Lithostratigraphic analysis and geochemistry of a vitric spatter-bearing ignimbrite: the Quaternary Adeje Formation, Cañadas volcano, Tenerife.

P. Dávila Harris et al. Bulletin of Volcanology 2013

Electronic Supplementary Material 1 (ESM-1)

Table captions

Table 1 Lithofacies association for the Adeje Formation in southwest Tenerife, following the

scheme of Brown & Branney (2004) for other pyroclastic units across southern Tenerife (e.g.

Porís Formation).

Table 2 Description of selected juvenile types within the Adeje Formation illustrating the

wide variety of textures and crystal contents present within single clasts.

Figure captions

Figure 1 Stratigraphic contacts between the Adeje and San Juan Formations. A) Incipiently

welded lapilli-tuff (from the San Juan Formation) on an erosion surface over the Adeje

ignimbrite, at El Puertito by the coast. B) Detail of contact in A, rucksack is 0.3 m. C)

Irregular erosive contact between the Adeje and the San Juan ignimbrites, south of Adeje

town. Note palaeosol at the top of the Adeje ignimbrite. Hammer is 30 cm long.

Figure 2 A) At the base, the Adeje Formation showing massive agglomeratic lapilli-tuff

overlain by lava and on top the San Juan Formation sitting unconformably, Punta Negra. See

person for scale. B) The San Juan Formation unconformably overlying the Adeje Formation

at Playa de Diego Hernandez, probably representing an irregular coastal platform that has

been buried. C) Sketch of picture B.

Figure 1

Figure 2

Table 1

Lithofacies Name (code) Description InterpretationPumice lapilli (pL); massive pumice lapilli (mpL); stratified or bedded pumice lapilli (spL, bpL); difusse-stratified or diffuse-bedded pumice lapilli (dspL, dbpL); lithic-rich pumice lapilli (lpL)

Litohology: Clast-supported pumice lapilli (massive), well to moderately sorted. Pumice clasts are angular to sub-angular, smaller than 6.0 to 8.0 cm in diameter, commonly green to grey and pale-grey, and yellow when altered. It includes lithic lapilli in lower proportions (<20 %). Lithic clasts are generally smaller, platy and slightly altered, they comprise accidental volcanic lithologies.Sub-facies: stratified or bedded pumice lapilli (spL, bpL), like mpL but with grading patters due to grainsize variations showing stratification (thin layering) and bedding (thick, cm sized beds). Diffuse-stratifed/bedded pumice lapilli (dspL, dbpL), when grading is not obvious but subtle. Lithic-rich pumice lapilli (lmpL), when proportion of lithic clasts is larger than ~25% to up to ~40% at some levels of the deposit, it commonly results on grading patterns.Structure: It presents vertical grading, layers can variously grade upwards from massive to diffuse-stratified and massive again, for example.Geometry/occurrence: It is laterally extended; sheet like, mantles topography, lateral thickness changes are gradual. Boundaries usually parallel, with sharp lower contacts and more diffuse upper contacts, at places upper contact eroded by overlying lapilli-tuff.

Interpretation: Pumice fallout deposit on the basis of sorting, framework supported fabric, topography mantling and little lateral variations and laterally extended. Stratification and/or bedding can be the result of changes in lithic proportions or general grainsize variations, reflecting fluctuations on dispersal and deposition, consequence of wind, mass-flux, source location and paleotopography.

Massive lapilli-tuff (mLT) Lithology: massive lapilli-tuff (mLT) comprises fine to coarse-ash matrix of variable colours mainly pale-cream, supporting variable proportions of pumice and lithic lapilli. Pumice lapilli are rounded to sub-rounded, not exceeding 30% of lithofacies; the average diameter is 2-3 cm: usually weathered and grey to yellowish. Lithic lapilli occupies 3-5% of the total; they consist of angular to sub-angular clasts, with average sizes 1-2 cm in diameter, lithologies are variable, including fresh and altered basalt, phonolite, scoria and spare intermediate syenite clasts.Sub-facies: lithic-rich massive lapilli-tuff (lmLT); as mLT with an increase in lithic lapilli content of 20 to 25%; massive lapilli-tuff with accretionary lapilli (mLTacc); as mLT and contains matrix supported, multi-rimmed accretionary lapilli and broken pieces of ash-aggregates (pellets).Structure: massive; non-graded; presents localized, diffuse and discontinuous stratification; when lithic-rich often exhibits inverse grading, denoted with (i) or normal grading (n).Geometry/occurrence: massive lapilli-tuff usually forms thick lenticular, u-shaped and valley-fill deposits with maximum thicknesses in the range of 20 meters; passes laterally and gradually into massive tuff (mT) and bedded tuff (bT): grades vertically into dsLT, dbLT, mlBr, mAgT

