Misplaced Pages

#338661

67-490: Two papers dating the age of the Nuvvuagittuq Greenstone Belt have been published. One paper gave an age of c.  3,750 million years ( Ma ), while the other gave an age of c.  4,388   Ma. In March 2017, the age of the Nuvvuagittuq Greenstone Belt was still unresolved. In March 2017, a published report gave evidence for fossils of microorganisms in these rocks, which would be

134-402: A central stem and parallel side branches, and ellipsoids alongside the tubules and filaments. The filaments were said to resemble filaments of Mariprofundus ferrooxydans , a deep sea siderophilic bacterium . Critics pointed out that metamorphism and the effects of a crystal lattice could account for some of the effects seen, particularly the parallel filaments. In respect of having 'some of

201-449: A fixed frame of reference (such as the fixed stars, Latin sidera , singular sidus ). Its average duration is 365.256 363 004 days (365 d 6 h 9 min 9.76 s) (at the epoch J2000.0 = January 1, 2000, 12:00:00 TT ). Today the mean tropical year is defined as the period of time for the mean ecliptic longitude of the Sun to increase by 360 degrees. Since the Sun's ecliptic longitude

268-403: A foliation because the unroofing of a metamorphic belt is not accompanied by significant compressive stress. Thermal metamorphism in the aureole of a granite is also unlikely to result in the growth of mica in a foliation, although the growth of new minerals may overprint existing foliation(s). Alignment of tabular minerals in metamorphic rocks , igneous rocks and intrusive rocks may form

335-447: A foliation. Typical examples of metamorphic rocks include porphyroblastic schists where large, oblate minerals form an alignment either due to growth or rotation in the groundmass. Igneous rocks can become foliated by alignment of cumulate crystals during convection in large magma chambers , especially ultramafic intrusions, and typically plagioclase laths . Granite may form foliation due to frictional drag on viscous magma by

402-626: A leap year there are 366 days. A leap year occurs every fourth year during which a leap day is intercalated into the month of February. The name "Leap Day" is applied to the added day. In astronomy, the Julian year is a unit of time defined as 365.25 days, each of exactly 86,400 seconds ( SI base unit ), totaling exactly 31,557,600 seconds in the Julian astronomical year. The Revised Julian calendar , proposed in 1923 and used in some Eastern Orthodox Churches , has 218 leap years every 900 years, for

469-537: A meter in thickness. The word comes from the Latin folium , meaning "leaf", and refers to the sheet-like planar structure. It is caused by shearing forces (pressures pushing different sections of the rock in different directions), or differential pressure (higher pressure from one direction than in others). The layers form parallel to the direction of the shear, or perpendicular to the direction of higher pressure. Nonfoliated metamorphic rocks are typically formed in

536-408: A methodology allows eventual correlations in style, metamorphic grade, and intensity throughout a region, relationship to faults , shears , structures and mineral assemblages. In geotechnical engineering , a foliation plane may introduce anisotropy of stress, which is a vital consideration for geotechnical engineers. At some point, this foliation may form a discontinuity that may greatly influence

603-435: A person carrying a bundle of wheat denoting "harvest". Slavic besides godŭ "time period; year" uses lěto "summer; year". Astronomical years do not have an integer number of days or lunar months. Any calendar that follows an astronomical year must have a system of intercalation such as leap years. In the Julian calendar , the average (mean) length of a year is 365.25 days. In a non-leap year, there are 365 days, in

670-710: A reference event in the past (called the epoch ) as the beginning of the era. The Gregorian calendar era is the world's most widely used civil calendar . Its epoch is a 6th century estimate of the date of birth of Jesus of Nazareth . Two notations are used to indicate year numbering in the Gregorian calendar: the Christian " Anno Domini " (meaning "in the year of the Lord"), abbreviated AD; and " Common Era ", abbreviated CE, preferred by many of other faiths and none. Year numbers are based on inclusive counting , so that there

737-404: A reference, and/or with a substantial contribution to the development of geological sciences through history.' 58°18′N 077°45′W  /  58.300°N 77.750°W  / 58.300; -77.750 Year#Megaannum A year is the time taken for astronomical objects to complete one orbit . For example, a year on Earth is the time taken for Earth to revolve around

SECTION 10

#1732776491339

804-475: A rock. Usually, this is the result of some physical force and its effect on the growth of minerals. The planar fabric of a foliation typically forms at right angles to the maximum principal stress direction. In sheared zones , however, planar fabric within a rock may not be directly perpendicular to the principal stress direction due to rotation, mass transport, and shortening. Foliation may be formed by realignment of micas and clays via physical rotation of

