Taphonomy of insects in carbonates and amber

46 Pages·2004·2.09 MB·English

Palaeogeography, Palaeoclimatology,Palaeoecology 203 (2004)19^64
www.elsevier.com/locate/palaeo
Taphonomy of insects in carbonates and amber
Xavier Mart¤|nez-Delclo'sa, Derek E.G. Briggsb;(cid:1), Enrique Pen‹alverc
a Dept. Estratigra¢a, Paleontologia iGeocie'nciesMarines,Fac.Geologia,Universitat de Barcelona, 08028Barcelona,Spain
b Department of Geologyand Geophysics, Yale University, P.O.Box208109,New Haven,CT 06520-8109, USA
c Institut Cavanilles de Biodiversitat iBiologiaevolutiva, Universitat de Vale'ncia, Apart.2085Vale'ncia, Spain
Received15July 2002; receivedin revisedform 11August2003; accepted16September2003
Abstract
The major taphonomicprocesses that control insectpreservation in carbonaterocks (limestones, travertines and
nodules)arebiological: insectsizeandwingspan,degreeofdecomposition,presenceofmicrobialmats,predationand
scavenging; environmental: water surface tension, water temperature, density and salinity, current activity; and
diagenetic: authigenic mineralisation, flattening, deformation, carbonisation. The major taphonomic processes that
control the preservation of insects in fossil resins (amber and copal) are different, but can be considered under the
same headings ^ biological: presence of resin producers, size and behaviour of insects; environmental: latitude,
climate, seasonality, resin viscosity, effects of storms and fires, soil composition; and diagenetic: resin composition,
insect dehydration, pressure, carbonisation, thermal maturation, reworking, oxidation. These taphonomic processes
aregeographicallyandtemporallyrestricted,andgeneratebiasesinthefossilrecord.Nevertheless,whereinsectsoccur
theymaybeabundantandverydiverse.Taphonomicprocessesmayimpactonphylogeneticandpalaeobiogeographic
studies, in determining the timing of the origin and extinction of insect groups, and in identifying radiations and
majorextinctions.Taphonomic studiesarean essentialprerequisitetothe reconstructionoffossil insectassemblages,
tointerpretingthesedimentaryandenvironmentalconditionswhereinsectslivedanddied,andtotheinvestigationof
interactions between insects and other organisms.
: 2003 Elsevier B.V. All rights reserved.
Keywords: fossil insects; preservation; limestone; resin
1. Introduction their diversity through time have been reviewed
(Carpenter, 1992; Labandeira and Sepkoski,
Insects are by far the most diverse and success- 1993; Jarzembowski and Ross, 1996; Ross et
fulgroupofmacroscopicorganismsandtheyplay al., 2000; Jarzembowski, 2001b) as well as the
an important role in all the terrestrial ecosystems palaeobiology of insect feeding (Labandeira et
that they inhabit. The fossil record of insects and al., 1994; Labandeira, 1997). The earliest record
of the Insecta is from the Lower Devonian of
Gaspe¤ (Que¤bec) (Labandeira et al., 1988), but
* Corresponding author.Tel./Fax: [phone].
the group is not evident in the fossil record in
E-mail addresses: [email protected]
signi¢cant numbers until the Upper Carbonifer-
(X.Mart¤|nez-Delclo's),[email protected](D.E.G.Briggs),
[email protected] (E. Pen‹alver). ous (Brauckmann et al., 1995). The number of
0031-0182/03/$ ^ see frontmatter: 2003ElsevierB.V. All rightsreserved.
doi:10.1016/S0031-0182(03)00643-6
PALAEO32255-1-04
20 X.Mart¤|nez-Delclo's et al./Palaeogeography, Palaeoclimatology, Palaeoecology 203 (2004)19^64
insectorderspresentinthePermianwassimilarto sta«tten which preserve non-biomineralised tissues
that of now; the record of families identi¢es ma- are a critical source of palaeobiological data that
jor periods of origination in the Permo^Carbon- are not available from the ‘shelly’ fossil record
iferous, Early Jurassic, Early Cretaceous and Pa- (Briggs, 1995a). The preservation of delicate
laeocene (Jarzembowski and Ross, 1996). The structures allows for more detailed comparison
degree to which the recorded diversity of insects with recent organisms. The controls on the pres-
is a re£ection of taphonomic processes is very ervation of non-biomineralised tissues, so-called
di⁄cult to determine. A knowledge of the condi- soft-bodied fossils, are more complex than those
tions that led to the preservation of insect biotas, on shelly taxa, which are dominantly sedimento-
and of the biases introduced by taphonomic pro- logical (Kidwell, 1991) ^ they include organic
cesses, is also essential for interpreting the role of matter input, microbial activity, and environmen-
insects in terrestrial ecosystems, such as organic tal geochemistry (Allison and Briggs, 1991a,b;
matter recycling and the pollination and distribu- Briggs, 2003a).
