quaternary environmental change in the Vale of pickering, Yorkshire, England

Laboratory Report submitted as an integral part of the assessment of Geography Course GG2041 (Environmental Change), Department of Geography, Royal Holloway University of London, March 2014

A 7multi-proxy reconstruction of the Holocene’s environmental history in StarCarr

Candidate Number: 1400342

Word Count: 4320

Abstract

A multi-proxy environmental record for the Late Glacial and early Holoceneperiod, including pollen, plant macrofossil and stratigraphy data, is describedfrom a site at the Vale of Pickering, Yorkshire, UK. The methods are outlinedand the results are described. Thereafter these are interpreted in relation toquaternary environmental change. In doing so, the processes and climaticpatterns responsible for such changes are outlined. The major changes in theenvironment are compared to wider global climate change experienced in theNorthern Hemisphere during the Holocene. Findings include a period of warmerconditions recorded shortly after the last glaciation. Thereafter, coolingtakes place at about 12,500 Cal yrs BP, probably the result of the Youngerdryas. Finally, temperatures rise again at the beginning of the Holocene(11,500 Cal yrs BP). The characteristic of the landscape including those ofPalaeolake Lake Flixton are described at each stage and connections to climateand environmental processes are made.

Contents Page

Chapter 1: Introduction p1 & 2

Chapter 2: Methodology p2 & 3

Chapter 3: Results p3-13

Chapter 4: Data interpretation p14 & 15

Chapter 5: Conclusion p16

References p17

Appendices p18

Introduction

The Vale of Pickering is a gently undulating, low-lying basin renowned for thearchaeological site of Star Carr (Williams 2012). This site is of internationalsignificance for its completeness of record of human habitation. The Vale ofPickering also represents a very valuable site for the study ofpaleoclimatology. Different environmental proxies used for reconstructing pastclimates are found in the sediment stratigraphy records. This is possible dueto the exceptional preservation materials experience buried in anoxicconditions. For this reason Star Carr is very suited to study past variationsin climate and the environment.

The site of study is located in North Yorkshire, England, as can be seen in themap below. In the present day, the Vale of Pickering landscape is one of riversand wetlands which have been artificially drained for farming and for water control management purposes. This includes straightened and embanked channels,

arable land, grain production and some livestock (Williams 2012).

During the late glacial and early Holocene the area was dominated by a seriesof lakes. Palaeolake Lake Flixton used to be nearby the Vale of Pickering andtherefore is the most relevant for this study. The sediments collected in andaround this lake have become a tool to learn about the evolution of the Englishlandscape in times of deglaciation.

The study and reconstruction of past climates and environments represents agreat part of the literature written on the subject of paleoclimatology. Moreprecisely, it is the transition during the last cold stage to the presentinterglacial which has become a central theme in quaternary research (Walker etal 2002). In Britain, attempts to obtain high quality, continuous records haveprimarily taken place on former lakes where late glacial sediments are exposedor available through core digging (Walker et al 2002).

This is the case for Lake Flixton and the Vale of Pickering, site which hasalready been subject of research. For example, Barry Taylor (2011) produced adated record of Lake Flixton’s environmental change during the Mesolithic usingcore logging and macrofossil records. However, the present paper providespollen and macrofossil records as well as stratigraphy description andinstrumental techniques. The latter allows us to describe the sediment in termsof its magnetic field and carbon content (Low et al 1997). This informationmakes conclusions on lithostratigraphy more reliable. In addition, similarly toJ.J Lowe et al (1999) and Walker et al (2002) this paper aims to produce anenvironmental record from the Late Glacial through to the later Holocene. The

Figure 1 ‘Ancient’ Vale of Pickering Map. From Taylor (2011)

environmental sequence produced from Star Carr will be the tool through whichto achieve this.

The objectives of this paper are to investigate the stratigraphical record of shallow and deep lake cores, compare this data and produce a chronology for therecords; and finally, compare this to wider palaeoenvironmental and archaeological evidence with the ultimate purpose of understanding environmental change in England.

As Walker et al (2002) points out, the research undertaken in quaternaryscience and thereby this paper is more relevant than ever before becauseatmospheric scientists turn to late glacial records to better understandnatural analogues of climate change. This is done under the purpose of applyingthis knowledge to present climatic change and therefore better understand itspace and consequences.

