Original research/Glaciations

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Geologic time is annotated with glacial or ice age periods. Credit: William M. Connolley.
Earth at the last glacial maximum of the current ice age. Credit: Ittiz, based on: "Ice age terrestrial carbon changes revisited" by Thomas J. Crowley (Global Biogeochemical Cycles, Vol. 9, 1995, pp. 377-389.
Recent (black) and maximum (grey) glaciation of the northern hemisphere are during the Quaternary climatic cycles. Credit: Hannes Grobe/AWI.
Recent (black) and maximum (grey) glaciation of the southern hemisphere are during the Quaternary climatic cycles. Credit: Hannes Grobe/AWI.

Def. the "process of covering with a glacier,[1] or the state of being glaciated;[2] the production of glacial phenomena;[2] an ice age[3]" is called a glaciation.

The ice ages or glaciations on Earth occurred from the early Proterozoic (Huronian), late proterozoic (Cryogenian), early Paleozoic (Andean-Saharan) during the Ordovician and Silurian periods, late Paleozoic (Karoo Ice Age) during the Carboniferous and early Permian periods, and lately the Quaternary glaciation.

Although these ice ages are widely separated in geological time, "in most parts of the Earth major climatic and palaeoenvironmental units typically have a duration of the order of half a precession cycle (around 10 ka) rather than half an eccentricity cycle (around 50 ka) so that the level of stratigraphic resolution provided by the Middle Pleistocene [Marine Isotope Stage] MIS (typical duration 50 ka) is not sufficiently fine to constitute a universal stratigraphic template."[4]

Little Ice Ages[edit | edit source]

Changes in the 14C record, which are primarily (but not exclusively) caused by changes in solar activity, are graphed over time. Credit: Leland McInnes.

The Little Ice Age (LIA) appears to have lasted from about 1218 (782 b2k) to about 1878 (122 b2k).

A "climate interpretation was supported by very low δ’s in the 1690’es, a period described as extremely cold in the Icelandic annals. In 1695 Iceland was completely surrounded by sea ice, and according to other sources the sea ice reached half way to the Faeroe Islands."[5]

In the image at the top, "before present" is used in the context of radiocarbon dating, where the "present" has been fixed at 1950. The apparent decreases in solar activity are called the "Maunder Minimum", "Spörer Minimum", "Wolf Minimum", and "Oort Minimum".

"Northern Hemisphere summer temperatures over the past 8000 years have been paced by the slow decrease in summer insolation resulting from the precession of the equinoxes."[6]

Precisely "dated records of ice-cap growth from Arctic Canada and Iceland [show] that LIA summer cold and ice growth began abruptly between 1275 and 1300 AD, followed by a substantial intensification 1430-1455 AD. Intervals of sudden ice growth coincide with two of the most volcanically perturbed half centuries of the past millennium. [Explosive] volcanism produces abrupt summer cooling at these times, and that cold summers can be maintained by sea-ice/ocean feedbacks long after volcanic aerosols are removed. [The] onset of the LIA can be linked to an unusual 50-year-long episode with four large sulfur-rich explosive eruptions, each with global sulfate loading >60 Tg. The persistence of cold summers is best explained by consequent sea-ice/ocean feedbacks during a hemispheric summer insolation minimum; large changes in solar irradiance are not required."[6]

Weichselian glaciations[edit | edit source]

"Recent stratigraphical achievements and long time established chronologies exist for the Late Weichselian, i.e. 10-25 ka BP. During this period Denmark experienced the complex Main-Weichselian glaciation from 25 to about 14 ka BP (Jylland stade, Houmark-Nielsen 1989) followed by the Late Glacial climatic amelioration including the interstadial Bølling-Allerød oscillation (13-11 ka BP), finally leading to the interglacial conditions that characterize the Holocene (Hansen 1965)."[7]

"The Weichselian of Europe covers the interval from the end of MIS-5e (c. 119 kyr BP) to the start of the Holocene at c. 11.5 kyr BP and corresponds to the isotope stages 5d to 2. Much of the Weichselian chronology is relative only, determined by stratigraphic relationships of successive glacial and interglacial deposits. Radiocarbon ages for the younger interval and Thermo-Luminescence (TL), Optically Stimulated Luminescence (OSL) and Electron Spin Resonance (ESR) dates for the earlier period are used where available although reliable results remain few. We assume here, therefore, that the Russian􏰀European succession of major glacials and interglacials follows the oscillations of the global sea-level curve of Lambeck & Chappell (2001). The start of stadials is defined by the onset of a sea-level fall and the end is defined by the midpoint between successive lowstands and highstands, in recognition of the lag in icesheet and sea-level response to warming. The Early Weichselian spans the interval from c. 118 kyr BP to c. 80 kyr BP and corresponds to the two stadials MIS-5d and 5b and the two interstadials MIS-5c and 5a. The Middle Weichselian corresponds to the isotope stages MIS-4 and MIS-3 spanning the interval from c. 80 kyr BP to c. 32 kyr BP [...]. As more information becomes available, the interstadials 5c and 5a reveal a more complex structure and each may consist of two or three relative highstands (Potter et al. 2004), implying that ice margins were not constant during these intervals, [...]."[8]

"The early Middle Weichselian is assumed to correspond to the period 80-􏰀62kyr BP and to MIS-4. During this interval, average sea levels reached lower values than during the Early Weichselian and ice extent can be expected to have been substantial. But, as the global sea-level oscillations in this interval are also large, substantial ice-volume fluctuations can be anticipated across northern Eurasia within this stage."[8]

"The last substantial ice movement over arctic Russia is the retreat at the end of MIS-4 back to the Kara Sea and eventually back to the arctic islands such that after c. 55 kyr the major land areas were and remained essentially ice-free. The Scandinavian ice sheet, however, continued to fluctuate throughout Stage 3, with at least two periods of extensive ice-free conditions corresponding to the Bø interstadial (at c. 52 kyr BP) when the ice retreated to northern Sweden, and the Ålesund interstadial (at c. 35 kyr), when much of Scandinavia may have been ice-free. At least one major advance (the Jæren-Klintholm-Skjonghelleren advance at c. 45-40 kyr BP) occurred in between these two interstadials (Olsen 1997; Larsen et al. 2000; Arnold et al. 2003; Houmark-Nielsen & Kjær 2003). The LGM and post-LGM ice model adopted is that previously constrained by rebound data across Scandinavia and northern Europe (Lambeck et al. 1998b; Lambeck & Purcell 2003)."[8]

Baltic Glaciations[edit | edit source]

"After c. 22 ka BP during the Jylland stade (Houmark-Nielsen 1989), Late Weichselian glaciers of the Main Weichselain advance overrode Southeast Denmark from the northeast and later the Young Baltic ice invaded from southeasterly directions. Traces of the Northeast-ice are apparently absent in the Klintholm sections, although large scale glaciotectonic structures and till deposits from this advance are found in Hjelm Bugt and Møns Klint (Aber 1979; Berthelsen 1981, 1986). At Klintholm, the younger phase of glaciotectonic deformation from the southeast and south and deposition of the discordant till (unit 9) were most probably associated with recessional phases of the Young Baltic glaciation. In several cliff sections, well preserved Late Glacial (c. 14-10 ka BP) lacustrine sequences are present (Kolstrup 1982, Heiberg 1991)."[7]

Vistulian Glaciations[edit | edit source]

"The Lower Vistula formation is a distinct and spatially well defined lithostratigraphical unit [...]. It comprises sediments formed since the decline of the Middle Polish Glaciation up to the Toruń Glaciation (Early Vistulian)."[9]

"The till of the Toruń Glaciation (till BII) overlies the Lower Vistula formatian in almost the whole area, but pre-glacial sediments are included in this formation [...]."[9]

Skjonghelleren Glaciations[edit | edit source]

Skjonghelleren is a cave on the island of Valderøy. Credit: ElekTrond.

The Ebersdorf Stadial may correspond to the earlier two glaciation (I & L) of the Skjonghelleren Glaciations of Scandinavia where ice crosses the North Sea between 50-40 ka BP.

