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The Lower Monk’s Bay Sandstone Formation (formerly the Carstone) of 1 the : its distribution, litho- and bio-stratigraphy. 2 3 Peter M Hopsona,*, Ian P Wilkinsona and Mark A Woodsa, Andrew R Farranta 4 a 5 British Geological Survey, Sir Kingsley Dunham Centre, Keyworth, 6 Nottingham, NG12 5GG 7 8 *Corresponding author E-mail address: [email protected] 9 10 11 Abstract 12 The Monk’s Bay Sandstone Formation (MBSF) is the new name for the Lower 13 Albian ferruginous sandstone that was formerly known as the Carstone of the 14 15 Isle of Wight. The new term was proposed to remove any confusion with the 16 Carstone, of similar age and lithology, described from the separate Lower 17 sedimentary basin of Eastern . This paper formalises the 18 nomenclatural change outlined in the Lower Cretaceous Framework Report, 19 ratified by the Geological Society Stratigraphy Commission. 20 21 22 The MBSF, representing a major mid-Albian transgressive event, is described 23 from a series of boreholes drilled by the British Geological Survey across the Isle 24 of Wight, and from additional coastal exposures, together with reinterpretations 25 of sections described in earlier works. 26 27 28 The age range of the MBSF is determined in relation to recent biostratigraphical 29 schemes supported with new data from the previously unknown presence of 30 foraminifera. Deposits, belonging to the Leymeriella regularis Subzone, were 31 32 previously considered to be absent from the succession and represent the 33 stratigraphical gap separating the formation from the underlying Sandrock 34 Formation. However a first occurrence of tubular foraminifera resembling 35 Hyperammina/‘Rhizammina cf dichotomata suggest that the oldest part of the 36 formation in the northeast of the island may be of regularis Subzone age. This 37 38 unconformity is correlated with the sequence boundary LG4 of Hesselbo and the 39 presence of the Sonneratia kitchini Subzone at the base of the MBSF on the Isle 40 of Wight suggests that this boundary should be placed at the lower of two 41 candidate horizons within the successions of the Weald. 42 43 44 The formation is restricted to the Isle of Wight but is coeval with similar coarse- 45 grained sediments, e.g the Carstone and ‘JunctionBeds’ to the north. The 46 palaeogeography of the formation and the relationship with these similar 47 deposits and the implications for the timing of mid-Albian structural events is 48 49 briefly discussed. The identification of older Lower Greensand Group sediments 50 beneath the MBSF in boreholes north of the Isle of Wight structure, together 51 with new survey data indicating north-south orientated faulting affecting the 52 early Cretaceous implies a tectonic element to the distribution the Lower 53 54 Greensand Group sediments. Taken together these imply a complex interaction 55 of tectonics and transgressive events throughout the Aptian and Albian over this 56 structural high. 57 58 Keywords: Lower Cretaceous, Isle of Wight, Lower Greensand Group, 59 60 Lithostratigraphy, Biostratigraphy 61 62 63 64 65