Methodology

Lithostratigraphy

Each group was assigned a 50cm long section of the 7 meter long core extractedfrom Star Carr. To begin with the core was carefully unwrapped of its plasticfilm and cleaned using a scalpel. Thereafter the core was classified intohorizons. The boundaries were selected where there were significant changes insediment colour or texture. In order to interpret the sediment’s texture small1cm by 1cm cubes were extracted from each boundary using the scalpel. Thesewere analysed for particle size, dryness and elasticity. To address the colourof the soil a Munsell colour book was used.

A full core stratigraphy diagram was developed following the data from eachcore. Stratigraphy is extremely important for our research purpose as allother techniques used material taken from different stratigraphic levels fromthe sampled borehole.

The advantages of this method are: It provides the researcher with an insightto the formation processes of the environment, such as depositional rate. Inaddition, the study of the sediment properties enforces this understanding andallows placing boundaries of environmental shift in the landscape. Theweaknesses of this method include the low availability of long, undisruptedcores; and these may be distorted during recovery or extrusion from thesampling chamber, in particular in looser sediments (J.J Lowe et al 1997). Inaddition, having only extracted one borehole, it is more difficult to ascertainthe history of a site.

Magnetic Susceptibility

Cores were passed through a magnetic susceptibility loop at 3cm intervals andthe values were recorded for each interval. This method allows us todifferentiate between buried soils and windblown silts, which would not becharacteristic of the site of study. More broadly, it serves as a tool toindicate changes in sediment composition for magnetic-susceptible minerals.

Loss on Ignition

On this practical samples from each core were analysed for organic andinorganic carbon content. A 1cm by 1cm cube was extracted 4 cm into the core,and further samples were collected in 8cm intervals. The samples were firstweighed to determine the total weight. Then they were placed in a furnace wherecarbon was combusted and thereafter reweighed to determine the loss of organiccontent. This determines the ratio of organic to inorganic sediments in thesample. In addition, it is useful for our research purposes as organic contentis a measure of biological productivity which in turn depends on the characterof the environment (J.J Lowe et al 1997).

Pollen Analysis

Pollen analysis is one of the principal techniques used by quaternaryscientists to reconstruct past environments. Pollen-Stratigraphical resultshave greatly shaped ideas on the nature of the environment and climate duringthe quaternary glacial-interglacial cycles (Seppa 2007).

For the present paper, pollen recovered from the Vale of Pickering sedimentswas chemically treated to remove cellulose and organic material. Thereafter itwas prepared for slide analysis. Slides were distributed and analysed bycounting and classifying pollen grains. General size and shape, aperture,configuration and surface texture were looked for. Finally, a pollen diagramwas produced plotted on the basis of % of each major taxon per level.

There are some limitations with this method. Firstly, wind pollinated speciesproduce more pollen so they dominate the quaternary record. Secondly, thespread of airborne pollen results in difficulty to know whether small portionsof a given pollen grain represent a small group of plants from a local area ora larger population growing further away (Seppa 2007). In addition, the lack oftaxonomic precision weakens the quality of palaeoenvironmental reconstructions.

The main advantage of this method is that it provides with an Insight into longterm ecological patterns and processes such as dispersal dynamics anddistribution variations in tree species. In addition, layers of sediment laiddown annually leave high-resolution records. Moreover, under anoxic conditions,due to the hard and chemically resistant exines, pollen grains remain wellpreserved.

Macrofossils

Macrofossils are best preserved in low energy environments and are most oftenstudied from lakes or peat sediments (Birks 2007). The study of macrofossilsworks as a complimentary or alternative tool for studying past environments.These can be seeds, fruits, vegetative parts and animal remains (particularlyinsects) (Birks 2007).

Firstly, 4cm³ samples were taken and sieved through a 125µm sieve using 5litres of water, into a clean washing up bowl. Thereafter, the remaining plantmatter was transferred to a petri dish, which was placed under a low magnifyingmicroscope lens and analysed for macrofossil remains.

This method is useful for our research purpose because it provides withreliable data at the local level as macroremains are relatively heavy. Inaddition, these can be identified to a higher taxonomic resolution than pollen(Birks 2007). Similarly to pollen, with the assumption these species have thesame ecological requirements they do today, we can interpret what the climatemust have been like to support them. Disadvantages include under and overrepresentation of species due to their capacity to produce seeds and theirposition in the landscape (i.e species near a lake may have more data thanthose growing further away).

