils, were dramatically altered.
The Pleistocene, colloquially the Ice Age, is a geological epoch which lasted from about 2,588,000 to 11,700 years ago. More than 11 major glacial events have been identified. A minor excursion of ice into an area is termed a "stadial"; times between stadials are "interstadials". An Ice Age is a period of long-term reduction in the temperature of Earth's surface land and water surfaces and atmosphere, resulting in the presence or expansion of widespread continental as well as polar ice sheets and alpine glaciers. The individual pulses of cold climate are termed "glacial periods," Warm periods between them are referred to as "interglacial periods."
An ice age is defined as having ice at the earth's two poles, so technically we are not yet at an interglacial stage. With global warming it seems we are headed there but there will be climatic fluctuations due to unforeseen circumstances. If the climate continues to arm, more glacial ice will melt and...
The general topography of the ice sheets which had different origins and spread centres. Heights are expresses in metres. Orange dot Mahone Bay. The Laurentide Ice Sheet, which developed on land in the Hudson Bay area was extremely high but had no extreme internal topography toward the centre which sloped of at about 4º. The average ice cover in Nova Scotia was deep at about 1,000 metres. but no competition for that to the north west. This Wisconsinan Glaciation did not penetrate as far south as some earlier events.
That last glaciation was perceived differently in Europe and Asia, where other names are applied to the main advances. For North America four are recognized, dating as Nebraskan, Kansan, Illinoisan and Wisconsinan in order of appearance. Each was separated by interglacials when the planet was relatively free of ice, and the climate warm, warmer than is now the case. Glacial and interglacial periods alike experienced periods when ice advanced or retreated. Notice that two earlier glaciations drove ice further south into the central part of the United States.
The big thing to be recalled in all of this is the fact that the earth's crust is elastic over long periods of time. If overly stressed over a short time it will fracture, but if force is exerted gradually it will bend down into the plastic and liquid areas in the depths and displace crust at ice margins. These buildups of matter migrate very, very slowly in waves out from the ice centre as downward pressure fluctuates. When ice melts the crust rises and the wave reverses. Similar action is seen drastically speeded up when one wrestles with conditions on the surface of a water bed.
Here the stadial and interstadial phases can be seen in fluctuations in the chart between warm and cold times. When it gets colder more and more water converts to ice and sea levels fall. When it warm carbon dioxide tends to displace oxygen and that can become a problem for some species of life.
This chart corresponds with the last, but illustrates how world-wide temperatures have varied over time. This chart assumes we are now in an interglacial position. The glaciation of which we have most knowledge is the Wisconsinan, much of the evidence for the others having been obscured by the physical damage every glacier creates. In the middle of Wisconsinan time you will notice interstadial spikes and valleys where the climate was undecided. After that, there was a major readvance of ice which reached its climax 20,000 years ago. This memorable change saw ice covering fifteen million kilometres of land, tying up so much water that sea levels fell to 100 metres below present levels. The warmth reasserted itself a mere 18,000 years ago.
Generalization, let fine details through the information sieve, but this gives the essentials. In the north the elevation of coast lines was aided by isotasic balance, described above where we talked about the crust being displaced by ice forming and melting. By the way, the first proponent of the role of glacial ice in moulding land forms was Louis Agassiz in 1840, who researched the situation in Europe and North America. It was not a widely accepted theory until the 1860s.
The glacial history of Nova Scotia had long been considered associated with the Laurentide Ice Sheet shown above. The Reverend D. Honeyman, curator of the provincial museum, proposed that northern Nova Scotia had been glaciated by local . Robert Chalmers (1895) of the Geological Survey of Canada added that, "...Nova Scotia (has not) been glaciated by extra-peninsular ice from the north or northeast." Geologists L.W. Bailey and W.H. Prest working in Nova Scotia at the same time agreed, as did J.W. Goldthwait in 1924. Hence, this was "you are not from here" situation until the 1950s when Harcourt Cameron and Rupert MacNeill at Acadia University in Wolfville, Nova Scotia, found evidence for local glaciers in Nova Scotia.