Interpretation: massive lapilli-tuff records rapid aggradation from sustained, granular fluid-based density currents, where the lowermost part of the current and uppermost part of the deposit were poorly packed, with abundant ash and clasts. Absence of structures suggests that tractional processes and turbulence were suppressed by high clast concentrations (Kokelaar et al., 2007; Branney and Kokelaar, 2002).

Diffuse-stratified lapilli-tuff (dsLT)

Lithology: diffuse-stratified lapilli-tuff (dsLT) as mLT.Structure: thin, discontinuous, diffuse centimetre-thick, sub-parallel strata; in sets 0.1 to 3 m thick; defined by the alternation of ash-rich layers and lapilli-rich thin layers; presents low-angle truncations; convergence and bifurcation of laminae; scours and lateral impersistence.Sub-facies: lithic-rich, diffuse-stratified lapilli-tuff (ldsLT); marked by a higher proportion of lithic-lapilli over fines and pumice-lapilli.Geometry/occurrence: present in topography-filling facies and close to valley margins and palaeoridges; grades laterally into stratified lapilli-tuff (sLT) and vertically into massive lapilli-tuff (mLT).

Interpretation: diffuse-stratified lapilli-tuff represents relatively fast progressive aggradation from a high-concentration fluid escape to granular flow-dominated boundary-zone of a pyroclastic density current. The fluctuation and grading patterns of the impersistent stratification suggests unsteady deposition from a sustained current. (Branney and Kokelaar, 2002; Brown and Branney, 2004)

Diffuse-bedded lapilli-tuff (dbLT)

Lithology: diffuse-bedded lapilli-tuff (dbLT) as mLT; lithic-rich bedded lapilli-tuff (lbLT) as lmLT with bedding defined by sub-horizontal concentrations of lithic-lapilli; varied lithologies as mLT.Structure: it comprises centimetre to decimetres thick bed sets; internally massive; sub-parallel; with undulating lower and upper boundaries; imbrication common (f); low-angle scours common at basal

Interpretation: diffuse-bedded lapilli-tuff records similar conditions of emplacement that mLT: rapid aggradation. The slightly marked bedding does not correspond to tractional stratification,

Lithofacies Name (code) Description Interpretationboundary; occasional sharp upper boundary.Geometry/occurrence: sub-horizontal continuity mainly in packages of more than one or two beds; common in laterally persistent sheets; pinch-out upslope or laterally into valley margins; grades horizontally into dsLT and pLT; passes vertically into mLT, mLTacc; mT.

instead, it probably records localized unsteadiness in a nearly constant supply of ash/lapilli in a pyroclastic current. When lithic-rich (ldbLT), an inferred increase in lithic-lapilli supply is invoked, either from source, near to vent or entrained from substrate. The variation in bedding thicknesses records current non-uniformity, while low-angle strata and lateral truncations reflect current unsteadiness (Branney and Kokelaar, 2002; Brown and Branney, 2004; Kokelaar et al., 2007).

Pumice-rich lapilli-tuff (pLT)

Lithology: pumice-rich lapilli-tuff (pLT) is supported in a fine-tuff matrix; it comprises sub-rounded to sub-angular inflated pumice lapilli; coarse-pumice clasts (10-30 cm on diameter) form pumice lenses (plens) usually at the top of ignimbrite sheets; normally lithic-poor and with occasional thin strata of ash-tuff with accretionary lapilli.Sub-facies: pumice-rich bedded lapilli-tuff (pbLT); as pLT, with centimetre-thick layers of pumice-lapilli forming laterally discontinuous bedding; beds are internally massive with diffuse lower and upper boundaries except when defined by thin ash layers.Structure: generally massive: plensLT, forms cm- to m-long lenticular structures (pumice lens); usually in low angle; concave or convex upwards; internally non-graded and moderately sorted; crudely inverse-graded towards the top when forming beds; occasionally forming pods, pLT(pod), associated with branch moulds.Geometry/occurrence: plensLT usually appears at the top and valley margins of mLT and dbLT; pbLT usually in sheets and laterally discontinuous; pLT(pod), occurs in close contact with substrate, typically associated with shrub and branch moulds (Brown et al., 2004).