"Two radiocarbon dates on bones [from the Skjonghelleren (cave)] and three Uranium series dates on speleothems from this bed all cluster around 30,000 B.P. [Bed G: 29,600 ± 800, 32,800 ± 800], i.e., the end of the Ålesund interstadial. Above the uppermost laminated bed, bone fragments of birds, fish and mammals, deposited between c. 12,000 and c. 10,000 B.P. [Bed B: 10,360 ± 170, 11,510 ± 190] were found."[10]

"Three sequences of laminated clay [are Beds F, I & L], suggesting that the cave has survived at least three glaciations since its formation. Four blocky units were formed in ice-free periods prior to [Block K], between [Block G], and after the deposition [Block B] of the laminated sequences."[10]

Bed A is travertine, Beds C, H & J are silt, Bed D is granulated clay, Bed E is clay with intraclasts, Block M is above the Bedrock.[10]

Beds A and B "were deposited after the last deglaciation. The date 11,510 ± 190 B.P. [...] gives a minimum age for the last deglaciation in the Skjonghelleeren area. Previous work (Mangerud et al. 1981a), however demonstrates the the deglaciation occurred some time before 12.3 ka."[10]

The sequence from young to old is

  1. A - travertine,
  2. B - c. 10,000 - 12,000 a, ice-free period,
  3. C - silt,
  4. D - granulated clay,
  5. E - clay with intraclasts,
  6. F - glaciation, ~ 20,000 a,
  7. G - Block G, c. 29,000 - 34,000 a,
  8. H - silt,
  9. I - glaciation, ~ 40,000 a,
  10. J - silt,
  11. K - ice-free period,
  12. L - glaciation, ~ 50,000 a,
  13. M - ice-free period,
  14. N - Bedrock.

Devensian glaciations[edit | edit source]

"The results of paired terrestrial cosmogenic nuclide analyses 26
Al
/10
Be
constrain the timing of this extensive glaciation and provide, for the first time, an age for the exposure of Lundy granite following deglaciation. The results from nine paired samples yield 26
Al
/10
Be
exposure ages of 31.4-48.8 ka (10
Be
) and 31.7-60.0 ka (26
Al
)."[11]

"Bowen et al. (2002) used 36
Cl
to provide exposure ages for glacial landforms around Ireland and demonstrated that the most extensive phase of glaciation in many areas dates from the Early Devensian."[11]

" A 10
Be
exposure age of 19.8 ka from an upturned boulder on the Isles of Scilly (McCarroll et al., 2010), at the southernmost limit of an Irish Sea Ice Stream (ISIS), may suggest a Late Devensian age close to the global Last Glacial Maximum (LGM; 21 ka) a date which is supported by radiocarbon and thermoluminescence dates (Wintle, 1981; Scourse, 1991, 2006)."[11]

"Furthermore, this age for the glacial and related sediments on the Isles of Scilly is independently supported by ice rafted debris of Celtic Sea sources in continental margin cores from the Goban Spur that date to Heinrich Event 2 (Scourse et al., 2000, 2009; Haapaniemi et al., 2010). This pulse may well represent the Celtic Sea advance to Scilly during the LGM, as discussed in Scourse and Furze (2001)."[11]

Wisła Glaciations[edit | edit source]

"The whole post-Eemian complex has been previously referred by me to the North Polish (Baltic, Wisła, Vistulian) Glaciation; at present the lower tills BI and BII are connected with the Toruń Glaciation and only the upper tills (BIII, BIV and BV - with the Wisła Glaciation (A. Makowska, 1986b, 1992)."[9]

"The ice sheet of the Toruń Glaciation occupied a smaller area in comparison with the two younger ice sheets of the Wisła Glaciation."[9]

The Wisła Glaciation consists of four climatic variations:[9]

  1. Late Wisła: Oldest Dryas--Younger Dryas,
  2. Upper Wisła: Leszno-Pomorze Stadial,
  3. Middle Wisła: Grudziądz (Łęcze) Interstadial, and
  4. Lower Wisła: Świecie Stadial.

These were after the Krastudy Interglacial.[9]

The Toruń Glaciation preceded the Krastudy Interglacial.[9]

Eem Interglacial preceded the Toruń Glaciation.[9]

The Middle Polish Glaciation (decline) or Sztum Warming preceded the Eem Interglacial.[9]

North Polish Glaciations[edit | edit source]

The North Polish Glaciations include the Baltic, Vistulian and Wisła Glaciations.[9]

Karmøy glaciations[edit | edit source]

The Karmøy stadial begins in the high mountains of Norway about 58 kyr B.P. and expands to the outer coast by 60 kyr B.P.[12]

The Schalkholz Stadial in North Germany is equivalent.

In "the period 52-70 ka when the [ice rafted debris] IRD curves [...] show the highest peak during the entire Weichselian [...] the ice sheet [may have] reached the continental shelf during [the Karmøy glaciation]."[13]

It "appears likely that Scandinavia was colonised by European lemmings (Lemmus sp.) during an interstadial period sometime between the Karmøy glaciation, which ended ~ 60 kyr BP (Mangerud et al. 2011), and the last glacial advance ~ 30 kyr BP [...]."[14]

"The principal stadial during MIS 4 is assumed to be the Karmøy glaciation of Norway as it is correlated with the Ristinge and Old Baltic Ice Advance of Denmark, Göteborg I of Sweden, and Vuoddasjarvi of Finland. Ice coverage during this event peaked at c. 64 kyr BP, with its eastern extent over Russia and the Kara Sea as defined in [Lambeck et al. 2006]. Subsequent ice retreat was substantial but not without interruption and re-advance, culminating in the Ålesund interstadial."[15]

Toruń Glaciations[edit | edit source]

"In general stratigraphical schemes (A. Makowska, 1986b, 1992) the pre-glacial part of the Toruń Glaciation forms a relatively short time span between the end of the Eemian Interglacial determined at about 115 ka and the beginning of ice sheet advance during the Malbork Phase of the Toruń Glaciation, defined at 110 ka."[9]

At "present the lower tills BI and BII are connected with the Toruń Glaciation".[9]

"The till of the Toruń Glaciation (till BII) overlies the Lower Vistula formation in almost the whole area, but pre-glacial sediments are included in this formation [...]."[9]

The Toruń Glaciation begins with the Herning Stadial, Brørup interstadial, the Rederstall Stadial, the Odderade interstadial, the Karøy stadial, the Oerel interstadial, the Ebersdorf Stadial, and ends with the Glinde interstadial (or, Krastudy interstadial).[9]

Würm glaciations[edit | edit source]

Violet is the extent of the Alpine ice sheet in the Würm glaciation. Blue is earlier ice ages. Credit: Lencer.
Würm glaciation, shown in ice core data from Antarctica and Greenland. Credit: Leland McInnes.
Moraines and gravel beds formed in the Würm glaciation near Leutkirch, Westallgäu, Germany, Zeil castle can be seen on the left. Credit: Rhmaster.

The Würm glaciation or Würm stage or ice age, in the literature usually just referred to as the Würm,[16] often spelledt "Wurm", was the last glacial period in the Alpine region.

The Würm ice age may be dated to the time about 115,000 to 11,700 years ago, the sources differing depending on whether the long transition phases between the glacials and interglacials (warmer periods) are allocated to one or other of these periods. The average annual temperatures during the Würm ice age in the Alpine Foreland were below −3 °C (today +7 °C), determined from changes in the vegetation (pollen analysis) as well as differences in the facies.[17]

The corresponding ice age of North and Central Europe is known as the Weichselian glaciation. Despite the global changes in climate that were responsible for the major glaciations cycles, the dating of the Alpine ice sheet advances does not correlate automatically with the farthest extent of the Scandinavian ice sheet.[18][19] In North America the corresponding "last ice age" is called the Wisconsin glaciation.[20]

Wisconsin glaciations[edit | edit source]

The Wisconsin glaciation was the most recent glacial period of the North American ice sheet complex that included the Cordilleran Ice Sheet, which nucleated in the northern North American Cordillera; the Innuitian ice sheet, which extended across the Canadian Arctic Archipelago; the Greenland ice sheet; and the massive Laurentide Ice Sheet,[21] which covered the high latitudes of central and eastern North America.

On Kelleys Island in Lake Erie, northern New Jersey and in New York City's Central Park,[22] the grooves left in rock by these glaciers can be easily observed.