Erratics near Peggy's Cove, rocks or boulders that differ from the surrounding rock brought from a distance by glacial action. Charles Hickox (1962) later confirmed that granite erratics on the North Mountain had been transported northward from a local ice cap over the South Mountain Batholith in Nova Scotia and not southward from New Brunswick as Goldthwait (1924) had suggested.
The Caledonian Phase, showing the earliest supposed flow patterns from 75 to 40,000 years ago. In 1969, Victor Prest and Doug Grant postulated that several large local glaciers termed the "Appalachian Glacier Complex," developed in the region. They said that this local ice buildup was not due to climatic changes, but to re-directed ice flow into the Bay of Fundy and Gulf of St. Lawrence, as sea-level rose at the end of previous glaciation. D.R. Grant, who also worked for the Geological Survey of Canada, carried out research which uncovered difficulties correlating data from the Maritimes with that in Quebec. It was decided that Nova Scotia actually was overridden once by ice from the north (broken lines) during an early stade in Wisconsinan glaciation. During this phase of glaciation, the Appalachian Mountain "Northumberland Glacier" to the north of New Brunswick followed a raised interglacial marine bedrock terrace along the New Brunswick coast to Cape Breton. The ice sheet south west of that line built up a dome in New Brunswick, and was termed the "Gasperau Ice Centre".
These highlands would have been a barrier to Laurentide Ice. Local glaciers had climatic input from the high Appalachians of Vermont and New Hampshire. That created conditions which built up a massive ice dome over northwestern New Brunswick and it was the movement of this ice southeast across the Maritime provinces, which left tell-tail scratches or striae (dotted line on a previous map) in exposed bedrock. The oldest glacial deposits in Nova Scotia are called the "Bridgewater & Mabou" conglomerates, deeply weathered and iron-cemented drift and outwash products of Tertiary to early Pleistocene age. Mollusc shells, dated between 200-309 ka, have also been found in glacial debris in southwest Nova Scotia.
Prior of the Wisonsinan glaciation the climate was warmer than at present, possibly a bit like Georgia in the united States. The Sangamonian Interglaciation,128 to 75 years before the present is remembered in. buried forests hidden by glacial deposits throughout Nova Scotia. Pollen from buried forests and bogs shows that the climate fluctuated considerably during this interglacial period so that the the of great forest varied. As this period was ending, the bones of an adult and a juvenile mastodon were recovered from a pit being excavated in a gypsum quarry at East Milford not far from Mahone Bay even if you are not a crow.
The Esuminac Ice Centre arose in northern New Brunswick (left dotted line). The flow trajectories out of New Brunswick and Nova Scotia were away from this pile up of ice, possibly created by the opposing Laurentian and Northumberland ice masses. Ice outflow from the Escuminac Centre may have been in the form of rapidly flowing ice streams within on at the surface of the glacier. These streams converged into inter-bank channels on the outer shelf, drawn by calving and the production of icebergs in the deeper water of the continental shelf edge. At first the stream paths were across Nova Scotia, Later, the divide became isolated on the shelf of Nova Scotia and ice flow was drawn southwestward into the Bay of Fundy directly into the ocean. The dominant passage of ice and water is now established as Gulf of St. Lawrence.
The Scotian Phase saw that "Scotia Ice Divide" move further southward as the Escuminac Centre began to become deflated as water and ice ended in the salt water due to global warming and sea level rise. Notice the spill back into the area destined to become the Gulf of Maine. The Scotian Divide may have extended as far as Sable Island at the east. That ice source finally moved offshore and settled up a rise of end moraine (glacial debris) pushed out there by earlier glaciation. Browns Bank and a portion of the Newfoundland Fishing Banks are now exposed as islands. They were never deeply downthrust as ice cover was less thick away from the largest highland sources of ice and snow.
Glaciation persisted over most of the land for another 1,500 years, but before this event ended ice stream cleared ice from the Gulf of Maine and Bay of Fundy leaving a deeply depressed landscape. Before the land could rebound, beaches, and deltas formed. Almost all of the fishing banks were islands at this time. Notice the downwarped lands in Maine and New Brunswick which would have flooded if the ice cover had allowed.