871-479: A thermal event after the first phase of deformation, and it is dated by O'Neil to be 2.7 Ga . This event is recorded by igneous intrusions in the NGB, and the formation of the nearby Boizard Suite , an intrusive igneous formation. This event is followed by a period of meter-scale folding that affects all parts of the belt. It has also been proposed that the NGB represents a zone of paleo subduction . Similarities between

938-565: A time interval in Julian years is a way to precisely specify an amount of time (not how many "real" years), for long time intervals where stating the number of ephemeris days would be unwieldy and unintuitive. By convention, the Julian year is used in the computation of the distance covered by a light-year . In the Unified Code for Units of Measure (but not according to the International Union of Pure and Applied Physics or

1005-495: Is 365.2425 days (97 out of 400 years are leap years). In English, the unit of time for year is commonly abbreviated as "y" or "yr". The symbol "a" (for Latin : annus , year) is sometimes used in scientific literature, though its exact duration may be inconsistent. English year (via West Saxon ġēar ( /jɛar/ ), Anglian ġēr ) continues Proto-Germanic *jǣran ( *j ē₁ ran ). Cognates are German Jahr , Old High German jār , Old Norse ár and Gothic jer , from

1072-765: Is a 12-month period used for calculating annual financial statements in businesses and other organizations. In many jurisdictions, regulations regarding accounting require such reports once per twelve months, but do not require that the twelve months constitute a calendar year. For example, in Canada and India the fiscal year runs from April 1; in the United Kingdom it runs from April 1 for purposes of corporation tax and government financial statements, but from April 6 for purposes of personal taxation and payment of state benefits; in Australia it runs from July 1; while in

1139-494: Is about 20 minutes shorter than the sidereal year. The mean tropical year is approximately 365 days, 5 hours, 48 minutes, 45 seconds, using the modern definition ( = 365.24219 d × 86 400 s). The length of the tropical year varies a bit over thousands of years because the rate of axial precession is not constant. The anomalistic year is the time taken for the Earth to complete one revolution with respect to its apsides . The orbit of

1206-408: Is an approximation of the number of days of the Earth's orbital period, as counted in a given calendar . The Gregorian calendar , or modern calendar, presents its calendar year to be either a common year of 365 days or a leap year of 366 days, as do the Julian calendars . For the Gregorian calendar, the average length of the calendar year (the mean year) across the complete leap cycle of 400 years

1273-534: Is an integral approximation to the year equaling 365 days, which wanders in relation to more exact years. Typically the vague year is divided into 12 schematic months of 30 days each plus 5 epagomenal days. The vague year was used in the calendars of Ethiopia , Ancient Egypt , Iran , Armenia and in Mesoamerica among the Aztecs and Maya . It is still used by many Zoroastrian communities. A heliacal year

1340-410: Is due to the preferred orientation of microscopic phyllosilicate crystals . In gneiss, the foliation is more typically represented by compositional banding due to segregation of mineral phases. Foliated rock is also known as S-tectonite in sheared rock masses. Examples include the bands in gneiss (gneissic banding), a preferred orientation of planar large mica flakes in schist (schistosity),

1407-427: Is measured with respect to the equinox, the tropical year comprises a complete cycle of the seasons and is the basis of solar calendars such as the internationally used Gregorian calendar . The modern definition of mean tropical year differs from the actual time between passages of, e.g., the northward equinox, by a minute or two, for several reasons explained below. Because of the Earth's axial precession , this year

SECTION 20

#1732776491339

1474-637: Is named after the 19th-century German astronomer and mathematician Friedrich Bessel . The following equation can be used to compute the current Besselian epoch (in years): The TT subscript indicates that for this formula, the Julian date should use the Terrestrial Time scale, or its predecessor, ephemeris time . The exact length of an astronomical year changes over time. Numerical value of year variation Mean year lengths in this section are calculated for 2000, and differences in year lengths, compared to 2000, are given for past and future years. In

1541-471: Is no "year zero". Years before the epoch are abbreviated BC for Before Christ or BCE for Before the Common Era . In Astronomical year numbering , positive numbers indicate years AD/CE, the number 0 designates 1 BC/BCE, −1 designates 2 BC/BCE, and so on. Other eras include that of Ancient Rome , Ab Urbe Condita ("from the foundation of the city ), abbreviated AUC; Anno Mundi ("year of