Two related movements have been termed Wisconsin: Early Wisconsin and Late Wisconsin.[23]

The first Wisconsin period erased all the Illinoian glacial topography that it extended over.[23] The Late Wisconsin ice sheet extended more towards the west than the earlier movements, perhaps due to changes in the accumulation center of the ice sheet, topographic changes introduced by the Early phase or by pressure changes in the ice mass in the north.[23]

Estimated Age of Glacial Episodes (Leverett)[23]
Age Years before Present (YBP)
Culmination of Late Wisconsin 50,000
Culmination of Early Wisconsin 100,000
Beginning of Wisconsin 150,000
Culmination of Illinoian 300,000
Beginning of Illinoian 350,000
Culmination of Pre-Illinoian, i.e., old Nebraskan[24][25] 550,000
Beginning of Pre-Illinoian 1,200,000
Ice Caps[26]
Keewatin ice sheet Laurentide Ice Sheet Nova Scotia Ice Cap Newfoundland Ice Cap Greenland Ice Cap

The Labrador Ice Sheet centered east of Hudson Bay, expanding towards the southwest, into the eastern edge of Manitoba and across the Great Lakes to the Ohio River, upwards of 1,600 miles (2,600 km) from its source, with its eastern lobes covering New England and reaching south to Cape Cod and Long Island, New York.[27]

Glacial lobes and sublobes of the southern Laurentide Ice Sheet during the late Wisconsin Glaciation.[28]
Major Lobes Minor Lobes
Des Moines Grantsburg St. Louis Rainey
Lake Superior[26] Wadena Chippewa[26] Wisconsin Valley[26] Langlade[26]
Green Bay[26]
Lake Michigan[26] Delavan Harvard-Princeton Peoria Decatur
Minor lobes: Milwaukee, Two Rivers; Straits of Mackinac
Saginaw
Lake Huron[26] East White[26] Miami[26] Scioto[26]
Lake Erie[26]
Lake Ontario[26] Lake Champlain[26] Hudson River[26]
unnamed lobe in Quebec – New England Connecticut Valley[26] Buzzards Bay[26] Cape Cod[26] Georges Bank[26]

The Keewatin Ice Sheet began west of Hudson Bay in the Canadian Territory of Keewatin, moving south some 1,500 miles (2,400 km) into Kansas and Missouri, west 1,000 miles (1,600 km) to the foothills of the Rocky Mountains.[27]

The Cordilleran Ice Sheet left remnants throughout the Northern Rocky Mountains, unlike the other two ice sheets was mountain based covering British Columbia and reaching into northern Washington and Montana, with more of an Alpine style of many glaciers merged into a whole and striations made by the ice field in moving over the bedrock show that it moved principally to the west through the passes of the coast range.[27]

Maxima of the Wisconsin ice sheets[29]
Western Ice Eastern Ice Proximate years ago Position of ice border
Mankato Valders 25,000 Northern Washington, Idaho, and Montana to the Continental Divide – north of Edmonton – 65 miles east of Edmonton – northwest corner of North Dakota – Des Moines – west end of Lake Superior – Milwaukee – Port Huron – Buffalo – Schuylerville – St. Johnsbury.
(Great reduction of ice) Cary 27,500 Minneapolis – north Wisconsin – south of Chicago – Central Ohio – 50 miles south of Buffalo – Binghamton - Northampton
Tazewell 40,000 Rockford, Ill. – Peoria – south of Indianapolis – north of Cincinnati – northwestern Pennsylvania – central Long Island
Iowan No known ice 65,500 Northern Washington, Idaho, and Montana – northwest North Dakota – east central Iowa - Minneapolis

Middle Polish Glaciations[edit | edit source]

The Middle Polish Glaciations end with the beginning of the Eem Interglacial.[9]

South Polish Glaciations[edit | edit source]

The South Polish Glaciations occurred before the beginning of the Middle Polish Glaciations.[9]

Riss Glaciations[edit | edit source]

Extent is of the Mindel and Riss glaciation (blue) in comparison with that of the Würm period. Credit: Lencer.
Alpine Riss glaciation (in the north: the Saale) is compared with the later Würm glaciation (in the north: the Weichselian). Credit: Juschki.

In the Riss stage, there were several advances of the ice sheet, so that it can be divided into interstadials (ice retreats) and stadials (ice advances), and at least one hitherto unnamed warm period.[30]

The Riss ice age is roughly contemporaneous with the Saale glaciation of the North German glacial sequence. The Riss is paralleled by Marine isotope stage (MIS) 6, 8 and 10, which would therefore place it about 350,000 and 120,000 years ago.[31]

Excluded from the Riss glaciation is the so-called Old Riss (Ältere Riß),[32] the time of the greatest ice advance in the Alpine region: today it is referred to as the Haslach-Mindel complex (in Bavaria and Austria), Hoßkirch complex (in Baden-Württemberg) or Great Glaciation in Switzerland.

Saale Glaciations[edit | edit source]

Maximum extent (Drenthe stadium) of the Saale complex (yellow line). The red line shows the greatest extent of the younger Weichselian glaciation. Credit: Christian Fischer.

The Saale complex is currently estimated, depending on the source, as existing from around 300,000 to 130,000 years ago or 347,000 to 128,000 years ago (duration: around 219,000 years), roughly contemporaneous with the glaciation of the Riss Glacial in the Alpine region.[33]

The Saale complex may be divided into a lower (also Saale Early Glacial[34]) and an upper section (also Middle and Upper Saale Glacial,[34] or Younger Saale glaciation[35]), with glacial advances into Northern Germany.

The "Late Saalian (c. 140 kyr BP) [the stadials of marine isotope stage 5 (MIS-5d and 5b) and MIS-4 is] when the ice sheets were larger than at any time during at least the last two glacial cycles, to the final retreat of the MIS-4 glacier ice from the arctic Russian plain at c. 60 kyr BP."[8]

"The Late Saalian corresponds to a prolonged cold period for Europe during which the ice extended further south than for any subsequent period (e.g. Svendsen et al. 2004) and the advance occurred in at least two phases: the Drenthe and the Warthe."[8]

"Interglacial conditions existed at c. 210 kyr BP, with global ice volumes similar to those of today. Ice growth commenced primarily in the Kara Sea area, similar to the development during the early part of the last cycle. An oscillatory increase in ice volume occurs from c. 195 kyr BP up to the Drenthe advance with ice volumes growing in the same ratio as the ice- volume equivalent-sea-level change. By 180 kyr BP the ice sheet has expanded over the Barents􏰀Kara Sea, the Taymyr and Putorana areas of arctic Russia, and over Norway, northern Sweden and Finland. The ice margins at this time are assumed to have been similar to those that occurred later during the stadials MIS-5d and 5b. The Drenthe maximum occurs at c. 155 kyr BP and has a duration of c. 5 kyr. Some ice retreat occurs between the Drenthe and Warthe, consistent with the sea-level rise inferred at c. 150 kyr BP. This is followed by a readvance to the Warthe maximum at c. 143 kyr BP. The Warthe maximum lasts until 140 kyr BP and is followed by rapid melting. The penultimate glacial maximum over Scandinavia ends at c. 135 kyr BP, corresponding to the midpoint between the onset of the Warthe deglaciation and the time sea levels globally reached their present level in the subsequent interglacial. By 135 kyr BP the Russian ice has retreated to the Kara Sea."[8]

"Two recent compilations have been used to establish the ice margins for the Warthe phase of the Late Saalian (Ehlers & Gibbard 2003, 2004; Svendsen et al. 2004) (Fig. 2A). At this time, the Barents Sea was glaciated with an ice sheet extending out to the shelf edge west of Svalbard and Bear Island (Mangerud et al. 1998) and into the Arctic Ocean (Spielhagen et al. 2004). The southern margin in Siberia lies some 1400 km south of the arctic coastline. In the west, the ice sheet extends across the North Sea and joins up with the British ice sheet, the ice margin of which is assumed to have been similar to that for the Late Devensian 􏰀 corresponding to the Late Weichselian. In so far as the model predictions will not be used for sites in the British Isles and because the volume of ice over the British Isles represents only a few percent of the volume of the MIS-6 Eurasian ice, this approximation is adequate."[8]

Illinois Episode glaciations[edit | edit source]

An almost complete adult Homo sapiens mandible is discovered at the Jebel Irhoud site in Morocco. Credit: Jean-Jacques Hublin/Max Planck Institute for Evolutionary Anthropology.{{fairuse}}
A composite reconstruction was made of the earliest known Homo sapiens skull from Jebel Irhoud in Morocco. Credit: Philipp Gunz/Max Planck Institute for Evolutionary Anthropology.{{fairuse}}
Stone tools have been found at the Jebel Irhoud site in the same level as Homo sapiens fossils. Credit: Mohammed Kamal/Max Planck Institute for Evolutionary Anthropology.{{fairuse}}
The Jebel Irhoud site in Morocco is shown. Credit: Shannon McPherron/Max Planck Institute for Evolutionary Anthropology.{{fairuse}}

"Ages of sediments immediately beneath the oldest till (Kellerville Mbr.) in the bedrock valley average 160 ka and provide direct confirmation that Illinois Episode (IE) glaciation began in its type area during marine isotope stage (MIS) 6. The oldest deposits found are 190 ka fluvial sands on bedrock in the deepest part of the valley. These correlate to earliest MIS 6. We now correlate the lowest deposits to the IE (Pearl Fm.)."[36]

"Illinoian [is] (ca. 220,000-430,000 yr BP)".[37]

"The [Jebel Irhoud site] Moroccan fossils [...] are roughly 300,000 years old. Remarkably, they indicate that early Homo sapiens had faces much like our own, although their brains differed in fundamental ways."[38]

"We did not evolve from a single 'cradle of mankind' somewhere in East Africa. We evolved on the African continent."[39]

"It now looks like Denisovans can be placed at the site from close to 300,000 years ago to about 50,000 years ago, with Neandertals there for periods in between."[40]

MIS Boundary 7/8 is at 243 ka.[41]

Mindel glaciations[edit | edit source]

The Mindel glaciation is commonly correlated to the Elster glaciation of northern Europe, but the more precise timing is controversial since Mindel is commonly correlated to two different marine isotope stages, MIS 12[42] (478-424 thousand years ago[43]) and MIS 10[44] (374-337 thousand years ago[43]).