That is precisely what did take place in the Chignecto Phase. In Maritime Canada there was a distinct loss of ice in the northeast and around the Gulf of Maine and Bay of Fundy. Small ice caps were generated after Scotian Phase retreat perhaps during a brief late-glacial climatic reversal over southern Nova Scotia, (South Mountain Ice Cap), the Northumberland Strait area (Chignecto Glacier) and the Antigonish Highland (Antigonish-Chedabucto Bay Glacier Complex). At the present time these mountainous regions get more than their share of snow and ice.
After the Chignecto Phase, the climate warmed still further and glaciers melted and disappeared from most of Nova Scotia. Forests with spruce and pine started to invade southern Nova Scotia, along with species of animal, possibly including man. The first human inhabitants of Nova Scotia came to the area as a group about 11,000 years ago possibly following migrating Caribou, whose range was now extended. Sea-level began to rise from a low point of 80-100 metres below present level at the outer banks.
This Pleistocene tundra represents the landscape these first immigrants would have seen, but their is no fossil evidence for most of these animals aside from caribou. The woolly mammoth did succeed the Mastodon in similar parts of North America. The sabre-toothed tigers, antique horses and the rhino are now extinct. The earliest casualties dated back to the start of the Late Pleistocene, however the great majority of extinctions in Afro-Eurasia and the Americas occurred during the transition from the Pleistocene to the Holocene epoch. Humans have long blamed themselves for overkilling these beasts, but in some cases that seems a bit ethno-centric.
The Great lakes were not always the greatest! Alternative hypotheses to the theory of human responsibility include climate change associated with the last glacial period and the Younger Dryas event. We all know that sudden global warming has consequences. In that time as the ice melted it created massive inland bodies of water surrounded on all sides by ice.
All these big bodies of water were separated from one another by ice dams and once upon a time... Orange dot those unfortunate residents of ancient Nova Scotia. What more can go wrong? Just about everything! The prevailing theory today is that the Younger Dryas Event was caused by significant reduction or complete shutdown of the North Atlantic "Conveyor", which circulates warm tropical waters northward, in response to a sudden influx of fresh water from Lake Agassiz and deglaciation in North America. This conveyance is the Gulf Stream, whose current tendency to feed back warm waters on Nova Scotia are now a worry.
The Younger Dryas was not just a single climatic event.
"Oxygen isotope record from the Greenland ice core showing an abrupt temperature drop 12,800 years ago, 1,300 years of cool climate, and sudden warming 11,500 years ago... The change was relatively sudden, taking place in decades, and it resulted in a decline of 2 to 6 degrees Celsius and advances of glaciers and drier conditions, over much of the temperate northern hemisphere." The above map was made possible following creation of "The Great Trench" for a Sable Island natural gas pipe line. This uncovered glacial deposits from this happening.
The end of the Younger Dryas has been dated to around 11,550 years ago, occurring at 10,000 years ago (uncalibrated radiocarbon year). "The effects of the Younger Dryas cooling impacted New England and parts of Maritime Canada more rapidly than the rest of the United States."
Summer temperature conditions in Maine decreased by up to 7.5ºC. Cool summers, combined with cold winters and low precipitation, resulted in a treeless tundra up to the onset of the Holocene, when the boreal forests shifted north.
The 1,300-year cold period known as the Younger Dryas stadia may explain why the Maritime Provinces were not seen as a tourist draw for a long, long time.
The colonization of our planet out of Africa was retarded in the North America and northern Asia by all that ice. Archaeological sites in Mongolia dating from 35,000 years ago indicate the arrival of hunting bands carrying sophisticated flint tipped weapons. These people faced a bleak terrain similar to that seen by Early European settlers. They were reliant on the seasonal migrations of tundra animals and their capacity to live through harsh winters. Although there was a "bridge" of land connecting with the New World it was not immediately useful.
DNA-testing of American natives has shown that there were four genetic clans which did penetrate to the heartland of America, which was not a desirable place at the height of Wisonsinan glaciation. All are known to have had genetic links with people living in either Siberia or northeast Asia. We now know enough about sea-level changes to understand that over the past 100,000 years there were two periods of opportunity when one might walk from Siberia to Alaska, the first about 50,000 years ago lasted for 12,000 years. The second coincided with the last great ice age, when land was again above sea level between 25,000 and 13,000 years past. There is fierce controversy concerning the possibility of colonization about 47,000 years ago. There is major evidence, genetic and physical, for entry within the last 13,000 years.