1608-815: Is the accusative singular ; annī is genitive singular and nominative plural; annō the dative and ablative singular) is from a PIE noun *h₂et-no- , which also yielded Gothic aþn "year" (only the dative plural aþnam is attested). Although most languages treat the word as thematic *yeh₁r-o- , there is evidence for an original derivation with an *-r/n suffix, *yeh₁-ro- . Both Indo-European words for year, *yeh₁-ro- and *h₂et-no- , would then be derived from verbal roots meaning "to go, move", *h₁ey- and *h₂et- , respectively (compare Vedic Sanskrit éti "goes", atasi "thou goest, wanderest"). A number of English words are derived from Latin annus , such as annual , annuity , anniversary , etc.; per annum means "each year", annō Dominī means "in

1675-413: Is the interval between the heliacal risings of a star. It differs from the sidereal year for stars away from the ecliptic due mainly to the precession of the equinoxes . The Sothic year is the heliacal year, the interval between heliacal risings, of the star Sirius . It is currently less than the sidereal year and its duration is very close to the Julian year of 365.25 days. The Gaussian year

1742-534: Is the sidereal year for a planet of negligible mass (relative to the Sun) and unperturbed by other planets that is governed by the Gaussian gravitational constant . Such a planet would be slightly closer to the Sun than Earth's mean distance. Its length is: The Besselian year is a tropical year that starts when the (fictitious) mean Sun reaches an ecliptic longitude of 280°. This is currently on or close to January 1. It

1809-539: Is the time taken for the Sun (as seen from the Earth) to complete one revolution with respect to the same lunar node (a point where the Moon's orbit intersects the ecliptic). The year is associated with eclipses : these occur only when both the Sun and the Moon are near these nodes; so eclipses occur within about a month of every half eclipse year. Hence there are two eclipse seasons every eclipse year. The average duration of

1876-444: The International Union of Geological Sciences , see below), the symbol a (without subscript) always refers to the Julian year, a j , of exactly 31 557 600 seconds . The SI multiplier prefixes may be applied to it to form "ka", "Ma", etc. Each of these three years can be loosely called an astronomical year . The sidereal year is the time taken for the Earth to complete one revolution of its orbit , as measured against

1943-472: The Proto-Indo-European noun *yeh₁r-om "year, season". Cognates also descended from the same Proto-Indo-European noun (with variation in suffix ablaut ) are Avestan yārǝ "year", Greek ὥρα ( hṓra ) "year, season, period of time" (whence " hour "), Old Church Slavonic jarŭ , and Latin hornus "of this year". Latin annus (a 2nd declension masculine noun; annum

2010-512: The Sun . Generally, a year is taken to mean a calendar year , but the word is also used for periods loosely associated with the calendar or astronomical year, such as the seasonal year , the fiscal year , the academic year , etc. The term can also be used in reference to any long period or cycle, such as the Great Year . Due to the Earth's axial tilt , the course of a year sees the passing of

2077-607: The United States the fiscal year of the federal government runs from October 1. An academic year is the annual period during which a student attends an educational institution . The academic year may be divided into academic terms , such as semesters or quarters. The school year in many countries starts in August or September and ends in May, June or July. In Israel the academic year begins around October or November, aligned with

Nuvvuagittuq Greenstone Belt - Misplaced Pages Continue

2144-579: The oldest trace of life yet discovered on Earth. However, these traces may be abiogenic . Formerly called the Porpoise Cove Greenstone Belt, the Nuvvuagittuq Greenstone Belt was first mapped in 1965 by the Quebec Ministry of Natural Resources. The area remained more or less unexamined until the 2000s when preliminary reports of U-Pb zircon dating in the area of the belt found zircons with ages up to 3,750 Ma. Since then,

2211-409: The perigee of the Moon's orbit. This period is associated with the apparent size of the full moon , and also with the varying duration of the synodic month . The duration of one full moon cycle is: The lunar year comprises twelve full cycles of the phases of the Moon, as seen from Earth. It has a duration of approximately 354.37 days. Muslims use this for celebrating their Eids and for marking

2278-480: The seasons , marked by changes in weather , the hours of daylight , and, consequently, vegetation and soil fertility . In temperate and subpolar regions around the planet, four seasons are generally recognized: spring , summer , autumn , and winter . In tropical and subtropical regions, several geographical sectors do not present defined seasons; but in the seasonal tropics , the annual wet and dry seasons are recognized and tracked. A calendar year