Penultimate Ice Ages[edit | edit source]

The glaciation complex between the end of the Holstein interglacial and the beginning of the Eem interglacials is referred to as the Penultimate Ice Age and the Great Glaciation.[45]

Elster glaciations[edit | edit source]

Schematic diagram shows the maximum glaciation of the last three cold periods on the North German Plain:
red line = extent of the Weichselian glaciation;
yellow line = extent of the Saale glaciation;
blue line = extent of the Elster glaciation. Credit: Botaurus.

The glacial period is named after the White Elster, a right tributary of the Saale.[46]

Elster was correlated with the Mindel glaciation of the Alps and the Anglian glaciation of Great Britain and Ireland, but analysis in the 1950s of oxygen isotopes in deep sea core samples introduced a global glacial history, with warm and cold phases identified by marine isotope stages (MISs), identifying two glacial stages in the time slot of the Elster/Mindel/Anglian, namely MIS 12 and MIS 10:[47]

  • MIS 12, 478-424 ka ago,[43] is globally the stronger of the two glacials and long the preferred correlation to Elster/Mindel/Anglian. There is strong evidence for widespread glaciation of Great Britain during MIS 12, and only disputed and weak signs of glaciation during MIS 10.[48] Thus, the correlation of the Anglian glaciation to MIS 12 is uncontroversial. The glacial history of Europe is much simplified if also Elster and Mindel are correlated to MIS 12. The Subcommission on Quaternary Stratigraphy (SQS) of the International Commission on Stratigraphy (ICS), a scientific organisation within the International Union of Geological Sciences (IUGS), correlates both the Anglian and the Elsterian to MIS 12 in the 2011 version of its correlation table.[42]
  • MIS 10, 374-337 ka ago,[43] is globally a weaker glacial. A correlation of Elster to MIS 10 implies a complicated glacial history in Europe, with various geographical areas showing evidense from different glacials. However, different chronologies of separate ice strems during the late Weichselian glaciation gives credence to such a scenario.[49] In the Netherlands there is evidense for correlations of Elster to both MIS 12 and MIS 10.[50] A correlation to MIS 10 is given in the comprehensive review of the glaciations of northern Germany by Litt et al. (2007).[51] Version 2016 of the correlation table by the German Stratigraphic Commission correlates both Elster and Mindel to MIS 10.[44]

Haslach glaciations[edit | edit source]

Haslach Ice Age was not included in the traditional glacial schema of the Alps.[52] The glacial stage was first described[53] from its type region is the Haslach Gravels (Haslach-Schotter) in the area of the Riß-Iller-Lech Plateau.

Gunz glaciation[edit | edit source]

Deep sea core samples have identified approximately 10 marine isotope stages (at least MIS 21 to MIS 11); i.e., 5 glacial cycles of varying intensity during Gunz.[44][54]

The Günz was thought to follow the Danube-Günz interglacial and was ended by the Günz-Haslach interglacial.[55][56][45]

The German Stratigraphic Commission puts the start of Gunz in the late Calabrian (approximately one million years ago, earlier than MIS 19) and shows a continuity of glacial cycles with the following Mindel stage, with the border arbitrarily put at the start of MIS 10 (approximately 374 000 years ago), corresponding roughly to the Cromerian stage in the glacial history of Northern Europe.[44]

During Gunz the 41,000 year glacial cycle of previous stages (Biber and Danube) had been replaced by a dominance of a 100,000-year cycle (Mid-Pleistocene Transition), where the most intense glacials of Gunz (MIS 16 and MIS 12) reached similar extents to those of the more recent Riss and Wurm glaciations.[57][58] These have not been easy to identify in the geological record of the Alps, but MIS 16 has been identified with the Don Glaciation of Eastern Europe.[59]

The strong glacial MIS 12 has been problematic, and has sometimes been identified with the Mindel glaciation, which would imply an end to Gunz already after MIS 13 (480 000 years ago).[60]

Biber ice age[edit | edit source]

The base of the marly layer overlying sapropel MPRS 250, located at 62 m in the Monte San Nicola section, is the defined base of the Gelasian Stage. Credit: D. Rio, R. Sprovieri, D. Castradori, and E. Di Stefano.

Some number of N tills occurred during the Olduvai subchron.[61]

The magnetic field reversal to the present geomagnetic poles (Olduvai subchron) occurred at 2,000,000 yr BP.

The oldest till group, R2 tills, consists of till units with a reversed polarity and >77% of sedimentary clasts. Low amounts of expandable clays, substantial amounts of kaolinite, and the absence of chlorite characterize the clay mineralogy of R2 tills. The mineralogy of the silt fraction of R2 tills is rich in quartz and depleted in calcite, dolomite, and feldspar. This till group includes a till unit that underlies the 2.0-Ma Huckleberry Ridge ash, thus indicating deposition sometime between ~2.5 Ma (onset of Northern Hemisphere glaciations) (Mix et al., 1995) and 2.0 Ma.[61]

During the Gelasian the ice sheets in the Northern Hemisphere began to grow, which is seen as the beginning of the Quaternary ice age. Deep sea core samples have identified approximately 40 marine isotope stages (MIS 103 – MIS 64) during the age. Thus, there have probably been about 20 glacial cycles of varying intensity during the Gelasian.

In the regional glacial history of the Alps this age is now called Biber. It corresponds to Pre-Tegelen and Tegelen in Northern Europe.[62]

During the Gelasian, the Red Crag Formation of Butley, Suffolk, the Newbourn Crag, the Norwich Crag Formation and the Weybourne Crag Formation (all from East Anglia, England) were deposited. The Gelasian is an equivalent of the Praetiglian and Tiglian stages as defined in the Netherlands, which are commonly used in northwestern Europe.

Biber or the Biber Complex is a timespan approximately 2.6–1.8 million years ago in the glacial history of the Alps. Biber corresponds to the Gelasian age in the international geochronology, which since 2009 is regarded as the first age of the Quaternary period. Deep sea core samples have identified approximately 20 glacial cycles of varying intensity during Biber.[44]

In 1953, Schaefer defined the Biber glaciation, Biber Glacial, or Biber Ice Age from gravel landforms of the Stauden Plateau in the area of the Iller-Lech Plateau and in the Aindling river terrace sequence, by grouping together the so-called Middle and Upper Cover Gravels or Deckenschotter. This corresponded to the Staufenberg Gravel Terrace on the Iller-Lech Plateau, identified in 1974 by Scheunenpflug, and the so-called High Gravels of the Aindling region.[63] The rich crystalline sedimentary facies, that Löscher distinguished in 1976 in the area of the Rhine Glacier of the western Riß-Iller Plateau may also be paralleled with these glacial landforms.[64] The gravels in the Iller-Lech region ascribed to the Biber glaciation are generally heavily weathered and originate from the Northern Limestone Alps. Löscher's Kristallinreiche Liegendfazies, by contrast, originates from the bedrock of the molasse zone.

The term Biber glaciation was not part of the traditional four-stage glaciation schema of the Alps by Albrecht Penck and Eduard Brückner, but was named after the Biberbach river north of Augsburg in 1953 by Ingo Schaefer, based on the naming system of the traditional Penck schema.[65][66] Its type locality or type region is the Stauden Plateau in the Iller-Lech Plateaux and the Staufenberg Gravel Terrace in the area of Aindling. The Biber glaciation was thought to be followed by the Biber-Danube interglacial and the Danube glacial.