1 2 1. Introduction 3 4 5 The Monk‟s Bay Sandstone Formation is a new name for the Carstone of the Isle of 6 Wight. It was first proposed in a British Geological Survey Research report (Hopson 7 et al., 2008) and subsequently ratified by the Stratigraphy commission of the 8 Geological Society. The term „Carstone‟ was first applied to the Isle of Wight 9 10 succession by Reid and Strahan (1889), who regarded it as a correlative of the 11 Carstone of Norfolk. Whilst the two units are of similar age and lithology they are not 12 contiguous. The Monk‟s Bay Sandstone Formation consists of interbedded units of 13 highly ferruginous, generally coarse-grained, weakly consolidated quartz-rich 14 15 sandstone, fine-grained pebbly sandstone (gritstone) and ironstone that form the upper 16 part of the Lower greensand Group of the Isle of Wight (Tab. 1). It equates to the 17 upper part of Fitton‟s (1847) Group XVI. 18 19 Group Formation Stage 20 Upper Greensand 21 Selborne 22 Albian 23 Monk‟s Bay Sandstone 24 25 Lower Sandrock 26 Greensand 27 Ferruginous Aptian 28 Atherfield Clay 29 30 Table 1. Simplified litho- and chrono-stratigraphy of part of the Lower Cretaceous of 31 the Isle of Wight. 32 33 The formation can be traced continuously beneath the base of the Gault Formation 34 from , in the west, through to Red Cliff (north of ) in the east 35 36 and around the southern downs in the south-east of the island (Fig 1). Much of the 37 outcrop-pattern along the northern flank of these southern downs is complicated by 38 landslides, and a downwash of Upper Greensand and Gault debris obscures much of 39 the Monk‟s Bay Sandstone outcrop. The coastal exposures at Luccombe [SZ 40 5828 7929] and the cliffs around that area and then southward around Dunnose [SZ 41 42 5818 7829] towards Monk‟s Bay offer the best exposures of the formation both 43 historically and during the recent survey. 44 45 Along the outcrop the Monk‟s Bay Sandstone rests with a slightly disconformable 46 47 contact on the Sandrock Formation and is seen to pass gradationally upwards, over 48 c.1.5 m), into the Gault. In this paper, the boundary between the Monk‟s Bay 49 Sandstone and the Gault is placed at the horizon. This is generally marked by a 50 distinct colour change from dark yellow brown below to dark greenish grey above. 51 However, where the clay and silt content is disseminated, probably by bioturbation, 52 53 rather than preserved in discrete laminae, then the uppermost part of the Monk‟s Bay 54 Sandstone takes on a brownish green/grey colour. The Monk‟s Bay Sandstone usually 55 forms a prominent feature, particularly where harder iron-cemented gritstones 56 predominate, but is less obvious where the formation is found along the steeply 57 58 dipping Brighstone and Sandown monoclines in the southwest and east, respectively, 59 of the island. However, in both the well-featured and steeply dipping outcrops, the 60 61 62 63 64 65 characteristic bright orange brown soils with ironstone clasts formed from this 1 formation, can be readily identified in most areas. 2 3 4 Place Fig.1. hereabouts 5 6 The Monk‟s Bay Sandstone varies considerably in thickness across the Isle of Wight 7 from a minimum of 1.1 m seen in the Borehole SZ38NE30 [SZ 8 36935 85182] to a maximum of 22.17 m at Red Cliff [SZ 6266 8553] (White, 1921, 9 10 p.30) north of Sandown. Details of the most important sites are given later in this 11 paper. 12 13 All of the sections are south of the Sandown and Brighstone monoclinal axes and 14 15 demonstrate a general north-easterly thickening of the formation that is contrary to the 16 south-easterly thickening of the other units of the Lower Greensand Group on the 17 island. To the west of the Isle of Wight the formation is known to thin further and at 18 Punfield in Dorset, it is represented by only a few centimetres of pebbly sandstone. 19 20 21 North of the monoclinal axes the Lower Greensand Group is severely attenuated in 22 deeper boreholes (for example in the hydrocarbon boreholes of Sandhills 1 and 2 and 23 Bouldnor Copse) of the island. It is principally the younger, Monk‟s Bay Sandstone 24 Formation that is represented in these structural high areas (see discussion). 25 26 27 Lithologically the formation comprises generally well- to poorly-sorted 28 unconsolidated sands and weakly consolidated sandstones, pebbly sandstones and 29 ironstones with minor thin interbeds/laminae of mudstone. The individual beds are 30 predominantly fining-upward, but with some coarsening-upward thicker beds where 31 32 the formation itself is at its thickest. Beds are often bioturbated (with a nodular 33 appearance when weathered where incomplete cementation occurs) and cross-bedded, 34 but rarely contain ripple lamination or planar bedding. The is predominantly 35 medium- to coarse-grained with varying proportions of fine sand. The sand grade 36 material is mainly sub-rounded to rounded quartz with the coarser grains often having 37 38 a polished surface. There are distinct coarse-grained beds with coarse- to very coarse- 39 grained sand and some fine grade pebble material (generally less than 10 mm and 40 often referred to as grit in the literature) and rare larger pebbles. Ironstone is present 41 as beds with a pervasive „framework‟ structure, as fragmentary framework beds, and 42 43 as ooidal ironstones. Dark orange brown colouration is typical at outcrop although in 44 boreholes a green glauconite is preserved. Limonitic ironstone ooids and fragmentary 45 angular ironstone are found throughout the formation together with some phosphatic 46 grains. Pebble clasts mainly comprise rounded quartz with phosphate and reworked 47 bored material (some with overgrowths) together with some chert and sandstone and 48 49 rare limonite. Dike (1972) described two sub-facies, namely a moderately- to well- 50 sorted pebbly medium and coarse sand that predominates in the lower part of the 51 formation and a very poorly sorted, pebbly, muddy sand heavily bioturbated by 52 Thalassinoides, in the upper part. 53 54 55 2. Description of the Sections and Boreholes 56 57 The principal sections in the Monk‟s Bay Sandstone Formation are described below, 58 starting with the stratotype at Monk‟s Bay, and then progressing from Red Cliff in the 59 60 east to Compton Bay in the west. Sections described from previous work, principally 61 62 63 64 65 White (1921), Dike (1972) and Ruffell and Garden (1997) have been converted to a 1 metric scale where necessary. 2 3 4 Monk’s Bay Stratotype Section 5 6 At Monk‟s Bay and northward to Dunnose, the visible coastal succession comprises 7 the upper part of the Sandrock Formation (Fig. 2), overlain successively by the 8 Monk‟s Bay Sandstone Formation and basal part of the Gault Formation. Early 9 10 descriptions of the succession are given in White (1921, p.44) who repeated the 11 section [SZ 5797 7801] given in Reid and Strahan (1889). He gives a total thickness 12 of 10.45 to 10.52 m of beds for the Monk‟s Bay Sandstone in Monk's Bay. 13 14 15 This description compares with that measured by one of us (Woods, 2009), during the 16 current survey, between SZ 58152 78284 and 58092 78164 near . The 17 section shows that the Monk‟s Bay Sandstone Formation is between 10.21 to 10.25m 18 thick (Fig. 3a and 4). This new description is proposed as the stratotype for the 19 formation given that the thickest and most complete outcrop at Red Cliff, near 20 21 Sandown, is usually overgrown, often obscured by slip material and relatively 22 inaccessible. 23 24 At Monk‟s Bay whilst much of the Sandrock Formation comprises beds of sandstone 25 with occasional thin beds of mudstone, the few metres immediately below the base of 26 27 the Monk‟s Bay Sandstone (Fig. 3a beds 8 to 19) includes numerous beds and lenses 28 of mudstone which forms a very distinctive interval at outcrop. This interval contains 29 channel structures and conspicuous cross bedding suggesting a relatively shallow 30 marine depositional environment. Dike (1972) considered the Sandrock Formation to 31 32 represent a succession deposited in a fluctuating offshore, barrier bar, shoreline and 33 near-shore environment representing, in its final depositional phase, a general 34 regression and shoreline advance towards the south. 35 36 A strong upward colour change in the cliff section, from the orange-grey and yellow- 37 38 grey sandstone of the Sandrock Formation, to dark, orange-brown sandstone, marks 39 the sharp erosive base of the Monk‟s Bay Sandstone Formation. Overall the formation 40 is much coarser grained than the underlying Sandrock. The formation predominantly 41 comprises coarse-grained and pebbly, bioturbated, ferruginous sandstone, with 42 43 subordinate thin mudstone horizons. At Monk‟s Bay the formation is divisible into 44 three broad intervals, comprising a relatively massive-bedded central unit, about 5.5 45 m thick, sandwiched between lower and upper thin-bedded intervals. Dike (1972) 46 considered the deposits of the Monk‟s Bay Sandstone Formation (his Carstone) to be 47 the basal deposits of the widespread mid-Albian transgression. 48 49 50 Place Fig. 2, Fig. 3a and Fig. 3b hereabouts 51 52 White (1921, p.44, Fig.11) recorded burrowing at the base of the Monk‟s Bay 53 Sandstone. In the currently exposed section this surface is seen to be slightly uneven 54 55 and erosional terminating cross-bedded units within the underlying Sandrock 56 Formation. The burrows penetrating the underlying Sandrock Formation contain a 57 dark orange brown sandy/gritty clay-rich infill and can be clearly seen in the current 58 exposure (Fig. 2). The base of the formation is marked by a 0.12 m thick pebble-rich 59 60 unit (Bed 21), containing small, polished quartzite pebbles, up to 10 mm in size. 61 62 63 64 65 Elsewhere on the island, Garden (1991, Fig. 7D) identified a clast assemblage of 1 rounded quartz pebbles but with significant numbers of „shelf chert‟ 2 and -derived chert pebbles from three sites exposing this basal unit (Red Cliff, 3 4 Rock and Compton Bay). Ruffell and Garden (1997, fig. 6, map 4), recorded 5 phosphate, limonite and locally derived pebbles from the same bed at Compton Bay, 6 St Catherine‟s Point (Blackgang) and [SZ 507 755]. The limonite is 7 prevalent at Compton and Red Cliff, perhaps indicating proximity to the structural 8 high that developed during Aptian/Albian times. 9 10 11 The overlying succession (Beds 22 to 34) comprises a few metres of alternating thin 12 beds of dark grey mudstone and orange-brown sandstone. Both sandstones and 13 mudstones are burrowed, with the softer mudstones weathering back to give a 14 15 distinctive „ribbed‟ appearance to this part of the succession. 16 17 Beds 35a, 35b and 36 collectively form the massive, sandstone-dominated part of the 18 formation that includes a few thin beds of mudstone. These weather out prominently 19 in the cliff profile. Bed 35a has a rather „nodular‟ weathering appearance and contains 20 21 abundant cemented burrows. Burrowing is much less obvious in the rest of this 22 massive-bedded succession, and some small pebbles in Bed 36 have their long axis 23 vertical to bedding, perhaps suggesting an effect of bioturbation or a high flow 24 regime. Thin seams of much coarser, pebbly sandstone occur throughout this massive- 25 bedded interval. 26 27 28 Place Fig. 4 hereabouts. 29 30 At Monk‟s Bay access to the topmost 1.5 m of the Sandstone, 31 32 immediately below the contact with the Gault, proved to be difficult during the survey 33 and the succession could not be examined in detail. However the highest few metres 34 of the Monks Bay Sandstone (Beds 37 to 39) are relatively thinly bedded, with three 35 coarse-grained, pebbly sandstone beds overlain by thin mudstone horizons and thicker 36 units of coarse sandstone. 37 38 39 Dike (1972) suggests that the massive units are attributable to sandwave and sand 40 ridge formation in moderate currents with the thinner pebbly coarse-grained 41 sandstones represent periodic storm deposition. Bioturbation has largely destroyed 42 43 any internal structures but lower energy mud-rich laminae are preserved in parts of 44 the succession. 45 46 Reference Sections 47 48 49 The Monk‟s Bay Sandstone is exposed in the Red Cliff () section [SZ 50 626 855] (Fig.5) within the highest and poorly accessible part of the cliffs northeast of 51 . The formation can be followed within the cliff top northward but is 52 generally obscured by landslip debris within a gully reaching to beach level that 53 follows the steeply dipping zone of the Sandown Monocline. This is the thickest 54 55 succession known for the formation on the Isle of Wight and comprises 22.17 m 56 (White, 1921, p.30) of interbedded brown clayey pebbly sandstones (“grits”) and sand 57 with quartz, quartzite and phosphatic pebbles and coarse ironstone sand grains. A 58 graphic log for the succession at Red Cliff is given in Ruffell and Garden (1997) 59 60 61 62 63 64 65 where 13.5 m (including an unspecified logging gap) are described as interbedded 1 sands, clays and pebble beds. 2 3