Getting into Alaska was possible before there was any way of moving southward. That area was accessible at the first waning of the Ice Age when sea levels were starting to rise. However, two great fused ice sheets met, and were fused, in the Rocky Mountain region. Eventually with a warming climate, people were able to pass through a narrow corridor between ice sheets after being stranded or a while in Alaska. Behind them that land bridge was flooded. They were not in a verdant valley, but made a slow but harsh passage southward finally emerging on the rich expanses of the Great Plains in the American northwest, an area now vastly more attractive as plants and animals were now prolific there. However, a lot of real estate was still unavailable for development.
From the Great Plains it was possibly for Paleolithic Indians to populate South America, which they managed within the first thousand years. In South America one clan genetically typed was shown to have no ancestor in either Siberia or Alaska, although the variant pattern is now found as far north as Vancouver Island. Geneticists say suggest that it is not impossible to suppose two maritime colonizations, one from Polynesian islands and another down the coast from some part of Asia as yet undetermined. "The rapid sea-level rises would have give a great incentive to find new land."
This illustration in a simplification. There are two early archaeological sites in South America which have been brought to light to support a much realier colinization. One is an open shelter at Pedro Furada in Brazil well known for its rock paintings. The second is Monteverde in Chile, where fragments of wood, possibly some part of a habitation, have been found beneath ground and dated first at 30,000 years. This date has since been revised upwards. No human remains have been found at either site, calling into question their authenticity.
That said, there is no equivocation concerning that second coming. The oral history of the Heiltsuk Nation, an Aboriginal group based on the Central Coast of British Columbia, tells of a coastal strip of land that did not freeze during the ice age, making it a place of refuge for early inhabitants of the territory. In April 2017 it was announced that an archaeological team digging on British Columbia’s Triquet Island unearthed a hearth which was about 14,000 years old. The area in which it was found is now represented as one of the oldest human settlements ever discovered in North America. The oldest human remains,so far have been those of a child, 13,300 years old, found at Sun River, Alaska in 2010.
In 1992, construction workers dug up mastodon bones while clearing earth to build a sound barrier along Route 54 in San Diego County, California. For years, Dr. Thomas Deméré, a paleontologist at the San Diego Natural History Museum struggled to figure out how it was killed and long ago it died. Bone fragments led to the conclusion that the animal had been killed by people and near the animal were five large rounded stones. Dr. Deméré speculated that the humans might have been trying to get marrow out of the mastodon bones to eat, while using fragments of the bones to fashion tools. The bones dated to 130,000 years past, ergo... Published in the journal Nature earlier this year.
The European "Iceman" named "Ötzi" is a glacial mummy from the Copper Age (40,000 years ago), discovered accidentally by hikers in Italy in 1991, together with his clothing and equipment, on the Schnalstal/Val Senales Valley glacie.
This study's evidence for inhabitation of California 130,000 years ago was criticized: “I was astonished, not because it is so good but because it is so bad,” said Donald K. Grayson, an archaeologist at the University of Washington. He suggested there was probably a mundane explanation for markings on the bones.
Geneticist Brian Sykes of Oxford University thinks that, "The greatest evidence against the earlier date for the colonization of the Americas is that one would expect the population, in a land full of game and without prior human occupation, to explode, leaving abundant evidence all over the place. It is not as if nobody has looked. American archaeologists have worked hard to find it; but without success. However, there is plenty of evidence of a continuous settlement after twelve thousand years ago, with hundreds of sites scattered all across both North and South America." In North America most of the actual remains have been found in the western parts of the continent which were clear of ice and tundra earlier on. The northeast was a firmly damp and acidic region a poor setting for the long survival of old bones.