tion of plant taxa. Here we review the major ta- Insect body fossils occur in a variety of envi-
phonomic processes that a¡ect insects. ronmental settings including peat deposits (Ken-
Insects lack biomineralised tissues and are usu- ward, 1976; Hayashi, 1994; Lavoie et al., 1997),
ally considered by palaeontologists as soft-bodied deserts (e.g. Chihuahuan Desert, USA, Quater-
organisms. Exceptional conditions are normally nary: Elias, 1990; desert sands Mauritania, Qua-
required to ensure their preservation, but where ternary, Azar pers. commun.), lakes and rivers
taphonomic processes are favourable, insects may (e.g. Montsec and Las Hoyas, Spain, Lower
be extremely abundant. However, there is clearly Cretaceous: Mart¤|nez-Delclo's, 1995; Mele¤ndez,
a signi¢cant range in susceptibility to decay, for 1995; Se¤zanneandAurioltravertines,France,Eo-
example between £ies and beetles, re£ecting con- cene: Nel and Blot, 1990; Papazian and Nel,
trasts in the degree of sclerotisation of the cuticle. 1989), deltas (e.g. Vosges, France, Middle Trias-
Nonetheless, laboratory experiments have shown sic: Gall, 1996; Marchal-Papier, 1998), lagoons
that even £y carcasses may survive in quiet sedi- (e.g. Solnhofen, Germany, Upper Jurassic:
mentary settings for more than a year without Malz, 1976; Frickhinger, 1994), open marine en-
disarticulating (Mart¤|nez-Delclo's and Martinell, vironments (e.g. northern Switzerland, Lower Ju-
1993). rassic: Etter and Kuhn, 2000), and deeper marine
The most exceptionally preserved insects in turbidites (e.g. Borreda', Spain, Eocene: Gaudant
sedimentary rocks occur in ¢ne-grained laminated and Busquets, 1996).The spatiotemporal distribu-
carbonates in lacustrine and shallow marine set- tion of these palaeoenvironments was a major
tings, where conditions may be suitable for the control on the insect fossil record.
preservation of truly labile soft-tissues (e.g. Soln- Where insects are preserved in calcium carbon-
hofen, Germany: Frickhinger, 1994). They pro- ate, precipitation may occur as calcite mud (e.g.
vide a basis for contrasting preservation with Green River, USA, Eocene: Ferber and Wells,
thatinamber.Thedi¡erent taphonomicprocesses 1995), aragonite mud (e.g. Rubielos de Mora,
that control the preservation of insects in carbon- Spain, Miocene: Pen‹alver, 1998), and dolomite
ate rocks and in amber result in samples of di¡er- mud (e.g. Karatau, Kazakhstan, Upper Jurassic:
entinsectcommunities.Ambernormallypreserves Seilacher et al., 1985). Fossil insects also are pre-
insects regardless of their susceptibility to decay, served in a variety of other sedimentary contexts:
but selective preservation is often a feature of in- clays and marls (Nel, 1986), siltstones (Mart¤|nez-
sect assemblages in carbonates. The occurrence of Delclo's and Nel, 1991), sandstones (Nel et al.,
insects is normally considered to identify a fossil 1993), lacustrine diatomites (Hong, 1985; Riou,
deposit as a Konservat-Lagersta«tte or conserva- 1995), cherts (Whalley and Jarzembowski, 1981),
tion deposit (sensu Seilacher, 1970) where the em- evaporites (Priesner and Quievreux, 1935; Schlu«-
phasis is on the quality of preservation rather ter and Kohring, 2001), phosphates (Handschin,
than the abundance of fossils. Konservat-Lager- 1944), coal measures (Bartram et al., 1987; Shear
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X.Mart¤|nez-Delclo's et al./Palaeogeography, Palaeoclimatology, Palaeoecology 203 (2004)19^64 21
and Kukalova¤-Peck, 1990; Jarzembowski, 2001a), Evidence of ecologic relationships between in-
and asphalt (Miller, 1983, 1997; Iturralde-Vinent sects and other animals is sometimes preserved in