4 Place Fig. 5 hereabouts. 5 6 The formation is exposed about 5 km to the west in the Knighton Sand Pit [SZ 574 7 866]. Here a near complete succession in the Sandrock Formation is seen and 8 workings over recent years have gradually exposed the lower part of the Monk‟s Bay 9 10 Sandstone Formation in a poorly accessible part of the quarry. A graphic log for the 11 exposed Monk‟s Bay Sandstone Formation is shown in Fig. 6, together with three 12 boreholes drilled to the north of the quarry face (Figs. 7a, b). These boreholes proved 13 all but the highest part of the formation, the stratigraphically highest part being 14 15 obscured by slipped Gault and Upper Greensand debris. It is estimated, by 16 comparison with nearby boreholes and with the Red Cliff section, that only 2 to 4 17 metres of the formation are missing from the described boreholes. 18 19 Place Fig. 6, Fig. 7a and Fig. 7b hereabouts. 20 21 22 The current exposure at Marvel Wood Sand Pit [SZ 4988 8690], south of Newport 23 in the centre of the island, shows much of the formation, including its base, but is 24 otherwise greatly overgrown and was not logged in detail during the recent survey. 25 White (1921) gives the following description (with the position of the Sandrock 26 27 reconsidered) for the locality when a clearer section was available (Fig. 8). 28 m 29 Monk’s Bay Sandstone Formation 30 Ferruginous grit, irregularly cemented in bands of iron oxide; small 31 32 pebbles in lower part 3.66 33 Sandrock Formation 34 Grey sand with fragments of clay, having the appearance of a 35 reconstructed bed of the Sandrock Fm resting on the edges of 36 the current-bedding below 0.91 37 38 White sands with current-bedding and fine seams of grey clay 9.14+ 39 40 Place Fig. 8 hereabouts. 41 42 43 The current exposures confirm the view of Reid and Strahan (1889, p.42) that the 44 „reconstructed‟ grey sand should be considered as the uppermost Sandrock Formation 45 and not the lowermost bed of the Monk‟s Bay Sandstone Formation as in White 46 (1921, p.39) and that its apparent place above truncated cross-bedding and its 47 disturbed nature can be regarded as a function of the burrowing at this horizon and/or 48 49 the likelihood that there are a number of erosional surfaces within the Sandrock 50 Formation itself. Certainly the exposure shown in Fig. 8 shows a clear base to the 51 Monk‟s Bay Sandstone at the incoming of coarse-grained sandstone with ironstones at 52 this locality. 53 54 55 About 3 km further to the south the Rookley Brickworks section is located at [SZ 56 5133 8395] in Owen (1971) and a log of the upper 9 m of the Monk‟s Bay Sandstone 57 Formation, below the Gault Formation, is modified from that given by Dike (1972) 58 (Fig. 9). The section is no longer visible, being within the heavily landscaped Rookley 59 60 Country Park. 61 62 63 64 65