The absolute timing and the connexion with the glacial classification of North Germany and the Netherlands has been problematic. The Biber glacial was fought to correlate either to the Eburonian complex or the Pre-Tiglian complex in the Netherlands. In the former case it would correspond to Marine isotope stage (MIS) 56 to 62, which would place it in the period between 1.6 and 1.8 million years ago,[67][68] in the latter case it would roughly correspond to MIS 96 to 100, and would therefore have taken place about 2.4 to 2.588 million years ago.[68][69][70] The correlation was fraught with problems however due to the fact that the corresponding depositions in the Netherlands were probably not governed by climatic changes. Similar doubts on climatic grounds for the depositions assessed as Biber-related also exist in the Alpine region. It is possible that there were tectonic influences perhaps in the wake of the uplift phases of the Alps. The succession and appearance of the gravel bodies makes it possible that during their formation there were several periods of alternating fluvial erosion and accumulation. The Biber cold period at least corresponds partly with the Swiss cover gravel glaciations.[71]

The 2016 version of the detailed stratigraphic table by the German Stratigraphic Commission firmly places Biber in the Gelasian and gives a correspondence to Pre-Tegelen and Tegelen in the glacial geology of northern Europe. There is continuity between Biber and the glacial cycles of the following Danube stage[44]

Deep sea core samples have identified approximately 40 marine isotope stages (MIS 103 – MIS 64) during Biber.[44] Thus, there have probably been about 20 glacial cycles of varying intensity during Biber. The dominant trigger is believed to be the 41 000 year Milankovitch cycles of axial tilt.[72][73]

Gravels ascribed to Biber (also called the Highland Gravel or Oldest Gravel occur northwest of Augsburg as the Stauffenberg Gravel, as well as northeast as the Hohenried Gravel and southwest of Augsburg as the Stauden Plateau Gravel. Also included are isolated gravels of the Hochfirst near Mindelheim and the Stoffersberg near Landsberg am Lech.[74]

Holarctic-Antarctic Ice Age[edit | edit source]

"This late Cenozoic ice age began at least 30 million years ago in Antarctica; it expanded to Arctic regions of southern Alaska, Greenland, Iceland, and Svalbard between 10 and 3 million years ago. Glaciers and ice sheets in these areas have been relatively stable, more-or-less permanent features during the past few million years."[75]

"During the last one million years, large ice sheets developed in North America, Eurasia, the Andes, and elsewhere. These ice masses were unstable, growing and self-destructing in cycles averaging about 100,000 years, which correspond to eccentricity in the Earth's orbit around the Sun (Mangerud et al. 1996). The most recent great ice sheets disappeared only 10,000 years ago, but the Holarctic-Antarctic Ice Age still continues in regions of stable glaciation."[75]

Karoo Ice Age[edit | edit source]

Ice flow in the Karoo basins over southern Africa during maximum glaciation is indicated. Credit: J. N. J. Visser.
North-south section across the Kalahari and Karoo basins illustrating the relief of the basin floor and the lithostratigraphic units. Credit: Visser.

A "glacial marine facies [occurs] on the Falkland Islands [Frakes and Crowell, 1967]."[76]

In "a complex situation, like the Karoo Basin and adjoining highlands [...] a marine ice sheet bounded the highlands during the last phase of glaciation".[76]

The "influence of Gondwana topography on glaciation about 275 to 300 m.y. ago, [...] is preserved as thick (up to 700 m) glacial and proglacial sequences in the Karoo, Kalahari, and Warmbad basins as well as other smaller basins toward the north. These deposits, known as the Dwyka Formation, cover an area close to a million square kilometers in southern Africa".[76]

"Valleys that had been incised into the Windhoek Highlands attained lengths up to 250 km, had striated floors and walls, and contained roches moutonnées [Martin, 1961]."[76]

"The Whitehill Formation (White Band) was taken as a datum [in the stratigraphic diagram on the lower right]. The Permo-Carboniferous boundary on the platform is based on microflora assemblages [Anderson, 1977]. Ms is massive; St, stratified; dmt, diamictite; Drg, dropstone argillite; Cb, carbonaceous; mds, mudstone; Sst, sandstone; Lm, laminated; cgl, conglomerate; sh, shale; Fs, fossiliferous; Cc, carbonate; and conc, concretions."[76]

"Glaciation is known from all continents that were once part of Gondwana, including: Africa, South America, Antarctica, India, Arabia and Australia. Glaciation began in the early Carboniferous (360 Ma), reached a peak in late Carboniferous, continued into early Permian, and mostly came to an end by late Permian (260 Ma) time, thus spanning 100 million years. Multiple glacial centers were active; each experienced repeated glacier advances and retreats. Particularly well-known glacial strata include the Dwyka Tillite (Karoo basin) in South Africa, Talchir Boulder Beds in India, and Wynyard Formation of Tasmania. Overall, two major glacial cycles took place. Both expanded gradually over periods of about 20 million years each to reach their maximum extents in late Pennsylvanian and early Permian times. Each major cycle then ended abruptly during only 1-10 thousand years (Gastaldo et al. 1996)."[75]

"Although precise dating is not possible for many of the Gondwana glacial deposits, a general migration of glaciation through time is apparent. Carboniferous glaciation took place mainly in South America, southern Africa, India, and western Antarctica; whereas Permian glaciation was located mostly in Australia and eastern Antarctica. This migration corresponded to the drifting of Gondwana over the South Pole [...] The Karoo ice age is marked by cyclothems, cyclic sedimentary sequences in continental areas that were located in low latitudes. Pennsylvanian and Permian cyclothems are well known throughout the mid-continent of the United States, particularly eastern Kansas. The cyclothems were created by repeated marine transgressions and regressions over a stable continental platform. These cycles are interpreted as results of frequent changes in global sea level associated with glaciation in Gondwana. Glacial cycles and variations in sea level are documented in oxygen-isotope variations within fossils of Pennsylvanian cyclothems [...]. Late Pennsylvanian sea-level fluctuations were at least 80 m and likely greater than 100 m in amplitude (Soreghan and Giles 1999)."[75]

Andean-Saharan ice age[edit | edit source]

The "glacial episodes that occurred on Earth during the Palaeozoic (the Andean-Saharan between 450 and 420 Ma, and the Karoo between 360 and 260 Ma) did not achieve a global extent."[77]

"Glaciation is known from Arabia, central Sahara, western Africa, the lower Amazon of Brazil, and the Andes of western South America. Spectacular erosion of underlying rocks took place over large areas of the Sahara; whereas a good sedimentary record is preserved in Arabia. Continental ice sheets were developed in Africa and eastern Brazil, while alpine glaciers formed in the Andes region. The center of glaciation appears to have migrated through time: Ordovician (450-440 Ma) in Sahara, and Silurian in South America (Brazil 440-430 Ma, and Andes 430-420 Ma). The two continents were joined as parts of Gondwana, which was located over the South Pole".[75]

Gaskiers glaciation[edit | edit source]

The Gaskiers glaciation is a period of widespread glacial deposits (e.g. diamictites) that lasted under 340 thousand years, between 579.63 ± 0.15 and 579.88 ± 0.44 million years ago – i.e. late in the Ediacaran Period – making it the last major glacial event of the Precambrian.[78]

Deposits attributed to the Gaskiers - assuming that they were all deposited at the same time - have been found on eight separate palaeocontinents, in some cases occurring close to the equator (at a latitude of 10-30°), where the 300 m-thick name-bearing section at Gaskiers-Point La Haye (Newfoundland) is packed full of striated dropstones.[79] Its δ13
C
values are really low (pushing 8 ‰), consistent with a period of environmental abnormality.[79] The bed lies just below some of the oldest fossils of the Ediacaran biota, where there is in fact a 9 million year gap between the diamictites and the 570 Ma macrofossils.[79]

Varanger glaciation[edit | edit source]

The Varangian apparently spans 610 to 575 Ma.

Elatina glaciation[edit | edit source]

Elatina Formation diamictite is below the Ediacaran Global Boundary Stratotype Section and Point (GSSP) site in the Flinders Ranges National Park, South Australia. An Australian $1 coin is for scale. Credit: Bahudhara.{{free media}}

"The Elatina glaciation has not been dated directly, and only maximum and minimum age limits of c. 640 and 580 Ma, respectively, are indicated."[80]

"The Elatina glaciation is of global importance for several reasons:

  1. its diverse and excellently preserved glacial and periglacial facies represent a de facto type region for late Cryogenian glaciation in general;
  2. the Elatina Fm. has yielded the most robust palaeomagnetic data for any Cryogenian glaciogenic succession; and
  3. the recently established Ediacaran System and Period (Knoll et al. 2004, 2006; Preiss 2005) has its Global Stratotype Section and Point (GSSP) placed near the base of the Nuccaleena Fm. overlying the Elatina Fm. in the central Flinders Ranges [...]."[80]

"Feeder dykes for volcanic rocks near the base of the [Adelaide Geosyncline] sedimentary succession have been dated at 867 ± 47 and 802 ± 35 Ma (Zhao & McCulloch 1993; Zhao et al. 1994) and 827 ± 6 Ma (Wingate et al. 1998)."[80]

"No volcanism is known in the region during the Elatina glaciation."[80]

"The Neoproterozoic–early Palaeozoic succession in the Adelaide Geosyncline was deformed by the Delamerian Orogeny at 514 – 490 Ma (Drexel & Preiss 1995; Foden et al. 2006)."[80]

"The Yerelina Subgroup at the top of the Cryogenian Umberatana Group embraces all the glaciogenic formations of the Elatina glaciation (Preiss et al. 1998)."[80]