et al., 2000). Here we focus on the two most im- limestones, where it is usually con¢ned to plant^
portant sources of fossil insects, carbonates and insect interactions (Labandeira, 1998; Waggoner,
amber. 1999). Such behaviour is inferred on the basis of
Repositories are abbreviated as follows: functional morphology, or gut contents (Schaal
MNHN, Muse¤um National d’Histoire Naturelle, and Ziegler, 1992; Krassilov et al., 1997) or
Paris, France; PIN, Palaeontological Institute, more commonly coprolites (Rothwell and Scott,
Russian Academy of Sciences, Moscow, Russia; 1988), or an array of primary evidence for insect
MCAM, Museu de la Cie'ncia, Fundacio¤ ‘La feeding (Ro«Mler, 2000; Labandeira and Phillips,
Caixa’, Barcelona, Spain; EPGM, Dept. Estrati- 2002). Amber, on the other hand, commonly re-
gra¢a,PaleontologiaiGeocie'ncies Marines,Univ. veals interactions, such as reproduction (mating,
Barcelona, Barcelona, Spain; MCNA, Museo egg laying), commensalism and parasitism be-
Ciencias Naturales de AŁlava, Vitoria^Gasteiz, tween di¡erent insects, and between insects and
Spain; MCCM, Museo de Ciencias de Castilla^ other organisms such as nematodes, spiders, pseu-
La Mancha, Cuenca, Spain; MPV, Museu Pale- doscorpions, mites and ticks, and vertebrates
ontolo'gic de Vale'ncia, Vale'ncia, Spain; JME, (Poinar, 1984; Poinar et al., 1994; Grimaldi,
Jura-Museum, Eichsta«tt Germany; QM, Queens- 1996; Weitschat and Wichard, 1998). Plant dam-
land Museum, Brisbane, Australia; IEI, Institut age is very rarely recorded in amber (e.g. Poinar
d’Estudis Ilerdencs, Lleida, Spain. and Brown, 2002).
Konservat-Lagersta«tten reveal other features of
an ecosystem. The presence of certain taxa, such
2. The importance of insect as termites (Nel and Paicheler, 1993), or assem-
Konservat-Lagersta«tten blages of insects, may indicate particular climatic
conditions (McCobb et al., 1998; Poinar et al.,
Konservat-Lagersta«tten reveal the diversity of 1999; Duringer et al., 2000; Miller and Elias,
insects in the past. Di¡erent taphonomic process- 2000). Adult and worker termites have been
es bias the preservation of insects in carbonates found in the Lower Cretaceous of Spain and Si-
and amber in di¡erent ways. A more diverse beria indicating that social behaviour had evolved
range of taxa and sizes is preserved in carbonates in this group by this time, earlier than it did in
whereas amber is usually dominated by particular ants or bees (Mart¤|nez-Delclo's and Martinell,
taxonomic groups and size categories (Zherikhin 1995). Some taxa imply the presence of others.
et al., 1999). In the Lower Cretaceous of Spain, Rasnitsyn (1968) described the oldest cephid saw-
for example, only a few families of insects occur £ies (Hymenoptera, Cephidae) from the Lower
in both the Montsec limestones (Pen‹alver et al., Cretaceous of Baissa in Transbaikalia. Cephid
1999) and AŁlava amber (Mart¤|nez-Delclo's et al., saw£ies are associated exclusively with angio-
1999; Alonso et al., 2000). The occurrence of in- sperms and, as predicted, angiosperm leaves and
sect compression fossils in sediment that also seeds subsequently were found at the locality
yields insect-bearing resin is extremely rare. Nota- (Rasnitsyn, pers. commun.). The occurrence in
bly, a well preserved cockroach wing was found the Lower Cretaceous ambers of Spain of wasps
associated with amber from the Palaeocene Due (Evaniidae), for example, which are parasitic on
Formation at Urtuy, on the Naiba River of Sa- the eggs of cockroaches, suggests that cock-
khalin Island, Russia (Zherikhin, pers. commun., roaches were present even though they have not
2001). Fossil insects also have been found in both been recorded.