In the Algonquian legends there are tales of an El-folk, an elder race which occupied the lands in the northeast long before their day. Obviously, they populated Nova Scotia and other adjacent areas out of the southwest. The first closed boreal forest of spruce, fir and beech trees, developed 10,000 years ago. A paleo-Indian site near Truro has brought in radiocarbon datings of from 10,500 to 11,000 years before the present, Archaeologists at first concluded that this was an a camp of caribou hunters, who probably sheltered in nearby woods, but "living floors" were uncovered subsequently. "The excavations at Debert identified a number of occupation loci over an area of 9 hectares (22 acres). The archaeologists recovered 4500 artifacts, many characteristic of the Palaeo-Indian tool kit."
The Debert site is significant because it is the most northeasterly Palaeo-Indian site discovered to date and one of a few identified with an area once heavily glaciated. That Debert site is located at the head of the lower arm of the Bay of Fundy on a Triassic plain featuring low sand dunes. The First Peoples migrated to the Debert area just prior to the Younger Dryas stadial (third map from left).
"Archaeologists have hypothesized that these early settlers were nomadic big game hunters who relied on migrating herds of caribou for survival. Small game such as fish and fowl would have also been an important food resource for the Palaeo-Indians. To survive the freezing cold climatic conditions, the early settlers likely wore tailored clothing and constructed skin covered tents with wooden frames for shelter." - Wikipedia. "Limited testing was carried out at the new sites in 1990 under the direction of Dr. Stephen Davis of Saint Mary's University. An intact living floor was uncovered at Belmont II and over 700 artifacts were recovered during the excavation, including the first fluted point discovered in a buried context in Nova Scotia since 1964." - Nova Scotia Museum.
This map shows the extent of the continental ice sheet at this time and indicates additional real estate, now lost to submergence of the crust, coupled with sea-level rise. "Clovis fluted points are named after the city of Clovis, New Mexico, where examples were first found in 1929 by Ridgely Whiteman... Around 10,000 radio carbon years before present, a new type of fluted projectile point called Folsom appeared in archaeological deposits, and Clovis-style points disappeared from the continental United States. Most Folsom points are shorter in length than Clovis points and exhibit different fluting and pressure flaking patterns."
Debert is at the red dot. The Younger-Dryas Event, which saw the glacial ice reinvigorated, has been implicated in ending human interest in that Debert camp site. In their study (1995) Impact of the Younger Dryas Cooling Event Upon Lowland Vegetation of Maritime Canada, Francis E. Mayle and Les C. Cwynar found that, "The climate warming signifying the end of the Younger Dryas caused succession from shrub—tundra to boreal forest, or from herb—tundra to shrub—tundra...Vegetation changes in response to the climate cooling and warming, marking the onset and termination of the Younger Dryas respectively, were very rapid, taking only 50—100 yr."
Orange dot, Debert. Bloody Creek crater is a 420-by-350-meter (1,380 by 1,150 ft) in diameter elliptical "feature" located in southwestern Nova Scotia. It may be an extraterrestrial impact crater or an impact structure. It is informally known as the Astrid Crater, and the age, like its status, is unsettled at this writing. Notwithstanding several authorities agree that, "The morphology, internal structure, and abundant evidence of shock metamorphism clearly indicate that the Bloody Creek structure is likely either an impact crater or a structure that is the result of an extraterrestrial hypervelocity impact. The elliptical morphology of it strongly indicates that it is likely the result of an oblique impact." If so, that would have been sufficient cause for the Younger-Dryas Extinction and the supposed archaeological hiatus which followed.
In 1982, Nova Scotia geologist Albert E. Roland mentioned, "A younger site (than Debert), possibly around 8,000 years old, has been discovered by Dr. Ronald Nash on Ingonish Island in northern Cape Breton. Ten years earlier, Nash working out of Saint Xavier University, found artifacts at two quarries on the island. The larger one was located on the side facing the village of Ingonish, and provided 40 boxes for study. At the time he gave them an age of 7,000 years. The configuration of projectile points suggested a time span of 7,000 years of deposition.
At this same time, Sanger and Tuck introduced the hypothesis of a "Great Hiatus" in archeology, which Sanger admitted might be due to "incomplete information." By the 1990s, it was beginning to be accepted that Early and Middle Archaic archaeological sites could be under water due to post glacial melting and flooding and the sinking of coast lines as that wave motion through the crust moved to the north west. "Limited underwater research and accidental finds of fishermen have identified drowned sites from this period." One of these, shown above was, was a primitive scraper used to flay dead marine animals, such as walruses which used to frequent these waters. Gorden Fader (2005) said that this artifact typically dated from 5,000 to 9,000 years ago (which would make it Archaic) and that they were used as "multipurpose knives."