Interpretation: pumice-rich massive lapilli-tuff as mLT and with high concentration of juvenile pumice from source (pumice-rich currents); plensLT –lenses or framework-supported pumice-lapilli records accumulation of pumice clasts at the lateral margin of the current (pumice levees), where conditions of the flow-boundary (concentration and shear rates) favour deposition; accumulation of pumice at the top levels of ignimbrite sheets reflects deposition in waning stages of the current (Branney and Kokelaar, 2002; Brown and Branney, 2004); pbLT – like pmLT with unsteady current conditions and fluctuation in pumice supply.

Cross-stratified tuff and lapilli-tuff (xsT/xsLT)

Lithology: cross-stratified tuff (xsT) comprises poorly-sorted, fine-grained pumice and lithic lapilli in ash-tuff matrix; cross-stratified lapilli-tuff is poorly-sorted, ash-matrix supported pumice- and lithic-lapilli in higher proportions that xsT. Pumice-lapilli are rounded to sub-rounded in xsT and xsLT whilst lithic lapilli are angular to sub-angular in xsT and xsLT.Structure: forms low-angle cross-stratification with dips along 5 to 15˚ up-current and down-current; stratification is defined by lithic-lapilli, pumice-lapilli or thin layers of fines; thickness of cross-strata ranges from 5 to 20 cm thick; internally massive or diffusely-stratified; lateral and down-stream truncations common.Geometry/occurrence: laterally discontinuous, sub-parallel sets that can extent for 10 to 20 meters across; thickness of sets can be from 0.1 to 1.5 m thick; dunes and antidune bedforms with wavelengths from 2 to 15 meters; sharp lower contact with mLT and dbLT; gradational upper contact with mLT and dbLT; scoured upper contact occasionally; passes laterally and vertically into mLT, dbLT and ldbLT.

Interpretation: records deposition from traction-dominated flow-boundaries (Branney and Kokelaar, 2002). However, many variations may exist regarding type of structures, continuity and context; stratified and cross-stratified tuff and lapilli-tuff generally reflects unsteadiness in pyroclastic density current. The intergradational character of xsT/xsLT with mLT and dbLT indicates that the parent currents had intermediate boundary zones between tractional and granular-flow dominated flow-boundaries (Branney and Kokelaar, 2002).

Eutaxitic massive lapilli-tuff (emLT)

Lithology: green to dark brown eutaxitic massive lapilli-tuff (emLT) is matrix-supported in highly- to incipiently-welded groundmass formed by shards, pyroclasts and small lithic and crystal particles; it contains high proportion (≤ 20%) of deformed, elongated juvenile pumice (fiamme) and flattened shards; sizes of fiamme range from a few millimetres to 10 cm across; length-to-thickness ratios of fiamme increases with increasing welding intensity and decreases progressively; oblate pyroclasts of obsidian are common in partly- and incipiently-welded lapilli tuff, grading into fiamme when welding

Interpretation: eutaxitic massive lapilli-tuff occurs mostly above the massive lithic-breccia facies (mlBr) and thus, is more likely to record hotter material later in the eruption rather than the effect of loading. Some of the fiamme could probably have been originally poorly-vesiculated