1 2 Place Fig. 9 hereabouts. 3 4 5 The formation outcrops around the southern downs of the island and can be seen in 6 the section at Luccombe () Chine [SZ 583 793]. The section in the low 7 cliffs adjacent to the chine is illustrated graphically in Ruffell and Garden (1997, Fig. 8 5) and comprises 3 m of fine- to medium-grained sand in three units representing the 9 10 Sandrock Formation overlain by about 5.6 m of three fining-upward cycles of the 11 Monk‟s Bay Sandstone and in turn overlain by the Gault. Each cycle commences with 12 a coarse-grained sand unit fining-upward into weakly cross-bedded medium- to 13 coarse-grained sand that includes bioturbation in places. The current exposure in the 14 15 cliffs at the mouth of the chine is illustrated in Figure 10. 16 17 Place Fig. 10 hereabouts. 18 19 Further south within the area where the Monk‟s Bay Sandstone Formation is not 20 21 visible the two boreholes at provide a link southwards from the stratotype at 22 Monk‟s Bay. Two cored boreholes drilled in the Undercliff landslide at Ventnor No. 2 23 (SZ57NE27 [SZ 55666 77576]) and No.3, (SZ57NE25 [SZ 55747 77510]), covering 24 the basal Chalk Group through to the Sandrock Formation were donated to the BGS 25 by the Isle of Wight Centre for the Coastal Environment. 26 27 28 Detailed logs of the relevant parts of these boreholes are shown in Fig. 11. The 29 Monk‟s Bay Sandstone is incomplete in the Ventnor No. 2 borehole as a result of land 30 sliding within the Undercliff. The sequence in Ventnor No 3, however, probably 31 32 represents a complete succession through the formation as it contains the units that are 33 lithologically transitional into the Gault. 34 35 Place Fig. 11 hereabouts. 36 37 38 Inland from Ventnor on the northern crop of the southern downs the Monk‟s Bay 39 Sandstone Formation is frequently involved in and obscured by landslides. Three 40 boreholes (Fig. 12) were drilled adjacent to Hobbit House Farm [SZ 521 786] 41 through the Gault into the underlying Lower Greensand Group to capture a 42 43 representative section through the Monk‟s Bay Sandstone and the boreholes probably 44 record the whole of the formation, which is about 9 metres in this area. Some of the 45 overlying Gault shown in Figure 12 is interpreted as slipped material. 46 47 Place Fig. 12 hereabouts. 48 49 50 The most westerly sections around the southern downs within the Monk‟s Bay 51 Sandstone Formation are at Blackgang [SZ 486 768]. The most recently described 52 section is that of Ruffell and Garden (1997, Fig. 5) that gives a thickness for the 53 formation of about 6.4 m. Reid and Strahan (1889, p. 57 to 59; see also Ibbetson and 54 55 Forbes, 1845) described the occurrence of the formation eastward of St Catherine‟s 56 Point [SZ 508 706] and within the much disturbed westward outcrop of the Undercliff 57 landslide. At that time the formation was not considered to be present in situ within 58 blocks containing phosphorite-cemented coarse-grained sandstone nodules on the 59 60 foreshore from which Jackson (1939) described a significant fauna. Subsequently 61 62 63 64 65 Casey (1961) described the fauna from similar nodules within the formation in Reeth 1 Bay [SZ 507 756] that he considered to be in situ. In the cliff below the memoir 2 (White, 1921) described 3.4 m of the formation as interbedded brown grit and clay 3 4 resting on a thin pebbly and ferruginous band. 5 6 Six boreholes were drilled in the area of Mottistone immediately to the east of 7 Longstone Cottages [SZ 4075 8429] in the moderately dipping limb of the Brighstone 8 monoclinal feature. Four of these boreholes penetrated part of the Monk‟s Bay 9 10 Sandstone Formation and a correlation of these is shown in Figure 13 and this gives 11 an approximate thickness of 6 metres for the Monk‟s Bay Sandstone Formation. 12 13 Place Fig. 13 hereabouts. 14 15 16 The most westerly occurrence of the Monk‟s Bay Sandstone on the island is at 17 Compton Bay [SZ 367 852] where the section was described by White (1921, p. 28) 18 is 1.83 m thick (Fig. 14). The Compton Chine borehole drilled adjacent to the mere 19 at the top of the cliff proved a complete succession through the Monk‟s Bay 20 21 Sandstone. As interpreted, the graphic log (Fig. 15) shows that the formation thins 22 here to only 1 m. However, if the sandy clay above is considered to be part of the 23 Monk‟s Bay Sandstone Formation, rather than the basal Gault, then it may be 2.5m 24 thick. Ruffell and Garden (1997) give an expanded thickness of about 3 m for their 25 section in the cliffs below. 26 27 28 Place Fig. 14 and Fig. 15 hereabouts. 29 30 A number of additional sites (listed in Table 2) many of which are now overgrown or 31 32 otherwise obscured, are described in Reid and Strahan (1889) and White (1921, p.39 33 to 44). The boreholes that encountered the formation and are described in this paper 34 are shown in Table 3 35 36 Location Grid Reference 37 38 Rock SZ 4251 8397 39 Marvel Wood SZ 4988 8690 40 Billingham Cottages SZ 4831 8244 41 42 Birchmore SZ 5062 8529 43 Whitecroft SZ 4989 8631 44 Knighton Brook SZ 5677 8676 45 Itchall SZ 5198 7930 46 47 Itchall SZ 5219 7961 48 Table 2. Additional locations described in White (1921) for the Monk‟s Bay 49 Sandstone Formation. 50 51 52 Location Locality Grid Registered Number(s) 53 Reference 54 Knighton Sand Pit SZ 575 867 SZ58NE 98 to 100 55 Whitwell (Hobbit SZ 520 786 SZ57NW 51 to 53 56 House Farm) 57 58 Mottistone SZ 408 843 SZ48SW 26 to 31 59 Compton Chine SZ 36935 85182 SZ38NE 30 60 61 62 63 64 65 Ventnor* SZ 557 775 SZ57NE 27 and 25 1 Table 3. The BGS boreholes described in this paper. 2 *Two cores, derived from the landslide studies in Ventnor, and donated to BGS by the 3 4 Isle of Wight Centre for the Coastal Environment (Ventnor No2 and No3) were re- 5 examined in detail for the successions through the Monk‟s Bay Sandstone Formation. 6 7 3. Biostratigraphy 8 9 10 Macro-biostatigraphical framework 11 12 The macrofossil biostratigraphy of the Aptian and Albian is based on ammonites, and 13 this forms the framework for the calibration of other biostratigraphical schemes based 14 15 on microfossils (see below). In recent years variations of two different macrofossil 16 schemes have been proposed, and the relationship between these is shown on Figure 17 16. 18 19 Ammonites and other diagnostic macrofossils are generally very rare in the Monk‟s 20 21 Bay Sandstone, and no new specimens were found during the current work. Previous 22 investigations have shown that the formation is coextensive with the D. mammillatum 23 Superzone sensu Owen (1988), which forms the youngest part of the Early Albian 24 (Fig. 16). This biostratigraphical interval comprises a complex succession of zones 25 26 and subzones (Fig. 16), and many localities exposing this interval in southern, central 27 and eastern England show mixing or breaks in the faunal succession, caused by 28 laterally variable marine erosion. Casey (1961) believed that the representation of his 29 „mammillatum Zone‟ was relatively complete in the Isle of Wight, but the more 30 refined scheme of Owen (1988) shows that some horizons are unrepresented. 31 32 33 Place Fig. 16 hereabouts. 34 35 The unconformity between the top of the Sandrock and the base of the Monks Bay 36 37 Sandstone cuts out the highest part of the L. (L.) tardefurcata Zone, equating with the 38 L. regularis Subzone (Casey, 1961). A much larger stratigraphical break occurs in the 39 north of the Isle of Wight, where boreholes proved Jurassic strata beneath Monks Bay 40 Sandstone (Gale et al., 1996). Above the unconformity, the basal part of the formation 41 contains ammonites indicative of the S. kitchini Subzone, and this interval is also 42 43 indicated by many of Casey‟s (1961) faunal records from the formation, including 44 Anadesmoceras bayeli (Spath) from Blackgang and Reeth Bay, and Sonneratia (S.) 45 parenti Jacob and Cleoniceras (C.) morgani Spath from Compton Bay. Owen (1988) 46 recorded the top of the S. chalensis Zone (C. floridum Subzone) in the Monks Bay 47 Sandstone, and Otohoplites at Reeth Bay (Casey, 1961) which suggests that the upper 48 49 part of the mammillatum Superzone (O. auritiformis Zone) is present. The top of the 50 Monks Bay Sandstone on the coast at Compton Bay and Bonchurch, and inland at 51 Rookley Brickworks, contains records of Hoplites (Isohoplites) eodentatus Casey 52 (Owen, 1971a), conspecific with Pseudosonneratia (Isohoplites) steinmanni Jacob 53 54 which is the subzonal index for the top of the mammillatum Superzone (Owen, 1988). 55 56 On the Isle of Wight there is no evidence of the S. (G.) perinflatum Subzone at the 57 base of the S. chalensis Zone; the O. bulliensis Subzone, near the top of the O. 58 auritiformis Zone, has yet to be proved anywhere in the UK (Owen, 1988). 59 60 61 62 63 64 65 Foraminiferal zonation: Previous work 1 2 The best known early Albian foraminifera are from Germany and France (e.g. Hecht, 3 4 1938; Magniez-Jannin, 1975) where two foraminiferal zones have been recognised 5 (Price, 1977) (Fig. 17). In Britain, early Albian foraminiferal data comes from two 6 studies: the Speeton Clay Formation (Mitchell and Underwood, 1999) and the 7 Carstone Formation (Dilley, 1969) both in Yorkshire, although assemblages in the 8 latter formation are rare and patchily distributed. The established foraminiferal 9 10 zonation for the mid and late Albian, based on the work of Carter and Hart (1977), 11 commences with zone 3 (subzone 3i). 12 13 14 Place Fig. 17 hereabouts. 15 16 17 Microfaunal Results from the BGS Boreholes 18 19 The microfaunal evidence from the BGS boreholes is sparse with significant parts of 20 the successions proving barren. However there is some evidence to place the base and 21 top of the Monk‟s Bay Sandstone Formation within the schemes shown in Fig. 17. 22 23 The results from the base of the Gault Formation further limit the subzonal age of the 24 top of the Monk‟s Bay Sandstone. 25 26 From macropalaeontological data it can be concluded that the Sandrock Formation is 27 of H. Jacobi, Proleymeriella schrammeni and L. tardefurcata zonal (Leymeriella 28 29 acuticostata subzonal) age. Foraminiferal Zone 1 should be confined to the Sandrock 30 Formation but this could not be confirmed from the examination of the samples 31 derived from the BGS boreholes. 32 33 34 As already stated the Sandrock and Monk‟s Bay Sandstone formations are separated 35 by an erosive boundary, representing all or part of the L. regularis Subzone. However 36 a single sample from the base of the Monks Bay Sandstone in a borehole at Knighton 37 contained tubular foraminifera resembling Hyperammina/„Rhizammina cf 38 dichotomata’. This occurrence suggests the presence of Foraminifer Zone 1. Either 39 40 the formation at this locality is older (perhaps regularis zonal age) or the 41 foraminiferal zonal boundary is stratigraphically higher in the Isle of Wight. 42 Reworking, perhaps the most likely scenario, cannot be ruled out, but if this were the 43 case, then the survival of these agglutinated foraminifera is surprising. 44 45 46 Early Albian Foraminifera from the majority of samples within the Monks Bay 47 Sandstone Formation comprise predominantly long ranging and patchily distributed 48 taxa, often of small dimensions, including Glomospirella gaultina, Reophax minuta, 49 Cribrostomoides nonionoides rotunda and Trochammina concavus. At the top of the 50 51 formation Cribrostomoides nonoionoides rotunda, Cribrostomoides concavus, 52 Arenobulimina macfadyeni and Ammobaculites sp cf parvispira were recorded. This 53 association within the formation are typical of Foraminiferal Zone 2. 54 55 56 The foraminiferal assemblages recorded from the BGS boreholes within the overlying 57 Gault Formation of the Isle of Wight differ considerably from those of Kent and 58 Sussex. Foraminifera are sparse, associations are of low diversity, and faunas are 59 almost entirely agglutinated. The Gault is characterised by Arenobulimina 60 61 62 63 64 65 macfadyeni, Tritaxia singularis, Cribrostomoides nonionoides rotunda, Reophax 1 minuta, Haplophragmoides chapmani, Trochammina cf concavus, Trochammina sp cf 2 wetteri, Ammodiscus cretaceus and Glomospirella gaultina, indicating a position in 3 4 Foraminiferal Zones 3 and 4 and above. 5 6 4. Sedimentation and correlation 7 8 Although the Monks Bay Sandstone Formation is geographically restricted to the Isle 9 10 of Wight, it is coeval with similar coarse-grained, glauconitic and phosphate-bearing 11 sediments belonging to the D. mammillatum Superzone, of Early Albian age, across 12 southern England, Bedfordshire, East Anglia, and Lincolnshire and east Yorkshire. In 13 the Weald and Bedfordshire, these strata have traditionally been known as „Junction 14 15 Beds‟ (e.g. Owen, 1972; 1992), and in East Anglia, Lincolnshire and east Yorkshire 16 as „Carstone‟. Hopson et al. (2008) introduced the name Munday's Hill Phosphatic 17 Sandstone Formation for the Bedfordshire „Junction Beds‟ and the slightly older (L. 18 tardefurcata Zone, L. regularis Subzone) Shenley Limestone Member. Like the 19 Monks Bay Sandstone, the „Junction Beds‟ and Carstone show great lateral variability 20 21 in their development, reflected in their detailed biostratigraphy, thickness and 22 changing relative proportion of dominant lithological components. This variability 23 reflects a dynamic depositional environment that was strongly influenced by Early 24 Albian palaeogeography and basin architecture. For example, the unusually expanded 25 „Junction Beds‟ seen at Folkestone probably reflect the role of extensional fault 26 27 control (Ruffell and Wach, 1998), whilst further west in Sussex, equivalent sediments 28 („Iron Grit‟) are highly condensed on the flanks of an emergent structure, with 29 primary iron-enrichment occurring in a lagoonal or marginal marine setting 30 (Anderson, 1986). Further north, across the East Midlands Shelf, the base and top of 31 32 the Carstone both appear to be younger than elsewhere (Mitchell and Underwood, 33 1999). 34 35 The unconformity immediately underlying the Monk‟s Bay Sandstone represents a 36 sequence boundary, reflecting a major relative fall in sea level and named LG4 in the 37 38 eastern Weald by Hesselbo et al. (1990). Whilst this sequence boundary can be 39 matched with a conspicuous erosion surface at the base of correlative strata at many 40 localities across central and eastern England, it is less obvious in the expanded Weald 41 successions. Here, strata equivalent to the Monk‟s Bay Sandstone are represented by 42 43 phosphate-rich sandstones at the top of what is conventionally regarded as the 44 Folkestone Formation, and designated „Gault – Lower Greensand Junction Beds‟ by 45 Owen (1992). There are two candidate positions for sequence boundary LG4 in the 46 eastern Weald; in the expanded Folkestone succession these are either at the base of 47 the locally developed mammillatum Superzone (S. kitchini Subzone), or at the base of 48 49 a conspicuous concentration of phosphates slightly higher in the succession („Main 50 Mammillatum Bed‟ of Casey, 1961), spanning the S. chalensis and O. auritiformis 51 zones (Hesselbo et al., 1990). The „Main Mammillatum Bed‟ can also be interpreted 52 as the product of condensed sedimentation associated with a maximum flooding 53 surface (Hesselbo et al., 1990); this and the presence of the S. kitchini Subzone in the 54 55 Monk‟s Bay Sandstone favours the lower horizon as the position of the sequence 56 boundary. 