Age Modelling

Radio carbon dating works on the basis of measuring 14C isotope half-lives.Samples used for radiocarbon dating were identified macrofossil samples fromterrestrial species removed from the core and cleared of contamination. Thesesamples represent 5cm core intervals. This method is very useful for ourresearch because it allows us to date the changes in the environment that wesee through the use of the other methods. By dating these changes we can relatethem to other chronologies found in the wider literature. In doing so, if theevents from our records match the main geological records our conclusionsbecome more reliable.

Results

Stratigraphy: Depth, Colour and ComponentsFigure 2 Troels-Smith classification of sediments

Depth (cm) Colour/Main Components

220-225 BrownishBlack

Tb2/th2

225-250 BrownishBlack

Th3/th1

250-260 Brownish Th4

Depth (Cm)

Black260-293 Black Sh2/Th2

293-295 Olive Brown As3/Lc1

295-297 Dark GreyishBrown

As3/Ag1

297-300 Olive Brown As4


Lc4

302-305 Darkyellowish

Brown

As4

305-310 Very darkyellowish

brown

Lc4

310-315 Light olivebrown

As3/Dh1

315-325 Brown As4

325-330 Olive Brown Lc3/Dh1

330-332 LightYellowish

Brown

As3/Lc1

332-340 Olive Brown Ld3/Lc1

340-342 Olive Brown Th4

342-344 Black Lc4

344-350 Greyish Brown Ld2/Lc2


Lc3/Ag1


As2/Ag2

364-366 Dark Grey As3/Ag1



400-420 Dark Grey As4

420-430 Brown As3/Gg1

2.5Y 3/2 DarkGreyish Brown

As4


As3/Lc1

2.5Y 3/1 VeryDark Grey

As4

10Y 4/4 Dark Yellowish Brown

As2/Lc2

2.5Y 3/2 VeryDark Greyish

Brown

As4

2.5Y 4/1 DarkGrey

Ag3/As1

5Y 3/1 Very DarkGrey

Ag3/As1


Ag3/As1

5Y 3/2 Ag4

5Y 2/2 As4


Ag3/Lc1

5Y 4/2 Olive Grey Ag2/Lc2

5Y 4/1 Dark Grey Ag3/Lc1


(580cm)

Ag2/Lc2


Ag3/Lc1

(585cm)

2.5Y 4/4 OliveBrown (590cm)

Ag2/Lc2

Lc2/As2

As4

Lc2/As2

Lc3/As1

As2/Ac2

Th4

As4

Lc4

As2/Lc2 (675-676cm)

As4 (676-680cm)

As2/Lc2 (680-687cm)

Lc3/As1 (687-690cm)

As2/Lc2 (690-697cm)

As4 (697-710cm)

10 YR 4/3 Brown

As4

2.5 Y 2.5/1 Black

Lc3/As1

5Y 2.5/1 Black

As2(Lc2

10YR 4/3 Brown

As4

2.5/N Black Lc4

2.5Y 3/3 Dark Olive Brown

As4

2.5/1 Black Lc4

10YR 2/1 Black

Lc4

10YR 2/1 Black

As2/Lc2

10YR 5/4 Yellowish Brown

Lc3/As1 (858-870cm)

25Y 4/2 DarkGreyish Brown

Lc4 (870-895cm)

10YR 2/1 Black

Lc4 (895-906cm)

10YR 4/1 Dark Grey

Lc4 (906-910cm)

Description

First two and a half meters are predominantly composed of turfa material. Inthe first 150cm some substantia humosa is present, usually combined with turfa.The following 2 meters or so are mainly composed by a mixture between clays andsilts and limus calcareous (marl). Between 310 and 33cm there are somefragments of herbaceous plants. Sediments from 420cm to 460cm are almostentirely composed of clays. From 460cm to 500cm there is a decrease of clays infavour of silts. At this point, silts together with some marl dominate thesediment record. From 580cm to 600cm the concentration of clays increases,however at around 600cm marl raises and these two become the major componentsof the sediment record until 640cm. Shortly before 640cm there is a briefperiod dominated by humus substances. Thereafter the record becomes dominatedby marl until 675cm, where clays increase again. From this point to 697cm thereis a mixture of clays and marl. Beyond this depth clays briefly prevail until710cm, where once again the sediment becomes a mixture of clays and marl. From740cm to 820cm the sediment composition varies between levels dominated byArgilla and levels dominated by Limus. Thereafter, these elements mix until870cm; where Limus materials become the prevailing sediment down to the end ofthe record at 910cm.