2345-424: The Earth is elliptical; the extreme points, called apsides, are the perihelion , where the Earth is closest to the Sun, and the aphelion , where the Earth is farthest from the Sun. The anomalistic year is usually defined as the time between perihelion passages. Its average duration is 365.259636 days (365 d 6 h 13 min 52.6 s) (at the epoch J2011.0). The draconic year, draconitic year, eclipse year, or ecliptic year

2412-677: The NGB and the Izu-Bonin-Mariana forearc , a modern subduction zone, suggest that the NGB may have experienced episodic subduction in its lifetime. This theory does not depend on the timing of the formation of the belt, and either ages would represent subduction occurring at a remarkable age. The banded iron formation bears many similarities to similar formations found in Algoma-type iron deposits. It has been suggested that Algoma-type iron deposits can precipitate due to bacterial activity in an anoxic environment, as would be found in

2479-418: The NGB reported a maximum age of 3,780 Ma. The latter study states that the 4,321 Ma age is not reflective of the NGB, but rather, reflects isotope ratios inherited from Hadean crust that was melted to form the parent rocks of the NGB. As of March 2017, this disagreement in dating remained unresolved. The Nuvvuagittuq Greenstone Belt contains 3 major components: The cummingtonite amphibolite that dominates

2546-696: The Nuvvuagittuq Greenstone Belt has become the focus of intense study. There is still considerable disagreement between scientists regarding the history and age of this structure. The Nuvvuagittuq Greenstone Belt is part of a mafic unit called the Ujaraaluk unit, both of which are in the Inukjuak subprovince of the Minto Block in North Eastern Superior Province(NESP) . In 2007, using uranium–lead dating on zircons ,

2613-452: The Nuvvuagittuq Greenstone Belt remains poorly understood in many regards. However, attempts have been made to constrain the history using structural techniques, and geochronometric high-pressure deformation is evident throughout the belt as one of the earliest periods of deformation. This period caused significant foliation and meter-scale folding in the faux-amphibolite and banded iron formations. The work of Nadeau and O'Neil both agree on

2680-498: The Nuvvuagittuq was dated to be a minimum of 3.75 billion years old (3,750 Ma). This measurement was made using uranium–lead dating on zircons found within granitic intrusions that cut portions of the belt, and therefore, are younger than the features it cuts. This measurement is widely accepted. However, it alone does not provide a maximum age. In 2012 samarium–neodymium dating and neodymium isotope fractionation

2747-725: The United Kingdom, and 200 for pupils in Australia. In India the academic year normally starts from June 1 and ends on May 31. Though schools start closing from mid-March, the actual academic closure is on May 31 and in Nepal it starts from July 15. Schools and universities in Australia typically have academic years that roughly align with the calendar year (i.e., starting in February or March and ending in October to December), as

Nuvvuagittuq Greenstone Belt - Misplaced Pages Continue

2814-637: The United States, notably Boston Latin School , may divide the year into five or more marking periods. Some state in defense of this that there is perhaps a positive correlation between report frequency and academic achievement. There are typically 180 days of teaching each year in schools in the US, excluding weekends and breaks, while there are 190 days for pupils in state schools in Canada, New Zealand and

2881-493: The absence of significant differential pressure or shear. Foliation is common in rocks affected by the regional metamorphic compression typical of areas of mountain belt formation ( orogenic belts ). More technically, foliation is any penetrative planar fabric present in metamorphic rocks. Rocks exhibiting foliation include the standard sequence formed by the prograde metamorphism of mudrocks ; slate , phyllite , schist and gneiss . The slatey cleavage typical of slate

2948-595: The authors to conclude that they were produced by "biological activity" more than 3.77 billion years ago. This conclusion was greeted with both approval and skepticism. The authors vigorously defended their conclusions, and are confident that their conclusions will stand the test of time. It was reported in a 2019 paper that hematite tubes and filaments with the same shape and chemical makeup can be produced abiotically by chemical gardens , which may form naturally in some hydrothermal settings. A 2022 paper added that large (up to 1 cm), complex structures were present, with

3015-477: The average (mean) year length of 365.242 2222 days, close to the length of the mean tropical year, 365.242 19 days (relative error of 9·10). In the year 2800 CE, the Gregorian and Revised Julian calendars will begin to differ by one calendar day. The Gregorian calendar aims to ensure that the northward equinox falls on or shortly before March 21 and hence it follows the northward equinox year , or tropical year . Because 97 out of 400 years are leap years,