"The Yerelina Subgroup is unconformably to disconformably overlain by the Ediacaran Wilpena Group."[80]

"Deposition in the North Flinders Zone commenced, possibly following an erosional break, with the 1070-m-thick Fortress Hill Fm., which comprises laminated siltstone with gritty lenses and scattered dropstones, some faceted, marking the onset of glacial deposition (Coats & Preiss 1987; Preiss et al. 1998). Clast lithologies include granite, quartzite, limestone, oolitic limestone and dolostone. The Fortress Hill Fm. is typical of the dominantly fine-grained units of the Yerelina Subgroup that are interpreted by Preiss (1992) as outer marine-shelf deposits."[80]

"The Fortress Hill Fm. is sharply overlain by sandstone and conglomerate at the base of the Mount Curtis Tillite (90 m) that may record a lowering of relative sea level and mark a sequence boundary (Preiss et al. 1998)."[80]

"The Mount Curtis Tillite is a sparse diamictite with erratics of pebble to boulder size, some faceted and striated, in massive and laminated, grey-green dolomitic siltstone. Clast lithologies are mostly quartzite, limestone and dolostone, but also include granite and porphyry (Coats & Preiss 1987). Granite boulders attain 3 x 8 m."[80]

"The Mount Curtis Tillite is overlain by the medium-grained, feldspathic Balparana Sandstone (130 m), which contains interbeds and lenses of calcareous siltstone and pebble conglomerate."[80]

"The Balparana Sandstone is disconformably overlain by the Wilpena Group. The main source for the glaciogenic deposits may have been the Curnamona Province to the present east [...] and possibly the now-buried Muloorina Ridge immediately north of the North Flinders Zone (Preiss 1987)."[80]

"The lower-most, laminated siltstone facies of the Fortress Hill Fm. shows progressively greater amounts of scattered, ice-rafted granules and pebbles. The shallow-water Gumbowie Arkose (45 – 90 m) disconformably overlies these early deposits at a possible sequence boundary and is conformably succeeded by the Pepuarta Tillite (120 – 197 m), which is a sparse diamictite with scattered clasts up to boulder size in massive and laminated, grey calcareous siltstone. Faceted and striated boulders reach 2.5 m in diameter. Clast lithologies include pink granite, granite gneiss, grey porphyry, quartz-granule conglomerate, various quartzites, and vein quartz. The siltstone facies with scattered large clasts of extrabasinal provenance implies deposition from floating ice."[80]

"The widespread Grampus Quartzite (60 m) disconformably overlies the Pepuarta Tillite, possibly at a sequence boundary defining a third genetic sequence of the Yerelina Subgroup (Preiss et al. 1998)."[80]

"It is conformably overlain by the laminated to cross-laminated, calcareous, pale grey Ketchowla Siltstone (271 m) (Preiss 1992). The Ketchowla Siltstone contains scattered ice-rafted granules, pebbles and boulders up to 1 m across, and is ascribed by Preiss (1992) to outer marine-shelf deposition under generally waning glacial conditions. It is overlain disconformably by the Nuccaleena Fm., with any Ketchowla Siltstone deposited in the North Flinders Zone having been completely removed by erosion at this sequence boundary (Preiss 2000)."[80]

"The outer marine-shelf successions of the Fortress Hill Fm. and Ketchowla Siltstone record the waxing and waning of glacial conditions, respectively. The Pepuarta Tillite and the correlative Mount Curtis Tillite mark the glacial maximum of the Elatina glaciation (Preiss et al. 1998)."[80]

"A U–Pb age of 657 ± 17 Ma was obtained for a zircon grain of uncertain provenance from the Marino Arkose Member of the underlying Upalinna Subgroup (Preiss 2000). Re – Os dating gave an age of 643.0 ± 2.4 Ma for black shale from the Tindelpina Shale Member at the base of the Tapley Hill Fm., which overlies glacial deposits of Sturtian age in the Adelaide Geosyncline (Kendall et al. 2006). Zoned igneous zircon from a tuffaceous layer near the top of the Sturtian-age glaciogenic succession gave a SHRIMP U – Pb age of c. 658 Ma (Fanning & Link 2006). Mahan et al. (2007) reported a Th–U–total Pb age of 680 ± 23 Ma for euhedral laths of monazite, interpreted as authigenic, from the Enorama Shale of the Upalinna Subgroup."[80]

Nantuo glaciation[edit | edit source]

The Nantuo glaciation apparently occurred 654 ± 3.8 Ma.

Ice Brook glaciation[edit | edit source]

The Ice Brook glaciation apparently spans 651 to 659 Ma.

Ghaub glaciation[edit | edit source]

"Dropstone-bearing glaciomarine sedimentary rocks of the Ghaub Formation within metamorphosed Neoproterozoic basinal strata (Swakop Group) in central Namibia contain interbedded mafic lava flows and thin felsic ash beds. U-Pb zircon geochronology of an ash layer constrains the deposition of the glaciomarine sediments to 635.5 ± 1.2 Ma, providing an age for what has been described as a “Marinoan-type” glaciation. In addition, this age provides a maximum limit for the proposed lower boundary of the terminal Proterozoic (Ediacaran) system and period. Combined with reliable age constraints from other Neoproterozoic glacial units—the ca. 713 Ma Gubrah Member (Oman) and the 580 Ma Gaskiers Formation (Newfoundland)—these data provide unequivocal evidence for at least three, temporally discrete, glacial episodes during Neoproterozoic time with interglacial periods, characterized by prolonged positive δ13C excursions, lasting at most ∼50–80 m.y."[81]

"Dropstones are ubiquitous within the finer-grained (Ghaub) lithofacies, and their presence, along with the facies context for subglacial and near grounding-line deposition, indicates a glacigenic origin for the Ghaub Formation, despite its subtropical paleolatitude and distal foreslope setting."[82]

Marinoan glaciations[edit | edit source]

This diamictite is from the Neoproterozoic Pocatello Formation, a 'Snowball Earth'—type deposit. Credit: Qfl247.{{free media}}

The term Marinoan glaciation has been applied globally to any glaciogenic formations assumed (directly or indirectly) to correlate with the Elatina glaciation in South Australia.[83] Recently, there has been a move to return to the term Elatina glaciation in South Australia because of uncertainties regarding global correlation and because an Ediacaran glacial episode (Gaskiers) also occurs within the wide-ranging Marinoan Epoch.[84]

The Marinoan glaciation was a period of worldwide glaciation that lasted from approximately 650 to 635 Ma and may have covered the entire planet, in an event called the Snowball Earth, where the end of the glaciation may have been sped by the release of methane from equatorial permafrost.[85][86] Great uncertainty surrounds the dating of pre-Gaskiers glaciations: the status of the Kaigas is not clear; its dating is very tentative and many researchers do not recognize it as a glaciation.[87]

During the Marinoan glaciation, characteristic glacial deposits indicate that Earth suffered one of the most severe ice ages in its history: glaciers extended and contracted in a series of rhythmic pulses, possibly reaching as far as the equator.[88][89]

Apparently the major glacial period the Marinoan occurred during the Cryogenian.[90]

A similar period of rifting, to the break up along the margins of Laurentia, at about 650 Ma occurred with the deposition of the Ice Brook Formation in North America, contemporaneously with the Marinoan in Australia.[91]

The Marinoan glaciation ended approximately 635 Ma, at the end of the Cryogenian.[92]

The Marinoan glaciation was a period of worldwide glaciation that lasted from approximately 650 to 635 Ma, where the end of the glaciation may have been sped by the release of methane from equatorial permafrost.[92][93]

The name is derived from the stratigraphic terminology of the Adelaide Geosyncline (Adelaide Rift Complex) in South Australia and taken from the Adelaide suburb of Marino to subdivide the Neoproterozoic rocks of the Adelaide area and encompass all strata from the top of the Brighton Limestone to the base of the Cambrian.[94] The corresponding time period, referred to as the Marinoan Epoch, spanned from the middle Cryogenian to the top of the Ediacaran and included a glacial episode within the Marinoan Epoch, the Elatina glaciation, after the 'Elatina Tillite' (now Elatina Formation).[95] The term Marinoan glaciation came into common usage because it was the glaciation that occurred during the Marinoan Epoch.[94]

The term Marinoan glaciation was applied globally to any glaciogenic formations assumed to correlate with the Elatina glaciation in South Australia.[96] The Elatina glaciation in South Australia and the Gaskiers also occurs within the wide ranging Marinoan Epoch.[84]

The Earth may have underwent a number of glaciations during the Neoproterozoic era.[97]

There were three (or possibly four) significant ice ages during the late Neoproterozoic, periods of nearly complete glaciation of Earth are often referred to as "Snowball Earth", where it is hypothesized that at times the planet was covered by ice 1–2 km (0.62–1.24 mi) thick.[98]

During the Marinoan glaciation, characteristic glacial deposits indicate that Earth suffered one of the most severe ice ages in its history, where glaciers extended and contracted in a series of rhythmic pulses, possibly reaching as far as the equator.[99][100]

The melting of the Snowball Earth is associated with greenhouse warming due to the accumulation of high levels of carbon dioxide in the atmosphere.[101]

Glacial deposits in South Australia are approximately the same age (about 630 Ma), confirmed by similar stable carbon isotopes, mineral deposits (including sedimentary barite), and other unusual sedimentary structures.[98]

Two diamictite-rich layers in the top 1 km (0.62 mi) of the 7 km (4.3 mi) Neoproterozoic strata of the northeastern Svalbard archipelago represent the first and final phases of the Marinoan glaciation.[102]

The Marinoan "is separated from the Sturtian by a thick succession of sedimentary rocks containing no evidence of glaciation. This glacial phase could correspond to the recently described Ice Brooke formation in the northern Canadian Cordillera."[91]

Gucheng[edit | edit source]

The Gucheng is apparently comparable to the Marinoan.