57 58 In the Isle of Wight, the L. regularis Subzone (Casey, 1961) is missing below the 59 60 sequence boundary and above it the Monk‟s Bay Sandstone and its lateral equivalents 61 62 63 64 65 represent a major transgressive sedimentary package, with deposition in shallow and 1 offshore marine settings (Ruffell, 1992; Ruffell & Wach, 1991). The sediment 2 includes material (pebbles) reworked from Carboniferous and Jurassic strata, the 3 4 weathered and oxidized pyritic mudstones of the latter contributing to the iron-rich 5 character of the Monk‟s Bay Sandstone (Garden, 1991; Ruffell & Garden, 1997). For 6 example, a considerable proportion of limonite grains and small clasts is present in the 7 Monk‟s Bay Sandston at Compton and Red Cliff, indicating proximity to a structural 8 high source area. 9 10 11 The change in the depositional regime associated with the Monk‟s Bay Sandstone is 12 highlighted by its thickness trend and distribution (Ruffell, 1992, fig. 4). The 13 formation‟s westerly thinning, and presence north of the faulted margin of the Isle of 14 15 Wight palaeo-high, contrasts with underlying units displaying southerly thickening 16 and confinement south of this palaeo-high. However, re-examination of borehole 17 records in the northern part of the Isle of Wight suggests that some occurrences of 18 Monk‟s Bay Sandstone might be underlain by older Lower Greensand Group 19 sediments. A number of well-records contain descriptions of very fine- to fine-grained 20 21 well-sorted sands with an argillaceous matrix (e.g. Bouldnor Copse No1; SZ39SE1 22 [SZ38537 90179]), or show a lower unit beneath coarse-grained sandstone and pebbly 23 sandstone that comprise very variable but generally finer-grade sands and argillaceous 24 beds some with plant remains (e.g. Portsdown No2; SU60NW5 [SU 6393 0737]). If 25 these deposits represent a marine depositional environment it suggests that marine 26 27 transgressions onto the Isle of Wight palaeo-high were complex, episodic and earlier 28 than previously supposed. Further to that hypothesis, structural observations during 29 the resurvey of the island suggest that the development of the Isle of Wight palaeo- 30 high and eventually the monoclinal structure was not simple and that generally north 31 32 – south orientated faulting divides the monoclinal areas into blocks with slightly 33 differing strike orientations. It is very likely that these structures are nucleated on 34 earlier Jurassic structures and that mid-Cretaceous deposition and palaeogeography is 35 not be a function of eustacy alone. There is likely to be a tectonic influence to the 36 distribution of Lower Greensand Group sediments, and the preservation/erosion of 37 38 thin Lower Greensand Group sediments below the Monk‟s Bay Sandstone is therefore 39 be related to differential block movement (a far-field „Alpine‟ tectonic influence 40 perhaps) as well as general regressive/transgressive eustatic cycles. 41 42 43 It is noticeable that coastal sections in the Monk‟s Bay Sandstone between Monk‟s 44 Bay and show a persistent depositional pattern, comprising thinner 45 bedded intervals in the lower and upper parts, and a thicker, massively-bedded and 46 more conspicuously bioturbated central part. This pattern is formed by thin units of 47 intercalated mudstone in the lower and upper parts of the succession, with few 48 49 mudstone horizons in the central part. The mudstones indicate lower-energy phases of 50 marine deposition compared to the intervening coarse, pebbly sandstones, and may be 51 primary evidence for pulses of marine inundation during transgression. The 52 conspicuous bioturbation in the massive beds could have destroyed mudstone 53 horizons if they were ever present, but may also indicate relatively less reworking 54 55 during deposition compared to adjacent pebbly sandstone units. 56 57 Acknowledgements 58 59 60 61 62 63 64 65 The authors would like to thank the following for their help and cooperation during 1 the completion of this study and the Isle of Wight resurvey. Roger Morgan of 2 Knighton Sandpit Ltd, for access to the quarry at Knighton that exposes the topmost 3 4 Ferruginous Sand Formation the entire Sandrock Formation and the most extensive 5 inland exposure of the Monk‟s Bay Sandstone Formation. Robin Lang and the staff at 6 the National Trust for access to the Mottistone and Compton Chine borehole sites. Mr 7 Oswald Hoskyns of Hobbit House Farm, Whitwell for permission to complete the 8 three boreholes on his land. 9 10 11 The BGS drilling crew under chief driller Steve Thorpe during the four campaigns on 12 the Isle of Wight comprised Chris Slater, Carl Horabin, Ricky Terrington, Helen 13 Smith, Barry Adkin, and Ian Longhurst. 14 15 16 We are very grateful to the reviewers, both within BGS and to Peter Rawson and an 17 anonymous reviewer on behalf of Elsevier for their constructive comments which 18 enabled us to improve the original manuscript. 19 20 21 P. M. Hopson, I.P. Wilkinson, M. A. Woods and A.R. Farrant publish with the 22 permission of the Executive Director of the British Geological Survey (N.E.R.C.). 23 24 25 References 26 27 28 Anderson, I.D., 1986. The Gault Clay- Folkestone Beds junction in West Sussex, 29 southeast England. Proceedings of the Geologists‟ Association 97, 45-58. 30 31 32 Carter, D.J., Hart, M.B., 1977. Aspects of mid-Cretaceous stratigraphical 33 micropalaeontology. Bulletin of the British Museum (Natural History), Geology 34 Series 29, 1-135. 35 36 Casey, R., 1961. The stratigraphical palaeontology of the Lower Greensand. 37 38 Palaeontology 3, 487-621. 39 40 Dike, E.F., 1972. Sedimentology of the Lower Greensand of the Isle of White. 41 Unpublished PhD thesis, University of Oxford. 42 43 44 Dilley, 1969. The foraminifera of the Melton Carstone. Proceedings of the Yorkshire 45 Geological Society 37, 321-322. 46 47 Fitton, W.H., 1847. A stratigraphical account of the section from Atherfield to 48 49 Rocken End on the south-west coast of the Isle of Wight. Quarterly Journal of the 50 Geological Society of London 3, 289-327. 51 52 Gale, A.S., Huggett, J.M., Gill, M., 1996. The stratigraphy and petrography of the 53 Gault Clay Formation (Albian, Cretaceous) at Redcliff, Isle of Wight. Proceedings of 54 55 the Geologists‟ Association 107, 287-298. 56 57 Garden, I.R., 1991. Changes in the provenance of pebbly detritus in southern Britain 58 and northern France associated with basin rifting. In: Morton, A.C., Todd, S.P., 59 60 61 62 63 64 65 Haughton, P.D.W. (Eds.), Developments in Sedimentary Provenance Studies. 1 Geological Society Special Publication 57, 273-289. 2 3 4 Hecht, F.E., 1938. Standard-Glederung der nordwestdeutschland Unterkriede nach 5 Foraminiferen. Abhandlungen der. Senckenbergischen Naturforschenden 6 Gessellschaften 443, 1-42. 7 8 Hesselbo, S.P., Coe, A.L. and Jenkyns, H.C., 1990. Recognition and documentation 9 10 of depositional sequences from outcrop: an example from the Aptian and Albian on 11 the eastern margin of the Wessex Basin. Journal of the Geological Society of London 12 147, 549-559. 13 14 15 Hopson, P.M., Wilkinson, I.P., Woods, M.A., 2008. A stratigraphical framework for 16 the Lower Cretaceous of England. British Geological Survey Research Report 17 RR/08/03, 77pp. 18 19 Ibbetson, L.L.B., Forbes, E., 1845. On the section between and 20 21 Atherfield Point. Quarterly Journal of the Geological Society of London 1, 190-197. 22 23 Jackson, J. F. 1939. Notes on the discovery of fossiliferous nodules in the Carstone 24 near Niton. Proceedings of the Isle of Wight Natural History and Archaeological 25 Society 3, 73-80. 26 27 28 Magniez-Jannin, F., 1975. Les foraminifères de l'Albien de l'Aube: Paléontologie, 29 stratigraphie, écologie. Cahiers de Paléontologie, Éditions du Centre National de la 30 Recherche Scientifique, 360pp. 31 32 Mitchell, S.F. and Underwood C.J., 1999. Lithological and faunal stratigraphy of the 33 Aptian and Albian (Lower Cretaceous) of the type Speeton Clay, Speeton, north-east 34 35 England. Proceedings of the Yorkshire Geological Society 52, 277-296. 36 37 Mutterlose, J., Bornemann, A., Kirsch, K.H., Luppold, F., Ruffell, A., Weiss, W., 38 Wray, D., Owen, H.G., 2003. The Vöhrum section (NW Germany) and the 39 Aptian/Albian boundary. Cretaceous Research 24, 203-252. 40 41 42 Owen, H.G., 1971a. Middle Albian stratigraphy in the Anglo-Paris Basin. Bulletin of 43 the British Museum (Natural History) Geology Series Supplement 8. 44 45 Owen, H.G., 1971b. The stratigraphy of the Gault in the Thames Estuary and its 46 47 bearing on the Mesozoic tectonic history of the area. Proceedings of the Geologists' 48 Association 82, 187-207. 49 50 Owen, H. G., 1972. The Gault and its junction with the Woburn Sands in the Leighton 51 52 Buzzard area, Bedfordshire and Buckinghamshire. Proceedings of the Geologists' 53 Association 83, 287-312. 54 55 Owen, H.G., 1975. The stratigraphy of the Gault and Upper Greensand of the Weald. 56 Proceedings of the Geologists' Association 86, 475-498. 57 58 59 60 61 62 63 64 65 Owen, H.G., 1988. The ammonite zonal sequence and ammonite taxonomy in the 1 Douvilleiceras mammillatum Superzone (Lower Albian) in Europe. Bulletin of the 2 British Museum (Natural History) Geology Series 44, 177-231. 3 4 5 Owen, H.G., 1992. The Gault-Lower Greensand Junction Beds in the northern Weald 6 (England) and Wissant (France), and their depositional environment. Proceedings of 7 the Geologists' Association 103, 93-110. 8 9 10 Owen, H.G. 1999. Correlation of Albian European and Tethyan ammonite zonations 11 and the boundaries of the Albian Stage and substages: some comments. Scripta Geol., 12 Special Issue 3, 129-149, 5 figs., Leiden, December 1999. 13 14 15 Owen, H.G., 2007. Ammonite biostratigraphy of the Albian in the KirchrodeII 16 Borehole, Hannover, Germany. Cretaceous Research 28, 921-938. 17 18 Price, R.J., 1977. The stratigraphical zonation of the Albian sediments of north-west 19 Europe, as based on foraminifera. Proceedings of the Geologists' Association 88, 65- 20 21 91. 22 Reid, C., Strahan, A. 1889. The geology of the Isle of Wight (2nd Edition). Memoir of 23 24 the British Geological Survey. 25 26 Ruffell, A.H., 1992. Early to mid-Cretaceous tectonics and unconformities of the 27 Wessex Basin (southern England). Journal of the Geological Society of London 149, 28 443-454. 29 30 31 Ruffell, A.H., Garden, I.R., 1997. Tectonic controls on the variation in thickness and 32 mineralogy of pebble-beds in the Lower Greensand Group (Aptian-Albian) of the Isle 33 of Wight, southern England. Proceedings of the Geologists‟ Association 108, 215- 34 35 229. 36 37 Ruffell, A.H., Wach, G.D., 1991. Sequence stratigraphic analysis of the Aptian- 38 Albian Lower Greensand in southern England. Marine and Petroleum Geology 8, 39 341-353. 40 41 42 White, H.J.O., 1921. A short account of the geology of the Isle of Wight. Memoir of 43 the British Geological Survey. 44 45 Woods, M.A., 2009. Macrofossils from the Upper Greensand Formation and Chalk 46 47 Group of the Isle of Wight. British Geological Survey Internal Report IR/09/056. 48 49 50 List of Figures 51 52 53 Fig.1. The outcrop of the Monk‟s Bay Sandstone Formation on the Isle of Wight, 54 including the locations of the principal exposures and boreholes mentioned in the text 55 (outcrop derived from BGS, 1976 without modification). 56 57 58 Fig. 2. The strongly colour-contrasted and burrowed boundary between the pale 59 yellow, fine-grained, cross-bedded, sandstone of the Sandrock Formation (below) 60 with the coarse-grained, pebbly, ferruginous sandstone of the Monk‟s Bay Sandstone 61 62 63 64 65 Formation (above) at the stratotype in Monk‟s Bay. Burrows, infilled with coarse- 1 grained sand, extend downwards from the Monk‟s Bay Sandstone Formation into the 2 Sandrock Formation. Field of view 0.35 x 0.5 m approx. BGS image P732202. [SZ 3 4 58099 78122]. 5 6 Fig. 3a. The stratotype section of the Monk‟s Bay Sandstone Formation at Monk‟s 7 Bay near Bonchurch, Isle of Wight [SZ 581 782] (after Woods, 2009, fig 12.). See 8 Fig. 3b for key. 9 10 11 Fig. 3b. Key to Figure 3a and subsequent lithological graphic logs. Each log shows a 12 representation of the maximum grain size up to very coarse-grained sand based on 13 visual examination. 14 15 16 Fig. 4. View of the Monk‟s Bay section from [SZ 58099 78122] looking north. The 17 pale yellow sandstones of the Sandrock Formation overlain, in the mid-cliff, by the 18 orange-brown coarse-grained sandstones of the Monk‟s Bay Sandstone Formation 19 (arrow marks the boundary). The basal Gault Formation is evident within the 20 21 shallower slopes at the top of the exposure. Here the formation about 10 m thick. BGS 22 image P 732203 [SZ 58099 78122]. 23 24 Fig. 5. The section northeast of Red Cliff. The base of the Monk‟s Bay Sandstone 25 Formation is arrowed. It lies at the distinct colour change from the paler sandstones of 26 27 the Sandrock Formation below, to the orange-coloured coarse sandstones of the 28 Monk‟s Bay Sandstone Formation above. BGS image P732243 [SZ 62199 85436]. 29 30 Fig. 6. The section of Monk‟s Bay Sandstone Formation at Knighton Sand Pit and the 31 32 logs from the three cored boreholes completed to the north of the exposure visible in 33 2008. See Fig. 3b for key. 34 35 Fig. 7a. The lower part of the exposure of Monks Bay Sandstone Formation exposed 36 in the Knighton Sand Pit [SZ 57474 86712]. At this locality the formation rests with a 37 38 sharp erosive contact (arrowed) (hoe head 0.6 m long) on laminated/finely-bedded 39 sandy clayey silts at the top of the the Sandrock Formation. BGS image P683907. 40 41 Fig. 7b. The upper part of the Monk‟s Bay Sandstone Formation at the Knighton Sand 42 43 Pit (hammer 0.28 m). BGS image P683932. 44 45 Fig. 8. Marvel Sand Pit [SZ 4992 8687]. Boundary (arrowed), between the Sandrock 46 Formation and the Monks Bay Sandstone Formation, just below ferruginous ironstone 47 band. Field of view approx 40 x 55 m. BGS image P 692204. 48 49 50 Fig. 9. Graphic log for Rookley Brickworks [SZ 5133 8395] modified after Dike 51 (1972). See Fig. 3b for key. 52 53 Fig. 10. The contact (arrowed) of the Sandrock Formation and the Monk‟s Bay 54 55 Sandstone Formation in the cliff adjacent to Luccombe Chine [SZ 58325 79278], Isle 56 of Wight. BGS image P732232. 57 58 Fig. 11. Graphic borehole log for The Monk‟s Bay Sandstone Formation and adjacent 59 60 units from the Ventnor No. 2 and 3 boreholes. See Fig. 3b for key. 61 62 63 64 65