Lithofacies Name (code) Description Interpretationbecomes intense. Accidental lithic-clasts can vary in volume across welding horizons, lithic-rich eutaxitic lapilli-tuff (lemLT) usually contains ≥ 10% of lithic lapilli; from mm up to 20 cm in size.Structure: its fabric is usually elongated in the direction of flow; high-grade kinematic indicators exist at the margins of lithic lapilli or phenocrysts of different sizes; in microscopic scale, vitroclastic texture show rotational features around complete and dislocated phenocrysts.Geometry/occurrence: emLT is exposed in the study area as a 0.5 to 1.5 m thick, longitudinal layer of eutaxitic tuff; sheet-like horizons of different welding intensities are exposed in the unit; it exhibit truncations and common changes laterally and vertically; the lower and upper contacts are gradational from and to non-welded massive lapilli-tuff; sharp boundaries are rare except when associated with horizons of lithic-breccia (lemLT); it passes gradually, upwards and laterally into mLT.

hot clasts rather than pumice (as has been inferred for the Arico Formation in southeast Tenerife; Bryan et al., 1998; Brown et al., 2003).

Massive tuff (mT), diffuse-stratified-tuff (dsT) and cross-stratified tuff (xsT)

Lithology: fine-grained ash matrix supporting 5 to 10% of fine lapilli; negligible amount of coarse-grained clasts are present in this lithofacies; fines-rich ash is the dominant component and it can be formed by microscopic-scale glass-shards, broken crystals, devitrified glass and highly-fragmented accidental lithic accessory.Structure: internally massive; maximum thickness recorded 2 m; common lateral changes in thickness; sharp and gradational boundaries; grades into diffuse-stratified tuff (dsT).Geometry/occurrence: presents lenticular shapes in valley-fill; mantles topography but thins drastically over palaeoridges, from 1 to 300 cm; condensed sequences; grades laterally into mT, mLT, mLTacc, mTacc; passes vertically into dsT and mTpel draping topography.

Interpretation: broadly similar emplacement processes as mLT and dsLT with the absence of abundant lapilli.

Massive lithic-breccia (mlBr)

Lithology: consists of matrix- to clast-supported, lithic lapilli and blocks (pebble to boulder size) in poorly-sorted lapilli-tuff; maximum clast size recorded ~0.5 m; average clast size 10 to 30 cm in diameter; lithic blocks are usually sub-rounded but can be angular and rounded; usually present exfoliation rims; pumice-lapilli is sparse and in similar proportion as mLT in interclast sections; lithologies are very variable and comprise in descending abundance: basalt; phonolite; basanite; scoria; fine-grained syenite; obsidian; porphyritic glassy blocks and occasionally welded tuffs.Structure: internally massive; can present crude to diffuse bedding (dblBr) or well-developed bedding (blBr). Boulders commonly aligned with long-axis parallel to flow direction; usually normal graded; lower contact can present load structures; upper contact transitional and gradational into mLT or ldbLT.Geometry/occurrence: highly variable; sub-horizontal sheet-like; irregular; localized, pods (loaded), connected to main breccia body or isolated; thickness varies from 0.3 m to 3 m thick; grades laterally into ldbLT and lmLT; passes vertically into normal-graded lithic breccia.

Interpretation: massive co-ignimbrite lithic breccias (mlBr) are deposited similarly to other lithofacies (e.g. mLT) but more energetically; mlBr derive from granular flow- and/or fluid escape-dominated flow boundaries of pyroclastic density currents. Stratified or bedded breccias in ignimbrite (blBr) are commonly imbricated and it is inferred they deposit at traction dominated flow-boundary zones with rolling and saltation of big lithic clasts. Lithic breccias may originate from erosion or collapse of the eruptive conduits/vent, avalanches into the pyroclastic density current, or substrate erosion from waxing gravity currents (Branney and Kokelaar, 2002).

Massive tuff with accretionary lapilli (mTacc)

Lithology: mTacc – matrix supported in fine ash-tuff; pumice and lithic lapilli subordinated (≤2%); poorly sorted; contains variable proportions of ash aggregates (accretionary lapilli) in the range of 2 to 8%; they can be complete circular to oblate shape or debris from brittle broken bits, multi-rimmed or single rimmed.Structure: internally massive; crudely stratified and bedded with sharp to diffuse boundaries; longitudinal variations common; normal grading common.Geometry/occurrence: 3 to 100 cm thick; geometry influenced by topography as mLT; lenticular, sheet-like, thinning in valley-margins and thickening towards valley-axis; grade upwards into mTpel and mLT and laterally into mT, mLT and dsLT.