Loss on Ignition, CaCo3 and Magnetic susceptibility

Description Magnetic Susceptibility

Between 1 and around 3.5 meters magnetic susceptibility in the core remainsvery stable with few variations. At a depth of 3.7 meters, it slightlyincreases to about 5%. Thereafter it gently fluctuates between 5 and 10% untilabout 5.3 meters where it increases more abruptly to 15%. Following on there isa rapid decrease followed by an equally fast increase followed by anotherdecrease, ending around 5.8 meters. The value stabilises briefly until 6 meterswhere, for a very short core length raises and falls stabilising at about 5%.At the 8 meter mark there is a very pronounced, short lived increase to over20%. After decreasing, MS raises at about 8.8 meters to extremely high levels.This once again is very short lived as it quickly decreases to normal valuesaround 10%.

Description CaCo3

Carbonate content in sediments begins around 2.9 meters, shortly before LOIreaches the 0% mark. Carbonates quickly rise to almost 100% around 3 meters.

Description Loss on Ignition

In the first 2 meters around80% of the weight is lossafter the samples were burntin the furnace. From 2 toaround 2.7 meters loss onignition gradually decreasesto 60%. Thereafter LOIexperiences a steep, quickdecrease to 0% finalising atthe 3 meter mark.

Figure 3 % LOI/CaCO3 and MS

Depth (M)

There is a pronounced, short lived decrease at about 3.4 meters to about 30%,followed by a quick increase to around 90% followed by another abrupt fall;this time to 20%. At this point carbonate content slowly increases between 4and 6.9 meters and in doing so it constantly fluctuates up and down. At thedepth of 7 meters carbonate content rapidly falls and increases once again,becoming fairly stable with small fluctuations until about 8.5 meters. Here itexperiences a rapid decrease to minimum levels followed by a short lived riseas it falls once again around the 9 meter mark.

Pollen (See Pollen diagram below)

Zone 1: From 900cm to 800cm, this zone is characterised by a large yetfluctuating presence of Poaceae grass. There are also important and steadylevels of Cyperaceae sedges and Betula trees. Herbs populate the landscape toless extent but still to significant levels (Artimisia, Rumex).

Zone 2: From 800cm to 540cm, the biozone is characterised by the dominance ofherbaceous taxa and rise of new taxa. Furthermore, Betula is present insignificant amounts but it rapidly decreases between 720cm and 660cm where itrises again. Pine tree is present in low but consistent frequencies. Shrubs andaquatic species appear for the first time in significant numbers but theyfluctuate and disappear towards the borderline with zone 3. Similarly,Filipendula, Populus and Juniperus are introduced in the landscape but decreaseshortly after.

Zone 3: From 540cm to 360cm, the landscape is very much dominated by grasses andherbaceous taxa. There are fewer types of taxa present in the landscape. Pineagain remains fairly stable whereas other taxa like Betula and Cyperacea varyin different amounts.

Zone 4: From 360cm to 240cm. The abundance of open habitat taxa comes to an endwith Poacea and Cyperaceae suffering important decreases and fluctuating duringthe record. Artemisia and Caryophyllaceae disappear whereas Filipendula andsome semi aquatic species increase their numbers. The main characteristic ofzone 4 is the increase and dominant presence of Betula and Pine woodland. Inaddition, Juniperus and Salix once again raise to meaningful numbers as so doesPopulus. This builds a landscape which is predominantly consisting of woodland.

Zone 5: From 240cm to 150cm. Zone 5 is marked by the fall in Betula and Pinusand the raise in Alnus and other new tree species. These include Corylus, Ulmusand Quercus. In addition, there is an important increase in Corylus towards theend of zone 4, and these new high concentrations remain fairly stable duringzone 5. Sedges experience a rise in Cyperaceae whereas grasses, especially forPoaceae, remain poor. Between zone 4 and 5 Typha latifolia appears in theenvironment for its first and last time, disappearing around 180cm. Dryopterishowever, raises once more and stays in the landscape until the end of thesequence.

Z6: From 150cm to 0cm. Poaceae, early impoverished, increases and Cyperaceaewhich was abundant now falls. Ulmus, although still present in the landscapestarts to decrease alike Corylus. Quercus, Filipendula and Dryopteris fluctuateacross the record. Moreover, Plantago Lanceolata flourishes for its first timein the landscape where it occupies over 10% of the pollen grains over most ofzone 6.