1 Fig. 12. Graphic log, as a composite of the three boreholes completed at Hobbit 2 House Farm, Whitwell. See Fig. 3b for key. 3 4 5 Fig. 13. Correlation of the four boreholes at Mottistone. See Fig. 3b for key. 6 7 Fig. 14. Compton Bay. The attenuated Monk's Bay Sandstone Formation, 1.83 m 8 thick, exposed at beach level adjacent to Compton Chine. Dark glauconitic sandy 9 10 mudstone of the Sandrock Formation is visible below and dark grey basal sandy 11 mudstone of the Gault Formation above. [SZ 436736 085214]. Hammer 28 cm. BGS 12 image P732435. 13 14 15 Fig. 15. Graphic log of the Monk‟s Bay Sandstone at Compton Chine borehole 16 compared to that from Compton Bay (Ruffell and Garden, 1997). See Fig. 3b for key. 17 18 Fig. 16. The ammonite zonal scheme adopted by Casey (1961) and others for the 19 Early and Mid Albian of the UK, compared to that of Owen (1999, 2007). 1. 20 21 Leymeriella acuticosta in Europe; 2. Farnhamia farnhamensis is synonymn of 22 Proleymeriella schrammeni (e.g. Mutterlose et al. 2003). 23 24 Fig. 17 The lithostratigraphy of the Lower and Middle Albian of southern and eastern 25 England related to the ammonite zones/subzones (Casey 1961, Owen 1999). Shaded 26 27 area depicts the erosional gap in the succession, which Casey (1961) considered to 28 occupy the entire L. regularis Zone. Ranges of selected Early Albian foraminifera and 29 the foraminiferal zonation are correlated to ammonite biostratigraphy (not the 30 lithostratigraphy). 31 32 33 List of Tables 34 35 Table 1. Simplified litho- and chrono-stratigraphy of part of the Lower Cretaceous of 36 the Isle of Wight. 37 38 39 Table 2. Additional locations described in White (1921) for the Monk‟s Bay 40 Sandstone Formation. 41 42 Table 3. The BGS boreholes described in this paper. 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig 1. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 2 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 3a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 3b 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 4 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 5 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 6 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 7a 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 7b 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 9 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 10 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 11 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 12 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 13 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 14 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Fig. 16 1 2 Casey 1961; Owen 1971a&b, 1975 Isle of Owen, 1999, 2007 3 Stage Zone Subzone Wight Subzone Zone Superzone Stage 4 Euhoplite