limestone and amber from the same exposure. Konservat-Lagersta«tten provide evidence of
Such amber localities include the Lower Creta- factors controlling the growth of authigenic min-
ceous of Lebanon (Azar, 2000) and the Upper erals in sediments and amber. In carbonate rocks
Cretaceous of New Jersey (Grimaldi et al., 2000). fossil insects are usually preserved as organic re-
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22 X.Mart¤|nez-Delclo's et al./Palaeogeography, Palaeoclimatology, Palaeoecology 203 (2004)19^64
mains of the cuticle, or as a mould where the 3. The role of microbial mats in insect preservation
cuticle has been lost during diagenesis or weath-
ering (Mart¤|nez-Delclo's et al., 1995). Early min- Microbial mats may facilitate the preservation
eralisation may replicate insect morphology in of insects in a number of ways (Briggs, 2003b).
calcite (McCobb et al., 1998; X.M.-D., pers. ob- Mats are complex communities of photosynthetic
servation in Las Hoyas), pyrite transformed to prokaryotes (cyanobacteria), diverse unicellular
goethite (Grimaldi and Maisey, 1990), or in cal- algae, and chemautotrophic micro-organisms
cium phosphate (Duncan et al., 1998). 3-D pres- (Gall, 1990). Anaerobic and aerobic species coex-
ervation may occur in calcium sulphate, such as ist. Cyanobacteria may be spherical or ¢lament-
gypsum from the Miocene of Alba, Italy (Chiam- like and they form a mat by secreting mucilage.
bretti and Damarco, 1993; Schlu«ter and Kohring, Details of fossilised microbial mats may be re-
2001). Authigenic minerals rarely form in resin. vealed by scanning electron microscopy (Gall et
Pyrite may penetrate amber along fracture planes al., 1985).
(Karwowski and Matuszewska, 1999), coating Where microbial mats form on the surface of
the insect inclusion (Schlu«ter and Stu«rmer, standing bodies of water, they may trap insect
1982; Krzeminska et al., 1992; Grimaldi et al., carcasses and transport them to the sediment^
2000). water interface when the mat sinks (Gall, 1995;
Exceptionally preserved deposits may yield an- Harding and Chant, 2000). Where a carcass is
cient biomolecules. DNA has been reported from overgrown by a mat, it is protected from erosion
insects in amber (Desalle et al., 1992; Cano et al., and from scavengers and burrowing animals
1992, 1993) but its preservation is controversial (Gall, 1990, 1995) and is prevented from £oating.
due to its susceptibility to both hydrolytic and Microbial mats may reduce decay by acting as a
oxidative damage (Lindahl, 1993; Smith and Aus- barrier and promoting conditions unfavourable to
tin,1997; Austinetal.,1997),andtothedi⁄culty certain bacteria (Gall, 1990, 2001). Microbial
ofeliminating contamination byrecentDNA. De- mats may also prevent the transfer of ions, lead-
cay-resistant tissues, such as the cuticles of some ing to concentrations within the carcass su⁄cient
insects, have a higher preservation potential that to promote mineralisation of soft-tissues or of the
is controlled by three major factors (Briggs, mat itself (Briggs and Kear, 1993; Gall et al.,
1999): (1) the nature and composition of the cu- 1994; Sagemann et al., 1999). Where the mat be-
ticle, exempli¢ed by its better preservation in the comes mineralised, as in fossils from the Messel
thick sclerotised elytra of beetles than in other Shale and from Enspel (Wuttke, 1983; Toporski
insects; (2) the depositional environment, such et al., 2002), it may form a pseudomorph of the
as resin vs. sediment, which in£uences decay carcass, preserving the gross morphology of the
rate; and (3) diagenetic history, including poly- soft-tissues.
