122 MALCOLM B. HART, MELISSA J. OXFORD & WENDY HUDSON
carbonate-rich environments. The earliest
Globigerinina have been placed in the Super-
family Favusellacea (Simmons et al. 1997), a
group which continues through until the mid-
Cretaceous (Fig. 2). In the Albian and Ceno-
manian the Favusella spp. recorded in the UK
(Carter & Hart 1977) do not appear to be
aragonitic, being found well-preserved in the
chalk facies (in which few other aragonitic fossils
are recorded in such a good state of preser-
vation). At the present time there is little
evidence as to when the transition from arago-
nitic to calcitic tests is to be found. The lack of
information on the faunas of the Tithonian to
Valanginian interval may be critical in this
respect.
The major evolutionary changes in the
Toarcian and Bajocian are potentially related to
sea-level highstands (Haq et al. 1988) and appear
coincident with intervals of marked ammonite
diversification (O'Dogherty et al. 2000). If one
plots the distribution of the fauna through the
Jurassic and Cretaceous (Fig. 2) it is clear that
the major change in evolutionary rate occurs in
the Aptian (Hart 1999; Premoli Silva & Sliter
1999). Both specific and generic diversity (Fig. 4)
also increase at this level and this change
appears to be coincident with a major increase in
ocean crust production (Larson 1991a,b; Larson
et al. 1993)
In the earliest Oxfordian the planktonic
foraminifera (mainly Globuligerina oxfordiana
(Grigelis 1958) and G. bathoniana (Pazdrowa
1969)) expanded their distribution (Fig. 5) and
are reported from much of Europe, including
the UK (Oxford et al. in press) and the Grand
Banks (Ascoli 1976). The work of Oxford et al
(in press) in Dorset has demonstrated the
presence of G. oxfordiana, Haeuslerina helveto-
jurassica (Haeusler, 1881) and Compactogerina
stellapolaris (Grigelis in Grigelis et al. 1977) in
the Furzedown Clays (Q. mariae Zone) of the
Oxfordian. This is a comparable level to the
occurrence of G. oxfordiana in the Marnes de
Villers of the Vaches Noires cliffs of Normandy
and subsurface material from near Le Havre
(Bignot & Guyader 1966, 1971; Samson et al.
1992). All these occurrences are coincident with
the Q. mariae Zone highstand of the early
Oxfordian (Haq et al. 1988; Jacquin et al. 1998)
and appear to represent a distinctive pulse of
migration into the area of NW Europe. Infor-
mation from the latest Jurassic and earliest
Cretaceous is rather limited and the distribution
and evolution of the planktonic foraminifera
are poorly known. Sea levels during this time
interval are, generally, low and many of the
shelf areas covered during the Oxfordian and
Kimmeridgian are either non-marine or exposed
land. Even in the Valanginian the distribution of
the planktonic foraminifera (Fig. 6) is essentially
that seen in the earliest Oxfordian. In the
Barremian stage, however, diversification
begins (Figs 2 and 4) and continues through the
Aptian and Albian. By the latest Albian (Fig. 7)
the near-global distribution of the planktonic
foraminifera is established and continues
through until the end-Maastrichtian extinction
event.
It is during the latest Albian that the distinc-
tive 'keeled
1
morphotypes appear as, prior to
that time, only 'hedbergellid' taxa are known.
Within the early Albian a number of lineages
appear (Ticinella, Globigerinelloides, etc.) that
indicate a diversification of the hedbergellid
stock, but it is difficult to assess if these taxa were
depth-stratified in the same way as the younger
faunas (Hart 1999). The single-keeled morpho-
types appear in the latest Albian, possibly
associated with the sea-level changes in the 5.
dispar Zone. The twin-keeled morphotypes
appear in the latest Cenomanian which, again,
marks a time of significant sea-level rise.
Throughout the mid- to late Cretaceous the
succession is punctuated by a number of
'events' beginning with the Faroni Event in the
Barremian. All of these events (Selli, Paquier,
Amadeus, Bonnarelli, etc.) are associated with
black shales and/or mudstones and have often
been described as 'anoxic events'. Their effects
on the planktonic foraminifera have been
documented by a wide range of authors (e.g.
Premoli Silva & Sliter 1999) and while the
changes at some of these levels are significant,
they cannot be described as controlling the
evolution of the planktonic foraminifera (Hart
1999; Premoli Silva & Sliter 1999). Hart (1999)
showed that there were significant changes to
the fauna at the level of the Bonnarelli event
(latest Cenomanian) with a number of extinc-
tions and first appearances, but other events
(e.g. the Selli event in the earliest Aptian) record
few, if any, changes.
The palaeolatitudinal distribution of the
Cretaceous planktonic foraminifera has recently
been documented by Hart (2000) and Hudson
(2000). This work continues and a series of maps
for the Jurassic and Cretaceous is currently in
production. The changes recorded at any of the
events during the Cretaceous cannot, however,
be compared to that at the end of the Cretaceous
(Hart 1999, fig. 5). At the end of the Maastricht-
ian the fauna was decimated and only two or
three survivors provided the foundation for the
Cenozoic fauna. Only the tiny, hedgergellid taxa
survived and the evolutionary clock is returned