s lautus slautus

(pars) 5 6 Euhoplites nitidus Euhoplites nitidus

7

(pars) s lautuss

8 Euhoplite 9 Euhoplites Euhoplites

Euhoplites l Euhoplites

10 Formation Gault meandrinus meandrinus

11 Albian Mid

12 Mojsisovicsia Mojsisovicsia oricatus 13 subdelaruei subdelaruei

14 Dimorphoplites Dimorphoplites oricatus 15 niobe niobe 16

Mid Albian Anahoplites Anahoplites

17 Euhoplites l 18 intermedius intermedius

19 Hoplites (Hoplites) dentatus Hoplites Hoplites spathi 20 spathi 21

22 Lyelliceras lyelli Lyelliceras lyelli

23 plites dentatus Ho Hoplites Psuedosonneratia 24 (Hoplites) 25 (Isohoplites) Formation Sandstone Bay Monk’s (Isohoplites) auritiformis Otohoplites 26 eondentatus steinmanni 27 Equivalent of

Otohoplites mammillatum Douvilleiceras bulliensis Subzone 28 bulliensis not proven in IoW 29 30 Protohoplites Protohoplites 31 (Hemisonneratia) (Hemisonneratia) 32 puzosianus puzosianus

33 Otohoplites Otohoplites 34 raulianus raulianus 35 36 Cleoniceras Cleoniceras

floridum floridum Sonneratia 37 c

halensis

Early Albian Early

38 Sonneratia kitchini Sonneratia kitchini

39 Douvilleiceras mammillatum 40 Sonneratia

41 (Globosonneratia)

42 absent perinflatum

43 Early Albian

44 tardefurcata

Leymeriella Leymeriella 45 Leymeriella Leymeriella 46 regularis regularis 47 48

Sandrock Formation Sandrock

Hypacanthhoplites Leymeriella 49 1 50 milletioides acuticostata

51 Proleymeriella

schrammeni

52 tardefurcata 53 Equivalent of the

54 schrammeni Zone Leymeriella (Leymeriella) 55 not proven

2

56 57 58 59 60 61 62 63 64 65 Fig. 17 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 Table

Monks Bay Sandstone Tables File

Group Formation Stage Upper Greensand Selborne Gault Albian Monk’s Bay Sandstone

Lower Sandrock Greensand Ferruginous Sands Aptian Atherfield Clay Table 1. Simplified litho- and chrono-stratigraphy of part of the Lower Cretaceous of the Isle of Wight.