Jiangkou[edit | edit source]

The Jiangkou spans the Chang'an through the Gucheng.

Chang'an[edit | edit source]

The Chang'an occurred about 715.9 ± 2.8 Ma.

Port Askaig glaciation[edit | edit source]

The Port Askaig glaciation is above the Elbobreen-Wilsonbreen glaciation.

Elbobreen-Wilsonbreen glaciation[edit | edit source]

The Elbobreen-Wilsonbreen glaciation in Svalbard occurred c. 720 Ma.

Cryogenian ice age[edit | edit source]

The Cryogenian Ice Age, or the Stuartian-Varangian Ice Age, a "Late Proterozoic ice age was apparently the greatest of all. Glacial strata are known from all modern continents (except Antarctica) with an overall time range of about 950 to 600 million years old. Glacial strata from several intervals during this time are well preserved in Africa, China, Australia, Europe, Arabia, North America, and elsewhere. Multiple glaciations are the rule. In Scotland and Ireland, for example, three glacial episodes took place between 700 and 580 million years ago (McCay et al. 2006)."[75]

It apparently consists of

  1. glaciation of the Lower Congo region, Africa occurring 950-750 and 620-600 Ma,
  2. Stuartian glaciation, Australia, 800-780 Ma,
  3. Sinian glaciation, China, 800-760, 740-700, and 600 Ma,
  4. glaciation in Western Canada/U.S.A., 850-800 Ma,
  5. glaciation of the Saharan region, Africa, 730-650 Ma,
  6. Marinoan glaciation, Australia, 690-680 Ma, and
  7. Varangian glaciation, Norway, about 650 Ma.[75]

"Late Proterozoic glaciogenic deposits are known from all the continents. They provide evidence of the most widespread and long-ranging glaciation on Earth."[91]

Def. "a geologic period within the Neoproterozoic era from about [720] to 600 million years ago"[103] is called the Cryogenian.

The end of the period also saw the origin of heterotrophic plankton, which would feed on unicellular algae and prokaryotes, ending the bacterial dominance of the oceans.[104]

Apparently two major glacial periods occurred during the Cryogenian: the Marinoan and the Sturtian,[90][79] formerly considered together as the Varanger glaciations, from their first detection in Norway's Varanger Peninsula.

The Cryogenian is a geologic period that lasted from 720-635 Mya.[105]

The Cryogenian period was ratified in 1990 by the International Commission on Stratigraphy.[106]

Several glacial periods are evident, interspersed with periods of relatively warm climate, with glaciers reaching sea level in low paleolatitudes.[91]

Glaciers extended and contracted in a series of rhythmic pulses, possibly reaching as far as the equator.[107]

The deposits of glacial tillite also occur in places that were at low latitudes during the Cryogenian, a phenomenon which led to the hypothesis of deeply frozen planetary oceans called "Snowball Earth".[108][109]

"Most Neoproterozoic glacial deposits accumulated as glacially influenced marine strata along rifted continental margins or interiors."[91]

Fossils of testate amoeba (or Arcellinida) first appear during the Cryogenian period.[110]

During the Cryogenian period, the oldest known fossils of sponges, Otavia the first sponge-like animal[111] (and therefore animals) make an appearance.[112][113][114]

New groups of life evolved during this period, including the red algae and green algae, stramenopiles, ciliates, dinoflagellates, and testate amoeba.[115]

The base of the period is defined by a fixed rock age, that was originally set at 850 million years,[116] but changed in 2015 to 720 million years.[105]

Sturtian[edit | edit source]

The Sturtian glaciation was a glaciation, or perhaps multiple glaciations,[117] during the Cryogenian Period.[90][79]

The break up along the margins of Laurentia at about 750 Ma occurs at about the same time as the deposition of the Rapitan Group in North America, contemporaneously with the Sturtian in Australia.[91]

The Sturtian glaciation persisted from 720 to 660 million years ago.[92]

A Sturtian age was assigned to the Numees diamictites.[118]

The duration of the Sturtian glaciation has been variously defined, with dates ranging from 717 to 643 Ma.[119][120][117] Or, the period spans 715 to 680 Ma.[121]

"Glaciogenic rocks figure prominently in the Neoproterozoic stratigraphy of southeastern Australia and the northern Canadian Cordillera]. The Sturtian glaciogenic succession (c. 740 Ma) unconformably overlies rocks of the Burra Group."[91]

The Sturtian succession includes two major diamictite-mudstone sequences, which represent glacial advance and retreat cycles, stratigraphically correlated with the Rapitan Group of North America.[91]

The Sturtian is named after the Sturt River Gorge, near Bellevue Heights, South Australia.

Reusch's Moraine in northern Norway may have been deposited during this period.[122]

Numees[edit | edit source]

The Numees has a Sturtian age.

Tereeken[edit | edit source]

The Tereeken occurred < 727 ± 8 Ma.

Rapitan glaciation[edit | edit source]

"The Rapitan Group (Cryogenian) of western Canada is similar to the Chuos Formation in both lithofacies and basin context, representing deposition in a paraglacial rift basin (Young, 1976; Eisbacher, 1985). An iron-rich, dropstone-bearing unit (the Sayunei Formation) is capped by a diamictite unit (the Shezal Formation) (Hoffman and Halverson, 2011). Measured sections (Fig. 3 of Eisbacher, 1985) illustrate that the most complete successions have a basal ferruginous shale sequence bearing occasional dropstones. These deposits pass gradationally upward, via 5–40 m jaspillite-hematite ironstone at the top of the Sayunei Formation, into diamictites. The ironstone is laterally persistent in depocentres (Eisbacher, 1985). Sea-ice removal may have triggered local grounding line advance, resulting in deposition of the Shezal Formation (Eisbacher, 1985): Hoffman and Halverson (2011) recognised this as a possible catalyst for ironstone precipitation. In addition to an abiotic “rusting of the seas” model, a biologically-mediated mechanism was also considered. Once “the ice cover thinned and finally disappeared, anoxic and oxygenic photosynthesis could have precipitated Fe2O3-precursor from anoxic Fe(II)-rich basin waters” (Hoffman et al., 2011). [...] Such a biogenic mechanism for ironstone precipitation, via for example photosynthetic stromatolites, would be in agreement with our observations in Namibia."[123]

Port Nolloth[edit | edit source]

The Port Nolloth extends from the Kaigas formation upwards to the Murmees.

Kaigas formation[edit | edit source]

The Kaigas glaciation was a hypothesized snowball earth event in the Neoproterozoic Era, preceding the Sturtian glaciation inferred based on the interpretation of Kaigas Formation conglomerates in the stratigraphy overlying the Kalahari Craton as correlative with pre-Sturtian Numees formation glacial diamictites;[124] however, the Kaigas formation was later determined to be non-glacial, and a Sturtian age was assigned to the Numees diamictites.[125]

Vendian[edit | edit source]

The Vendian occurred about 740 Ma.