Still,more evidence is needed to fully support a Maritime
Archaic archaeological period for all of Nova Scotia, as there is for the coastal areas of surrounding provinces and states. It may be forthcoming: In 2005, Nova Scotia Power was repairing six power generating stations on the Mersey River and drained parts of the riverbed. That allowed archaeologists to collect 10,000 artifacts from amidst stumps and rocks embedded in mud. These included fragments of native pottery, a wide range of flaked and ground stone tools (spear points, knives, axes, adzes and gouges as well as stone chips or flakes left behind from tool manufacture).
Archaeologist Bruce Stewart said that,"The identification of a number of Archaic Period sites was absolutely fantastic because we don't know much about the archaic period in Nova Scotia." His crew turned up another ulu, explaining that this was a semi-circular knife used to process sea mammals. "It's made from a piece of slate with bevelled edges and is about 4,500 years old." Stewart also told the interviewer that a stone harpoon head was in such perfect he thought at first it was made of modern plastic. It
was instead an outstanding example of groundstone technology.
The community of Liverpool is (population 2,653), situated on the Atlantic coast along Nova Scotia's South Shore less than an hour west of Mahone Bay. The community occupies the west bank at the mouth of the Mersey River and its harbour front faces the smaller community of Brooklyn. Liverpool's harbour was an ancient seasonal camp of Nova Scotia's native Mi'kmaq and was known not only as Ogomkigeak meaning "dry sandy place" but also as Ogukegeok, meaning "place of departure" The departure was north along a water route through Kejimikujik National Park's, Loon Lake and beyond, portaging to the Allain River debouching near present-day Annapolis Royal. Not all of the artifacts found along these rivers are locally made but were presumably on this route from places of manufacture and somehow lost in transit.
Writing for the Cumberland News, Sept. 22, 2017, midnight, journalist Lawrence Powell featured this photo in reporting archaeological finds at Keji earlier this year. Charles Burke reminded readers of that water connection between Liverpool and Annapolis Royal, "There are an estimated 250 known indigenous archaeological sites which makes up the Mersey River corridor – it contains 25 % of all the (indigenous) archaeological sites in Nova Scotia." This time an opportunity was opened at Eel River Bridge when it was decided to create a new 150 foot suspension bridge. "As part of the replacement of the older bridge with the new bridge we undertook an archaeological assessment which suggested we had to do some serious testing in the area,” said Burke. “Essentially the nexus of most of the sites in the park on the river are in that location." They dug 50 test pits."
What they found was evidence that this had been a place where tools were manufactured. "We have artifacts as old as the archaic era which would be five to six thousand years before the present and right up to recent woodland (Acadian Forest stage) which is 500 to 1,500 hundred years ago,” Burke said. No post-contact artifacts were found in the 2017 excavations which he said was unusual. “Each artifact," he continued, " – all of its diagnostic attributes will be recorded, an attempt will be made to date it, associate it with a specific time period,” he said. “There’s a plan afoot at the moment to see if we have a sufficient number of artifacts that might be created as reproductions so they can be used on site as part of the interpretive program." The game may well be afoot in filling in some blank pages in the archaeological story.
Ice retired from the Fundy coast 14,000 years ago and those local icecaps had melted by 11,000 years before the present. As noted earlier, polar ice did not disappear and we are still emerging from an Ice Age. Even if climate change were suddenly, dramatically reversed, it is estimated that it would take 30,000 years for another continental disaster of this kind to shape up. On the other hand, all ice could potential vanish in half that time and that could be catastrophic. As far as Nova Scotia is concerned, the last 100,000 years have been devoid of glacial events, as illustrated by numerous studies of the species of plant pollen in peat bogs. When it is very cold plants do not reproduce by shedding pollen. The full effects of glaciation appeared in the largely non-glacial Holocene Period, which is "NEXT."