merisation, which is controlled by thermal e¡ects Microbial mats develop today in extreme envi-
and reactiontime.The chitin andprotein ininsect ronments, such as sabkhas, intertidal £ats, and
cuticle have only been reported from later Ceno- anoxic marine bottom water, conditions that are
zoic deposits (Miller et al., 1993; Stankiewicz et hostile to most organisms. Marine microbial mats
al., 1998a; Flannery et al., 2001); weevil cuticle in have been reported in the Upper Jurassic Solnho-
the Oligocene lacustrine shales of Enspel, Ger- fen Limestone, Germany, which yields a signi¢-
many, preserves the oldest traces (Stankiewicz et cant assemblage of insects (Keupp, 1977; Frick-
al., 1997b).Inolder examples theoriginalbiomol- hinger, 1994). Most of these insects are preserved
ecules are altered to kerogen (Briggs and Eglin- as moulds or by precipitation of calcite or pyro-
ton, 1994; Stankiewicz et al., 1997a, b; Briggs, lusite; phosphate mineralisation is rare, amount-
1999). Stankiewicz et al. (1998b) demonstrated ing to 68% of individuals (Wilby et al., 1995).
that chitin is not preserved in Dominican amber, Lacustrine microbial mats have been reported in
con¢rmingthatthepreservationofDNAishighly the Miocene basins of Rubielos de Mora and Bi-
improbable (Austin et al., 1997). corp,Spain,which yieldimportantassemblagesof
PALAEO32255-1-04
X.Mart¤|nez-Delclo's et al./Palaeogeography, Palaeoclimatology, Palaeoecology 203 (2004)19^64 23
insects (Pen‹alver et al., 2002a). 3-D caddis£y pu- against herbivores and pathogens such as insects
pae are preserved in Miocene freshwater lime- andfungi.Theyarecommonanddiverseinrecent
stones in Saint-Ge¤rard-le-Puy, France, associated tropical ecosystems (Farrell et al., 1991). Neither
with possible mats (Hugueney et al., 1990). How- oils nor oleo-resins are known to be a source of
ever, more decay prone soft-tissues may not be amber(Langenheim, 1995).Copals areresins with
mineralised even where microbial mats occur, as a low oil content, mainly from the araucariacean
in the Middle Triassic Gre's a' Voltzia, Vosges, Agathis (Philippines, New Zealand) and the legu-
France, which yields a diversity of insects (Gall, minoseans Hymenaea and Copaifera (Africa, Ca-
1990; Marchal-Papier, 1998). Additionally, in- ribbean and South America), used to make hard
sects have not been reported from the Upper Ju- and elastic varnishes. Some dipterocarpaceans
rassic of Cerin, France, which preserves phospha- fromSoutheastAsiaproducedammarresins.Fos-
tised soft-tissues in association with microbial sil copal of both araucariacean and leguminosean
mats (Gall et al., 1985; Wilby et al., 1996). origin with insect inclusions is known from sev-
eral localities in the Southern Hemisphere (Poi-
nar, 1991a; Schlu«ter, 1993). Araucariacean copal
4. Resin as a preservational medium occurs in northern New Zealand and Victoria,
Australia, where it is known as kauri, and in the
Resins are produced by specialised tree cells South Paci¢c region, Indonesia and the Philip-
and exuded through ¢ssures. Amber is a fossilised pines, where it is known as Manila copal. Legu-
natural resin with properties similar to amor- minosean copal occurs mainly in Africa, in the
phous polymeric glass (Poinar, 1992). Resins are Caribbean and South America. Copal from Hy-
a complex mixture of terpenoid and/or phenolic menaea spp. is known from northwestern Mada-
compounds (Anderson and Crelling, 1995). Their gascar, in the eastern parts of Kenya and Tanza-
chemical composition is diverse but they are solu- nia, the Santander region in Colombia, Minas
ble in alcohol and insoluble in water. Terpenoids Gerais in Brazil, and the eastern part of the Do-
may be volatile, where mono- and sesquiterpenes minican Republic. Copals produced by Copaifera
provide £uidity and act as plasticisers, or they are known from West Africa, and that produced
may be non-volatile, as in the case of diterpenoids by dipterocarpaceans from Malaysia and Suma-
or sometimes triterpenoids (Langenheim, 1995). tra, where it is known as dammar. Insects and
Among terpenoids, themost common areoxygen- other arthropods are abundant in copals, partic-
ated terpenes: acids, alcohols and esters secreted ularly in kauris from New Zealand and copals
from plant parenchyma cells. The polymerisation from Madagascar, Kenya, Tanzania and Colom-
of non-volatile terpenoids promotes copal and bia. Due to the young age of these resins, which
amber formation, as volatile terpenoids escape range up to a thousand years old, the entombed
to the atmosphere. The chemical composition of insect associations are similar to those of today
amber is only partially known, due to its insolu- (Schlu«ter, 1993).