Figure 4

Depth (Cm)Z= Pollen Zone

Values expressed as % of Total Land Pollen

Macrofossils (see diagram below)

Although subject to fluctuations, herbaceous components dominate the record.However, organic matter practically occupies the entire record during the first50cm. Thereafter, alike the other components it is subject to variation. Insectremains are predominantly found between 400 and 650cm. Chironomid Sergentia-type is present at the end and towards the middle of the record. Chironomusanthricinus-type rises when the latter falls around the end of the record andonce again above 425cm. This leaves a gap between 400 and 550cm which isdominated by Paradadius type. Aquatic macrofossils are present in two clearsections of the core. These are between 700 and 625cm and between 400 and225cm.

0 50

100

150

200

250

300

350

400

450

500

550

600

650

700

Depth (cm)

020

4060

801000

2040

020

4060

801000

2040

020

020

400

020

00

00

020

00

00

2040

00

00

020

00

020

020

0

Comp

onent d

ataTre

esShrub

s and

herbs

Aquat

icsInsect

sCh

ironom

ids

Figure 5 Macofossil record Vale of Pickering

Values Expressed as % of TotalLand Macrofossil

Values expressed as individual fossil remains

Code 14-C error depthCal Max BP95% Cal Min BP 95%

Geological period (FromJJ Lowe 1999)

OxA-32000 200 35 2 307 4

Flandrian

OxA-32001 1100 35 21 1070 932

OxA-32002 2000 35 25 2041 1874

OxA-32003 3800 40 76 4405 4008

OxA-32004 5400 40 97 6293 6020

OxA-32005 6000 40 100 6945 6741

OxA-32006 6690 40 110 7650 7479

OxA-32007 7450 40 200 8361 8186

OxA-32008 8300 45 228 9436 9136

OxA-32009 9300 45 314 10651 10298

OxA-32010 10000 45 360 11705 11270

OxA-32011 10200 50 400 12086 11709 YoungerDryascoolingOxA-32012 10300 50 560 12386 11836

OxA-32013 11020 50 600 13090 12706

OxA-32014 11200 50 700 13260 12904

Bølling-Allerød

interstadial

OxA-32015 12000 50 720 14000 13734

OxA-32016 12600 50 810 15198 14266

OxA-32017 13000 60 895 16315 15134

End of glaciated age

Radiocarbon dates

The following are the radiocarbon dates obtained from the sediment profile which was used for pollen investigation. Samples used for dating were identified macrofossil samples from terrestrial species. The record goes as far back as 16315 Cal (Max) years BP.

Data interpretation

After having observed the results, the following chapter will go through themain findings. This analytical work is the core of the report as it will givemeaning in the background of quaternary science to the results. In order to doso the environmental record produced has to be studied and data from allmethods has to be linked to produce the larger picture of what environmentalchanges took place, when they did and what were the driving forces involved. Inaddition, these changes observed in the results will be compared to the widerliterature on quaternary climatic change.

To begin with, major global climate change events such as the younger dryas andthe Allerod interstadial (Figure 6) should affect the landscape at the Vale ofPickering. Therefore, according to the radiocarbon dates this should bereflected in our record by an initial warming around 8 meters, followed bycooling at 6 meters and warming from 4 meters onwards.

Evidence from the core suggests that earlier sediments (9 to 8 meters) werecharacteristic of a landscape composed by open habitat taxa with some woodland;predominantly pine and some birch (figure 4). This suggests a colderenvironment which didn’t support the wide range of species which habitat theecosystem on more recent times. Pine dominates the tree species at this stage.According to the British and Irish atlas of flora, it grows in relatively coldenvironments, with average summer temperatures of 11.7 °C and winter averagetemperatures of 0.8 °C. Sediment composition during this period is almostentirely made of marl. This is reflected by increasing values of CaCo3 infigure 3. This suggests the presence of a lake, which Taylor (2011) suggested,was formed after the retreat of glaciers. In addition, magnetic susceptibilityabruptly increases around 9 meters and quickly stabilises. This could suggestan increase in soil erosion resulting in a large transfer of minerogenicmaterial; process which is common in cold environments where processes of soilbreakdown are more vigorous (JJ Lowe 1997).