Chuos glaciation[edit | edit source]

"The "grainstone prism" was a major submarine drainage system localized in a paleovalley carved during the Chuos glaciation, which was occupied by a transverse ice-stream that cut the Duurwater trough during the Ghaub glaciation."[82]

"Despite early indications of two distinct glaciations (Kröner and Rankama, 1972; Guj, 1974), the prevailing view of a single glaciogenic horizon that could serve as a basis for correlation throughout the Otavi Group (Hedberg, 1979; SACS, 1980; Miller, 1997) led to the former "Otavi Tillite" (le Roex, 1941) being assigned to the Chuos Formation of Gevers (1931), a glaciogenic diamictite with an intimately associated banded iron formation that is widely distributed within the orogens bounding the Otavi platform (Martin, 1965a, 1965b). More recently, two glaciations have been firmly established in the Otavi Group (Hoffmann and Prave, 1996; Hoffman et al., 1998a; Hoffman and Halverson, 2008), the older Chuos Formation and a younger glaciation represented by the "Otavi Tillite" (le Roex, 1941), and its correlative carbonate-clast breccia unit of the Fransfontein homocline (Frets, 1969; Guj, 1974). Hoffmann and Prave (1996) renamed this younger glaciogenic unit the Ghaub Formation, after a farm near the section originally described by le Roex (1941)."[82]

The "Chuos glaciation occurred during a period of active faulting, which is reflected by the diversity of its debris and a low-angle (1.5°) structural unconformity [...] that cuts out ~2 km of strata (Hoffman et al., 1998a)."[82]

The Rasthof Formation [is] the postglacial cap carbonate overlying the Chuos diamictite".[82]

Below the Chuos glaciation is the Naauwpoort dated at 746 ± 2 Ma giving an upper age limit to the base of the Chuos.[82]

"U–Pb ages from the Askevold Formation (Hoffman et al., 1996) [Nabis Formation 747 ± 2 Ma (Hoffman et al., 1996)] are from further west: this formation is not preserved beneath the Chuos Formation in [the Ghaub and Varianto farm areas of the Otavi Mountain Land]."[123]

"Earlier analyses of the Chuos Formation concentrated on meta-sediments in the vicinity of its type section south of Windhoek and in the Damara Belt (Gevers, 1931; de Kock and Gevers, 1933; Martin et al., 1985; Henry et al., 1986; Badenhorst, 1988). More modern stratigraphic analyses several hundred kilometres to the west of the Otavi Mountain Land demonstrate that the Chuos Formation is cradled in a rift-related, fault bounded palaeotopography (Hoffman and Halverson, 2008), and hence its substrate also changes along strike, across the southern flank of the Owambo Basin. In the area of Ghaub and Varianto farms, the study interval comprises the Nabis Sandstone Formation of the Nosib Group, overlain by the Chuos Formation and succeeded by the Berg Aukas Formation [...]. This particular area has been mapped at the 1:250,000 scale (Geological Survey of Namibia, 2008). Age constraints include 747 ± 2 Ma from the Naauwport volcanics, locally beneath the Chuos Formation (Hoffman et al., 1996) and 635 ± 1 Ma from ash beds in the younger Ghaub Formation (Hoffmann et al., 2004)."[123]

Beiyixi glaciaton[edit | edit source]

The Beiyixi is later than 755 Ma.

Makganyene glaciation[edit | edit source]

"In its eastern domain, the Transvaal Supergroup of South Africa contains two glacial diamictites, in the Duitschland and Boshoek Fms. The base of the Timeball Hill Fm., which underlies the Boshoek Fm., has a Re-Os date of 2,316 ± 7 My ago (13). The Boshoek Fm. correlates with the Makganyene diamictite in the western domain of the Transvaal Basin, the Griqualand West region. The Makganyene diamictite interfingers with the overlying Ongeluk flood basalts, which are correlative to the Hekpoort volcanics in the eastern domain and have a paleolatitude of 11° ± 5° (14). In its upper few meters, the Makganyene diamictite also contains basaltic andesite clasts, interpreted as being clasts of the Ongeluk volcanics. The low paleolatitude of the Ongeluk volcanics implies that the glaciation recorded in the Makganyene and Boshoek Fms. was planetary in extent: a snowball Earth event (15). Consistent with earlier whole-rock Pb–Pb measurements of the Ongeluk Fm. (16), the Hekpoort Fm. contains detrital zircons as young as 2,225 ± 3 My ago (17), an age nearly identical to that of the Nipissing diabase in the Huronian Supergroup."[126]

The "Makganyene glaciation begins some time after 2.32 Ga and ends at 2.22 Ga, the three Huronian glaciations predate the Makganyene snowball."[126]

Huronian ice age[edit | edit source]

Proposed correlation is of the Huronian Supergroup and the upper Transvaal Supergroup. Credit: Robert E. Kopp, Joseph L. Kirschvink, Isaac A. Hilburn, and Cody Z. Nash.

The Huronian Ice Age is known "mainly from Canada and the United States in North America, where dated rocks range from 2500 to 2100 million years old. The Gowgonda Formation of Ontario is especially noteworthy for its excellent preservation of glaciogenic strata dated about 2300 million years old. Other glacial deposits are found in Wyoming, Michigan, Quebec, and the Northwest Territories. These rocks record extensive Early Proterozoic continental glaciation through a time span of about 400 million years, during which three or more glacial expansions took place. The configuration of the continents during this time is highly speculative."[75]

"The period from 2.45 Ga until some point before 2.22 Ga saw a series of three glaciations recorded in the Huronian Supergroup of Canada (11) [in the above centered image]. The final glaciation in the Huronian, the Gowganda, is overlain by several kilometers of sediments in the Lorrain, Gordon Lake, and Bar River formations (Fms.). The entire sequence is penetrated by the 2.22 Ga Nipissing diabase (12); the Gowganda Fm. is therefore significantly older than 2.22 Ga."[126]

"The three Huronian glacial units, penetrated and capped by the Nipissing diabase, predate the Makganyene diamictite in the Transvaal. The uppermost Huronian glacial unit, the Gowganda Fm., is overlain by hematitic units, perhaps reflecting a rise in O2. The basal Timeball Hill Fm. contains pyrite with minimal [mass-independent fractionation] MIF (26), whereas the upper Timeball Hill Fm., which we suggest is correlative to the Lorrain or Bar River Fms., contains red beds. The Makganyene diamictite records a low-latitude, snowball glaciation (29), perhaps triggered by the destruction of a CH4 greenhouse. It is overlain by the Kalahari Mn Field in the Hotazel Fm., the deposition of which requires free O2."[126]

"In its eastern domain, the Transvaal Supergroup of South Africa contains two glacial diamictites, in the Duitschland and Boshoek Fms. The base of the Timeball Hill Fm., which underlies the Boshoek Fm., has a Re-Os date of 2,316 ± 7 My ago (13). The Boshoek Fm. correlates with the Makganyene diamictite in the western domain of the Transvaal Basin, the Griqualand West region. The Makganyene diamictite interfingers with the overlying Ongeluk flood basalts, which are correlative to the Hekpoort volcanics in the eastern domain and have a paleolatitude of 11° ± 5° (14). In its upper few meters, the Makganyene diamictite also contains basaltic andesite clasts, interpreted as being clasts of the Ongeluk volcanics. The low paleolatitude of the Ongeluk volcanics implies that the glaciation recorded in the Makganyene and Boshoek Fms. was planetary in extent: a snowball Earth event (15). Consistent with earlier whole-rock Pb–Pb measurements of the Ongeluk Fm. (16), the Hekpoort Fm. contains detrital zircons as young as 2,225 ± 3 My ago (17), an age nearly identical to that of the Nipissing diabase in the Huronian Supergroup. As the Makganyene glaciation begins some time after 2.32 Ga and ends at 2.22 Ga, the three Huronian glaciations predate the Makganyene snowball."[126]

"In contrast to the Makganyene Fm., the three Huronian diamictites are unconstrained in latitude. Poles from the Matachewan dyke swarm, at the base of the Huronian sequence, do indicate a latitude of ≈5.5° (18), but ≈2 km of sedimentary deposits separate the base of the Huronian from the first glacial unit (19), which makes it difficult to draw conclusions about the latitude of the glacial units based on these poles. Low latitude poles in the Lorrain Fm. (20, 21), which conformably overlies the Gowganda diamictite, are postdepositional overprints (22)."[126]

"Some of the earliest continental red beds were deposited in the Firstbrook member of the Gowganda Fm. and in the Lorrain and Bar River Fms. in Canada, as well as in the upper Timeball Hill Fm. in South Africa. The basal Timeball Hill Fm. has recently been dated at 2,316 ± 7 My ago (13). In our proposed correlation, all of the red bed-bearing units were deposited after the last Huronian glaciation and before the Makganyene glaciation. The formation of the red beds could involve local O2, although it does not demand it (34). Syngenetic pyrite from the basal Timeball Hall Fm. shows only slight MIF of S (26), consistent with the initiation of planetary oxygenation or enhanced glacial activity."[126]

Pongola glaciation[edit | edit source]

The Pongola glaciation is dated "at 2.9 Ga".[126] It extends to 2780 Ma.

"The oldest known midlatitude glaciation, recorded in the Pongola Supergroup diamictite, occurred at 2.9 Ga (10)."[126]

See also[edit | edit source]

References[edit | edit source]

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