Crustal structure, gravity anomalies, and subsidence history of the Parnaíba cratonic basin, Northeast Brazil

Abstract

Cratonic basins cover more than 10% of Earth's continental surface area, yet their origin remains enigmatic. Here we use a 1400 km long, deep (20 s two‐way travel time) seismic reflection profile, five wide‐angle split‐spread receiver gathers, gravity anomaly, and well data to constrain the origin of the Parnaíba Basin, a cratonic basin in Northeast Brazil. In the center of the basin, the depth to pre‐Paleozoic basement is ~3.3 km, a zone of midcrustal reflectivity (MCR) can be traced laterally for ~250 km at depths between 17 and 25 km and Moho depth is ~42 ± 2 km. Gravity and P wave modeling suggests that the MCR represents the upper surface of a high density (2985 kg m−3) and Vp (6.75–7.0 km s−1) lower crustal body, likely of magmatic origin. Backstripping of well data shows a concave up decreasing tectonic subsidence, similar in form to that observed in rift‐type basins. We show, however, that our seismic and gravity data are inconsistent with an extensional origin. Other basin forming mechanisms are therefore required. We show that an intrusive body in the lower crust that has loaded and flexed the surface of the crust, combined with sediment loading, provides a satisfactory fit to the observed gravity anomaly. A buried load model is consistent with seismic data, which suggest that the Moho is as deep or deeper beneath the basin center than its flanks and accounts for at least part of the tectonic subsidence through a viscoelastic stress relaxation that occurs in the lithosphere following load emplacement.

Gondwana breakup: Messages from the North Natal Valley

“…The lateral velocity variations observed in the lower crust of the NNV (Figures and ) have already been imaged for other regions such as in the Palaeoproterozoic block of the Ukrainian Shield (Thybo & Artemieva, ; Thybo et al, ), the intracontinental lake Baikal rift (Thybo & Nielsen, ) or the intracontinental Parnaïba basin (Tozer, Watts, & Daly, ). Such variations are interpreted as a presence of mafic and ultramafic mantle materials in the lower or middle continental crust and as magmatic intrusions (DeRito, Cozzarelli, & Hodge, ; Nunn & Aires, ; Tozer et al, ) or eclogitization of the lower crust (Baird, Knapp, Steer, Brown, & Nelson, ; Haxby, Turcotte, & Bird, ). As described for the Arctic Ocean (Shulgin et al, ), this part of the Indian Ocean has also experienced several magmatic events at different periods (the Karoo volcanic event, the Turonian trapps event, Eocene, Miocene, etc.…”

“…This anomalous topography must be related to the presence of lateral variations in the velocity structure of the crust and the presence of multiple magmatic events recorded in the sedimentary layers. In the Parnaïba basin, Tozer et al () proposed that the lower part of the continental crust is overloaded by mafic intrusions, inducing subsidence and the formation of the sedimentary basin. Shulgin et al, , equally proposed a deep originating process with emplacement of intrusive mafic bodies at the transition crust/upper mantle.…”

Subsidence and exhumation of the Mesozoic Qiangtang Basin: Implications for the growth of the Tibetan plateau

“…Reconstructing the subsidence histories of sedimentary basins provides data to directly interrogate the tectonic evolution of a basin (e.g. Abadi, Wees, Dijk, & Cloetingh, ; Brunet, Korotaev, Ershov, & Nikishin, ; Carrapa & Garcia‐Gastellanos, ; Holt, Allen, Hunen, & Bjørnseth, ; Holt, Allen, & Hunen, ; Kuhn, Echtler, Littke, & Alfaro, ; Sciunnach & Garzanti, ; Abdullayev, Kadirov, & Guliyev, ; Dressel, Scheck‐Wenderoth, & Cacace, ; Silvia et al, ; Tozer, Watts, & Daly, ). The most commonly applied method to recover the 1‐D subsidence history of a sedimentary basin is ‘backstripping’ (Sclater & Christie, ; Watts & Ryan, ), which relies on physical properties of the stratigraphic sequences (thickness and porosity), combined with depositional ages, palaeobathymetry and eustsay at the time of accumulation.…”

Analysis and Interpretation of Time-Lapse Micorgravity Data Case Study in Kota Lama Semarang Tourism Area

“…A simple Bouguer anomaly contour map in the January and June 2019 periods is shown in FIGURE 7 below. Based on theoretical studies [12], [13], the results of modeling and contour of gravity data, in general, are interesting is the intermittent microgravity anomaly, not the value of gravity for each period. In each period, we only know the value (quantity) and have no physical artist at that time.…”