3082-527: The belt is unusual that sections of the rock have a grayish-beige color, compared to the dark green of common amphibolites, giving it the nickname "faux-amphibolite". The cummingtonite amphibolite displays gneissic foliation , with cummingtonite, quartz , biotite and plagioclase feldspar being the primary components. The cummingtonite amphibolites range from garnet -rich to garnet-poor and are interpreted to be highly metamorphosed volcano-sedimentary rocks. Ultramafic and gabbroic sills appear commonly on

3149-473: The direction of principal stress, records the direction of shortening. This is related to the axis of folds, which generally form an axial-planar foliation within their axial regions. Measurement of the intersection between a fold's axial plane and a surface on the fold will provide the fold plunge . If a foliation does not match the observed plunge of a fold, it is likely associated with a different deformation event. Foliation in areas of shearing, and within

3216-407: The eclipse year is This term is sometimes erroneously used for the draconic or nodal period of lunar precession , that is the period of a complete revolution of the Moon's ascending node around the ecliptic: 18.612 815 932 Julian years ( 6 798 .331 019 days; at the epoch J2000.0). The full moon cycle is the time for the Sun (as seen from the Earth) to complete one revolution with respect to

3283-491: The historical Jalali calendar , known as the Solar Hijri calendar (1925), is a purely solar calendar with an irregular pattern of leap days based on observation (or astronomical computation), aiming to place new year ( Nowruz ) on the day of vernal equinox (for the time zone of Tehran ), as opposed to using an algorithmic system of leap years. A calendar era assigns a cardinal number to each sequential year, using

3350-543: The mean length of the Gregorian calendar year is 365.242 5 days; with a relative error below one ppm (8·10) relative to the current length of the mean tropical year ( 365.242 189 days) and even closer to the current March equinox year of 365.242 374 days that it aims to match. Historically, lunisolar calendars intercalated entire leap months on an observational basis. Lunisolar calendars have mostly fallen out of use except for liturgical reasons ( Hebrew calendar , various Hindu calendars ). A modern adaptation of

3417-415: The minerals within the rock. Often this foliation is associated with diagenetic metamorphism and low-grade burial metamorphism. Foliation may parallel original sedimentary bedding, but more often is oriented at some angle to it. The growth of platy minerals, typically of the mica group, is usually a result of prograde metamorphic reactions during deformation. Often, retrograde metamorphism will not form

SECTION 50

#1732776491339

3484-471: The northern portion of the belt. These sills range from 5 to 30 m (16 to 98 ft) in width, and have serpentine and talc rich interiors with amphibole rich margins. They represent a significant intrusion event in the history of the NGB. The banded iron formation can be traced continuously across the northern portion of the belt. The formation is composed mainly of quartz , magnetite , and grunerite . The history of alteration and metamorphism in

3551-482: The oldest, if not the oldest, rocks on Earth, with potentially earliest traces of life', the International Union of Geological Sciences (IUGS) included the 'Hadean to Eoarchean Nuvvuagittuq greenstone belt' in its assemblage of 100 'geological heritage sites' around the world in a listing published in October 2022. The organisation defines an IUGS Geological Heritage Site as 'a key place with geological elements and/or processes of international scientific relevance, used as

3618-473: The plane of thrust faults , can provide information on the transport direction or sense of movement on the thrust or shear. Generally, the acute intersection angle shows the direction of transport. Foliations typically bend or curve into a shear, which provides the same information, if it is of a scale which can be observed. Foliations, in a regional sense, will tend to curve around rigid, incompressible bodies such as granite. Thus, they are not always 'planar' in

3685-495: The preferred orientation of small mica flakes in phyllite (with its planes having a silky sheen, called phylitic luster – the Greek word, phyllon , also means "leaf"), the extremely fine grained preferred orientation of clay flakes in slate (called " slaty cleavage "), and the layers of flattened, smeared, pancake-like clasts in metaconglomerate . Foliation is usually formed by the preferred orientation of minerals within

3752-429: The result of nucleation processes which cause chemical and mineralogical differentiation into bands. This typically follows the same principle as mica growth, perpendicular to the principal stress. Metamorphic differentiation can be present at angles to protolith compositional banding. Crenulation cleavage and oblique foliation are particular types of foliation. Foliation, as it forms generally perpendicular to