bility. Notably, Lebanese amber has been dis- Resin is produced by at least three families of
solvedwithchloroforms, butthechemical compo- conifers and twelve of angiosperms, but only
sition has not been published (Azar, 1997). some of these generate amber in the fossil record.
Infrared Spectrometry (IRS) has been employed The conifers are Pinaceae, Araucariaceae and
in comparative studies of fossil and modern res- Taxodiaceae (Taxodiaceae is now included within
ins, allowing the tree producers to be identi¢ed Cupressaceae: Stefanovic et al., 1998); the angio-
(Beck, 1999; Kosmowska-Ceranowicz, 1999), sperms are Leguminosae, Burseraceae, Diptero-
and the categorisation of amber into di¡erent carpaceae, Hamamelidaceae (Langenheim, 1995),
types. A classi¢cation of fossil resins was pro- and Combretaceae (Nel et al., in press). The Le-
posed by Anderson and Crelling (1995). guminoseae include the Southern HemisphereHy-
Oils, oleo-resins and resins are produced by menaea which yields copious quantities of resin
both gymnosperms and angiosperms for defence (Langenheim, 1995). Dominican and Mexican
PALAEO32255-1-04
24 X.Mart¤|nez-Delclo's et al./Palaeogeography, Palaeoclimatology, Palaeoecology 203 (2004)19^64
ambers were produced by an extinct relative of mous number of localities involved and the range
the West Indian locust (H. protera) (Poinar, in quality of preservation and assemblage diver-
1991b). Most Mesozoic ambers and Eocene Baltic sity (Allison and Briggs, 1991b). Amber deposits,
amber are considered to be a product of araucar- on the other hand, are geographically and tempo-
iacean conifers as shown by their similarity to the rally restricted (Poinar, 1992; Grimaldi, 1996).
resin of Recent Agathis (Langenheim, 1995; Beck, The earliest known fossilised resins are from
1999). Anderson and LePage (1995) suggested, Upper Carboniferous pteridosperms of England
however, that Baltic amber originates from a pi- (van Bergen et al., 1995), but amber did not be-
naceous conifer similar to Pseudolarix. come abundant until the Early Cretaceous with
the rise of the coniferous Araucariaceae, particu-
larly in tropical and subtropical forests. The ear-
5. Distribution of amber through time liest ambers with inclusions are from Jezzine and
Hammana, in the Lower Cretaceous of Lebanon.
It is di⁄cult to produce a comprehensive list of More than 60% of the insects in amber from
insect occurrences in carbonates due to the enor- Hammana are £ies, including taxa that indicate
Fig. 1. Palaeogeographic maps showing the principal localities (see Appendix 1) that yield amber. (A) Lower Cretaceous. (B)
Upper Cretaceous. (C)Palaeocene.(D) Eocene. (E) Oligocene.(F) Miocene.
PALAEO32255-1-04
X.Mart¤|nez-Delclo's et al./Palaeogeography, Palaeoclimatology, Palaeoecology 203 (2004)19^64 25
that the resin formed in a warm climate within a thys Ocean (Barron et al., 1989), allowing the for-
wet leafy forest (Azar, 2000). While some of mation of coals (Parrish et al., 1982). In North
the earliest Cretaceous amber-bearing deposits America amber localities border the epicontinen-
(Fig. 1A) formed between the equator and 4‡N tal seaway £anked by warm temperate wet vege-
(Israel and Lebanon), they are concentrated in tation (biome 5 of Horrell, 1991), which includes
northern mid-latitudes, between 29‡N (Azerbai- Cupressaceae. The insect amber assemblage from
jan) and 50‡N (Japan), the moist megathermal the Upper Cretaceous Raritan Formation of New
zone based on vegetation distributions of Morley Jersey (Grimaldi et al., 2000) suggests a warm
(2000). By the end of the Early Cretaceous, while temperate or subtropical climate, similar to that
occupying a similar equatorial range, amber ex- of Siberian and Canadian Upper Cretaceous am-
tended north from 27‡N (Spain) to near 70‡N ber forests. Grimaldi et al. (2000) estimated a pa-
(Khatanga, Russia), coinciding with the moist laeolatitude of 32‡N for this amber, but palaeo-
megathermal zone of the Northern Hemisphere. geographic considerations place it at 40‡N.