As we approach the 8 meter mark sediment composition varies from marl to clayand back to marl. Under the presence of aquatic taxa this suggests two things,firstly, material low in organic content is being washed into a waterbody andsecondly, pondweeds such as Potamogeton, which appears around this core depth,precipitate lime and marl, hence the high marl content (JJ Lowe 1997). In

addition, magnetic susceptibility increases around this level of the core, thusreinforces the idea of inorganic material being carried into the water. Furthermore, the pollen diagram suggests warmer conditions represented by anincrease in Betula, Populus and particularly Juniperus, which tends to be thefirst coloniser when temperatures become warmer (Walker et al 2003). Thereforesome tree species would have expanded to sites previously occupied byherbaceous taxa. This, together with the gentle decrease in Artemisia, speciesthat is encouraged by disturbed landscapes; points to the direction of a morestable and developed soil supporting a wider range of taxa during a warmerperiod of time. This could be representative for the beginning of the Bølling-Allerød interstadial.

Between 7 and 6 meters sediments continue to vary between clays and marls. Theshort lived Turfa Lignosa material in the record (639cm) could be the result ofa warmer more productive environment. The macrofossil record supports this withan increase in organic matter and wood. In addition, the presence of Characeaecospore indicates the continuity of the water system. For vegetation, there isa short-lived decrease in trees (Betula, Alnus, Salix). During this shortperiod (around 660cm) Empetrum increases, a shrub which grows well after forestfires; and there is a presence of charcoal both in the pollen and macrofossilrecord. Therefore a fire could have caused a decrease in certain taxa, some ofwhich recovered shortly after.

Around six meters herbaceous taxa begins to rise (Poaceae, Filipendula,Taraxicum). This appears in the macrofossil record too. The presence of Rumexand the increasing frequency of grasses suggests the landscape began to open upand there was a loss in woodland. The significant loss of Betula at 550cmsupports this, and similarly, other tree species become less abundant ordisappear. This is most likely the result of cooling climate. Moreover, thedisappearance of aquatic species in the pollen and macrofossil record inclinesthe environment to colder and dryer conditions. The stratigraphic record showsa shift from predominantly clay to silt (600/480cm). This may represent thesilting or infilling of the lake hence the disappearance of aquatic taxa.

Furthermore, higher erosion should follow colder conditions however; magneticsusceptibility only varies very slightly and does not seem enough to supportthis. Nevertheless, a drop in temperature is definitely supported by evidencecoming from other proxies. Besides pollen it is also supported by macrofossildata; according to Van Asch (2012), the introduction of Chirominid Paracladiussuggests a reduction in temperatures. This is the case for our core at 575cm(figure 5).

This cooling event could be the consequence of the Younger dryas, whichaccording to the GRIP record began around 12,560 years ago (Walker et al 2003).This matches the radiocarbon dates for the described period of cooling (figure6).

The period of colder conditions comes to an end around 350cm into our core.This translates to about 11,500 Cal years BP (Figure 6) thus it corresponds tothe beginning of the Holocene set at around 11,400 years BP according to Walker(2003). The lithological changes involve a higher presence of detritus materialin comparison to the older records. This may be the result of a higherbiological productivity set by higher temperatures. There is also a trendtowards marls, perhaps suggesting the return of an aquatic environment (Taylor2011). This is supported by the pollen and macrofossil records. Firstly,frequency of Potamogeton and Typha latifolia (Figure 4) increases tosignificant levels. Secondly, the concentration of Characeae oospores risesaround the same depth (Figure 5).

Similarly to the warmer period before the Younger dryas, an increase inwoodland cover around 3 meters leads to the subsequent loss of grass andsedges. This resembles the succession pattern reconstructed in Walker et al(2003) from Llanilid, Wales. Nevertheless, macrofossil data suggest woodlandcover was low until about 225cm and herbaceous taxa dominated the landscape atthe depth of 300cm (figure 5). This is in conflict with the data from thepollen record and therefore makes it harder to establish an accurate core depthor time line for vegetation succession. Nevertheless, macrofossils can be lessreliable as they do not often preserve as well and there is a smaller recordcompared to pollen.

Magnetic susceptibility throughout the Holocene remains stable and low. Thiscould be the result of less erosion of minerogenic materials and a higheruptake by plants (JJ Lowe et al 1997). In addition, a more stable environmentwould also contribute to these values.