3819-605: The second month of the Hebrew calendar. Some schools in the UK, Canada and the United States divide the academic year into three roughly equal-length terms (called trimesters or quarters in the United States), roughly coinciding with autumn, winter, and spring. At some, a shortened summer session, sometimes considered part of the regular academic year, is attended by students on a voluntary or elective basis. Other schools break

3886-475: The southern hemisphere experiences summer from December to February. The Julian year, as used in astronomy and other sciences, is a time unit defined as exactly 365.25 days of 86,400 SI seconds each (" ephemeris days "). This is the normal meaning of the unit "year" used in various scientific contexts. The Julian century of 36 525 ephemeris days and the Julian millennium of 365 250 ephemeris days are used in astronomical calculations. Fundamentally, expressing

3953-512: The start of the fasting month of Ramadan . A Muslim calendar year is based on the lunar cycle. The Jewish calendar is also essentially lunar, except that an intercalary lunar month is added once every two or three years, in order to keep the calendar synchronized with the solar cycle as well. Thus, a lunar year on the Jewish (Hebrew) calendar consists of either twelve or thirteen lunar months. The vague year, from annus vagus or wandering year,

4020-408: The strictest sense and may violate the rule of being perpendicular to the regional stress field, due to local influences. This is a megascopic version of what may occur around porphyroblasts. Often, fine observation of foliations on outcrop, hand specimen and on the microscopic scale complements observations on a map or regional scale. When describing a foliation it is useful to note Following such

4087-413: The tables a day is 86,400 SI seconds long. Some of the year lengths in this table are in average solar days , which are slowly getting longer (at a rate that cannot be exactly predicted in advance) and are now around 86,400.002 SI seconds . Foliation (geology) Foliation in geology refers to repetitive layering in metamorphic rocks . Each layer can be as thin as a sheet of paper, or over

SECTION 60

#1732776491339

4154-709: The very early Earth. These iron formations may be one of the oldest fingerprints of life, indicating that there may have been biological activity at the time that the NGB was being formed. A controversial paper published in March 2017 reported evidence for early life in these rocks. The paper describes putative fossilized microorganisms. The structures seen are interpreted as hematite tubes, and filaments, similar in morphology and size to those produced today by bacteria living in subsea hydrothermal vents . Several detailed microstructures, both shape and chemical makeup match modern structures. Collectively these multiple observations led

4221-460: The wall rocks. Lavas may preserve a flow foliation, or even compressed eutaxitic texture, typically in highly viscous felsic agglomerate , welded tuff and pyroclastic surge deposits. Metamorphic differentiation, typical of gneisses , is caused by chemical and compositional banding within the metamorphic rock mass. Usually, this represents the protolith chemistry, which forms distinct mineral assemblages. However, compositional banding can be

4288-560: The world"), used for the Hebrew calendar and abbreviated AM; and the Japanese imperial eras . The Islamic Hijri year , (year of the Hijrah , Anno Hegirae abbreviated AH), is a lunar calendar of twelve lunar months and thus is shorter than a solar year. Financial and scientific calculations often use a 365-day calendar to simplify daily rates. A fiscal year or financial year

4355-454: The year into two main semesters, a first (typically August through December) and a second semester (January through May). Each of these main semesters may be split in half by mid-term exams, and each of the halves is referred to as a quarter (or term in some countries). There may also be a voluntary summer session or a short January session. Some other schools, including some in the United States, have four marking periods. Some schools in

4422-680: The year of the Lord". The Greek word for "year", ἔτος , is cognate with Latin vetus "old", from the PIE word *wetos- "year", also preserved in this meaning in Sanskrit vat-sa-ras "year" and vat-sa- "yearling (calf)", the latter also reflected in Latin vitulus "bull calf", English wether "ram" (Old English weðer , Gothic wiþrus "lamb"). In some languages, it is common to count years by referencing to one season, as in "summers", or "winters", or "harvests". Examples include Chinese 年 "year", originally 秂 , an ideographic compound of

4489-411: Was used to establish an age of 4321 Ma for the Nuvvuagittuq Greenstone Belt. This was accomplished by dating intruding gabbros and measuring neodymium isotope fractionation in less-deformed members of the Ujaraaluk unit. The age of 4321 Ma would make the Nuvvuagittuq Greenstone Belt the oldest known rocks on Earth. In 2012, further studies of detrital zircons taken from quartz – biotite schists in

#338661