Location Grid Reference Rock SZ 4251 8397 Marvel Wood SZ 4988 8690 Billingham Cottages SZ 4831 8244 Birchmore SZ 5062 8529 Whitecroft SZ 4989 8631 Knighton Brook SZ 5677 8676 Itchall SZ 5198 7930 Itchall SZ 5219 7961 Table 2. Additional locations described in White (1921) for the Monk’s Bay Sandstone Formation.

Location Locality Grid Registered Number(s) Reference Knighton Sand Pit SZ 575 867 SZ58NE 98 to 100 Whitwell (Hobbit SZ 520 786 SZ57NW 51 to 53 House Farm) Mottistone SZ 408 843 SZ48SW 26 to 31 Compton Chine SZ 368 852 SZ38NE 30 Ventnor* SZ 557 775 SZ57NE 27 and 25 Table 3. The BGS boreholes described in this paper. Figure

Monks Bay Sandstone Figures File

List of Figures

Fig.1. The outcrop of the Monk’s Bay Sandstone Formation on the Isle of Wight, including the locations of the principal exposures and boreholes mentioned in the text (outcrop derived from BGS, 1976 without modification).

Fig. 2. The strongly colour-contrasted and burrowed boundary between the pale yellow, fine- grained, cross-bedded, sandstone of the Sandrock Formation (below) with the coarse-grained, pebbly, ferruginous sandstone of the Monk’s Bay Sandstone Formation (above) at the stratotype in Monk’s Bay. Burrows, infilled with coarse-grained sand, extend downwards from the Monk’s Bay Sandstone Formation into the Sandrock Formation. Field of view 0.35 x 0.5 m approx. BGS image P732202. [SZ 58099 78122].

Fig. 3a. The stratotype section of the Monk’s Bay Sandstone Formation at Monk’s Bay near Bonchurch, Isle of Wight [SZ 581 782] (after Woods, 2009, fig 12.). See Fig. 3b for key.

Fig. 3b. Key to Figure 3a and subsequent lithological graphic logs. Each log shows a representation of the maximum grain size up to very coarse-grained sand based on visual examination.

Fig. 4. View of the Monk’s Bay section from *SZ 58099 78122+ looking north. The pale yellow sandstones of the Sandrock Formation overlain, in the mid-cliff, by the orange-brown coarse-grained sandstones of the Monk’s Bay Sandstone Formation (arrow marks the boundary). The basal Gault Formation is evident within the shallower slopes at the top of the exposure. Here the formation about 10 m thick. BGS image P 732203 [SZ 58099 78122].

Fig. 5. The section northeast of Red Cliff. The base of the Monk’s Bay Sandstone Formation is arrowed. It lies at the distinct colour change from the paler sandstones of the Sandrock Formation below, to the orange-coloured coarse sandstones of the Monk’s Bay Sandstone Formation above. BGS image P732243 [SZ 62199 85436].

Fig. 6. The section of Monk’s Bay Sandstone Formation at Knighton Sand Pit and the logs from the three cored boreholes completed to the north of the exposure visible in 2008. See Fig. 3b for key.

Fig. 7a. The lower part of the exposure of Monks Bay Sandstone Formation exposed in the Knighton Sand Pit [SZ 57474 86712]. At this locality the formation rests with a sharp erosive contact (arrowed) (hoe head 0.6 m long) on laminated/finely-bedded sandy clayey silts at the top of the the Sandrock Formation. BGS image P683907.

Fig. 7b. The upper part of the Monk’s Bay Sandstone Formation at the Knighton Sand Pit (hammer 0.28 m). BGS image P683932.

Fig. 8. Marvel Sand Pit [SZ 4992 8687]. Boundary (arrowed), between the Sandrock Formation and the Monks Bay Sandstone Formation, just below ferruginous ironstone band. Field of view approx 40 x 55 m. BGS image P 692204.

Fig. 9. Graphic log for Rookley Brickworks [SZ 5133 8395] modified after Dike (1972). See Fig. 3b for key.

Fig. 10. The contact (arrowed) of the Sandrock Formation and the Monk’s Bay Sandstone Formation in the cliff adjacent to Luccombe Chine [SZ 58325 79278], Isle of Wight. BGS image P732232.

Fig. 11. Graphic borehole log for The Monk’s Bay Sandstone Formation and adjacent units from the Ventnor No. 2 and 3 boreholes. See Fig. 3b for key.

Fig. 12. Graphic log, as a composite of the three boreholes completed at Hobbit House Farm, Whitwell. See Fig. 3b for key.

Fig. 13. Correlation of the four boreholes at Mottistone. See Fig. 3b for key.

Fig. 14. Compton Bay. The attenuated Monk's Bay Sandstone Formation, 1.83 m thick, exposed at beach level adjacent to Compton Chine. Dark glauconitic sandy mudstone of the Sandrock Formation is visible below and dark grey basal sandy mudstone of the Gault Formation above. [SZ 436736 085214]. Hammer 28 cm. BGS image P732435.

Fig. 15. Graphic log of the Monk’s Bay Sandstone at Compton Chine borehole compared to that from Compton Bay (Ruffell and Garden, 1997). See Fig. 3b for key.

Fig. 16. The ammonite zonal scheme adopted by Casey (1961) and others for the Early and Mid Albian of the UK, compared to that of Owen (1999, 2007). 1. Leymeriella acuticosta in Europe; 2. Farnhamia farnhamensis is synonymn of Proleymeriella schrammeni (e.g. Mutterlose et al. 2003).

Fig. 17 The lithostratigraphy of the Lower and Middle Albian of southern and eastern England related to the ammonite zones/subzones (Casey 1961, Owen 1999). Shaded area depicts the erosional gap in the succession, which Casey (1961) considered to occupy the entire L. regularis Zone. Ranges of selected Early Albian foraminifera and the foraminiferal zonation are correlated to ammonite biostratigraphy (not the lithostratigraphy).

Fig 1.

Fig. 2

Fig. 3a

Fig. 3b

Fig. 4

Fig. 5

Fig. 6

Fig. 7a

Fig. 7b

Fig. 8

Fig. 9

Fig. 10

Fig. 11

Fig. 12

Fig. 13

Fig. 14

Fig 15

Fig. 16

Casey 1961; Owen 1971a&b, 1975 Isle of Owen, 1999, 2007 Stage Zone Subzone Wight Subzone Zone Superzone Stage

Euhoplite

s lautus slautus

(pars)

Euhoplites nitidus Euhoplites nitidus

(pars)

s lautuss Euhoplite

Euhoplites Euhoplites

Euhoplites l Euhoplites

meandrinus Formation Gault meandrinus

Mojsisovicsia Mojsisovicsia Albian Mid oricatus subdelaruei subdelaruei

Dimorphoplites Dimorphoplites oricatus

niobe niobe

Mid Albian Anahoplites Anahoplites

Euhoplites l intermedius intermedius

Hoplites (Hoplites) dentatus Hoplites Hoplites spathi

spathi

es es

Lyelliceras lyelli Lyelliceras lyelli dentatus

Hoplit Hoplites Psuedosonneratia (Hoplites)

(Isohoplites) Formation Sandstone Bay Monk’s (Isohoplites) auritiformis Otohoplites eondentatus steinmanni Equivalent of

Otohoplites mammillatum Douvilleiceras bulliensis Subzone bulliensis

not proven in IoW

Protohoplites Protohoplites (Hemisonneratia) (Hemisonneratia) puzosianus puzosianus

Otohoplites Otohoplites raulianus raulianus Cleoniceras Cleoniceras

floridum floridum Sonneratia

c

halensis

Early Albian Early

Sonneratia kitchini Sonneratia kitchini

Douvilleiceras mammillatum Sonneratia

(Globosonneratia)

absent perinflatum

Early Albian

tardefurcata

Leymeriella Leymeriella Leymeriella Leymeriella

regularis regularis

Sandrock Formation Sandrock

Hypacanthhoplites Leymeriella milletioides1 acuticostata

Proleymeriella Proleymeriella

schrammeni tardefurcata Equivalent of the schrammeni Zone Leymeriella (Leymeriella) not proven

2

Fig 17.