Interpretation: accretionary lapilli in massive-tuff (mTacc) is formed by the fallout of ash-pellets from a plume, dropping into rapid, ground-hugging pyroclastic density currents; accreting successive concentric laminations then dried out to be deposited in low aspect ratio ignimbrites (Brown et al., 2010).

(see sketch above) Massive ash-pellet tuff Lithology: poorly-sorted, fine-grained tuff; pumice and lithic lapilli subordinated (<2%) and Interpretation: ash-pellet bearing tuff (mTpel)

Lithofacies Name (code) Description Interpretation(mTpel) occasionally at base or top of lithofacies.

Structure: internally massive; framework-supported with localized and sparse interstitial ash-matrix; formed mainly by clast-supported pellets (mTpel); lower contact usually gradational, top contact sharp and gradational.Geometry/occurrence: sheet-like; 3 to 10 cm thick; drapes topography; usually at the upper part of ignimbrite sheets with accretionary lapilli (mTacc).

has been interpreted as from a fallout origin; ash-pellets are formed in buoyant co-ignimbrite ash-plumes and deposited by direct fallout (Brown et al., 2010).

Massive agglomeratic lapilli-tuff (mAgLT)

Lithology: matrix-supported juvenile-rich breccia in lithic- and crystal-rich lapilli-tuff matrix; it comprises ≤ 30% of mainly black, dense juvenile blocks of varied textures including: porphyritic black, poorly vesiculated juvenile blocks; feldspar-rich (swallow-tail texture abundant) in aphyric groundmass blocks; glassy obsidian; mingled green and black glassy blocks with spherulitic texture and lithophysae; scoriaceous amoeboid blocks; spatter-like and cauliflower structures; chilled-rims and bread-crusted blocks. The clast sizes range from 1 to 50 cm. Inflated pumice is ubiquitous and appears only at the lower levels and in low proportions; lithic lapilli abundant throughout the lithofacies and it comprises basalt, phonolite and crystalline syenite blocks.Structure: massive to diffuse and crudely bedded; graded to non-graded; in parts mixed with lithic-breccias (lmAg); imbrication is common (mAgf) with long axis dipping upslope; lower and upper contacts are gradational except when mixed with lithic-breccias; thickness range from 0.5 to 5 m.Geometry/occurrence: it can form essential parts on massive agglomerate; layers or crudely bedded accumulations of juvenile clasts at certain levels of the deposit; it forms elongated clusters that fade out laterally; lenticular shapes are common with lengths up to 10 meters across; diffuse layering and imbrication in direction of flow is common when elongated shapes.

Interpretation: massive agglomeratic lapilli-tuff (mAgLT) like lithic breccias, are consistent with emplacement from rapidly aggrading pyroclastic density currents in a granular-fluid based regime (Branney and Kokelaar 1992, 2002). Most of the blocks in this lithofacies, represent juvenile pyroclasts/spatter that were deposited ca. 15 km from source; hence a fallout origin is discarded. A highly energetic eruption is invoked for the emplacement of massive agglomerates in distal facies; two hypotheses may be suggested: 1) the presence of a shallow lava-lake or spatter cone during the eruption, with subsequent disruption by explosive magma fragmentation, convective column and entrainment of poorly vesiculated blocks into PDC’s. 2) The origin of the phonolite agglutinate may have originated via intrinsic eruption processes while emptying of magma chamber caused partial roof collapse and fragmentation of poorly vesicular magma that formed the spatter clasts then incorporated into the currents once optimum fragmentation and highly vesiculated magma was fragmented. A combination of both may also be possible.

Lithic-rich massive agglomeratic lapilli-tuff (lmAgLT) and with directional fabric (mAgLTf)

Lithology: lithic-rich massive agglomerate (lmAg) as mAg with an increased proportion of lithic-clasts that range from lapilli to blocks of varied lithologies: basalt; phonolite; vesicular scoria and fine-grained syenitic clasts. mAgLTf – as mAgLT and with overall directional fabric in one or more horizons.Structure: lmAg – as mAg with smaller percentage of interstitial matrix as this is replaced by abundant (~30 %) lithic clasts; mAgLTf – like mAg, with crude thick layers of elongated juvenile clasts with long axes orientated in the direction of flow; dips upslope.Geometry/occurrence: lmAg – as mAg with sharper lower and upper contacts; mAgf – as mAg with lateral discontinuity of imbrication due to changes in supply, palaeotopography; variability of matrix-cognate clasts ratio; local intergradations with lithic-breccias (mlBr) or lapilli-tuff (mLT; Branney and Kokelaar, 2002; references therein). Passes laterally into mAgLT, mAgf, mLT and vertically into, mAgLT, mLT and emLT.