Galle (2000) regarded the climate of the Tethys Greenhouse conditions, with particularly high
Region, where a large number of amber-bearing temperatures during the Middle Cretaceous (Hu-
localities are to be found, as generally humid dur- beretal., 2002)areevidencedbythenatureofthe
ing the Lower Cretaceous and becoming more terrestrial vegetation which indicates a cool tem-
arid in the Upper Cretaceous. The presence of perate regime even at high latitudes. In this con-
amber in extensive lower-latitude coals in the text, ambers are found at s80‡N in Alaska.
Lower Cretaceous of Lebanon and Spain is con- Berner(1990)consideredthatlevelsofatmospher-
sistent with very humid conditions (Barro¤n et al., icCO wereeighttotentimesthoseofthepresent
2
2001). A small number of localities, such as those day, reaching a maximum at the beginning of the
in northern Siberia, represent cool temperate con- Late Cretaceous.
ditions. Equatorial occurrences, corresponding to The climatic history of the Cenozoic can be di-
hot, relatively dry conditions, occur in Brazil and vided into two episodes (Pickering, 2000): the Pa-
the Middle East. Only one amber locality is laeocenetoEoceneintervalwascharacterisedbya
known in the Southern Hemisphere, in South continuation of the greenhouse conditions of the
Africa (Gomez et al., 2002). Upper Cretaceous whereas cooling occurred dur-
NoUpperCretaceousamberisknownfromthe ing the Oligocene to Recent period with occasion-
Southern Hemisphere (Fig. 1B). The only equato- al short and warmer episodes. There is a paucity
rial occurrence is from the earliest Upper Creta- of Palaeocene amber (Fig. 1C): only 0.5 major
ceous of Burma, which predates the widespread occurrences per million years, compared to 1.65
developmentofmegathermalangiosperm-richfor- in the Upper Cretaceous and nearly 2 in the Eo-
ests in equatorial latitudes towards the end of the cene. There also are no Palaeocene occurrences in
Cretaceous (Morley, 2000). Localities are mainly the Southern Hemisphere nor in the tropical rain
in the northern, moist, megathermal zone along forests of the equatorial Palmae Province. The
the northern margin of the Tethys Ocean and in few amber occurrences are in the northern rain
North America. Barron and Peterson (1990) con- forests of the Boreotropical Province, or in tem-
sidered that the Tethys Ocean would have been perate latitudes further to the north.
dominated by two clockwise gyres of ocean sur- The number and geographical spread of amber
face currents during the Cretaceous, with a dom- localities is much more extensive during the Eo-
inantly easterly £ow along its the northern side. cene (Fig. 1D). Amber is represented in the trop-
Climate modelling (Barron et al., 1989) predicted ical rain forests of the Southern Megathermal
a strongly developed monsoon in the Tethys area Province (Argentina) and the African Province
during the Cretaceous. Elevated temperatures re- (Nigeria) but the majority of localities (including
sulted in high rates of evaporation and precipita- Baltic amber) occur in the Boreotropical Prov-
tion, which produced very high seasonal rainfall ince. Amber is present in the dry subtropics of
on the northern and southern borders of the Te- China and the Kamchatka Peninsula to the south
PALAEO32255-1-04
26 X.Mart¤|nez-Delclo's et al./Palaeogeography, Palaeoclimatology, Palaeoecology 203 (2004)19^64
PALAEO32255-1-04
X.Mart¤|nez-Delclo's et al./Palaeogeography, Palaeoclimatology, Palaeoecology 203 (2004)19^64 27
of the Boreotropical Province and in more tem- mineralised and non-biomineralised remains of
perate latitudes to the north. other organisms are found in association, and
Following the terminal Eocene cooling event often soft-tissues or delicate structures are pre-
the global extent of rain forests was substantially served, as in the Lower Cretaceous of Liaoning,
reduced. Tropical rain forest remained in the Ca- China (Fig. 2A). Insect assemblages preserved in
