UPHESC Assistant Professor Geology PYQs

Concept: At the Gutenberg discontinuity (core–mantle boundary, ~2900 km) density jumps from about 5.6 to about 9.9 g/cm³ – the largest jump inside the Earth.

1. Moho (crust–mantle): ~2.9 → 3.3 g/cm³ (small jump).
2. Lehmann (outer–inner core): ~12.2 → 12.8 g/cm³.
3. Lithosphere–asthenosphere is a rheological (strength) boundary with hardly any density change.

Short trick: Gutenberg = Greatest jump (≈4.3 g/cm³).

Concept: Archaeopteryx, the earliest generally accepted bird, comes from the Solnhofen Limestone of Bavaria – Upper (Late) Jurassic, ~150 Ma (Tithonian).

1. It shows reptilian features (teeth, clawed fingers, long bony tail) with true feathers.
2. Cretaceous birds (Confuciusornis, Hesperornis, Ichthyornis) came later.

Short trick: Archaeopteryx – Solnhofen – Late Jurassic, 150 Ma.

Concept: Skolithos is a simple, straight, unbranched vertical burrow (pipe) in sandstones, made by suspension feeders in high-energy shallow water (Skolithos ichnofacies).

1. Cruziana – bilobed horizontal trilobite furrows (crawling traces).
2. Trypanites – borings into hard substrates (rock/shell), not tubes in loose sand.
3. 'Pipe-rock' of Cambrian quartzites is full of Skolithos.

Short trick: Skolithos = Straight Sand tubes (S-S-S).

Concept: Palynology is the study of pollen, spores and other organic-walled microfossils (palynomorphs), living and fossil.

1. Limnology – study of lakes/inland waters.
2. Dendrochronology – dating by tree rings.
3. Tephrochronology – dating/correlation by volcanic ash (tephra) layers.

Short trick: Palyno = dust (pollen) → palynology.

Concept: Benthic forams date from the Cambrian, but the first planktonic foraminifera (e.g. Conoglobigerina) appear only in the Middle Jurassic – i.e. in Mesozoic time.

1. They radiated strongly in the Cretaceous (Globotruncana) and again in the Cenozoic (Globigerina).
2. Palaeozoic forams (fusulinids etc.) were all benthic.

Short trick: Planktonic forams: born in Jurassic (Mesozoic), boomed in Cretaceous.

Concept: In Kutch, the upper, plant-bearing part of the Umia Member (Lower Cretaceous sandstones with Ptilophyllum flora) is called the Bhuj Formation (Bhuj Series/Bhuj sandstone).

1. Kutch Jurassic succession: Patcham → Chari → Katrol → Umia.
2. Ukra beds are marine Aptian beds within the Umia; Umia ammonite beds are marine.
3. Umaria marine beds belong to Madhya Pradesh (Permian marine bed in Gondwana).

Short trick: Bhuj = Umia plant beds (Ptilophyllum sandstones).

Concept: The Rajmahal Formation (Upper Gondwana, Early Cretaceous, Rajmahal Hills, Jharkhand) – intertrappean beds between lava flows – preserves one of the richest and best-preserved Mesozoic floras in the world, made famous by Birbal Sahni.

1. Typical plants: Ptilophyllum, Williamsonia, the unique Pentoxylon (described by Sahni), conifers and ferns, many petrified.
2. Talchir – glacial tillite with scanty flora; Barakar and Raniganj – coal-bearing Lower Gondwana with Glossopteris flora.

Short trick: Rajmahal = Sahni's treasure-house of fossil plants (Pentoxylon).

Concept: Rhynia is a primitive leafless, rootless vascular land plant preserved in the Rhynie Chert of Scotland – Early (Lower) Devonian, ~410 Ma.

1. Rhynie chert also yields Aglaophyton, Horneophyton and early arthropods.
2. Carboniferous is the age of coal forests (Lepidodendron, Calamites); Permian – Glossopteris.

Short trick: Rhynia – Rhynie chert – Devonian.

Concept: Jaduguda (Singhbhum shear zone, Jharkhand) is India's first uranium mine (UCIL, 1967).

1. Khetri (Rajasthan) – copper, not lead.
2. Panna (MP) – diamonds (Majhgawan kimberlite), not gold.
3. Malanjkhand (MP) – India's largest copper (porphyry-type) deposit, not iron.

Short trick: Jaduguda-U, Khetri-Cu, Panna-diamond, Malanjkhand-Cu.

Concept: Bombay (Mumbai) High is a large NNW–SSE doubly plunging anticlinal (domal) structure in the offshore Mumbai basin; oil and gas are trapped mainly in Miocene (L-III) limestones.

1. A doubly plunging anticline closes in all directions – a perfect four-way structural trap.
2. Synclines collect water, not oil.

Short trick: Oil rises to the crest: dome / doubly plunging anticline.