Interpretation: lmAg – as mAgLT with the emphasis that dense juvenile clasts/blocks behave similarly to accidental lithic blocks in massive lithic-breccias (mlBr) and thus a similar emplacement process is invoked; it involves particle segregation during rapid deposition of cognate clasts, fluid escape, elutriation and overpassing of highly vesiculated pumice and fines. mAgLTf – as mAg with variations in the conditions of sedimentation at the flow boundary-zone, reflected in the strength of the directional fabric (Branney and Kokelaar, 2002).

Table 2

Picture Type of juvenile

Description Lithofacies occurrence

Layer/ location Summarized interpretation Localities

Pumice Framework-supported, green to grey, highly angular, crystal-poor, pumice-lapilli with fibrous texture. Grades from pale and highly-inflated to green and glassy; generally fresh

dbL, mpL, Layer 1, basal framework-supported pumice lapilli

Records initial Plinian pumice-fall deposit; high phonolite magma fragmentation

Barranco del Agua, Playa de Diego Hernández, El Puertito, Playa Paraíso and Barranco de Erques (see Fig.1)

Green pumice, glassy porphyri-tic core

Matrix-supported, sub-rounded to rounded, dark-green lapilli and blocks, microvesicular, with crystal content of c. 3% mainly alkali feldspar (sanidine, anorthoclase), with glassy core and fibrous margins

dsLT, mLT, Layer B; at 1.5 m from base of ignimbrite

Partially degassed green pumice entrained into pyroclastic density current

Most localities

Porphyri-tic obsidian

Lapilli and blocks of sub-rounded to sub-angular poorly-inflated glass, with conchoidal fracture and ≤20% alkali feldspars in swallowtail texture, up to 5 mm in diameter

dsLT, mLT, emLT, mAgLT, lmLT, mlBr

Layer B; at 1.5 m from base of ignimbrite

Occurs in pyroclastic density current deposit; poorly vesiculated phonolite glassy juvenile with swallow-tail texture of potassic feldspars

Most localities

Green and black banded

Pale-green and black, mingled blocks: a) Green glass: crystal-poor, dense, in streaks and bands, spherulitic and with lithophysae, sharp contact with black glass; b) Black glass: microvesicular, crystal-rich, swallowtail feldspars, in bands with sharp contacts

mAgLT, mlBr, lmLT

Layer B; ~4 m from the base of ignimbrite

Occurs in pyroclastic density current deposit; clasts exhibit mingling of glasses of contrasting colour but apparently similar composition that probably cooled at different rates

El Puertito

Massive obsidian /crystal-rich obsidian

Sub-angular to sub-rounded blocks and lapilli of black to dark-green glassy obsidian, with conchoidal fracture; co-existing crystal-rich and completely aphyric

mlBr, mLT, mAgLT,

Layer B; 5 m from base of ignimbrite.

Pyroclastic density current eruption; ignimbrite flow unit 1; probably entrained as undegassed cognate clasts into the pyroclastic density currents

El Puertito, Fañabe and Barranco de Erques

Spatter ‘bomb- like’ clast

Black blocks to lapilli, microvesicular, scoriaceous and crystal-rich, highly angular (amoeboid) to sub-angular, elongated and with fluidal shapes; bread-crusted margins; forms imbricated and massive agglomerates (mAgf); phenocrysts orientated in sense of clast elongation

mAgLT, mAgLTf, mlBr, mLT, lmLT

Layers B and D Proximal spatter-like clasts incorporated into PDC’s and transported as cognate blocks, probably behave similar to lithics in massive lithic-breccias

El Pris and El Puertito, Playa de Morteros, Barranco del Burro and Barranco del Agua