ribbean region, as evidenced by Dominican Re- carbonate are often dominated by species that
public and Mexican amber derived from Hyme- rely on water for ecological reasons such as hab-
naea, and apart from localities in Tunisia and itat, for hunting, or for laying eggs. Assemblages
Sicily where the climate was presumably dry, of may£ies, termites, and £ying ants, for example,
most Oligocene amber is found in a mid-latitude may be the result of a mass mortality, and/or
belt across Eurasia (Fig. 1E). Oligocene amber is show a bias toward a particular size range. Smith
unknown from the Southern Hemisphere, but the (2000), for example, demonstrated that the insect
mid-latitude belts and tropical rain forests have assemblage that accumulated around a recent
yielded amber during the Miocene in both the ephemeral lake in Arizona is biased towards
Northern and Southern Hemispheres (Fig. 1F). smaller robust species, and also to ground-dwell-
Most Mesozoic ambers and Eocene Baltic amber ing forms. She compared the diversity of living
are a product of araucariacean conifers (but see insects, mainly beetles, that occur in di¡erent en-
Anderson andLePage,1995).Astheclimatic con- vironments around the lake with the assemblage
straints on the distribution of these taxa are preserved in the shallow, subsurface sediments
poorly known, they cannot be used directly to along the lakeshore. 65% of living beetle families
infer the climatic controls on amber. and 28% of living beetle genera were represented
in the sediments; 100% ofthe families and 91% of
the genera found dead were present in the live
6. Insect taphonomy fauna. The relative abundance of beetle families
in the living assemblage is signi¢cantly di¡erent
Taphonomy deals with the incorporation of or- from their relative abundance in the sediments,
ganicremainsintosedimentsorothercontexts,such from which the best represented groups are the
asresin,andthefateofthesematerialsafterburial. families of hymenopterans (62%) and coleopter-
Itis normally divided into: necrolysis, referringto ans (30%).
death and its causes; biostratinomy, involving the Soft-tissues of all organisms are quickly de-
sedimentary history of the remains prior to buri- graded by bacteria and fungi, which may com-
al; and diagenesis, comprising physical and chem- pletely destroy a carcass in a few days, depending
ical modi¢cations within the sediment or resin. on its size, the water temperature and other am-
bient factors. Mart¤|nez-Delclo's and Martinell
6.1. Necrolysis (1993) studied the death of insects in aquatic en-
vironments to determine the taphonomic process-
6.1.1. Necrolysis in aquatic settings es that in£uence insect fossilisation. Observations
Where fossil insects occur in carbonates, bio- were made on cockroaches, crickets, earwigs, ter-
Fig. 2. (A) Bellabrunetia catherinae, terrestrial dragon£y with aquatic conchostracans (white arrows). MNHN-LP-R 55232a,
UpperJurassic/LowerCretaceous, Liaoning(China); photobyA.Nel; scalebar=10mm.(B)Coproliteorregurgitatewithdrag-
on£y wings. PIN 2904/3; Upper Jurassic, Karatau (Kazakhstan); scale bar=10 mm. (C) Homopteran showing wings and body
movements. MCAM0043; Miocene amber from Hispaniola (Dominican Republic); scale bar=5 mm. (D) Isolated insect mandi-
ble. MCAM0005; Miocene amber, Hispaniola; scale bar=0.5 mm. (E) Isolated ant head. MCAM0095; Miocene amber, Hispa-
niola; scale bar=1 mm. (F) Worker termite with an air bubble extending from its body due to the activity of gut microbes.
MCAM0508; Mioceneamber,Hispaniola; scalebar=2mm.(G)FemaleofDiptera,Keroplatidaelayingeggsduringentrapment,
EPGM-RD-0048; Miocene amber, Hispaniola; scale bar=1 mm. (H) Copal stalactites, Mart¤|n-Closas collection, EPGM; Holo-
cene, Madagascar; scale bar=10mm.
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28 X.Mart¤|nez-Delclo's et al./Palaeogeography, Palaeoclimatology, Palaeoecology 203 (2004)19^64
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