Concept: In the classical textbook treatment 'Nautilus' stands for the nautilid stock (Nautilidae/Nautilaceae in the broad sense), whose range is given as Triassic to Recent; this is the range the question expects.

1. Cambrian to Recent is the range of the nautiloids as a whole (sub-class Nautiloidea), not of Nautilus.
2. Jurassic and Cretaceous are too late for the start of the nautilid stock in that classical sense.
3. Note: the modern genus Nautilus in the strict sense has fossils only from the Late Eocene onwards; the Triassic start refers to its family-level lineage.
4. Nautilus is the only living cephalopod with an external chambered shell, a central siphuncle and simple sutures.

Short trick: Nautiloids: Cambrian→Recent; Nautilus stock: Triassic→Recent.

Concept: At Kolar, gold occurs in the Champion Reef – auriferous quartz lodes in Dharwar amphibolites; the gold-bearing quartz is characteristically bluish-grey to smoky (the 'Champion lode'), while milky white quartz is generally barren.

1. Native gold is associated with scheelite, pyrrhotite, arsenopyrite in this grey quartz.
2. Kolar mines (now closed, 2001) reached over 3 km depth.

Short trick: Kolar Champion reef: grey-blue quartz = gold; milky quartz = barren.

Concept: Cassiterite (SnO₂) of the Bastar–Koraput tin belt occurs in granite pegmatites and associated quartz veins intruding Precambrian granitic gneisses/metasediments.

1. Tin is a classic granitophile (lithophile) element – it concentrates in late-stage granite, greisen and pegmatite.
2. Basalt, diorite and conglomerate are not tin hosts here (alluvial cassiterite is derived from the pegmatites).

Short trick: Tin ↔ granite–pegmatite–greisen.

Concept: The first tetrapods/amphibians (Ichthyostega, Acanthostega) are known from Late Devonian rocks of East Greenland (~365 Ma).

1. Devonian = 'Age of Fishes'; lobe-finned fishes (Tiktaalik, Eusthenopteron) gave rise to amphibians.
2. Carboniferous is the 'Age of Amphibians' (their peak), not their first appearance.

Short trick: Fish age (Devonian) ends with first amphibian – Ichthyostega.

Concept: A zonule is the smallest biostratigraphic unit – a subdivision of a biozone (subzone) recognised by its fossil content.

1. Biostratigraphic hierarchy: biozone → subzone → zonule.
2. Lithostratigraphic: Supergroup–Group–Formation–Member–Bed.
3. Chronostratigraphic: Eonothem–Erathem–System–Series–Stage–Chronozone.

Short trick: Zone → Subzone → Zonule: all fossil-based.

Concept: In a conoscopic interference figure, the melatope is the point where an optic axis emerges in the field of view; around it the isochromes are centred and the isogyres pass through it.

1. Uniaxial optic-axis figure: one melatope at the cross centre.
2. Biaxial acute-bisectrix figure: two melatopes on the isogyres (on the optic axial plane trace).

Short trick: Melatope = 'black spot' where the optic axis comes out.

Concept: Stromatolites are laminated structures built by cyanobacterial mats; the oldest are Archaean (≈3.5–3.4 Ga, Warrawoona/Strelley Pool, Pilbara; ≈3.2–3.0 Ga in South Africa) – so of the options only ~3200 m.y. fits.

1. 500 and 1000 m.y. are far too young; stromatolites were abundant in the Proterozoic but began in the Archaean.
2. Indian examples: Aravalli (Udaipur) and Vindhyan stromatolites (Proterozoic).

Short trick: Stromatolites = oldest visible evidence of life, >3 billion years.

Concept: The Archaean–Proterozoic boundary is fixed chronometrically (GSSA) at 2500 Ma.

1. Proterozoic: 2500–541 Ma (Palaeo-, Meso-, Neo-).
2. Archaean: 4000–2500 Ma; Phanerozoic begins at 541 (≈538.8) Ma.

Short trick: 2.5 Ga = Archaean ends, Proterozoic begins.

Concept: Bauxite forms by intense chemical (lateritic) weathering of aluminous rocks in hot, humid climates: silica and bases are leached away and Al-hydroxides (gibbsite, boehmite, diaspore) remain behind – a residual concentration.

1. Indian examples: East Coast bauxites (Panchpatmali, Odisha) on khondalite; Deccan-trap cappings in Maharashtra/Gujarat.
2. Not magmatic or replacement; transported bauxite is minor.

Short trick: Leach the rest, Al stays – residual bauxite (and laterite).

Concept: Placers form by mechanical concentration: running water, waves or wind sort grains, and heavy, chemically resistant minerals (gold, cassiterite, ilmenite, monazite, diamond) settle where velocity drops.

1. Residual liquid segregation – magmatic (e.g. chromite, Ti-magnetite).
2. Residual concentration – weathering in place (bauxite, laterite).

Short trick: Placer = Heavy + Hard + Hydraulic sorting.