Between 3 and 2 meters the water system experiences a new infilling, this timeby humus substances or peat (Figure 2 and Figure3-LOI). The succession processis reflected by the disappearance of aquatic taxa and its replacement by Typhalatifolia, which grows best in swamps and fens (OABIF 2014). Thereafter, around2 meters, Typha latifolia disappears. This is probably due to the swampbecoming further in filled with peat making the habitat no longer suitable.Macrofossils, LOI and stratigraphy corroborate an increase in organic content.This is supported by Taylor (2011) study of Lake Flixton during the Mesolithic,where he argues “an environment of open water existed at the site until 8700Cal BC, when the transition to organic sediments marks the point when aquaticand emergent plants began to colonise the area”.

Nevertheless, whether these changes are of climatic importance or merely theresult of succession processes is difficult to establish.

Finally, similar conditions prevail until the beginning of the core. These arepredominantly high organic, rich soils supporting a variety of tree species,mainly Alnus, Quercus and Corylus; and some open habitat taxa including

grasses, perennial herbs and some ferns. In addition, according toarchaeological evidence, at this point humans would have lived in the landscapeand exerted an influence upon it. This may be reflected by the regular amountsof charcoal in the pollen record.

Conclusions

In conclusion, the main findings are 4 periods of climatic shift. Firstly,there is an initial warming shortly after the last glacial which according tothe records coincides with the Bølling-Allerød interstadial, supported by theradio carbon dates between 8 and 7 meters. Thereafter, there is a coolingassociated to the Younger dryas where the landscape loses woodland in favour ofopen taxa and the watercourse may become infilled, dried out or no longersuitable for aquatic vegetation. Radio carbon dates corroborate the timescaleat which this occurs (11,500 BP). Following on, the climate becomes warmeragain marking the beginning of the Holocene. At this point the vegetationexperiences a shift in woodland composition by introducing Quercus and Ulmus,and aquatic species return suggesting wetter or/and warmer conditions. Thesehowever are brought to an end as the lake fills with peat and plants begin tocolonise the area (Taylor 2011).

Further research on the Vale of Pickering could include the extraction of morethan one core to increase the reliability, accuracy and scope of the results.In addition, macrofossil data for the entire core would have proven useful inthe study of the oldest sediments.

References

-H H Birks (2007) Plant Macrofossils introduction, University of Bergen, Norway

-H Seppa (2007) Pollen Analysis, Principles. University of Helsinki, Finland

-J.J Lowe and MJC Walker (1997) Reconstructing Quaternary Environments 2nd Edition

-J.J Lowe, H.H Birks, S.J Brooks, G.R Coope, D.D Harkness, F.E Mayle,C.Sheldrick, C.S.M Turney and M.J.C Walker (1999) The chronology ofpalaeoenvironmental changes during the Last Glacial-Holocene Transition: Towards an event stratigraphyfor the British Isles. Journal of the Geological Society, London, Vol 156 pp 397-410

-Mike Williams, Nancy Stedman and Robert Goodison (2012) Vale of Pickering ProfileAccessed from [www.naturalengland.org.uk ] Last accessed 9th March

-M.J.C. Walker, G.R. Coope, C. Sheldrick, C.S.M. Turney, J.J. Lowe, S.P.E.Blockley, D.D. Harkness (2002) Devensian Lateglacial environmental changes in Britain: a multi-proxy environmental record from Llanilid, South Wales, UK. Quaternary Science Reviews 22

- Nelleke van Asch, Arthur F. Lutz, Miriam C.H. Duijkers, Oliver Heiri, StephenJ. Brooks, Wim Z. Hoek (2012) Rapid climate change during the Weichselian Lateglacial inIreland: Chironomid-inferred summer temperatures from Fiddaun, Co. Galway. Palaeogeography,Palaeoclimatology, Palaeoecology

-Online Atlas of The British and Irish Flora (OABIF) (2014) [Availableat:http://www.brc.ac.uk/plantatlas/] Last Accessed 11th March.

Appendices

Vegetation Data Table produced from The Online Atlas of The British and IrishFlora

GenusName

Mean temp January

MeanTempJuly

Annual Precipitation

Category

Other information

Alnus 3.5 14.5 1100 Deciduous Tree

Seedlings drought and shade sensitive, little regeneration on woodland

Betula

3.3 14.6 1073 Deciduous Tree

rapidly colonise open ground, particularly burned areas

Fagus 3.5 14.7 1061 TreeFraxinus


It can tolerate periodically waterlogged soils, rapid coloniser of waste ground

Pinus 0.8 11.7 1930 Conifer Tree

It prefers sandy and stony, acidic soils, though will also grow on waterlogged peats.

Populus

Broad Habitat

tree grows by watercourses, by ponds and in hedgerows, especially on lowland flood plains

Quercus


high forest, coppice woodland

Tilia 3.5 15.5 873 Tree occurs mostly in mixed deciduous Quercus orFraxinus woodland

Ulmus 3.4 14.7 1056 Tree of hedges

field-borders and streamsides, also in woodland

Calluna

3.5 14.3 1157 Low Shrub

heaths, moors and nutrient-poor grasslands, open woodland, can colonise newly available habitat,ranging from dry exposed habitats to wet peat bogs

Corylus type

3.5 14.6 1094 deciduous shrub

Empetrum

2.7 13.2 1381 evergreen shrub

it can increase greatly after burning or wheredry surfaces have been bared by erosion

Prunus Type

3.4 14.8 1024 Small fruit tree

Juniperus

2.8 13.4 1380 dioeciously evergreen conifer

wide range of habitats,in Betula, Quercus and Pinus woods

Salix 3.7 15.1 938 conspicuous tree

grows in marshes and wet hollows and by ponds,ditches, streams and rivers

Sorbus

Broad Habitat

shrub orsmall tree

Cyperaceae

Broad Familyspecies

Sedge

Poaceae

Broad Familyspecies

Grasses

Artemisia

3.7 14.9 984 perennial herb

Caryophyllaceae

Broad Habitat

Herbaceous plants

Asteraceae

3.5 14.5 1105 herbaceous flowering plant

Broad Family species (This is for Daisy)

Apiaceae

4.0 15.0 989 Perennial Herbs

Broad Family species, Broad Habitat(This is for Carrot)

Adoxa 3.3 14.9 1005 perennial herb

on the shaded banks of rivers and streams, in deciduous woodlands and shaded hedge banks

Chenopodium

3.4 15.2 883 Weed, Vegetable

Broad Family. Annuals of disturbed, nutrient-rich habitats

typeFilipendula

3.6 15.8 776 Herb/Flowering plant

Polygonum

Broad Habitat

Herbaceous plants

Plantago Lanceolata

Broad (3.5)

14.5 1105 perennial herb

It occurs in meadows and pastures, in upland grasslands,sand dunes and cliffs (Broad)

Ranunculus

Broad Habitat

perennial herb

Broad Habitats, Broad Family. Some prefer slightly warmer conditions (aroudn 4 and 16 like Ranunculus sardous and tripartitus)

Rumexundiff

Broad Habitat/Family

Perennial herb

Some grow on disturbed grounds, river banks, streamsides and lake shores, open grasslands

Taraxicum

Broad Habitats

perennial herbs

prefer disturbed sites such as pastures, roadside verges, lawns, tracks, paths and waste ground

Tulipa Sylvestris

Broad Habitats

Perennial herb

perennial herb of open woodlands, hedgerows, riversides. Plants often flower poorly and setlittle seed, but populations can be very long-lived

Urtica

3.6 14.5 1102 perennial herb

wide range of habitats, woods, scrub, grasslands, fens, It prefers damp, nutrient-rich soils.

Crassulaceae

No information

Flowering plant

typically in dry and/or cold areas where watermay be scarce

Myriophyllum

3.8 15.7 765 (Aquatic) perennial plant

Most species grow in wide range of meso-eutrophic or eutrophic and often calcareous waters. These include lakes, ponds, rivers, canals and ditches

Potamogeton

3.4 15.9 697 (Aquatic) perennial plant

lakes, sluggish rivers, ditches, fens, marsh, pond weed

Typhalatifolia

3.8 15.1 958 rhizomatous perennial

growing in shallow water or on exposed mud at the edge of lakes( Fen, marsh and swamp (not wooded))

Dryopteristype

3.5 14.5 1096 DecidousFern

Broadleaved, mixed and yew woodland (250 species)

Polypodium

Broad Habitats

perennial rhizomatous fern

Thelyptris

3.9 15.5 869 perennial fern

Broadleaved, mixed and yew woodlandFen, marsh and swamp (not wooded), soil is

permanently wet and organic

quaternary environmental change in the Vale of pickering, Yorkshire, England

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